GENERATION Klaus Fuchs, Nuclear Spy Extraordinary and the End of “Modus Vivendi”

GENERATION Klaus Fuchs, 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 Birmingham 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 Germany 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- energize - October 2006 - Page 38 GENERATION 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.

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