GENERATION , nuclear spy extraordinary and the end of “Modus Vivendi”

by CM Meyer, technical journalist

This is the first part of a series of articles that will be published in Energize tracing the history of nuclear energy throughout the world.

The first step towards nuclear power. University, who “promised to get it to the right as they were considered “actual or former person.” ‘enemy aliens’”, the work would be continued “Then one day, in February or March 1940, by others, and that would be the last they Frisch said “Suppose someone gave The memorandum arrived just in time: the British would hear of it. you a quantity of pure 235 isotope of government committee concerned with the uranium – what would happen?” possibilities of a nuclear chain reaction had But, fortunately for the allied war effort, Peierls [Peierls, 1985: 153-154] seen no possibilities in this (they had been did not accept this nonsense. He wrote to the investigating natural uranium, not uranium- chairman of the committee (whose name he The answer theoretical physicist Rudolf Peierls 235), and was just about to disband. Instead, did not yet know), pointing out that he and sat down and worked out with Robert Frisch in this memorandum galvanised them into the Frisch had thought “a great deal” about many in early 1940 astounded them first research aimed at using nuclear energy, of the problems associated with releasing both. Only “about a pound” of uranium- then focused on the first atom bomb. Ironically, nuclear energy, and “might well know the 235 would be necessary to release a huge this step had been taken by Peierls, a German answers to important questions”. Common amount of energy, as Peierls later put it in his immigrant married to a Russian wife, both of sense won, and Peierls and Frisch were placed autobiography, “the equivalent of thousands whom had only recently been naturalised as on the subcommittee that started the first work of tons of ordinary explosive.” British citizens. on the atom bomb.

His estimate of the critical mass of uranium- Like Peierls, Robert Frisch was also a German However, common sense is not very common, 235 later turned out to be too low (the actual immigrant. The nephew of the physicist especially in wartime. Frisch, still classed as critical mass is said to be more than 15 kg Lise Meitner, he had fled with her. an “enemy alien” even after he had later [Rhodes,1996: 48], but it was of the right Together, they had estimated the energy moved to Liverpool to start work on the atom magnitude. Thus, the first step towards the use released by fission (the splitting of the uranium bomb project, found he needed a permit of nuclear power – and the first atom bomb atom: Frisch was the first to coin the term to live there, and even special permission to – was taken in Britain in 1940, when Peierls and “fission”). Fission had then only recently been own a bicycle and ride around in the evening Frisch summarised their findings in a secret discovered: in 1939, by Hahn and Strasman (Peierls, 1985: 152-156, 159). memorandum. in Berlin. Research for MAUD The reply Peierls and Frisch received was typical Neither of them knew how to write a secret “Even if this (uranium-235 enrichment) plant of the time. It went something like this: the memorandum – or who to give it to. After some costs as much as a battleship, it would be worth authorities were grateful for the information, thought, they gave it to Prof. Mark Oliphant, having” Peierls and Frisch discussing the value but they would have to understand that, then in charge of physics at Birmingham of an enrichment plant to produce uranium- 235 [Peierls, 1985: 154]

Today, with the United States being the leading superpower, especially in nuclear technology, it is hard to believe that research on nuclear power and the atom bomb started in the United Kingdom. But it was in the United Kingdom that many of the key ideas and concepts for this first took shape. Later, it was the huge manufacturing base of the USA that transformed these concepts into practical realities: and the first atom bomb.

The work Peierls handled for the committee was growing rapidly. By now, the committee had the strange code name MAUD (to hide its purpose). Later, the research was named “Tube Alloys”: another deliberately meaningless name to hide its purpose.

Peierls had been getting more and more problems to solve. Very early on, when doing the first rough calculations on the critical mass of uranium-235, he saw the need for a process Klaus Fuchs, the quiet man on the extreme left, at Harwell in 1949. Next to him are Herbert Skinner, a close friend, Bruce Chalmers, Harold Tongue, Egon Bretscher, to separate uranium-235 from natural uranium Robert Spence and Sir John Cockroft, the Director. Photo: Courtesy of UKAEA. (only one atom in 140 of uranium is uranium-

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235, the rest are atoms of uranium-238). He To begin to understand why the US and soon realised that the only possible way of doing Great Britain followed different routes to this would be to convert the uranium to uranium nuclear power stations after World War Two, hexafluoride, a highly corrosive gas, and in some we must first understand something of Klaus way use the difference in physical properties of Fuchs. As we shall see, Fuchs was not only the two isotopes to separate them. spying for Russia but also for Britain, and he actually played a key role not only in At first he thought of thermal diffusion, which developing the first atom bomb, but also in did not work. After further discussions, Peierls early work on the first hydrogen bomb. and Frisch decided that “the most promising method was to use gaseous diffusion through Klaus Fuchs was born into a family where the membranes with fine pores”. This idea later father, Emil Fuchs, encouraged his children became the huge gaseous diffusion plant set to stand up for their own beliefs and go their up at Oak Ridge, Tennessee, in the USA. From own way. His early life was not as happy as this came uranium-235 (eventually at the rate of he later described it, as his mother committed 100 kg per month (Rhodes, 1996: 192)), used for suicide while he was quite young, and one the first atom bomb to be dropped on Japan, of his two sisters, Elizabeth, later killed herself on Hiroshima on 6 August 1945. by jumping into the path of an oncoming Later, also in Britain, theoretical work by Feather train. His other sister, Kristel, who emigrated and Bretscher in Cambridge showed that “the to America, had to be hospitalised at one new element, plutonium, which resulted from time because of mental illness. the capture of neutrons by uranium-238 in a As a student in Hitler’s Germany, Fuchs slow-neutron chain reaction, might be as good became increasingly drawn to the left. a nuclear explosive as uranium-235, or better” Active in politics, he first joined the SDP (Social [Peierls, 1985: 160]. Later, once huge reactor Democratic Party) while studying at Leipzig, facilities had been set up at Hanford in the USA, and then later the Communist Party while plutonium was also produced in large enough a student in Kiel. He also turned against his amounts, (eventually at the rate of 20 kg per father’s pacifism (his father was a minister, month (Rhodes, 1996: 192)) to make atom later becoming a Quaker). At Kiel, as a bombs, including the one for the very first test student leader, he displayed considerable and the one later dropped on Nagasaki, Japan courage by actively taking a public stand on 9 August 1945. against the Nazis, and later having to flee But, in those early days, more and more crucial for his life. He reached Britain as a refugee work was being handled by Peierls. He therefore in September 1933, later being accepted needed an assistant, and he thought of Klaus by professor Nevill Mott as a PhD student at Fuchs. Like himself, Fuchs was a refugee from Bristol University. Hitler’s Germany and a theoretical physicist of After graduating, he went to work for considerable promise. Prof Max Born in Edinburgh, publishing several At the time, Fuchs seemed a good choice. research papers and earning a DSc as a But, eight years later, Peierls was to bitterly regret research assistant. Then, in little more than that he chose Klaus Fuchs to work on nuclear three weeks (between 10 and 30 May 1940), energy. Nazi invasions conquered three countries: Holland, Belgium and France. The man who stole nuclear energy Many in authority in Great Britain could not “He is the only physicist I know who changed understand that German military skill and history,” Hans Bethe, head of theoretical advanced strategies had made these rapid research at Los Alamos, commented on Klaus victories possible, and instead blamed Fuchs [Rhodes, 1996: 259] German agents: and, indeed, any Germans Klaus Fuchs not only made nuclear history, he and Italians they could find. This meant, in also changed it. One of the less well-known Britain, a wave of hysteria and a rush to classify results of his work, both as a scientist and as a and intern the 27 000 Germans and Italians spy, is that Great Britain was unable to access then living in Britain (many of them refuges) as American reactor technology when planning its enemy aliens, and get as many as possible first power stations, and was forced to develop out of the country. gas-cooled reactors. Classed as an enemy alien, Fuchs was Dr. Klaus Fuchs is better known as the man who arrested in May 1940 without being able to gave the most sensitive secrets of the atom inform Born of his plight. He was deported by bomb to the then at a critical time ship to Canada, where he was interned: in the in world history, enabling the Soviets to save an same camp as several Nazi’s. Clearly, in this, estimated two years in their race to develop he saw a side of Britain that he did not like. nuclear weapons. Some blame him for the Eventually, Born managed to intercede for Korean War, saying Stalin would never have Fuchs, and get him reclassified and returned dared to support North Korea in 1950 without to Britain on 17 December 1940. Fuchs was having the atom bomb, and that Fuchs’s inputs working under Born when Peierls offered him were crucial. work (Rhodes, 1986: 56-57).

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Fuchs accepted, and started work in May 1941, bomb dropped on Hiroshima, Japan. The 100 different urban locations’ in the USSR” having no problems on working on a possible uranium mass exceeds that of critical mass, [Rhodes, 1996: 298] atom bomb (Peierls, 1985: 163). But, on goes critical, and a nuclear explosion results By the end of June 1947, both the UK and the 22 June 1941 something happened that [Rhodes, 1996: 115-116] [Peierls, 1985: 199]. USA had made embarrassing discoveries. Great changed his life: Germany attacked the USSR, But, the same design cannot be used for Britain would, in a few months, be out of dollars. and the Soviet Union was soon engaged in a plutonium. Because plutonium can undergo In technical terms, this meant that in a few grim struggle for survival: a struggle that, at spontaneous fission something like ten times months, the UK would have only $500- million least for the first six months, it appeared to be as easily as uranium-235, a “gun-design” left of the original US loan of $7,5- billion, and losing. Fuchs decided, without any prompting bomb using plutonium would start to detonate would be practically bankrupt. from anyone, that the work he was doing (predetonate) before the two pieces had could help the Soviet Union militarily, and that, The United States, in turn, was desperately reached each other, and would blow apart as a communist, it was his duty to inform the short of uranium. There was not nearly enough before most of the plutonium had a chance Russians. More importantly, he later decided uranium for reactors at Hanford to generate to fission [Rhodes, 1996:115- 117]. to keep the Russians informed after he had the plutonium needed to produce the 150 moved with Peierls to the USA, to start work on The only practical way researchers at the ‘Nagasaki type bombs’ it needed for its national the top-secret Manhattan Project. Manhattan Project found to detonate a security. With less than 1,5-million men under plutonium bomb was using implosion. Here, a arms, the USA was now relying on atom bombs Thus, a few months after Fuchs started work for small, central ball of plutonium (below critical to fill in the gap against the Soviet Union: by Peierls, in late 1941, he had also started work mass) was surrounded by a hollow sphere of then the USSR had more than five million men of a very different kind: as a spy supplying plutonium (also below critical mass). This hollow under arms and was perceived as an increasing information to Soviet Military Intelligence, the sphere, held in place by wires, was covered threat. GRU. by special shapes of high explosive, called In 1946, the MacMahon Act had been passed The beginnings of Harwell “lenses”. When the time came to detonate the by Congress, transferring control of atomic bomb, electronic detonators in each lens were “The British flew rather than shipped Fuchs home research from the US Military to the Atomic set off within microseconds of each other, in a (after the war in a British bomber) because they Energy Commission (AEC). In it, supplying carefully calculated sequence. This sequence wanted him promptly at Harwell…(they) were information about nuclear weapons and then resulted in a powerful shock wave that preparing secretly to build their own atomic reactor technology to foreign countries was compressed the plutonium into a ball greater bomb, and what Fuchs knew was valuable to prohibited. Only after the act had been passed than the critical mass: but so quickly that the them. He thus became a vector for nuclear and signed into law did senior congressmen plutonium did not have time to predetonate proliferation to England as well as the Soviet and senators become aware of the secret [Peierls, 1985: 199-200]. Union.” [Rhodes, 1996: 259]. wartime Quebec Agreement of 1943. In this The correctness of this design was tested on 16 agreement, Great Britain, Canada and the Today, when some parts of the former top- July 1945, when the first ever nuclear bomb USA had agreed not to use the atom bomb secret atomic research centre at Harwell have was detonated, and later used on Nagasaki. against each other - and for Britain to have a say been demolished to make way for a business Fuchs had extensively studied implosion, and (effectively a veto) on targets the atom bomb park, it is difficult to understand the excitement wrote no fewer than seven secret research was to be used against. This had worked well when it was first founded after World War 2. papers on it. He also knew many other aspects when the war against Japan was still ongoing, When Klaus Fuchs arrived there in 1946 as head of producing nuclear weapons, and knew of but key members in the AEC were appalled at of the theoretical physics section, there was the earliest theoretical resarch on a possible the prospect of Britain vetoing American use of huge excitement at the prospects of nuclear hydrogen bomb [Rhodes,1996: 118-119, the bomb: especially now it was the cornerstone power: and nuclear weapons. Japan had 252-254]. While in the USA, he had kept the of US defence policy. just been forced into surrender by two atomic Soviets informed of the most significant work There was also the question of the world’s richest bombs, World War 2 was finally over, and Britain done at Los Alamos: including a plan of an supply of uranium ore, produced in the then was secretly preparing to make its own atomic actual plutonium bomb and very detailed Belgian Congo. Although Great Britain had weapons: and develop peaceful applications background information. paid for half of all the uranium ore, it had all of nuclear energy. Small wonder that, at Harwell, he was placed in gone to the USA while the Manhattan project Fuchs had distinguished himself in the top-secret charge of theoretical aspects to develop the was operational. But, when the war ended, wartime Manhattan project, where practical British atomic bomb. But, even though Fuchs and the British wanted to start their own nuclear atomic weapons had been developed in worked diligently at Harwell, he continued to programme, half the uranium produced the USA and Canada from British research supply the Soviets with information. had once more gone to Britain, where it was stockpiled. coordinated by the MAUD committee. He Unknown to him, the defection of a cipher had been at the heart of work to solve some clerk, Igor Gouzenko from the Russian Embassy Huge pressure was brought to bear against of the most difficult problems to produce a in Canada in 1944, had started a chain of Britain by the US: in exchange for Marshall aid practical nuclear weapon using plutonium, (in essence, dollars to stave off their looming events that would ultimately lead to his work and helped very considerably to solve the bankruptcy), Great Britain was forced to yield as a spy being discovered: and to a crisis in problem of implosion. up its veto, once more allow all uranium ore to Anglo-American relations that would affect go to the USA, and give up its uranium stockpile Making a nuclear weapon out of uranium- British nuclear research profoundly. to the United States. 235 is, as historian Richard Rhodes ably The Modus Vivendi agreement between explains, comparatively simple. Two pieces This agreement, known as the “Modus Vivendi” the USA and Great Britain of uranium-235 each below the critical mass (literally, way of co-existing) was duly signed on are carefully machined so as to fit perfectly, “The Joint Chiefs (of Staff in the USA) decided 7 January 1948 after some tough negotiations, and then placed at opposite ends of their that the United States could use no more than and was to last until the end of 1949 [Rhodes, bomb. When detonation is required, one part 150 ‘Nagasaki type’ bombs (against Russia 1996: 300-301]. The agreement did mean that is blasted into the other by high explosive: the in 1947), basing that number on a Pentagon Great Britain had to postpone its programme to so-called “gun design”, used in the first atomic study that envisioned ‘attacks on approximately develop nuclear weapons by some years. But

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it did allow Britain access to nuclear reactor cooperation to something approaching the Manhattan Project was accused of being technology. That is, until the news broke of level that existed during World War 2. Knowing “another Fuchs” [Rhodes, 1996: 530]. Fuchs’ spying activities in January 1950. that Britain wanted to develop nuclear Later in 1950 the Korean War started, probably weapons, Dean Acheson, the US Secretary as a direct result of the USSR having the bomb. The end of the modus vivendi and British of State, wanted to improve the working It took some four years for the hysteria to access to nuclear reactor technology relationship with the UK, and had arranged for subside and nuclear cooperation between a proposal for both countries to share research “Then a bomb exploded in London. A the USA and Great Britain to resume. British scientist – Klaus Fuchs, who had been and development in all aspects of nuclear working in this country (the USA) on the research [Moss, 1987: 168-170]. But the damage was done. The Modus Vivendi had expired, with nothing to replace it. As Manhattan Project during the war – was Acheson had good reason to improve relations Acheson put it, there was now a “deep freeze” arrested…..and later tried and convicted. with the British. Only some three months that he could do nothing to change. And this Also, in February, Senator Mc Carthy began earlier, the Soviet Union had exploded its first had considerable implications for nuclear his attacks on the State Department. The atom bomb (on 29 August 1949) [Rhodes, power generation. This as secret work was talks with the British and Canadians returned 1996: 365-6], and the communist forces of then starting in the USA, and was to lead to the to square one, where there was a deep Mao Zedong had seized control of China development of new technology (pressurised freeze from which they did not return in my (forming the PRC on 1 October 1949). But water reactors) to power submarines. This time (1949-1953 as Secretary of State)”. Dean Acheson had not reckoned on Klaus Fuchs! technology was denied to the United Kingdom Acheson, US Secretary of State 1949 - 1953 At first, everything went very well. The Americans (see parts 6 and 7 in this series “The long [Moss, 1987: 169]. were receptive to the British proposals, and shadow of Admiral Hyman Rickover”). This In November 1949, shortly before Fuchs was it looked like the US Congress could be ultimately forced the British to develop gas- arrested, a meeting was held of the little-known persuaded to change the MacMahon Act that cooled reactors (see part 8 in this series, “From Combined Development Agency in the USA. denied the UK access to the technology it so MonteBello to Magnox reactors”). desperately wanted. Present were representatives of Great Britain, References the USA and Canada. Although the meeting And then, in January 1950 came the news [1] Moss, N (1987). Klaus Fuchs – the man who was technically held to discuss uranium of Fuchs’ arrest, and the shattering news of stole the atom bomb. London: Grafton supply, the discussions centred on a far more all he had given to the Russians (for which he Books. important topic. received a sentence of 14 years in jail). [2] Peierls, R (1985). Bird of passage. Princeton: For the first time since the signing of the secret The next month, Senator McCarthy started to Princeton University Press Modus Vivendi nearly two years ago, something stir up anti-communist hysteria, culminating [3] Rhodes, R (1986). Dark sun: the making of better seemed in the offing. An invitation three years later when J Robert Oppenheimer, the hydrogen bomb. London: Simon and had come to Britain to increase nuclear who had directed the scientific side of the Schuster. 

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