草稿:曼哈顿计划

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Manhattan District
A fiery mushroom cloud lights up the sky.
The Trinity test of the Manhattan Project on 16 July 1945 was the first detonation of a nuclear weapon.

存在時期1942–1946
國家或地區
  • 美國
  • 英國
  • 加拿大
部門U.S. Army Corps of Engineers
駐軍/總部Oak Ridge, Tennessee, U.S.
參與戰役
紀念日13 August 1942
指挥官
著名指揮官
佩章
Manhattan District shoulder sleeve insignia英语shoulder sleeve insignia
Oval shaped shoulder patch with a deep blue background. At the top is a red circle and blue star, the patch of the Army Service Forces. It is surrounded by a white oval, representing a mushroom cloud. Below it is a white lightning bolt cracking a yellow circle, representing an atom.
Manhattan Project emblem (unofficial)
Circular shaped emblem with the words "Manhattan Project" at the top, and a large "A" in the center with the word "bomb" below it, surmounting the US Army Corps of Engineers' castle emblem

The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom (which initiated the original Tube Alloys project) and Canada. From 1942 to 1946, the project was under the direction of Major General英语Major general (United States) Leslie Groves of the U.S. Army Corps of Engineers. Nuclear physicist Robert Oppenheimer was the director of the Los Alamos Laboratory英语Los Alamos Laboratory that designed the actual bombs. As engineer districts by convention carried the name of the city where they were located, the Army component of the project was designated the Manhattan District; Manhattan gradually superseded the official codename, Development of Substitute Materials, for the entire project. Along the way, the project absorbed its earlier British counterpart, Tube Alloys. The Manhattan Project began modestly in 1939, but grew to employ more than 130,000 people and cost nearly US$2 billion (equivalent to about $23 billion in 2018).[1] Over 90 percent of the cost was for building factories and to produce fissile material, with less than 10 percent for development and production of the weapons. Research and production took place at more than thirty sites across the United States, the United Kingdom, and Canada.

Two types of atomic bombs were developed concurrently during the war: a relatively simple gun-type fission weapon英语gun-type fission weapon and a more complex implosion-type nuclear weapon. The Thin Man gun-type design proved impractical to use with plutonium, and therefore a simpler gun-type called Little Boy was developed that used uranium-235, an isotope that makes up only 0.7 percent of natural uranium. Since it was chemically identical to the most common isotope, uranium-238, and had almost the same mass, separating the two proved difficult. Three methods were employed for uranium enrichment: electromagnetic, gaseous and thermal. Most of this work was performed at the Clinton Engineer Works at Oak Ridge, Tennessee.

In parallel with the work on uranium was an effort to produce plutonium, which was discovered at the University of California in 1940. After the feasibility of the world's first artificial nuclear reactor, the Chicago Pile-1, was demonstrated in 1942 at the Metallurgical Laboratory in the University of Chicago, the Project designed the X-10 Graphite Reactor at Oak Ridge and the production reactors at the Hanford Site in Washington state, in which uranium was irradiated and transmuted into plutonium. The plutonium was then chemically separated from the uranium, using the bismuth phosphate process英语bismuth phosphate process. The Fat Man plutonium implosion-type weapon was developed in a concerted design and development effort by the Los Alamos Laboratory.

The project was also charged with gathering intelligence on the German nuclear weapon project. Through Operation Alsos, Manhattan Project personnel served in Europe, sometimes behind enemy lines, where they gathered nuclear materials and documents, and rounded up German scientists. Despite the Manhattan Project's tight security, Soviet atomic spies英语atomic spies successfully penetrated the program. The first nuclear device ever detonated was an implosion-type bomb at the Trinity test, conducted at New Mexico's Alamogordo Bombing and Gunnery Range on 16 July 1945. Little Boy and Fat Man bombs were used a month later in the atomic bombings of Hiroshima and Nagasaki, respectively, with Manhattan Project personnel serving as bomb assembly technicians, and as weaponeers on the attack aircraft. In the immediate postwar years, the Manhattan Project conducted weapons testing at Bikini Atoll as part of Operation Crossroads, developed new weapons, promoted the development of the network of national laboratories, supported medical research into radiology and laid the foundations for the nuclear navy英语nuclear navy. It maintained control over American atomic weapons research and production until the formation of the United States Atomic Energy Commission in January 1947.

源起[编辑]

1938年,德国化学家奥托·哈恩弗里茨·施特拉斯曼共同发现了核裂变现象,不久后莉泽·迈特纳奥托·弗里施又洞晓了其背后的理论原理,使得核武器的开发从理论上可行。当时人们很担心德国会率先造出原子弹,从納粹德國法西斯国家流亡的科学家对此更是恐慌不已。[2]1939年8月,匈牙利裔物理学家利奧·西拉德尤金·维格纳共同起草愛因斯坦-西拉德信,警告有人可能要研发一种“极为强力的新型炸弹”。信中还强烈建议美国政府大量囤积铀矿英语uranium ore,督促恩里科·费米等学者进行核連鎖反應的有关研究。信件由阿尔伯特·爱因斯坦落款署名,递送至时任美国总统富兰克林·德拉诺·罗斯福的手中。罗斯福命国家标准局局长莱曼·布里格斯组建铀顾问团,详议爱因斯坦-西拉德信提及的问题。布里格斯在1939年10月21日召开了一次会议,出席者有西拉德、维格纳和愛德華·泰勒。该年11月,委员会回禀罗斯福称,铀“或可被制成炸弹,其破坏力将远大于目前所知的任何武器”。[3]

美國海軍哥伦比亚大学资助了6,000美金,费米和西拉德将这笔钱基本都花在了购置石墨上。二人联手尤金·布思英语Eugene T. Booth约翰·邓宁等哥伦比亚大学教授实现了美国首个核裂变反应,验证了哈恩和施特拉斯曼的发现。他们随后又陆陆续续在哥伦比亚大学卜平樓制造了一系列核反应堆原型,但未能实现链式反应[4]1940年6月27日,国防部科研委员会NDRC)成立,铀顾问团被划入NDRC旗下。[5]布里格斯申请了167,000美元的经费用来研究铀(尤其是同位素鈾-235)和1940年在加利福尼亞大學发现的元素。[6][note 1]1941年6月28日,罗斯福签署了第8807号总统令,成立了科学研究与开发办公室(简写为OSRD),[9]万尼瓦尔·布什担任主管。除了研究任务外,OSRD还获准许参与大型工程项目。[6]NDRC的铀委员会也成了OSRD的“S-1分部”,安全起见“铀”一字被从委员会名称中移除。[10]

1939年6月,弗里施和魯道夫·佩爾斯在英国伯明翰大学对铀-235的臨界質量研究取得了重大突破。[11]他们的计算显示,铀-235臨界質量的数量级在10公斤(22英磅)左右,可以搭载到轰炸机上。[12]1940年3月,他们写下了《弗里施-佩尔斯备忘录》,正式开展英国原子弹计划,并成立穆德委员会[13]委员会全体一致建议展开原子弹的相关研发工作。[12]该年7月,英国向美国开放了自己的科研成果,[14]蒂泽德任务英语Tizard Mission的学者约翰·考克饶夫还向美国科学家通报了英国的研究进展。他留意到美国这边的计划规模不如英国那边的大,进展也没英国的快。[15]

在两国科学交流期间,穆德委员会将自己的研究成果展示给了美国。不过,委员会成员、澳大利亚物理学家马克·奥利芬特在1941年8月下旬访美期间留意到穆德委员会的数据尚未转交至美方物理学界的关键人物手中,于是开始调查穆德委员会的成果被忽视的原因。他和铀委员会碰面,访问了伯克利,并说服了欧内斯特·劳伦斯开始研究铀。劳伦斯随后又与詹姆斯·科南特阿瑟·康普顿乔治·皮格勒姆英语George B. Pegram交流意见。至此,奥利芬特得到了自己想要的结果——美国物理学界的关键人物均已了解原子弹背后蕴藏的巨大潜力。[16][17]

1941年10月9日,罗斯福总统在与万尼瓦尔·布什和副总统亨利·华莱士会面后批准了原子弹研究计划。为掌控计划进度,罗斯福设立了最高决策团(Top Policy Group),组员有他自己(虽然罗斯福从未与会)、华莱士、布什、柯南特、战争部长亨利·史汀生陆军参谋长乔治·马歇尔上将。罗斯福决定让陆军接手原子弹研究计划,因为他认为在管理大型工程建设项目方面陆军比海军更有经验。他亦准许英、美两国相互合作,并在10月11日建议英国首相温斯顿·丘吉尔就原子弹问题相互协商。[18]

可行性[编辑]

提议[编辑]

S-1委员会在1941年12月18日举行会议。前不久日本偷袭珍珠港导致美国对日本英语United States declaration of war upon Japan德国英语United States declaration of war upon Germany (1941)宣战,致使会议“充斥着热情和紧张的气氛”。[19][20]

随后,技术人员兵分三路,用三种不同的同位素分离技术尝试将铀-235从自然界大量存在的鈾-238中分离出来:劳伦斯在加利福尼亞大學带领团队研究电磁型同位素分离法哥伦比亚大学埃格尔·默弗里英语Eger Murphree杰西·比姆斯英语Jesse Wakefield Beams的团队负责氣體擴散法华盛顿卡内基研究院英语Carnegie Institution of Washington菲力普·艾貝爾森(后转战海軍研究實驗室)则将研究重心放在熱泳法上。[21]默弗里还牵头研究了氣體離心法,但未能成功。[22]与此同时,两批科学家也在各自研究核反应堆的有关原理。哈羅德·尤里在哥伦比亚大学继续研究重水;阿瑟·康普顿则将他麾下的科学家从哥伦比亚大学、加州大学和普林斯顿大学聚集到了芝加哥大学,并在1942年组建冶金实验室,研究钚和将石墨英语nuclear graphite用作中子减速剂的核反应堆。[23]

1942年5月23日,布里格斯、康普顿、劳伦斯、默弗里和尤里在会议上敲定了S-1委员会的最终建议,决定同时对上文提到的五种核技术展开研究工作。这项提议获布什、科南特和威廉·斯泰尔准将英语Brigadier General (United States)布里恩·萨默维尔少将英语Major General (United States)负责的物资供应局英语Services of Supply的参谋长,时任陆军核事务代表)的批准。[21]布什和科南特随后将此意见呈报至最高决策团,申请5400万美元用于美國陸軍工兵部隊的工程建设、3100万美元用于OSRD的科研活动以及500万美元作为1943财年的或有损失之用。最高决策团随后在1942年将议案提交给罗斯福总统,罗斯福则大笔一挥签下“OK FDR”批准了提案。[21][note 2]

设计构想[编辑]

一系列铅笔画
1942年7月会议上探讨了不同的核裂变炸弹组装方式。

格雷戈里·布莱特曾负责主导研究快中子的有关参数,该议题对计算临界质量和核武器的引爆至关重要。1942年5月18日,布莱特因运作安保问题退出后,康普顿邀请加州大学理论物理学家罗伯特·奥本海默接手相关研究工作。[24]在曼哈顿计划与美国全国各地物理实验室磋商协调后,冶金实验室科学家约翰·曼利英语John H. Manley被安排到奥本海默手下当助手。[25]奥本海默和伊利诺伊大学罗伯特·瑟伯尔共同探讨了中子扩散问题(中子在核链式反应中如何移动)与流體動力學问题(链式反应制造的核爆炸会带来怎样的冲击)。1942年6月,奥本海默同恩里科·费米在芝加哥大学会面,同年7月又在哥伦比亚大学再次会晤,分享对这些问题的见解,并进一步讨论裂变反应的基础理论。其他的列席者还有理论物理学家汉斯·贝特約翰·范扶累克、泰勒、埃米尔·科诺宾斯基英语Emil Konopinski、瑟伯尔、斯坦·弗兰克尔英语Stan Frankel和埃尔德雷德·C·尼尔森(Eldred C. Nelson), 其中后三者都曾是奥本海默的学生,以及实验物理学家埃米利奥·塞格雷费利克斯·布洛赫佛朗哥·拉塞蒂、曼利和埃德温·麦克米伦。他们初步确认核裂变炸弹的构想在理论上可行。[26]

不过,整个计划依然充满着未知数。彼时人们尚不了解纯铀-235的性质,对格伦·西博格研究团队1941年2月首次成功制取的钚元素也知之甚少。1942年7月伯克利的那次会议中,科学家曾提出让铀-235裂变产生的中子轰击铀-238,从而在核反应堆中制造钚。然而当时人们从未建造过核反应堆,钚也只有圣路易斯华盛顿大学等机构用回旋加速器制备的很少一点而已。[27]截止到1943年12月,人们也仅仅造出了两毫克的钚。[28]核裂变原料有好几种装填成临界质量的方式。最简单的一种是将“柱形塞”打入一个充满“活性材料”的球体,并佐以“填塞物”(tamper)——可以将中子聚集在内部、使核材料聚集在一处并让核反应效率增加的致密材料。[29]科学家们还对其他设计进行过探讨。理查德·托勒曼构想过一种用到類球面的“内爆式”设计草案。他们还考虑过利用自催化反应,在炸弹爆炸时可提升其反应速率。[30]

1942年,学者们在伯克利又召开了一次核武器研讨会议。鉴于核裂变炸弹的理论探讨告一段落,科学家将注意力转向了其他话题。爱德华·泰勒想要讨论一种更为强力的“超级炸弹”(即氢弹),利用核裂变带来的爆炸冲击来引爆并引发核聚变[31]泰勒提议了各种方案,但被贝特一一否决。核聚变的思路也被搁置,人们转为继续深入探讨核裂变炸弹的制造方法。[32]泰勒还推测,理论上通过一种氮原子核聚变反应,原子弹可能会“点燃”引爆点周围的大气。[note 3]贝特在经过一番计算后认为大气不会被点燃,[34]泰勒作为共同作者参与的一篇报告也指出“不会出现自发的核链式反应”。[35]瑟伯尔后来回忆道,奥本海默曾对阿瑟·康普顿顺口一提此事,后者“开始对此喋喋不休”,“这事情不知怎么被写进一份递至华府的文件中”,“就此没完没了起来”。[note 4]

组织[编辑]

曼哈顿区[编辑]

1942年6月,陆军工兵总监英语Chief of Engineers尤金·雷巴德少将指派詹姆斯·马歇尔上校担任核武器计划陆军方面的负责人。马歇尔在华盛顿特区设有联络办公室,又在纽约百老汇270号英语Tower 27018层建立了自己的临时总部,方便调动陆军工兵部队北大西洋师英语North Atlantic Division。此处距离核武器计划的主要承包商石威公司英语Stone & Webster在曼哈顿的办公地址很近,也离哥伦比亚大学不远。他还可以从自己之前指挥的雪城军区(Syracuse District)抽调人员。马歇尔第一个调用的人是肯尼斯·尼科尔斯中校,命他担任自己的副官。[37][38]

曼哈顿计划的组织结构示意图,最上方是计划的总部,中间是曼哈顿军区,底部是曼哈顿计划的各个分部
曼哈顿计划的组织结构示意图,1946年5月1日

有鉴于马歇尔的主要任务是工程建设,他与工兵部队建设师的师长托马斯·罗宾斯(Thomas M. Robbins)少将与其副官莱斯利·格罗夫斯上尉展开合作。雷诺德、萨默维尔和斯泰尔想要将这个计划称作“代用材料项目发展”(Development of Substitute Materials),但格罗夫斯担心这样做太过惹人注目。鉴于工程区通常以所在城市命名,马歇尔和格罗夫斯同意将核武器计划陆军负责的部分命名作“曼哈顿区”(Manhattan District)。8月13日,雷巴德正式下令建立曼哈顿区。私底下人们也称呼该计划“曼哈顿工程区”(Manhattan Engineer District)。不过和其他工程区不同的是,曼哈顿区并没有明确的地理边界,负责人马歇尔还是师级区监。“代用材料项目发展”依然是陆军核武器计划的正式官方代号,但逐渐被“曼哈顿区”的叫法取而代之。[38]

马歇尔日后写道:“我当时从未听说过原子裂变的事,但我也知道区区9000万美元是不可能盖好一整座工厂的,遑论盖四座。”[39]当时,尼科k尔斯在宾夕法尼亚州新盖的一座TNT工厂就花了1.28亿美元。[40]他们亦对估算数量级的精确度感到不满——格罗夫斯说这简直就是像请人置办酒席,然后告诉承办方参加人数可能在十人到一千人之间不等。[41]石威公司派出的调查组已先行挑了一个厂址。战时生产委员会则推荐在田纳西州諾克斯維爾附近建立工厂,该地荒芜人烟,加之田納西河谷管理局可以提供充足的电力,附近的河流亦能为反应堆冷却降温。在考察了几个不同的选址后,调查组选定了田纳西州埃尔扎英语Elza, Tennessee附近的一块地方。Conant advised that it be acquired at once and Styer agreed but Marshall temporized, awaiting the results of Conant's reactor experiments before taking action.[42] Of the prospective processes, only Lawrence's electromagnetic separation appeared sufficiently advanced for construction to commence.[43]

Marshall and Nichols began assembling the resources they would need. The first step was to obtain a high priority rating for the project. The top ratings were AA-1 through AA-4 in descending order, although there was also a special AAA rating reserved for emergencies. Ratings AA-1 and AA-2 were for essential weapons and equipment, so Colonel Lucius D. Clay, the deputy chief of staff at Services and Supply for requirements and resources, felt that the highest rating he could assign was AA-3, although he was willing to provide a AAA rating on request for critical materials if the need arose.[44] Nichols and Marshall were disappointed; AA-3 was the same priority as Nichols' TNT plant in Pennsylvania.[45]

军事政策委员会[编辑]

A man smiling in a suit in suit and one in a uniform chat around a pile of twisted metal.
Oppenheimer and Groves at the remains of the Trinity test in September 1945, two months after the test blast and just after the end of World War II. The white overshoes prevented fallout from sticking to the soles of their shoes.[46]

Vannevar Bush became dissatisfied with Colonel Marshall's failure to get the project moving forward expeditiously, specifically the failure to acquire the Tennessee site, the low priority allocated to the project by the Army and the location of his headquarters in New York City.[47] Bush felt that more aggressive leadership was required, and spoke to Harvey Bundy英语Harvey Bundy and Generals Marshall, Somervell, and Styer about his concerns. He wanted the project placed under a senior policy committee, with a prestigious officer, preferably Styer, as overall director.[45]

Somervell and Styer selected Groves for the post, informing him on 17 September of this decision, and that General Marshall ordered that he be promoted to brigadier general,[48] as it was felt that the title "general" would hold more sway with the academic scientists working on the Manhattan Project.[49] Groves' orders placed him directly under Somervell rather than Reybold, with Colonel Marshall now answerable to Groves.[50] Groves established his headquarters in Washington, D.C., on the fifth floor of the New War Department Building, where Colonel Marshall had his liaison office.[51] He assumed command of the Manhattan Project on 23 September 1942. Later that day, he attended a meeting called by Stimson, which established a Military Policy Committee, responsible to the Top Policy Group, consisting of Bush (with Conant as an alternate), Styer and Rear Admiral英语Rear Admiral (United States) William R. Purnell.[48] Tolman and Conant were later appointed as Groves' scientific advisers.[52]

On 19 September, Groves went to Donald Nelson英语Donald M. Nelson, the chairman of the War Production Board, and asked for broad authority to issue a AAA rating whenever it was required. Nelson initially balked but quickly caved in when Groves threatened to go to the President.[53] Groves promised not to use the AAA rating unless it was necessary. It soon transpired that for the routine requirements of the project the AAA rating was too high but the AA-3 rating was too low. After a long campaign, Groves finally received AA-1 authority on 1 July 1944.[54] According to Groves, "In Washington you became aware of the importance of top priority. Most everything proposed in the Roosevelt administration would have top priority. That would last for about a week or two and then something else would get top priority".[55]

One of Groves' early problems was to find a director for Project Y英语Project Y, the group that would design and build the bomb. The obvious choice was one of the three laboratory heads, Urey, Lawrence, or Compton, but they could not be spared. Compton recommended Oppenheimer, who was already intimately familiar with the bomb design concepts. However, Oppenheimer had little administrative experience, and, unlike Urey, Lawrence, and Compton, had not won a Nobel Prize, which many scientists felt that the head of such an important laboratory should have. There were also concerns about Oppenheimer's security status, as many of his associates were Communists, including his wife, Kitty (Katherine Oppenheimer)英语Katherine Oppenheimer; his girlfriend, Jean Tatlock英语Jean Tatlock; and his brother, Frank Oppenheimer英语Frank Oppenheimer. A long conversation on a train in October 1942 convinced Groves and Nichols that Oppenheimer thoroughly understood the issues involved in setting up a laboratory in a remote area and should be appointed as its director. Groves personally waived the security requirements and issued Oppenheimer a clearance on 20 July 1943.[56][57]

与英国合作[编辑]

The British and Americans exchanged nuclear information but did not initially combine their efforts. Britain rebuffed attempts by Bush and Conant in 1941 to strengthen cooperation with its own project, codenamed Tube Alloys, because it was reluctant to share its technological lead and help the United States develop its own atomic bomb.[58] An American scientist who brought a personal letter from Roosevelt to Churchill offering to pay for all research and development in an Anglo-American project was poorly treated, and Churchill did not reply to the letter. The United States as a result decided as early as April 1942 that if its offer was rejected, they should proceed alone.[59] The British, who had made significant contributions early in the war, did not have the resources to carry through such a research program while fighting for their survival. As a result, Tube Alloys soon fell behind its American counterpart.[60] and on 30 July 1942, Sir John Anderson, the minister responsible for Tube Alloys, advised Churchill that: "We must face the fact that ... [our] pioneering work ... is a dwindling asset and that, unless we capitalise it quickly, we shall be outstripped. We now have a real contribution to make to a 'merger.' Soon we shall have little or none."[61] That month Churchill and Roosevelt made an informal, unwritten agreement for atomic collaboration.[62]

A large man in uniform and a bespectacled thin man in a suit and tie sit at a desk.
Groves confers with James Chadwick, the head of the British Mission.

The opportunity for an equal partnership no longer existed, however, as shown in August 1942 when the British unsuccessfully demanded substantial control over the project while paying none of the costs. By 1943 the roles of the two countries had reversed from late 1941;[59] in January Conant notified the British that they would no longer receive atomic information except in certain areas. While the British were shocked by the abrogation of the Churchill-Roosevelt agreement, head of the Canadian National Research Council英语National Research Council (Canada) C. J. Mackenzie英语Jack Mackenzie was less surprised, writing "I can't help feeling that the United Kingdom group [over] emphasizes the importance of their contribution as compared with the Americans."[62] As Conant and Bush told the British, the order came "from the top".[63]

The British bargaining position had worsened; the American scientists had decided that the United States no longer needed outside help, and they wanted to prevent Britain exploiting post-war commercial applications of atomic energy. The committee supported, and Roosevelt agreed to, restricting the flow of information to what Britain could use during the war—especially not bomb design—even if doing so slowed down the American project. By early 1943 the British stopped sending research and scientists to America, and as a result the Americans stopped all information sharing. The British considered ending the supply of Canadian uranium and heavy water to force the Americans to again share, but Canada needed American supplies to produce them.[64] They investigated the possibility of an independent nuclear program, but determined that it could not be ready in time to affect the outcome of the war in Europe.[65]

By March 1943 Conant decided that British help would benefit some areas of the project. James Chadwick and one or two other British scientists were important enough that the bomb design team at Los Alamos needed them, despite the risk of revealing weapon design secrets.[66] In August 1943 Churchill and Roosevelt negotiated the Quebec Agreement, which resulted in a resumption of cooperation[67] between scientists working on the same problem. Britain, however, agreed to restrictions on data on the building of large-scale production plants necessary for the bomb.[68] The subsequent Hyde Park Agreement in September 1944 extended this cooperation to the postwar period.[69] The Quebec Agreement established the Combined Policy Committee to coordinate the efforts of the United States, United Kingdom and Canada. Stimson, Bush and Conant served as the American members of the Combined Policy Committee, Field Marshal Sir John Dill and Colonel J. J. Llewellin were the British members, and C. D. Howe was the Canadian member.[70] Llewellin returned to the United Kingdom at the end of 1943 and was replaced on the committee by Sir Ronald Ian Campbell英语Ronald Ian Campbell, who in turn was replaced by the British Ambassador to the United States, Lord Halifax, in early 1945. Sir John Dill died in Washington, D.C., in November 1944 and was replaced both as Chief of the British Joint Staff Mission英语British Defence Staff – US and as a member of the Combined Policy Committee by Field Marshal Sir Henry Maitland Wilson.[71]

When cooperation resumed after the Quebec agreement, the Americans' progress and expenditures amazed the British. The United States had already spent more than $1 billion ($12 billion today), while in 1943, the United Kingdom had spent about £0.5 million. Chadwick thus pressed for British involvement in the Manhattan Project to the fullest extent and abandoned any hopes of an independent British project during the war.[65] With Churchill's backing, he attempted to ensure that every request from Groves for assistance was honored.[72] The British Mission that arrived in the United States in December 1943 included Niels Bohr, Otto Frisch, Klaus Fuchs, Rudolf Peierls, and Ernest Titterton英语Ernest William Titterton.[73] More scientists arrived in early 1944. While those assigned to gaseous diffusion left by the fall of 1944, the 35 working under Oliphant with Lawrence at Berkeley were assigned to existing laboratory groups and most stayed until the end of the war. The 19 sent to Los Alamos also joined existing groups, primarily related to implosion and bomb assembly, but not the plutonium-related ones.[65] Part of the Quebec Agreement specified that nuclear weapons would not be used against another country without the mutual consent of the US and UK. In June 1945, Wilson agreed that the use of nuclear weapons against Japan would be recorded as a decision of the Combined Policy Committee.[74]

The Combined Policy Committee created the Combined Development Trust英语Combined Development Trust in June 1944, with Groves as its chairman, to procure uranium and thorium ores on international markets. The Belgian Congo and Canada held much of the world's uranium outside Eastern Europe, and the Belgian government in exile was in London. Britain agreed to give the United States most of the Belgian ore, as it could not use most of the supply without restricted American research.[75] In 1944, the Trust purchased 3,440,000英磅(1,560,000公斤) of uranium oxide ore from companies operating mines in the Belgian Congo. In order to avoid briefing US Secretary of the Treasury Henry Morgenthau Jr. on the project, a special account not subject to the usual auditing and controls was used to hold Trust monies. Between 1944 and the time he resigned from the Trust in 1947, Groves deposited a total of $37.5 million into the Trust's account.[76]

Groves appreciated the early British atomic research and the British scientists' contributions to the Manhattan Project, but stated that the United States would have succeeded without them.[65] He also said that Churchill was "the best friend the atomic bomb project had [as] he kept Roosevelt's interest up ... He just stirred him up all the time by telling him how important he thought the project was."[55]

The British wartime participation was crucial to the success of the United Kingdom's independent nuclear weapons program英语High Explosive Research after the war when the McMahon Act英语McMahon Act of 1946 temporarily ended American nuclear cooperation.[65]

项目地点[编辑]

加利福尼亚州伯克利加利福尼亚州因约克恩华盛顿州里奇兰不列颠哥伦比亚省特雷尔犹他州温多弗犹他州蒙蒂塞洛科罗拉多州铀钒镇新墨西哥州洛斯阿拉莫斯新墨西哥州阿拉莫戈多爱荷华州埃姆斯华盛顿州圣路易斯伊利诺伊州芝加哥印第安纳州达娜俄亥俄州代顿阿拉巴马州锡拉科加西弗吉尼亚州摩根敦田纳西州橡树岭粉笔河实验室纽约州羅徹斯特华盛顿哥伦比亚特区Map of the United States and southern Canada with major project sites marked
A selection of US and Canadian sites important to the Manhattan Project. 单击地图标示地点了解详情。

橡树岭[编辑]

Workers, mostly women, pour out of a cluster of buildings. A billboard exhorts them to "Make C.E.W. COUNT continue to protect project information!"
Shift change at the Y-12 uranium enrichment facility at the Clinton Engineer Works in Oak Ridge, Tennessee, on 11 August 1945. By May 1945, 82,000 people were employed at the Clinton Engineer Works.[77] Photograph by the Manhattan District photographer Ed Westcott英语Ed Westcott.

The day after he took over the project, Groves took a train to Tennessee with Colonel Marshall to inspect the proposed site there, and Groves was impressed.[78][79] On 29 September 1942, United States Under Secretary of War英语United States Under Secretary of War Robert P. Patterson authorized the Corps of Engineers to acquire 56,000英畝(23,000公頃) of land by eminent domain at a cost of $3.5 million. An additional 3,000英畝(1,200公頃) was subsequently acquired. About 1,000 families were affected by the condemnation order, which came into effect on 7 October.[80] Protests, legal appeals, and a 1943 Congressional inquiry were to no avail.[81] By mid-November U.S. Marshals were tacking notices to vacate on farmhouse doors, and construction contractors were moving in.[82] Some families were given two weeks' notice to vacate farms that had been their homes for generations;[83] others had settled there after being evicted to make way for the Great Smoky Mountains National Park in the 1920s or the Norris Dam in the 1930s.[81] The ultimate cost of land acquisition in the area, which was not completed until March 1945, was only about $2.6 million, which worked out to around $47 an acre.[84] When presented with Public Proclamation Number Two, which declared Oak Ridge a total exclusion area that no one could enter without military permission, the Governor of Tennessee英语Governor of Tennessee, Prentice Cooper, angrily tore it up.[85]

Initially known as the Kingston Demolition Range, the site was officially renamed the Clinton Engineer Works (CEW) in early 1943.[86] While Stone & Webster concentrated on the production facilities, the architectural and engineering firm Skidmore, Owings & Merrill designed and built a residential community for 13,000. The community was located on the slopes of Black Oak Ridge, from which the new town of Oak Ridge got its name.[87] The Army presence at Oak Ridge increased in August 1943 when Nichols replaced Marshall as head of the Manhattan Engineer District. One of his first tasks was to move the district headquarters to Oak Ridge although the name of the district did not change.[88] In September 1943 the administration of community facilities was outsourced to Turner Construction Company英语Turner Construction Company through a subsidiary, the Roane-Anderson Company (for Roane and Anderson Counties, in which Oak Ridge was located).[89] Chemical engineers, including William J. (Jenkins) Wilcox Jr. (1923–2013) and Warren Fuchs, were part of "frantic efforts" to make 10% to 12% enriched uranium 235, known as the code name "tuballoy tetroxide", with tight security and fast approvals for supplies and materials.[90] The population of Oak Ridge soon expanded well beyond the initial plans, and peaked at 75,000 in May 1945, by which time 82,000 people were employed at the Clinton Engineer Works,[77] and 10,000 by Roane-Anderson.[89]

Fine-arts photographer, Josephine Herrick英语Josephine Herrick, and her colleague, Mary Steers, helped document the work at Oak Ridge.[91]

洛斯阿拉莫斯[编辑]

The idea of locating Project Y at Oak Ridge was considered, but in the end it was decided that it should be in a remote location. On Oppenheimer's recommendation, the search for a suitable site was narrowed to the vicinity of Albuquerque, New Mexico, where Oppenheimer owned a ranch. In October 1942, Major John H. Dudley英语John H. Dudley of the Manhattan District was sent to survey the area. He recommended a site near Jemez Springs, New Mexico英语Jemez Springs, New Mexico.[92] On 16 November, Oppenheimer, Groves, Dudley and others toured the site. Oppenheimer feared that the high cliffs surrounding the site would make his people feel claustrophobic, while the engineers were concerned with the possibility of flooding. The party then moved on to the vicinity of the Los Alamos Ranch School英语Los Alamos Ranch School. Oppenheimer was impressed and expressed a strong preference for the site, citing its natural beauty and views of the Sangre de Cristo Mountains, which, it was hoped, would inspire those who would work on the project.[93][94] The engineers were concerned about the poor access road, and whether the water supply would be adequate, but otherwise felt that it was ideal.[95]

A group of men in shirtsleeves sitting on folding chairs
Physicists at a Manhattan District-sponsored colloquium at the Los Alamos Laboratory英语Los Alamos Laboratory on the Super in April 1946. In the front row are Norris Bradbury, John Manley英语John H. Manley, Enrico Fermi and J. (Jerome) M. B. Kellogg (1905-1981). Robert Oppenheimer, in dark coat, is behind Manley; to Oppenheimer's left is Richard Feynman. The Army officer on the left is Colonel Oliver Haywood英语Oliver Haywood.

Patterson approved the acquisition of the site on 25 November 1942, authorizing $440,000 for the purchase of the site of 54,000英畝(22,000公頃), all but 8,900英畝(3,600公頃) of which were already owned by the Federal Government.[96] Secretary of Agriculture英语Secretary of Agriculture Claude R. Wickard英语Claude R. Wickard granted use of some 45,100英畝(18,300公頃) of United States Forest Service land to the War Department "for so long as the military necessity continues".[97] The need for land, for a new road, and later for a right of way for a 25-英里(40-公里) power line, eventually brought wartime land purchases to 45,737英畝(18,509.1公頃), but only $414,971 was spent.[96] Construction was contracted to the M. M. Sundt Company of Tucson, Arizona, with Willard C. Kruger and Associates英语Willard C. Kruger and Associates of Santa Fe, New Mexico, as architect and engineer. Work commenced in December 1942. Groves initially allocated $300,000 for construction, three times Oppenheimer's estimate, with a planned completion date of 15 March 1943. It soon became clear that the scope of Project Y was greater than expected, and by the time Sundt finished on 30 November 1943, over $7 million had been spent.[98]

Map of Los Alamos site, New Mexico, 1943–45

Because it was secret, Los Alamos was referred to as "Site Y" or "the Hill".[99] Birth certificates of babies born in Los Alamos during the war listed their place of birth as PO Box 1663 in Santa Fe.[100] Initially Los Alamos was to have been a military laboratory with Oppenheimer and other researchers commissioned into the Army. Oppenheimer went so far as to order himself a lieutenant colonel's英语lieutenant colonel (United States) uniform, but two key physicists, Robert Bacher and Isidor Rabi, balked at the idea. Conant, Groves and Oppenheimer then devised a compromise whereby the laboratory was operated by the University of California under contract to the War Department.[101]

芝加哥[编辑]

An Army-OSRD council on 25 June 1942 decided to build a pilot plant for plutonium production in Red Gate Woods英语Red Gate Woods southwest of Chicago. In July, Nichols arranged for a lease of 1,025英畝(415公頃) from the Cook County Forest Preserve District英语Cook County Forest Preserve District, and Captain James F. Grafton (1908-1969) was appointed Chicago area engineer. It soon became apparent that the scale of operations was too great for the area, and it was decided to build the plant at Oak Ridge, and keep a research and testing facility in Chicago.[102][103]

Delays in establishing the plant in Red Gate Woods led Compton to authorize the Metallurgical Laboratory to construct the first nuclear reactor beneath the bleacher英语bleachers of Stagg Field英语Stagg Field at the University of Chicago. The reactor required an enormous amount of graphite blocks and uranium pellets. At the time, there was a limited source of pure uranium. Frank Spedding英语Frank Spedding of Iowa State University were able to produce only two short tons of pure uranium. Additional three short tons of uranium metal was supplied by Westinghouse Lamp Plant英语Westinghouse Lamp Plant which was produced in a rush with makeshift process. A large square balloon was constructed by Goodyear Tire to encase the reactor.[104][105] On 2 December 1942, a team led by Enrico Fermi initiated the first artificial[note 5] self-sustaining nuclear chain reaction in an experimental reactor known as Chicago Pile-1.[107] The point at which a reaction becomes self-sustaining became known as "going critical". Compton reported the success to Conant in Washington, D.C., by a coded phone call, saying, "The Italian navigator [Fermi] has just landed in the new world."[108][note 6]

In January 1943, Grafton's successor, Major Arthur V. Peterson英语Arthur V. Peterson, ordered Chicago Pile-1 dismantled and reassembled at Red Gate Woods, as he regarded the operation of a reactor as too hazardous for a densely populated area.[109] At the Argonne site, Chicago Pile-3英语Chicago Pile-3, the first heavy water reactor, went critical on 15 May 1944.[110][111] After the war, the operations that remained at Red Gate moved to the new site of the Argonne National Laboratory about 6英里(9.7公里) away.[103]

汉福德[编辑]

By December 1942 there were concerns that even Oak Ridge was too close to a major population center (Knoxville) in the unlikely event of a major nuclear accident. Groves recruited DuPont in November 1942 to be the prime contractor for the construction of the plutonium production complex. DuPont was offered a standard cost plus fixed-fee contract英语cost-plus contract, but the President of the company, Walter S. Carpenter, Jr.英语Walter S. Carpenter, Jr., wanted no profit of any kind, and asked for the proposed contract to be amended to explicitly exclude the company from acquiring any patent rights. This was accepted, but for legal reasons a nominal fee of one dollar was agreed upon. After the war, DuPont asked to be released from the contract early, and had to return 33 cents.[112]

A large crowd of sullen looking workmen at a counter where two women are writing. Some of the workmen are wearing identify photographs of themselves on their hats.
Hanford workers collect their paychecks at the Western Union office.

DuPont recommended that the site be located far from the existing uranium production facility at Oak Ridge.[113] In December 1942, Groves dispatched Colonel Franklin Matthias and DuPont engineers to scout potential sites. Matthias reported that Hanford Site near Richland, Washington, was "ideal in virtually all respects". It was isolated and near the Columbia River, which could supply sufficient water to cool the reactors that would produce the plutonium. Groves visited the site in January and established the Hanford Engineer Works (HEW), codenamed "Site W".[114]

Under Secretary Patterson gave his approval on 9 February, allocating $5 million for the acquisition of 40,000英畝(16,000公頃) of land in the area. The federal government relocated some 1,500 residents of White Bluffs英语White Bluffs, Washington and Hanford英语Hanford, Washington, and nearby settlements, as well as the Wanapum英语Wanapum and other tribes using the area. A dispute arose with farmers over compensation for crops, which had already been planted before the land was acquired. Where schedules allowed, the Army allowed the crops to be harvested, but this was not always possible.[114] The land acquisition process dragged on and was not completed before the end of the Manhattan Project in December 1946.[115]

The dispute did not delay work. Although progress on the reactor design at Metallurgical Laboratory and DuPont was not sufficiently advanced to accurately predict the scope of the project, a start was made in April 1943 on facilities for an estimated 25,000 workers, half of whom were expected to live on-site. By July 1944, some 1,200 buildings had been erected and nearly 51,000 people were living in the construction camp. As area engineer, Matthias exercised overall control of the site.[116] At its peak, the construction camp was the third most populous town in Washington state.[117] Hanford operated a fleet of over 900 buses, more than the city of Chicago.[118] Like Los Alamos and Oak Ridge, Richland was a gated community with restricted access, but it looked more like a typical wartime American boomtown: the military profile was lower, and physical security elements like high fences, towers, and guard dogs were less evident.[119]

加拿大地点[编辑]

英属哥伦比亚省[编辑]

Cominco had produced electrolytic hydrogen at Trail, British Columbia英语Trail, British Columbia, since 1930. Urey suggested in 1941 that it could produce heavy water. To the existing $10 million plant consisting of 3,215 cells consuming 75 MW of hydroelectric power, secondary electrolysis cells were added to increase the deuterium concentration in the water from 2.3% to 99.8%. For this process, Hugh Taylor英语Hugh Stott Taylor of Princeton developed a platinum-on-carbon catalyst for the first three stages while Urey developed a nickel-chromia one for the fourth stage tower. The final cost was $2.8 million. The Canadian Government did not officially learn of the project until August 1942. Trail's heavy water production started in January 1944 and continued until 1956. Heavy water from Trail was used for Chicago Pile 3英语Chicago Pile 3, the first reactor using heavy water and natural uranium, which went critical on 15 May 1944.[120]

安大略省[编辑]

The Chalk River, Ontario, site was established to rehouse the Allied effort at the Montreal Laboratory away from an urban area. A new community was built at Deep River, Ontario英语Deep River, Ontario, to provide residences and facilities for the team members. The site was chosen for its proximity to the industrial manufacturing area of Ontario and Quebec, and proximity to a rail head adjacent to a large military base, Camp Petawawa英语Camp Petawawa. Located on the Ottawa River, it had access to abundant water. The first director of the new laboratory was Hans von Halban英语Hans von Halban. He was replaced by John Cockcroft in May 1944, who in turn was succeeded by Bennett Lewis英语Bennett Lewis in September 1946. A pilot reactor known as ZEEP英语ZEEP (zero-energy experimental pile) became the first Canadian reactor, and the first to be completed outside the United States, when it went critical in September 1945, ZEEP remained in use by researchers until 1970.[121] A larger 10 MW NRX英语NRX reactor, which was designed during the war, was completed and went critical in July 1947.[120]

西北地区[编辑]

The Eldorado Mine英语Eldorado Mine (Northwest Territories) at Port Radium英语Port Radium was a source of uranium ore.[122]

重水生产地[编辑]

Although DuPont's preferred designs for the nuclear reactors were helium cooled and used graphite as a moderator, DuPont still expressed an interest in using heavy water as a backup, in case the graphite reactor design proved infeasible for some reason. For this purpose, it was estimated that 3短噸(2.7公噸) of heavy water would be required per month. The P-9 Project英语P-9 Project was the government's code name for the heavy water production program. As the plant at Trail, which was then under construction, could produce 0.5短噸(0.45公噸) per month, additional capacity was required. Groves therefore authorized DuPont to establish heavy water facilities at the Morgantown Ordnance Works, near Morgantown, West Virginia; at the Wabash River Ordnance Works英语Newport Chemical Depot, near Dana and Newport, Indiana; and at the Alabama Ordnance Works英语Alabama Army Ammunition Plant, near Childersburg and Sylacauga, Alabama. Although known as Ordnance Works and paid for under Ordnance Department contracts, they were built and operated by the Army Corps of Engineers. The American plants used a process different from Trail's; heavy water was extracted by distillation, taking advantage of the slightly higher boiling point of heavy water.[123][124]

[编辑]

矿石[编辑]

The majority of the uranium used in the Manhattan Project came from the Shinkolobwe英语Shinkolobwe mine in Belgian Congo.

The key raw material for the project was uranium, which was used as fuel for the reactors, as feed that was transformed into plutonium, and, in its enriched form, in the atomic bomb itself. There were four known major deposits of uranium in 1940: in Colorado, in northern Canada, in Joachimsthal in Czechoslovakia, and in the Belgian Congo.[125] All but Joachimstal were in allied hands. A November 1942 survey determined that sufficient quantities of uranium were available to satisfy the project's requirements.[126] Nichols arranged with the State Department for export controls to be placed on uranium oxide and negotiated for the purchase of 1,200短噸(1,100公噸) of uranium ore from the Belgian Congo that was being stored in a warehouse on Staten Island and the remaining stocks of mined ore stored in the Congo. He negotiated with Eldorado Gold Mines英语Eldorado Mining and Refining for the purchase of ore from its refinery in Port Hope, Ontario, and its shipment in 100-ton lots. The Canadian government subsequently bought up the company's stock until it acquired a controlling interest.[127]

While these purchases assured a sufficient supply to meet wartime needs, the American and British leaders concluded that it was in their countries' interest to gain control of as much of the world's uranium deposits as possible. The richest source of ore was the Shinkolobwe英语Shinkolobwe mine in the Belgian Congo, but it was flooded and closed. Nichols unsuccessfully attempted to negotiate its reopening and the sale of the entire future output to the United States with Edgar Sengier英语Edgar Sengier, the director of the company that owned the mine, the Union Minière du Haut-Katanga英语Union Minière du Haut-Katanga.[128] The matter was then taken up by the Combined Policy Committee. As 30 percent of Union Minière's stock was controlled by British interests, the British took the lead in negotiations. Sir John Anderson and Ambassador John Winant hammered out a deal with Sengier and the Belgian government in May 1944 for the mine to be reopened and 1,720短噸(1,560公噸) of ore to be purchased at $1.45 a pound.[129] To avoid dependence on the British and Canadians for ore, Groves also arranged for the purchase of US Vanadium Corporation's stockpile in Uravan, Colorado英语Uravan, Colorado. Uranium mining in Colorado英语Uranium mining in Colorado yielded about 800短噸(730公噸) of ore.[130]

Mallinckrodt Incorporated英语Mallinckrodt Incorporated in St. Louis, Missouri, took the raw ore and dissolved it in nitric acid to produce uranyl nitrate. Ether was then added in a liquid–liquid extraction process to separate the impurities from the uranyl nitrate. This was then heated to form uranium trioxide, which was reduced to highly pure uranium dioxide.[131] By July 1942, Mallinckrodt was producing a ton of highly pure oxide a day, but turning this into uranium metal initially proved more difficult for contractors Westinghouse and Metal Hydrides.[132] Production was too slow and quality was unacceptably low. A special branch of the Metallurgical Laboratory was established at Iowa State College in Ames, Iowa, under Frank Spedding to investigate alternatives. This became known as the Ames Project英语Ames Project, and its Ames process英语Ames process became available in 1943.[133]

同位素分离[编辑]

Natural uranium consists of 99.3% uranium-238 and 0.7% uranium-235, but only the latter is fissile. The chemically identical uranium-235 has to be physically separated from the more plentiful isotope. Various methods were considered for uranium enrichment, most of which was carried out at Oak Ridge.[134]

The most obvious technology, the centrifuge, failed, but electromagnetic separation, gaseous diffusion, and thermal diffusion technologies were all successful and contributed to the project. In February 1943, Groves came up with the idea of using the output of some plants as the input for others.[135]

Contour map of the Oak Ridge area. There is a river to the south, while the township is in the north.
Oak Ridge hosted several uranium separation technologies. The Y-12 electromagnetic separation plant is in the upper right. The K-25 and K-27 gaseous diffusion plants are in the lower left, near the S-50 thermal diffusion plant. The X-10 was for plutonium production.

离心分离[编辑]

1942年4月,离心分离在当时被认为是唯一有希望成功的分离方法。[136] 1930年代杰西·比姆斯英语Jesse Beams弗吉尼亚大学 已经发展出这样的方法,但是遇到了一些技术性的难点。该方法需要高速的离心机,但是在某些特定的速度下,会产生谐波振动,有可能使机器破裂。因此,需要很快的加速来避过这些速度。1941年,他开始使用六氟化铀,这是唯一已知的气态铀化合物,并且能够分离出铀235。 在哥伦比亚大学,哈罗德·乌里英语Harold Urey哈罗德·乌里让卡尔·科恩英语Karl CohenKarl Cohen研究了这一过程,他提出了一系列数学理论,从而有可能设计出由西屋电气公司承建的离心分离装置。[137]将其扩大到生产工厂规模的时候,面临巨大的技术挑战。乌里和科恩估计,如果每天生产1千克铀235,则需要使用50,000台1米转子的离心机,或使用10,000台4米转子的离心机(前提是可以建造4米的转子)。要保持如此多的转子连续高速运转面临巨大的挑战,[138]并且当Beams运行他的实验设备时,仅获得了预期产量的60%,这表明将需要更多的离心机。然后,比姆斯,乌里和科恩开始进行一系列改进,这些改进有望提高该过程的效率,但是高速电机,轴和轴承的频繁故障延迟了试验工厂的工作。 [139] 1942年11月,在Stone & Webster英语Stone & Webster公司的Conant,Nichols和August C. Klein的建议下,军事政策委员会放弃了离心分离方法。[140]

尽管离心分离方法被曼哈顿计划所放弃,但由于战后Z型离心机的引入,该方法的研究取得了显着进展。其中关键的Z型离心机是在苏联由苏联工程师和俘获的德国工程师共同开发。[141] 它最终成为铀同位素分离的首选方法,比第二次世界大战期间使用的其他分离方法经济得多。[142]

电磁分离[编辑]

Electromagnetic isotope separation was developed by Lawrence at the University of California Radiation Laboratory. This method employed devices known as calutrons, a hybrid of the standard laboratory mass spectrometer and the cyclotron magnet. The name was derived from the words California, university and cyclotron.[143] In the electromagnetic process, a magnetic field deflected charged particles according to mass.[144] The process was neither scientifically elegant nor industrially efficient.[145] Compared with a gaseous diffusion plant or a nuclear reactor, an electromagnetic separation plant would consume more scarce materials, require more manpower to operate, and cost more to build. Nonetheless, the process was approved because it was based on proven technology and therefore represented less risk. Moreover, it could be built in stages, and rapidly reach industrial capacity.[143]

A large oval-shaped structure
Alpha I racetrack at Y-12

Marshall and Nichols discovered that the electromagnetic isotope separation process would require 5,000短噸(4,500公噸) of copper, which was in desperately short supply. However, silver could be substituted, in an 11:10 ratio. On 3 August 1942, Nichols met with Under Secretary of the Treasury英语United States Deputy Secretary of the Treasury Daniel W. Bell英语Daniel W. Bell and asked for the transfer of 6,000 tons of silver bullion from the West Point Bullion Depository英语West Point Bullion Depository. "Young man," Bell told him, "you may think of silver in tons but the Treasury will always think of silver in troy ounces!"[146] Ultimately 14,700短噸(13,300公噸;430,000,000金衡制盎司) were used.[147]

The 1,000-金衡制盎司(31-公斤) silver bars were cast into cylindrical billets and taken to Phelps Dodge英语Phelps Dodge in Bayway, New Jersey, where they were extruded into strips 0.625英寸(15.9毫米) thick, 3英寸(76毫米) wide and 40英尺(12米) long. These were wound onto magnetic coils by Allis-Chalmers英语Allis-Chalmers in Milwaukee, Wisconsin. After the war, all the machinery was dismantled and cleaned and the floorboards beneath the machinery were ripped up and burned to recover minute amounts of silver. In the end, only 1/3,600,000th was lost.[147][148] The last silver was returned in May 1970.[149]

Responsibility for the design and construction of the electromagnetic separation plant, which came to be called Y-12, was assigned to Stone & Webster by the S-1 Committee in June 1942. The design called for five first-stage processing units, known as Alpha racetracks, and two units for final processing, known as Beta racetracks. In September 1943 Groves authorized construction of four more racetracks, known as Alpha II. Construction began in February 1943.[150]

When the plant was started up for testing on schedule in October, the 14-ton vacuum tanks crept out of alignment because of the power of the magnets, and had to be fastened more securely. A more serious problem arose when the magnetic coils started shorting out. In December Groves ordered a magnet to be broken open, and handfuls of rust were found inside. Groves then ordered the racetracks to be torn down and the magnets sent back to the factory to be cleaned. A pickling plant was established on-site to clean the pipes and fittings.[145] The second Alpha I was not operational until the end of January 1944, the first Beta and first and third Alpha I's came online in March, and the fourth Alpha I was operational in April. The four Alpha II racetracks were completed between July and October 1944.[151]

A long corridor with many consoles with dials and switches, attended by women seated on high stools
Calutron Girls英语Calutron Girls were young women who monitored calutron control panels at Y-12. Gladys Owens, seated in the foreground, was unaware of what she had been involved with until seeing this photo on a public tour of the facility 50 years later. Photo by Ed Westcott英语Ed Westcott.[152]

Tennessee Eastman英语Tennessee Eastman was contracted to manage Y-12 on the usual cost plus fixed-fee basis, with a fee of $22,500 per month plus $7,500 per racetrack for the first seven racetracks and $4,000 per additional racetrack.[153] The calutrons were initially operated by scientists from Berkeley to remove bugs and achieve a reasonable operating rate. They were then turned over to trained Tennessee Eastman operators who had only a high school education. Nichols compared unit production data, and pointed out to Lawrence that the young "hillbilly英语hillbilly" girl operators were outperforming his PhDs. They agreed to a production race and Lawrence lost, a morale boost for the Tennessee Eastman workers and supervisors. The girls were "trained like soldiers not to reason why", while "the scientists could not refrain from time-consuming investigation of the cause of even minor fluctuations of the dials."[154]

Y-12 initially enriched the uranium-235 content to between 13% and 15%, and shipped the first few hundred grams of this to Los Alamos in March 1944. Only 1 part in 5,825 of the uranium feed emerged as final product. Much of the rest was splattered over equipment in the process. Strenuous recovery efforts helped raise production to 10% of the uranium-235 feed by January 1945. In February the Alpha racetracks began receiving slightly enriched (1.4%) feed from the new S-50 thermal diffusion plant. The next month it received enhanced (5%) feed from the K-25 gaseous diffusion plant. By August K-25 was producing uranium sufficiently enriched to feed directly into the Beta tracks.[155]

气体扩散[编辑]

The most promising but also the most challenging method of isotope separation was gaseous diffusion. Graham's law states that the rate of effusion of a gas is inversely proportional to the square root of its molecular mass, so in a box containing a semi-permeable membrane and a mixture of two gases, the lighter molecules will pass out of the container more rapidly than the heavier molecules. The gas leaving the container is somewhat enriched in the lighter molecules, while the residual gas is somewhat depleted. The idea was that such boxes could be formed into a cascade of pumps and membranes, with each successive stage containing a slightly more enriched mixture. Research into the process was carried out at Columbia University by a group that included Harold Urey, Karl P. Cohen英语Karl P. Cohen, and John R. Dunning.[156]

Oblique aerial view of an enormous U-shaped building
Oak Ridge K-25 plant

In November 1942 the Military Policy Committee approved the construction of a 600-stage gaseous diffusion plant.[157] On 14 December, M. W. Kellogg accepted an offer to construct the plant, which was codenamed K-25. A cost plus fixed-fee contract was negotiated, eventually totaling $2.5 million. A separate corporate entity called Kellex was created for the project, headed by Percival C. Keith, one of Kellogg's vice presidents.[158] The process faced formidable technical difficulties. The highly corrosive gas uranium hexafluoride would have to be used, as no substitute could be found, and the motors and pumps would have to be vacuum tight and enclosed in inert gas. The biggest problem was the design of the barrier, which would have to be strong, porous and resistant to corrosion by uranium hexafluoride. The best choice for this seemed to be nickel. Edward Adler and Edward Norris created a mesh barrier from electroplated nickel. A six-stage pilot plant was built at Columbia to test the process, but the Norris-Adler prototype proved to be too brittle. A rival barrier was developed from powdered nickel by Kellex, the Bell Telephone Laboratories and the Bakelite英语Bakelite Corporation. In January 1944, Groves ordered the Kellex barrier into production.[159][160]

Kellex's design for K-25 called for a four-story 0.5-英里(0.80-公里) long U-shaped structure containing 54 contiguous buildings. These were divided into nine sections. Within these were cells of six stages. The cells could be operated independently, or consecutively within a section. Similarly, the sections could be operated separately or as part of a single cascade. A survey party began construction by marking out the 500-英畝(2.0-平方公里) site in May 1943. Work on the main building began in October 1943, and the six-stage pilot plant was ready for operation on 17 April 1944. In 1945 Groves canceled the upper stages of the plant, directing Kellex to instead design and build a 540-stage side feed unit, which became known as K-27. Kellex transferred the last unit to the operating contractor, Union Carbide and Carbon, on 11 September 1945. The total cost, including the K-27 plant completed after the war, came to $480 million.[161]

The production plant commenced operation in February 1945, and as cascade after cascade came online, the quality of the product increased. By April 1945, K-25 had attained a 1.1% enrichment and the output of the S-50 thermal diffusion plant began being used as feed. Some product produced the next month reached nearly 7% enrichment. In August, the last of the 2,892 stages commenced operation. K-25 and K-27 achieved their full potential in the early postwar period, when they eclipsed the other production plants and became the prototypes for a new generation of plants.[162]

热扩散[编辑]

The thermal diffusion process was based on Sydney Chapman and David Enskog英语David Enskog's theory英语Chapman–Enskog theory, which explained that when a mixed gas passes through a temperature gradient, the heavier one tends to concentrate at the cold end and the lighter one at the warm end. Since hot gases tend to rise and cool ones tend to fall, this can be used as a means of isotope separation. This process was first demonstrated by Klaus Clusius英语Klaus Clusius and Gerhard Dickel in Germany in 1938.[163] It was developed by US Navy scientists, but was not one of the enrichment technologies initially selected for use in the Manhattan Project. This was primarily due to doubts about its technical feasibility, but the inter-service rivalry between the Army and Navy also played a part.[164]

A factory with three smoking chimneys on a river bend, viewed from above
The S-50 plant is the dark building to the upper left behind the Oak Ridge powerhouse (with smoke stacks).

The Naval Research Laboratory continued the research under Philip Abelson's direction, but there was little contact with the Manhattan Project until April 1944, when Captain英语Captain (United States O-6) William S. Parsons英语William S. Parsons, the naval officer in charge of ordnance development at Los Alamos, brought Oppenheimer news of encouraging progress in the Navy's experiments on thermal diffusion. Oppenheimer wrote to Groves suggesting that the output of a thermal diffusion plant could be fed into Y-12. Groves set up a committee consisting of Warren K. Lewis, Eger Murphree and Richard Tolman to investigate the idea, and they estimated that a thermal diffusion plant costing $3.5 million could enrich 50公斤(110英磅) of uranium per week to nearly 0.9% uranium-235. Groves approved its construction on 24 June 1944.[165]

Groves contracted with the H. K. Ferguson Company of Cleveland, Ohio, to build the thermal diffusion plant, which was designated S-50. Groves's advisers, Karl Cohen and W. I. Thompson from Standard Oil,[166] estimated that it would take six months to build. Groves gave Ferguson just four. Plans called for the installation of 2,142 48-英尺-tall(15-米) diffusion columns arranged in 21 racks. Inside each column were three concentric tubes. Steam, obtained from the nearby K-25 powerhouse at a pressure of 100磅力每平方英寸(690千帕斯卡) and temperature of 545 °F(285 °C), flowed downward through the innermost 1.25-英寸(32-毫米) nickel pipe, while water at 155 °F(68 °C) flowed upward through the outermost iron pipe. The uranium hexafluoride flowed in the middle copper pipe, and isotope separation of the uranium occurred between the nickel and copper pipes.[167]

Work commenced on 9 July 1944, and S-50 began partial operation in September. Ferguson operated the plant through a subsidiary known as Fercleve. The plant produced just 10.5英磅(4.8公斤) of 0.852% uranium-235 in October. Leaks limited production and forced shutdowns over the next few months, but in June 1945 it produced 12,730英磅(5,770公斤).[168] By March 1945, all 21 production racks were operating. Initially the output of S-50 was fed into Y-12, but starting in March 1945 all three enrichment processes were run in series. S-50 became the first stage, enriching from 0.71% to 0.89%. This material was fed into the gaseous diffusion process in the K-25 plant, which produced a product enriched to about 23%. This was, in turn, fed into Y-12,[169] which boosted it to about 89%, sufficient for nuclear weapons.[170]

U-235总产量[编辑]

About 50公斤(110英磅) of uranium enriched to 89% uranium-235 was delivered to Los Alamos by July 1945.[170] The entire 50 kg, along with some 50%-enriched, averaging out to about 85% enriched, were used in Little Boy.[170]

[编辑]

The second line of development pursued by the Manhattan Project used the fissile element plutonium. Although small amounts of plutonium exist in nature, the best way to obtain large quantities of the element is in a nuclear reactor, in which natural uranium is bombarded by neutrons. The uranium-238 is transmuted into uranium-239, which rapidly decays, first into neptunium-239 and then into plutonium-239英语plutonium-239.[171] Only a small amount of the uranium-238 will be transformed, so the plutonium must be chemically separated from the remaining uranium, from any initial impurities, and from fission products.[171]

X-10石墨反应堆[编辑]

Two workmen on a movable platform similar to that used by window washers, stick a rod into one of many small holes in the wall in front of them.
Workers load uranium slugs into the X-10 Graphite Reactor.

In March 1943, DuPont began construction of a plutonium plant on a 112-英畝(0.5-平方公里) site at Oak Ridge. Intended as a pilot plant for the larger production facilities at Hanford, it included the air-cooled X-10 Graphite Reactor, a chemical separation plant, and support facilities. Because of the subsequent decision to construct water-cooled reactors at Hanford, only the chemical separation plant operated as a true pilot.[172] The X-10 Graphite Reactor consisted of a huge block of graphite, 24英尺(7.3米) long on each side, weighing around 1,500短噸(1,400公噸), surrounded by 7英尺(2.1米) of high-density concrete as a radiation shield.[172]

The greatest difficulty was encountered with the uranium slugs produced by Mallinckrodt and Metal Hydrides. These somehow had to be coated in aluminum to avoid corrosion and the escape of fission products into the cooling system. The Grasselli Chemical Company attempted to develop a hot dipping process英语tinning#Hot-dipping without success. Meanwhile, Alcoa tried canning. A new process for flux-less welding was developed, and 97% of the cans passed a standard vacuum test, but high temperature tests indicated a failure rate of more than 50%. Nonetheless, production began in June 1943. The Metallurgical Laboratory eventually developed an improved welding technique with the help of General Electric, which was incorporated into the production process in October 1943.[173]

Watched by Fermi and Compton, the X-10 Graphite Reactor went critical on 4 November 1943 with about 30短噸(27公噸) of uranium. A week later the load was increased to 36短噸(33公噸), raising its power generation to 500 kW, and by the end of the month the first 500 mg of plutonium was created.[174] Modifications over time raised the power to 4,000 kW in July 1944. X-10 operated as a production plant until January 1945, when it was turned over to research activities.[175]

汉福德反应堆[编辑]

Although an air-cooled design was chosen for the reactor at Oak Ridge to facilitate rapid construction, it was recognized that this would be impractical for the much larger production reactors. Initial designs by the Metallurgical Laboratory and DuPont used helium for cooling, before they determined that a water-cooled reactor would be simpler, cheaper and quicker to build.[176] The design did not become available until 4 October 1943; in the meantime, Matthias concentrated on improving the Hanford Site by erecting accommodations, improving the roads, building a railway switch line, and upgrading the electricity, water and telephone lines.[177]

An aerial view of the Hanford B-Reactor site from June 1944. At center is the reactor building. Small trucks dot the landscape and give a sense of scale. Two large water towers loom above the plant.
Aerial view of Hanford B-Reactor site, June 1944

As at Oak Ridge, the most difficulty was encountered while canning the uranium slugs, which commenced at Hanford in March 1944. They were pickled to remove dirt and impurities, dipped in molten bronze, tin, and aluminum-silicon alloy英语silumin, canned using hydraulic presses, and then capped using arc welding under an argon atmosphere. Finally, they were subjected to a series of tests to detect holes or faulty welds. Disappointingly, most canned slugs initially failed the tests, resulting in an output of only a handful of canned slugs per day. But steady progress was made and by June 1944 production increased to the point where it appeared that enough canned slugs would be available to start Reactor B on schedule in August 1944.[178]

Work began on Reactor B, the first of six planned 250 MW reactors, on 10 October 1943.[179] The reactor complexes were given letter designations A through F, with B, D and F sites chosen to be developed first, as this maximised the distance between the reactors. They would be the only ones constructed during the Manhattan Project.[180] Some 390短噸(350公噸) of steel, 17,400立方碼(13,300立方米) of concrete, 50,000 concrete blocks and 71,000 concrete bricks were used to construct the 120-英尺(37-米) high building.

Construction of the reactor itself commenced in February 1944.[181] Watched by Compton, Matthias, DuPont's Crawford Greenewalt英语Crawford Greenewalt, Leona Woods and Fermi, who inserted the first slug, the reactor was powered up beginning on 13 September 1944. Over the next few days, 838 tubes were loaded and the reactor went critical. Shortly after midnight on 27 September, the operators began to withdraw the control rods to initiate production. At first all appeared well but around 03:00 the power level started to drop and by 06:30 the reactor had shut down completely. The cooling water was investigated to see if there was a leak or contamination. The next day the reactor started up again, only to shut down once more.[182][183]

Fermi contacted Chien-Shiung Wu, who identified the cause of the problem as neutron poisoning from xenon-135英语xenon-135, which has a half-life of 9.2 hours.[184] Fermi, Woods, Donald J. Hughes英语Donald J. Hughes and John Archibald Wheeler then calculated the nuclear cross section英语nuclear cross section of xenon-135, which turned out to be 30,000 times that of uranium.[185] DuPont engineer George Graves had deviated from the Metallurgical Laboratory's original design in which the reactor had 1,500 tubes arranged in a circle, and had added an additional 504 tubes to fill in the corners. The scientists had originally considered this overengineering a waste of time and money, but Fermi realized that by loading all 2,004 tubes, the reactor could reach the required power level and efficiently produce plutonium.[186] Reactor D was started on 17 December 1944 and Reactor F on 25 February 1945.[187]

分离工序[编辑]

A contour map showing the fork of the Columbia and Yakima rivers and the boundary of the land, with seven small red squares marked on it
Map of the Hanford Site. Railroads flank the plants to the north and south. Reactors are the three northernmost red squares, along the Columbia River. The separation plants are the lower two red squares from the grouping south of the reactors. The bottom red square is the 300 area.

Meanwhile, the chemists considered the problem of how plutonium could be separated from uranium when its chemical properties were not known. Working with the minute quantities of plutonium available at the Metallurgical Laboratory in 1942, a team under Charles M. Cooper developed a lanthanum fluoride process英语fluoride selective electrode for separating uranium and plutonium, which was chosen for the pilot separation plant. A second separation process, the bismuth phosphate process英语bismuth phosphate process, was subsequently developed by Seaborg and Stanly G. Thomson.[188] This process worked by toggling plutonium between its +4 and +6 oxidation states in solutions of bismuth phosphate. In the former state, the plutonium was precipitated; in the latter, it stayed in solution and the other products were precipitated.[189]

Greenewalt favored the bismuth phosphate process due to the corrosive nature of lanthanum fluoride, and it was selected for the Hanford separation plants.[190] Once X-10 began producing plutonium, the pilot separation plant was put to the test. The first batch was processed at 40% efficiency but over the next few months this was raised to 90%.[175]

At Hanford, top priority was initially given to the installations in the 300 area. This contained buildings for testing materials, preparing uranium, and assembling and calibrating instrumentation. One of the buildings housed the canning equipment for the uranium slugs, while another contained a small test reactor. Notwithstanding the high priority allocated to it, work on the 300 area fell behind schedule due to the unique and complex nature of the 300 area facilities, and wartime shortages of labor and materials.[191]

Early plans called for the construction of two separation plants in each of the areas known as 200-West and 200-East. This was subsequently reduced to two, the T and U plants, in 200-West and one, the B plant, at 200-East.[192] Each separation plant consisted of four buildings: a process cell building or "canyon" (known as 221), a concentration building (224), a purification building (231) and a magazine store (213). The canyons were each 800英尺(240米) long and 65英尺(20米) wide. Each consisted of forty 17.7乘13乘20-英尺(5.4乘4.0乘6.1-米) cells.[193]

Work began on 221-T and 221-U in January 1944, with the former completed in September and the latter in December. The 221-B building followed in March 1945. Because of the high levels of radioactivity involved, all work in the separation plants had to be conducted by remote control using closed-circuit television, something unheard of in 1943. Maintenance was carried out with the aid of an overhead crane and specially designed tools. The 224 buildings were smaller because they had less material to process, and it was less radioactive. The 224-T and 224-U buildings were completed on 8 October 1944, and 224-B followed on 10 February 1945. The purification methods that were eventually used in 231-W were still unknown when construction commenced on 8 April 1944, but the plant was complete and the methods were selected by the end of the year.[194] On 5 February 1945, Matthias hand-delivered the first shipment of 80 g of 95%-pure plutonium nitrate to a Los Alamos courier in Los Angeles.[187]

武器设计[编辑]

Long, tube-like casings. In the background are several ovoid casings and a tow truck.
A row of Thin Man casings. Fat Man casings are visible in the background.

In 1943, development efforts were directed to a gun-type fission weapon英语gun-type fission weapon with plutonium called Thin Man. Initial research on the properties of plutonium was done using cyclotron-generated plutonium-239, which was extremely pure, but could only be created in very small amounts. Los Alamos received the first sample of plutonium from the Clinton X-10 reactor in April 1944 and within days Emilio Segrè discovered a problem: the reactor-bred plutonium had a higher concentration of plutonium-240, resulting in up to five times the spontaneous fission rate of cyclotron plutonium.[195] Seaborg had correctly predicted in March 1943 that some of the plutonium-239 would absorb a neutron and become plutonium-240.[196]

This made reactor plutonium unsuitable for use in a gun-type weapon. The plutonium-240 would start the chain reaction too quickly, causing a predetonation that would release enough energy to disperse the critical mass with a minimal amount of plutonium reacted (a fizzle英语fizzle (nuclear test)). A faster gun was suggested but found to be impractical. The possibility of separating the isotopes was considered and rejected, as plutonium-240 is even harder to separate from plutonium-239 than uranium-235 from uranium-238.[197]

Work on an alternative method of bomb design, known as implosion, had begun earlier under the direction of the physicist Seth Neddermeyer英语Seth Neddermeyer. Implosion used explosives to crush a subcritical sphere of fissile material into a smaller and denser form. When the fissile atoms are packed closer together, the rate of neutron capture increases, and the mass becomes a critical mass. The metal needs to travel only a very short distance, so the critical mass is assembled in much less time than it would take with the gun method.[198] Neddermeyer's 1943 and early 1944 investigations into implosion showed promise, but also made it clear that the problem would be much more difficult from a theoretical and engineering perspective than the gun design.[199] In September 1943, John von Neumann, who had experience with shaped charges used in armor-piercing shells, argued that not only would implosion reduce the danger of predetonation and fizzle, but would make more efficient use of the fissionable material.[200] He proposed using a spherical configuration instead of the cylindrical one that Neddermeyer was working on.[201]

Diagram showing fast explosive, slow explosive, uranium tamper, plutonium core and neutron initiator
An implosion-type nuclear bomb

By July 1944, Oppenheimer had concluded plutonium could not be used in a gun design, and opted for implosion. The accelerated effort on an implosion design, codenamed Fat Man, began in August 1944 when Oppenheimer implemented a sweeping reorganization of the Los Alamos laboratory to focus on implosion.[202] Two new groups were created at Los Alamos to develop the implosion weapon, X (for explosives) Division headed by explosives expert George Kistiakowsky and G (for gadget) Division under Robert Bacher.[203][204] The new design that von Neumann and T (for theoretical) Division, most notably Rudolf Peierls, had devised used explosive lens英语explosive lenses to focus the explosion onto a spherical shape using a combination of both slow and fast high explosives.[205]

The design of lenses that detonated with the proper shape and velocity turned out to be slow, difficult and frustrating.[205] Various explosives were tested before settling on composition B as the fast explosive and baratol英语baratol as the slow explosive.[206] The final design resembled a soccer ball, with 20 hexagonal and 12 pentagonal lenses, each weighing about 80英磅(36公斤). Getting the detonation just right required fast, reliable and safe electrical detonators, of which there were two for each lens for reliability.[207] It was therefore decided to use exploding-bridgewire detonator英语exploding-bridgewire detonators, a new invention developed at Los Alamos by a group led by Luis Alvarez. A contract for their manufacture was given to Raytheon英语Raytheon.[208]

To study the behavior of converging shock waves, Robert Serber devised the RaLa Experiment, which used the short-lived radioisotope lanthanum-140, a potent source of gamma radiation. The gamma ray source was placed in the center of a metal sphere surrounded by the explosive lenses, which in turn were inside in an ionization chamber英语ionization chamber. This allowed the taking of an X-ray movie of the implosion. The lenses were designed primarily using this series of tests.[209] In his history of the Los Alamos project, David Hawkins英语David Hawkins (philosopher) wrote: "RaLa became the most important single experiment affecting the final bomb design".[210]

Within the explosives was the 4.5-英寸(110-毫米) thick aluminum pusher, which provided a smooth transition from the relatively low density explosive to the next layer, the 3-英寸(76-毫米) thick tamper of natural uranium. Its main job was to hold the critical mass together as long as possible, but it would also reflect neutrons back into the core. Some part of it might fission as well. To prevent predetonation by an external neutron, the tamper was coated in a thin layer of boron.[207] A polonium-beryllium modulated neutron initiator英语modulated neutron initiator, known as an "urchin" because its shape resembled a sea urchin,[211] was developed to start the chain reaction at precisely the right moment.[212] This work with the chemistry and metallurgy of radioactive polonium was directed by Charles Allen Thomas英语Charles Allen Thomas of the Monsanto Company and became known as the Dayton Project英语Dayton Project.[213] Testing required up to 500 curies per month of polonium, which Monsanto was able to deliver.[214] The whole assembly was encased in a duralumin bomb casing to protect it from bullets and flak.[207]

A shack surrounded by pine trees. There is snow on the ground. A man and a woman in white lab coats are pulling on a rope, which is attached to a small trolley on a wooden platform. On top of the trolley is a large cylindrical object.
Remote handling of a kilocurie source of radiolanthanum for a RaLa Experiment at Los Alamos

The ultimate task of the metallurgists was to determine how to cast plutonium into a sphere. The difficulties became apparent when attempts to measure the density of plutonium gave inconsistent results. At first contamination was believed to be the cause, but it was soon determined that there were multiple allotropes of plutonium英语allotropes of plutonium.[215] The brittle α phase that exists at room temperature changes to the plastic β phase at higher temperatures. Attention then shifted to the even more malleable δ phase that normally exists in the 300 °C to 450 °C range. It was found that this was stable at room temperature when alloyed with aluminum, but aluminum emits neutrons when bombarded with alpha particles, which would exacerbate the pre-ignition problem. The metallurgists then hit upon a plutonium-gallium alloy英语plutonium-gallium alloy, which stabilized the δ phase and could be hot pressed英语hot pressing into the desired spherical shape. As plutonium was found to corrode readily, the sphere was coated with nickel.[216]

The work proved dangerous. By the end of the war, half the experienced chemists and metallurgists had to be removed from work with plutonium when unacceptably high levels of the element appeared in their urine.[217] A minor fire at Los Alamos in January 1945 led to a fear that a fire in the plutonium laboratory might contaminate the whole town, and Groves authorized the construction of a new facility for plutonium chemistry and metallurgy, which became known as the DP-site.[218] The hemispheres for the first plutonium pit (or core) were produced and delivered on 2 July 1945. Three more hemispheres followed on 23 July and were delivered three days later.[219]

三位一体[编辑]

Because of the complexity of an implosion-style weapon, it was decided that, despite the waste of fissile material, an initial test would be required. Groves approved the test, subject to the active material being recovered. Consideration was therefore given to a controlled fizzle, but Oppenheimer opted instead for a full-scale nuclear test, codenamed "Trinity".[220]

Men stand around a large oil-rig type structure. A large round object is being hoisted up.
The explosives of "the gadget" were raised to the top of the tower for the final assembly.

In March 1944, planning for the test was assigned to Kenneth Bainbridge英语Kenneth Bainbridge, a professor of physics at Harvard, working under Kistiakowsky. Bainbridge selected the bombing range near Alamogordo Army Airfield英语Alamogordo Army Airfield as the site for the test.[221] Bainbridge worked with Captain Samuel P. Davalos on the construction of the Trinity Base Camp and its facilities, which included barracks, warehouses, workshops, an explosive magazine and a commissary.[222]

Groves did not relish the prospect of explaining to a Senate committee the loss of a billion dollars worth of plutonium, so a cylindrical containment vessel codenamed "Jumbo" was constructed to recover the active material in the event of a failure. Measuring 25英尺(7.6米) long and 12英尺(3.7米) wide, it was fabricated at great expense from 214短噸(194公噸) of iron and steel by Babcock & Wilcox in Barberton, Ohio. Brought in a special railroad car to a siding in Pope, New Mexico, it was transported the last 25英里(40公里) to the test site on a trailer pulled by two tractors.[223] By the time it arrived, however, confidence in the implosion method was high enough, and the availability of plutonium was sufficient, that Oppenheimer decided not to use it. Instead, it was placed atop a steel tower 800碼(730米) from the weapon as a rough measure of how powerful the explosion would be. In the end, Jumbo survived, although its tower did not, adding credence to the belief that Jumbo would have successfully contained a fizzled explosion.[224][225]

A pre-test explosion was conducted on 7 May 1945 to calibrate the instruments. A wooden test platform was erected 800碼(730米) from Ground Zero and piled with 100短噸(91公噸) of TNT spiked with nuclear fission products in the form of an irradiated uranium slug from Hanford, which was dissolved and poured into tubing inside the explosive. This explosion was observed by Oppenheimer and Groves's new deputy commander, Brigadier General Thomas Farrell. The pre-test produced data that proved vital for the Trinity test.[225][226]

For the actual test, the weapon, nicknamed "the gadget", was hoisted to the top of a 100-英尺(30-米) steel tower, as detonation at that height would give a better indication of how the weapon would behave when dropped from a bomber. Detonation in the air maximized the energy applied directly to the target, and generated less nuclear fallout. The gadget was assembled under the supervision of Norris Bradbury at the nearby McDonald Ranch House英语McDonald Ranch House on 13 July, and precariously winched up the tower the following day.[227] Observers included Bush, Chadwick, Conant, Farrell, Fermi, Groves, Lawrence, Oppenheimer and Tolman. At 05:30 on 16 July 1945 the gadget exploded with an energy equivalent of around 20 kilotons of TNT, leaving a crater of Trinitite (radioactive glass) in the desert 250英尺(76米) wide. The shock wave was felt over 100英里(160公里) away, and the mushroom cloud reached 7.5英里(12.1公里) in height. It was heard as far away as El Paso, Texas, so Groves issued a cover story about an ammunition magazine explosion at Alamogordo Field.[228][229]

The Trinity test of the Manhattan Project was the first detonation of a nuclear weapon.

Oppenheimer later recalled that, while witnessing the explosion, he thought of a verse from the Hindu英语Hindu holy book, the Bhagavad Gita (XI,12):

कालोऽस्मि लोकक्षयकृत्प्रवृद्धो लोकान्समाहर्तुमिह प्रवृत्तः। ऋतेऽपि त्वां न भविष्यन्ति सर्वे येऽवस्थिताः प्रत्यनीकेषु योधाः॥११- ३२॥ If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendor of the mighty one ...[230][231]

Years later he would explain that another verse had also entered his head at that time:

We knew the world would not be the same. A few people laughed, a few people cried. Most people were silent. I remembered the line from the Hindu scripture, the Bhagavad Gita; Vishnu is trying to persuade the Prince that he should do his duty and, to impress him, takes on his multi-armed form英语Vishvarupa and says, 'Now I am become Death, the destroyer of worlds.' I suppose we all thought that, one way or another.[232][note 7]

人员[编辑]

In June 1944, the Manhattan Project employed some 129,000 workers, of whom 84,500 were construction workers, 40,500 were plant operators and 1,800 were military personnel. As construction activity fell off, the workforce declined to 100,000 a year later, but the number of military personnel increased to 5,600. Procuring the required numbers of workers, especially highly skilled workers, in competition with other vital wartime programs proved very difficult.[236] In 1943, Groves obtained a special temporary priority for labor from the War Manpower Commission英语War Manpower Commission. In March 1944, both the War Production Board and the War Manpower Commission gave the project their highest priority.[237]

A large crowd of men and women in uniform listens to a fat man in uniform speaking at a microphone. They are wearing the Army Service Forces sleeve patch. The women are at the front and the men at the back. Beside him is the flag of the Army Corps of Engineers. Behind them are wooden two-storey buildings.
Major General Leslie R. Groves, Jr., speaks to service personnel Oak Ridge Tennessee in August 1945.

Tolman and Conant, in their role as the project's scientific advisers, drew up a list of candidate scientists and had them rated by scientists already working on the project. Groves then sent a personal letter to the head of their university or company asking for them to be released for essential war work.[238] At the University of Wisconsin–Madison, Stanislaw Ulam gave one of his students, Joan Hinton, an exam early, so she could leave to do war work. A few weeks later, Ulam received a letter from Hans Bethe, inviting him to join the project.[239] Conant personally persuaded Kistiakowsky to join the project.[240]

One source of skilled personnel was the Army itself, particularly the Army Specialized Training Program英语Army Specialized Training Program. In 1943, the MED created the Special Engineer Detachment英语Special Engineer Detachment (SED), with an authorized strength of 675. Technicians and skilled workers drafted into the Army were assigned to the SED. Another source was the Women's Army Corps (WAC). Initially intended for clerical tasks handling classified material, the WACs were soon tapped for technical and scientific tasks as well.[241] On 1 February 1945, all military personnel assigned to the MED, including all SED detachments, were assigned to the 9812th Technical Service Unit, except at Los Alamos, where military personnel other than SED, including the WACs and Military Police, were assigned to the 4817th Service Command Unit.[242]

An Associate Professor of Radiology at the University of Rochester School of Medicine英语University of Rochester School of Medicine, Stafford L. Warren, was commissioned as a colonel in the United States Army Medical Corps英语United States Army Medical Corps, and appointed as chief of the MED's Medical Section and Groves' medical advisor. Warren's initial task was to staff hospitals at Oak Ridge, Richland and Los Alamos.[243] The Medical Section was responsible for medical research, but also for the MED's health and safety programs. This presented an enormous challenge, because workers were handling a variety of toxic chemicals, using hazardous liquids and gases under high pressures, working with high voltages, and performing experiments involving explosives, not to mention the largely unknown dangers presented by radioactivity and handling fissile materials.[244] Yet in December 1945, the National Safety Council英语National Safety Council presented the Manhattan Project with the Award of Honor for Distinguished Service to Safety in recognition of its safety record. Between January 1943 and June 1945, there were 62 fatalities and 3,879 disabling injuries, which was about 62 percent below the rate of private industry.[245]

保密[编辑]

A 1945 Life article estimated that before the Hiroshima and Nagasaki bombings "probably no more than a few dozen men in the entire country knew the full meaning of the Manhattan Project, and perhaps only a thousand others even were aware that work on atoms was involved." The magazine wrote that the more than 100,000 others employed with the project "worked like moles in the dark". Warned that disclosing the project's secrets was punishable by 10 years in prison or a $10,000 ($113,000 today) fine, they saw enormous quantities of raw materials enter factories with nothing coming out, and monitored "dials and switches while behind thick concrete walls mysterious reactions took place" without knowing the purpose of their jobs.[246][247][248][249][250]

In December 1945 the United States Army published a secret report analysing and assessing the security apparatus surrounding the Manhattan Project. The report states that the Manhattan Project was "more drastically guarded than any other highly secret war development." The security infrastructure surrounding the Manhattan Project was so vast and thorough that in the early days of the project in 1943, security investigators vetted 400,000 potential employees and 600 companies that would be involved in all aspects of the project for potential security risks.[251]

Uncle Sam has removed his hat and is rolling up his sleeves. On the wall in front of him are three monkeys and the slogan: What you see here/ What you do here/ What you hear here/ When you leave here/ Let it stay here.
A billboard encouraging secrecy among Oak Ridge workers

Oak Ridge security personnel considered any private party with more than seven people as suspicious, and residents—who believed that US government agents were secretly among them—avoided repeatedly inviting the same guests. Although original residents of the area could be buried in existing cemeteries, every coffin was reportedly opened for inspection.[250] Everyone, including top military officials, and their automobiles were searched when entering and exiting project facilities. One Oak Ridge worker stated that "if you got inquisitive, you were called on the carpet within two hours by government secret agents. Usually those summoned to explain were then escorted bag and baggage to the gate and ordered to keep going".[252]

Despite being told that their work would help end the war and perhaps all future wars,[252] not seeing or understanding the results of their often tedious duties—or even typical side effects of factory work such as smoke from smokestacks—and the war in Europe ending without the use of their work, caused serious morale problems among workers and caused many rumors to spread. One manager stated after the war:

Well it wasn't that the job was tough ... it was confusing. You see, no one knew what was being made in Oak Ridge, not even me, and a lot of the people thought they were wasting their time here. It was up to me to explain to the dissatisfied workers that they were doing a very important job. When they asked me what, I'd have to tell them it was a secret. But I almost went crazy myself trying to figure out what was going on.[249]

Another worker told of how, working in a laundry, she every day held "a special instrument" to uniforms and listened for "a clicking noise". She learned only after the war that she had been performing the important task of checking for radiation with a geiger counter. To improve morale among such workers Oak Ridge created an extensive system of intramural sports leagues, including 10 baseball teams, 81 softball teams, and 26 football teams.[249]

审查[编辑]

Security poster, warning office workers to close drawers and put documents in safes when not being used

Voluntary censorship of atomic information began before the Manhattan Project. After the start of the European war in 1939 American scientists began avoiding publishing military-related research, and in 1940 scientific journals began asking the National Academy of Sciences to clear articles. William L. Laurence英语William L. Laurence of The New York Times, who wrote an article on atomic fission in The Saturday Evening Post of 7 September 1940, later learned that government officials asked librarians nationwide in 1943 to withdraw the issue.[253] The Soviets noticed the silence, however. In April 1942 nuclear physicist Georgy Flyorov wrote to Josef Stalin on the absence of articles on nuclear fission in American journals; this resulted in the Soviet Union establishing its own atomic bomb project.[254]

The Manhattan Project operated under tight security lest its discovery induce Axis powers, especially Germany, to accelerate their own nuclear projects or undertake covert operations against the project.[255] The government's Office of Censorship英语Office of Censorship, by contrast, relied on the press to comply with a voluntary code of conduct it published, and the project at first avoided notifying the office. By early 1943 newspapers began publishing reports of large construction in Tennessee and Washington based on public records, and the office began discussing with the project how to maintain secrecy. In June the Office of Censorship asked newspapers and broadcasters to avoid discussing "atom smashing, atomic energy, atomic fission, atomic splitting, or any of their equivalents. The use for military purposes of radium or radioactive materials, heavy water, high voltage discharge equipment, cyclotrons." The office also asked to avoid discussion of "polonium, uranium, ytterbium, hafnium, protactinium, radium, rhenium, thorium, deuterium"; only uranium was sensitive, but was listed with other elements to hide its importance.[256][257]

苏联间谍[编辑]

The prospect of sabotage was always present, and sometimes suspected when there were equipment failures. While there were some problems believed to be the result of careless or disgruntled employees, there were no confirmed instances of Axis-instigated sabotage.[258] However, on 10 March 1945, a Japanese fire balloon英语fire balloon struck a power line, and the resulting power surge caused the three reactors at Hanford to be temporarily shut down.[259] With so many people involved, security was a difficult task. A special Counter Intelligence Corps英语Counter Intelligence Corps detachment was formed to handle the project's security issues.[260] By 1943, it was clear that the Soviet Union was attempting to penetrate the project. Lieutenant Colonel Boris T. Pash英语Boris T. Pash, the head of the Counter Intelligence Branch of the Western Defense Command英语Western Defense Command, investigated suspected Soviet espionage at the Radiation Laboratory in Berkeley. Oppenheimer informed Pash that he had been approached by a fellow professor at Berkeley, Haakon Chevalier英语Haakon Chevalier, about passing information to the Soviet Union.[261]

The most successful Soviet spy was Klaus Fuchs, a member of the British Mission who played an important part at Los Alamos.[262] The 1950 revelation of his espionage activities damaged the United States' nuclear cooperation with Britain and Canada.[263] Subsequently, other instances of espionage were uncovered, leading to the arrest of Harry Gold英语Harry Gold, David Greenglass英语David Greenglass, and Julius and Ethel Rosenberg.[264] Other spies like George Koval and Theodore Hall英语Theodore Hall remained unknown for decades.[265] The value of the espionage is difficult to quantify, as the principal constraint on the Soviet atomic bomb project was a shortage of uranium ore. The consensus is that espionage saved the Soviets one or two years of effort.[266]

外国情报[编辑]

In addition to developing the atomic bomb, the Manhattan Project was charged with gathering intelligence on the German nuclear energy project. It was believed that the Japanese nuclear weapons program was not far advanced because Japan had little access to uranium ore, but it was initially feared that Germany was very close to developing its own weapons. At the instigation of the Manhattan Project, a bombing and sabotage campaign was carried out against heavy water plants in German-occupied Norway.[267] A small mission was created, jointly staffed by the Office of Naval Intelligence, OSRD, the Manhattan Project, and Army Intelligence (G-2), to investigate enemy scientific developments. It was not restricted to those involving nuclear weapons.[268] The Chief of Army Intelligence, Major General George V. Strong英语George V. Strong, appointed Boris Pash to command the unit,[269] which was codenamed "Alsos", a Greek word meaning "grove".[270]

Soldiers and workmen, some wearing steel helmet, clamber over what looks like a giant manhole.
Allied soldiers dismantle the German experimental nuclear reactor at Haigerloch.

The Alsos Mission to Italy questioned staff of the physics laboratory at the University of Rome following the capture of the city in June 1944.[271] Meanwhile, Pash formed a combined British and American Alsos mission in London under the command of Captain Horace K. Calvert to participate in Operation Overlord.[272] Groves considered the risk that the Germans might attempt to disrupt the Normandy landings英语Normandy landings with radioactive poisons was sufficient to warn General Dwight D. Eisenhower and send an officer to brief his chief of staff, Lieutenant General Walter Bedell Smith.[273] Under the codename Operation Peppermint英语Operation Peppermint, special equipment was prepared and Chemical Warfare Service teams were trained in its use.[274]

Following in the wake of the advancing Allied armies, Pash and Calvert interviewed Frédéric Joliot-Curie about the activities of German scientists. They spoke to officials at Union Minière du Haut Katanga about uranium shipments to Germany. They tracked down 68 tons of ore in Belgium and 30 tons in France. The interrogation of German prisoners indicated that uranium and thorium were being processed in Oranienburg, 20 miles north of Berlin, so Groves arranged for it to be bombed英语Auergesellschaft#Russian Alsos on 15 March 1945.[275]

An Alsos team went to Stassfurt in the Soviet Occupation Zone and retrieved 11 tons of ore from WIFO英语WIFO (Nazi company).[276] In April 1945, Pash, in command of a composite force known as T-Force, conducted Operation Harborage英语Operation Harborage, a sweep behind enemy lines of the cities of Hechingen, Bisingen, and Haigerloch that were the heart of the German nuclear effort. T-Force captured the nuclear laboratories, documents, equipment and supplies, including heavy water and 1.5 tons of metallic uranium.[277][278]

Alsos teams rounded up German scientists including Kurt Diebner英语Kurt Diebner, Otto Hahn, Walther Gerlach, Werner Heisenberg, and Carl Friedrich von Weizsäcker, who were taken to England where they were interned at Farm Hall英语Farm Hall, a bugged house in Godmanchester. After the bombs were detonated in Japan, the Germans were forced to confront the fact that the Allies had done what they could not.[279]

广岛和长崎核爆[编辑]

准备[编辑]

A shiny metal four-engined aircraft stands on a runway. The crew pose in front of it.
Silverplate B-29 Straight Flush英语Straight Flush (B-29). The tail code of the 444th Bombardment Group英语444th Bombardment Group is painted on for security reasons.

Starting in November 1943, the Army Air Forces Materiel Command at Wright Field, Ohio, began Silverplate, the codename modification of B-29s to carry the bombs. Test drops were carried out at Muroc Army Air Field, California, and the Naval Ordnance Test Station at Inyokern, California英语Naval Air Weapons Station China Lake.[280] Groves met with the Chief of United States Army Air Forces (USAAF), General Henry H. Arnold, in March 1944 to discuss the delivery of the finished bombs to their targets.[281] The only Allied aircraft capable of carrying the 17-英尺(5.2-米) long Thin Man or the 59-英寸(150-厘米) wide Fat Man was the British Avro Lancaster, but using a British aircraft would have caused difficulties with maintenance.[282] Tests were carried out with modified Lancasters at Enstone Airfield英语Enstone Airfield,[283] but Groves hoped that the American Boeing B-29 Superfortress could be modified to carry Thin Man by joining its two bomb bay英语bomb bays together.[284] Arnold promised that no effort would be spared to modify B-29s to do the job, and designated Major General Oliver P. Echols英语Oliver P. Echols as the USAAF liaison to the Manhattan Project. In turn, Echols named Colonel Roscoe C. Wilson英语Roscoe C. Wilson as his alternate, and Wilson became Manhattan Project's main USAAF contact.[281] President Roosevelt instructed Groves that if the atomic bombs were ready before the war with Germany ended, he should be ready to drop them on Germany.[285]

The 509th Composite Group was activated on 17 December 1944 at Wendover Army Air Field英语Wendover Army Air Field, Utah, under the command of Colonel Paul W. Tibbets. This base, close to the border with Nevada, was codenamed "Kingman" or "W-47". Training was conducted at Wendover and at Batista Army Airfield英语Batista Army Airfield, Cuba, where the 393d Bombardment Squadron英语393d Bomb Squadron practiced long-distance flights over water, and dropping dummy pumpkin bombs. A special unit known as Project Alberta英语Project Alberta was formed at Los Alamos under Navy Captain William S. Parsons英语William S. Parsons from Project Y as part of the Manhattan Project to assist in preparing and delivering the bombs.[286] Commander Frederick L. Ashworth英语Frederick L. Ashworth from Alberta met with Fleet Admiral Chester W. Nimitz on Guam in February 1945 to inform him of the project. While he was there, Ashworth selected North Field英语North Field (Tinian) on the Pacific Island Tinian as a base for the 509th Composite Group, and reserved space for the group and its buildings. The group deployed there in July 1945.[287] Farrell arrived at Tinian on 30 July as the Manhattan Project representative.[288]

Most of the components for Little Boy left San Francisco on the cruiser Template:USS on 16 July and arrived on Tinian on 26 July. Four days later the ship was sunk by a Japanese submarine. The remaining components, which included six uranium-235 rings, were delivered by three C-54 Skymasters英语Douglas C-54 Skymaster of the 509th Group's 320th Troop Carrier Squadron.[289] Two Fat Man assemblies travelled to Tinian in specially modified 509th Composite Group B-29s. The first plutonium core went in a special C-54.[290] In late April, a joint targeting committee of the Manhattan District and USAAF was established to determine which cities in Japan should be targets, and recommended Kokura, Hiroshima, Niigata, and Kyoto. At this point, Secretary of War Henry L. Stimson intervened, announcing that he would be making the targeting decision, and that he would not authorize the bombing of Kyoto on the grounds of its historical and religious significance. Groves therefore asked Arnold to remove Kyoto not just from the list of nuclear targets, but from targets for conventional bombing as well.[291] One of Kyoto's substitutes was Nagasaki.[292]

轰炸[编辑]

In May 1945, the Interim Committee was created to advise on wartime and postwar use of nuclear energy. The committee was chaired by Stimson, with James F. Byrnes, a former US Senator soon to be Secretary of State, as President Harry S. Truman's personal representative; Ralph A. Bard英语Ralph A. Bard, the Under Secretary of the Navy; William L. Clayton, the Assistant Secretary of State; Vannevar Bush; Karl T. Compton; James B. Conant; and George L. Harrison英语George L. Harrison, an assistant to Stimson and president of New York Life Insurance Company英语New York Life Insurance Company. The Interim Committee in turn established a scientific panel consisting of Arthur Compton, Fermi, Lawrence and Oppenheimer to advise it on scientific issues. In its presentation to the Interim Committee, the scientific panel offered its opinion not just on the likely physical effects of an atomic bomb, but on its probable military and political impact.[293]

At the Potsdam Conference in Germany, Truman was informed that the Trinity test had been successful. He told Stalin, the leader of the Soviet Union, that the US had a new superweapon, without giving any details. This was the first official communication to the Soviet Union about the bomb, but Stalin already knew about it from spies.[294] With the authorization to use the bomb against Japan already given, no alternatives were considered after the Japanese rejection of the Potsdam Declaration.[295]

Two mushroom clouds rise vertically.
Little Boy explodes over Hiroshima, Japan, 6 August 1945 (left);
Fat Man explodes over Nagasaki, Japan, 9 August 1945 (right).

On 6 August 1945, a Boeing B-29 Superfortress (Enola Gay) of the 393d Bombardment Squadron, piloted by Tibbets, lifted off from North Field with a Little Boy in its bomb bay. Hiroshima, the headquarters of the 2nd General Army英语2nd General Army and Fifth Division and a port of embarkation, was the primary target of the mission, with Kokura and Nagasaki as alternatives. With Farrell's permission, Parsons, the weaponeer in charge of the mission, completed the bomb assembly in the air to minimize the risks of a nuclear explosion in the event of a crash during takeoff.[296] The bomb detonated at an altitude of 1,750英尺(530米) with a blast that was later estimated to be the equivalent of 13 kilotons of TNT.[297] An area of approximately 4.7平方英里(12平方公里) was destroyed. Japanese officials determined that 69% of Hiroshima's buildings were destroyed and another 6–7% damaged. About 70,000 to 80,000 people, of whom 20,000 were Japanese combatants and 20,000 were Korean slave laborers, or some 30% of the population of Hiroshima, were killed immediately, and another 70,000 injured.[298][299][300]

On the morning of 9 August 1945, a second B-29 (Bockscar), piloted by the 393d Bombardment Squadron's commander, Major Charles W. Sweeney英语Charles W. Sweeney, lifted off with a Fat Man on board. This time, Ashworth served as weaponeer and Kokura was the primary target. Sweeney took off with the weapon already armed but with the electrical safety plugs still engaged. When they reached Kokura, they found cloud cover had obscured the city, prohibiting the visual attack required by orders. After three runs over the city, and with fuel running low, they headed for the secondary target, Nagasaki. Ashworth decided that a radar approach would be used if the target was obscured, but a last-minute break in the clouds over Nagasaki allowed a visual approach as ordered. The Fat Man was dropped over the city's industrial valley midway between the Mitsubishi Steel and Arms Works in the south and the Mitsubishi-Urakami Ordnance Works in the north. The resulting explosion had a blast yield equivalent to 21 kilotons of TNT, roughly the same as the Trinity blast, but was confined to the Urakami英语Urakami Valley, and a major portion of the city was protected by the intervening hills, resulting in the destruction of about 44% of the city. The bombing also crippled the city's industrial production extensively and killed 23,200–28,200 Japanese industrial workers and 150 Japanese soldiers.[301] Overall, an estimated 35,000–40,000 people were killed and 60,000 injured.[302][303]

Groves expected to have another atomic bomb ready for use on 19 August, with three more in September and a further three in October.[304] Two more Fat Man assemblies were readied, and scheduled to leave Kirtland Field英语Kirtland Air Force Base for Tinian on 11 and 14 August.[303] At Los Alamos, technicians worked 24 hours straight to cast another plutonium core英语Demon core.[305] Although cast, it still needed to be pressed and coated, which would take until 16 August.[306] It could therefore have been ready for use on 19 August. On 10 August, Truman secretly requested that additional atomic bombs not be dropped on Japan without his express authority.[307] Groves suspended the third core's shipment on his own authority on 13 August.[307]

On 11 August, Groves phoned Warren with orders to organize a survey team to report on the damage and radioactivity at Hiroshima and Nagasaki. A party equipped with portable Geiger counters arrived in Hiroshima on 8 September headed by Farrell and Warren, with Japanese Rear Admiral Masao Tsuzuki, who acted as a translator. They remained in Hiroshima until 14 September and then surveyed Nagasaki from 19 September to 8 October.[308] This and other scientific missions to Japan provided valuable scientific and historical data.[309]

The necessity of the bombings of Hiroshima and Nagasaki became a subject of controversy among historians英语debate over the atomic bombings of Hiroshima and Nagasaki. Some questioned whether an "atomic diplomacy" would not have attained the same goals and disputed whether the bombings or the Soviet declaration of war on Japan was decisive.[304] The Franck Report was the most notable effort pushing for a demonstration but was turned down by the Interim Committee's scientific panel.[310] The Szilárd petition英语Szilárd petition, drafted in July 1945 and signed by dozens of scientists working on the Manhattan Project, was a late attempt at warning President Harry S. Truman about his responsibility in using such weapons.[311][312]

战后[编辑]

Men in suits and uniforms stand on a dais decorated with bunting and salute.
Presentation of the Army–Navy "E" Award英语Army–Navy "E" Award at Los Alamos on 16 October 1945. Standing, left to right: J. Robert Oppenheimer, unidentified, unidentified, Kenneth Nichols, Leslie Groves, Robert Gordon Sproul, William Sterling Parsons英语William Sterling Parsons.

Seeing the work they had not understood produce the Hiroshima and Nagasaki bombs amazed the workers of the Manhattan Project as much as the rest of the world; newspapers in Oak Ridge announcing the Hiroshima bomb sold for $1 ($11 today).[247][257] Although the bombs' existence was public, secrecy continued, and many workers remained ignorant of their jobs; one stated in 1946, "I don't know what the hell I'm doing besides looking into a ——— and turning a ——— alongside a ———. I don't know anything about it, and there's nothing to say". Many residents continued to avoid discussion of "the stuff" in ordinary conversation despite it being the reason for their town's existence.[250]

In anticipation of the bombings, Groves had Henry DeWolf Smyth prepare a history for public consumption. Atomic Energy for Military Purposes, better known as the "Smyth Report", was released to the public on 12 August 1945.[313] Groves and Nichols presented Army–Navy "E" Award英语Army–Navy "E" Awards to key contractors, whose involvement had hitherto been secret. Over 20 awards of the Presidential Medal for Merit英语Presidential Medal for Merit were made to key contractors and scientists, including Bush and Oppenheimer. Military personnel received the Legion of Merit英语Legion of Merit, including the commander of the Women's Army Corps英语Women's Army Corps detachment, Captain Arlene G. Scheidenhelm.[314]

At Hanford, plutonium production fell off as Reactors B, D and F wore out, poisoned by fission products and swelling of the graphite moderator known as the Wigner effect英语Wigner effect. The swelling damaged the charging tubes where the uranium was irradiated to produce plutonium, rendering them unusable. In order to maintain the supply of polonium for the urchin initiators, production was curtailed and the oldest unit, B pile, was closed down so at least one reactor would be available in the future. Research continued, with DuPont and the Metallurgical Laboratory developing a redox solvent extraction process as an alternative plutonium extraction technique to the bismuth phosphate process, which left unspent uranium in a state from which it could not easily be recovered.[315]

Bomb engineering was carried out by the Z Division, named for its director, Dr. Jerrold R. Zacharias英语Jerrold R. Zacharias from Los Alamos.[316] Z Division was initially located at Wendover Field but moved to Oxnard Field英语Oxnard Field, New Mexico, in September 1945 to be closer to Los Alamos. This marked the beginning of Sandia Base英语Sandia Base. Nearby Kirtland Field was used as a B-29 base for aircraft compatibility and drop tests.[317] By October, all the staff and facilities at Wendover had been transferred to Sandia.[318] As reservist officers were demobilized, they were replaced by about fifty hand-picked regular officers.[319]

Nichols recommended that S-50 and the Alpha tracks at Y-12 be closed down. This was done in September.[320] Although performing better than ever,[321] the Alpha tracks could not compete with K-25 and the new K-27, which had commenced operation in January 1946. In December, the Y-12 plant was closed, thereby cutting the Tennessee Eastman payroll from 8,600 to 1,500 and saving $2 million a month.[322]

Nowhere was demobilization more of a problem than at Los Alamos, where there was an exodus of talent. Much remained to be done. The bombs used on Hiroshima and Nagasaki were like laboratory pieces; work would be required to make them simpler, safer and more reliable. Implosion methods needed to be developed for uranium in place of the wasteful gun method, and composite uranium-plutonium cores were needed now that plutonium was in short supply because of the problems with the reactors. However, uncertainty about the future of the laboratory made it hard to induce people to stay. Oppenheimer returned to his job at the University of California and Groves appointed Norris Bradbury as an interim replacement; Bradbury remained in the post for the next 25 years.[318] Groves attempted to combat the dissatisfaction caused by the lack of amenities with a construction program that included an improved water supply, three hundred houses, and recreation facilities.[315]

Two Fat Man-type detonations were conducted at Bikini Atoll in July 1946 as part of Operation Crossroads to investigate the effect of nuclear weapons on warships.[323] Able was detonated on 1 July 1946. The more spectacular Baker was detonated underwater on 25 July 1946.[324]

After the bombings at Hiroshima and Nagasaki, a number of Manhattan Project physicists founded the Bulletin of the Atomic Scientists英语Bulletin of the Atomic Scientists, which began as an emergency action undertaken by scientists who saw urgent need for an immediate educational program about atomic weapons.[325] In the face of the destructiveness of the new weapons and in anticipation of the nuclear arms race several project members including Bohr, Bush and Conant expressed the view that it was necessary to reach agreement on international control of nuclear research and atomic weapons. The Baruch Plan英语Baruch Plan, unveiled in a speech to the newly formed United Nations Atomic Energy Commission (UNAEC) in June 1946, proposed the establishment of an international atomic development authority, but was not adopted.[326]

Following a domestic debate over the permanent management of the nuclear program, the United States Atomic Energy Commission (AEC) was created by the Atomic Energy Act of 1946英语Atomic Energy Act of 1946 to take over the functions and assets of the Manhattan Project. It established civilian control over atomic development, and separated the development, production and control of atomic weapons from the military. Military aspects were taken over by the Armed Forces Special Weapons Project英语Armed Forces Special Weapons Project (AFSWP).[327] Although the Manhattan Project ceased to exist on 31 December 1946, the Manhattan District was not abolished until 15 August 1947.[328]

成本[编辑]

Manhattan Project costs through 31 December 1945[329]
Site Cost (1945 USD) Cost (2019 USD) % of total
Oak Ridge $11.9億 $134億 62.9%
Hanford $3.9億 $44億 20.6%
Special operating materials $1.03億 $11.7億 5.5%
Los Alamos $7406萬 $8.35億 3.9%
Research and development $6968萬 $7.86億 3.7%
Government overhead $3726萬 $4.2億 2.0%
Heavy water plants $2677萬 $3.02億 1.4%
Total $18.9億 $213億

The project expenditure through 1 October 1945 was $1.845 billion, equivalent to less than nine days of wartime spending, and was $2.191 billion when the AEC assumed control on 1 January 1947. Total allocation was $2.4 billion. Over 90% of the cost was for building plants and producing the fissionable materials, and less than 10% for development and production of the weapons.[330][331]

A total of four weapons (the Trinity gadget, Little Boy, Fat Man, and an unused Fat Man bomb) were produced by the end of 1945, making the average cost per bomb around $500 million in 1945 dollars. By comparison, the project's total cost by the end of 1945 was about 90% of the total spent on the production of US small arms (not including ammunition) and 34% of the total spent on US tanks during the same period.[329] Overall, it was the second most expensive weapons project undertaken by the United States in World War II, behind only the design and production of the Boeing B-29 Superfortress.[332]

影响[编辑]

The political and cultural impacts of the development of nuclear weapons were profound and far-reaching. William Laurence英语William Laurence of The New York Times, the first to use the phrase "Atomic Age",[333] became the official correspondent for the Manhattan Project in spring 1945. In 1943 and 1944 he unsuccessfully attempted to persuade the Office of Censorship to permit writing about the explosive potential of uranium, and government officials felt that he had earned the right to report on the biggest secret of the war. Laurence witnessed both the Trinity test[334] and the bombing of Nagasaki and wrote the official press releases prepared for them. He went on to write a series of articles extolling the virtues of the new weapon. His reporting before and after the bombings helped to spur public awareness of the potential of nuclear technology and motivated its development in the United States and the Soviet Union.[335]

The Lake Ontario Ordnance Works英语Lake Ontario Ordnance Works (LOOW) near Niagara Falls became a principal repository for Manhattan Project waste for the Eastern United States.[336] All of the radioactive materials stored at the LOOW site—including thorium, uranium, and the world's largest concentration of radium-226—were buried in an "Interim Waste Containment Structure" (in the foreground) in 1991.[337][338][339]

The wartime Manhattan Project left a legacy in the form of the network of national laboratories: the Lawrence Berkeley National Laboratory, Los Alamos National Laboratory, Oak Ridge National Laboratory, Argonne National Laboratory, and Ames Laboratory. Two more were established by Groves soon after the war, the Brookhaven National Laboratory at Upton, New York英语Upton, New York, and the Sandia National Laboratories at Albuquerque, New Mexico. Groves allocated $72 million to them for research activities in fiscal year 1946–1947.[340] They would be in the vanguard of the kind of large-scale research that Alvin Weinberg, the director of the Oak Ridge National Laboratory, would call Big Science.[341]

The Naval Research Laboratory had long been interested in the prospect of using nuclear power for warship propulsion, and sought to create its own nuclear project. In May 1946, Nimitz, now Chief of Naval Operations, decided that the Navy should instead work with the Manhattan Project. A group of naval officers were assigned to Oak Ridge, the most senior of whom was Captain Hyman G. Rickover, who became assistant director there. They immersed themselves in the study of nuclear energy, laying the foundations for a nuclear-powered navy英语nuclear navy.[342] A similar group of Air Force personnel arrived at Oak Ridge in September 1946 with the aim of developing nuclear aircraft.[343] Their Nuclear Energy for the Propulsion of Aircraft英语Aircraft Nuclear Propulsion (NEPA) project ran into formidable technical difficulties, and was ultimately cancelled.[344]

The ability of the new reactors to create radioactive isotopes in previously unheard-of quantities sparked a revolution in nuclear medicine in the immediate postwar years. Starting in mid-1946, Oak Ridge began distributing radioisotopes to hospitals and universities. Most of the orders were for iodine-131 and phosphorus-32, which were used in the diagnosis and treatment of cancer. In addition to medicine, isotopes were also used in biological, industrial and agricultural research.[345]

On handing over control to the Atomic Energy Commission, Groves bid farewell to the people who had worked on the Manhattan Project:

Five years ago, the idea of Atomic Power was only a dream. You have made that dream a reality. You have seized upon the most nebulous of ideas and translated them into actualities. You have built cities where none were known before. You have constructed industrial plants of a magnitude and to a precision heretofore deemed impossible. You built the weapon which ended the War and thereby saved countless American lives. With regard to peacetime applications, you have raised the curtain on vistas of a new world.[346]

In 2014, the United States Congress passed a law providing for a national park dedicated to the history of the Manhattan Project.[347] The Manhattan Project National Historical Park英语Manhattan Project National Historical Park was established on 10 November 2015.[348]

注释[编辑]

注解
  1. ^ 加利福尼亚大学成立于1868年3月23日,校址位于奥克兰。1873年,加州大学迁校至伯克利[7]1951年3月,加州大学进行改制重组,将伯克利校址进行的项目同其他校址的区分开来。[8]
  2. ^ FDR”是罗斯福的姓名首字母。
  3. ^ 泰勒此处提及的反应方程式是:14
    7
    N
    + 14
    7
    N
    24
    12
    Mg
    + 4
    2
    He
    α粒子) + 17.7 MeV[33]
  4. ^ 贝特后来写道,1959年赛珍珠采访了阿瑟·康普顿,并将这一可能的灾难性后果告诉了H·C·达德利(H.C. Dudley)。1975年达德利写的一篇杂志文章中提到了这件事情。有的人就连在三位一體核试验前夕都在对这一猜想惴惴不安。[36]
  5. ^ Natural self-sustaining nuclear reactions have occurred in the distant past.[106]
  6. ^ The allusion here is to the Italian navigator Christopher Columbus, who reached the Caribbean in 1492.
  7. ^ Oppenheimer spoke these words in the television documentary The Decision to Drop the Bomb (1965).[232] Oppenheimer read the original text in Sanskrit, "kālo'smi lokakṣayakṛtpravṛddho lokānsamāhartumiha pravṛttaḥ" (XI,32),[233] which he translated as "I am become Death, the destroyer of worlds". In the literature, the quote usually appears in the form shatterer of worlds, because this was the form in which it first appeared in print, in Time magazine on November 8, 1948.[234] It later appeared in Robert Jungk's Brighter than a Thousand Suns: A Personal History of the Atomic Scientists (1958),[230] which was based on an interview with Oppenheimer. See Hijiya, The Gita of Robert Oppenheimer[235]
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参考资料[编辑]

行政外交历史文件及通史[编辑]

技术历史文件[编辑]

亲历者口述[编辑]

外部链接[编辑]

Template:New Mexico during World War II

Category:Military history of Canada during World War II英语Category:Military history of Canada during World War II Category:1946 disestablishments in the United States英语Category:1946 disestablishments in the United States Category:Projects established in 1942英语Category:Projects established in 1942