Half-Life: The Divided Life of Bruno Pontecorvo, Physicist or Spy

by Close, Frank

  Nuclear reactors were a key part of the Manhattan strategy, as they had the potential to make plutonium for a bomb. Led by the pugnacious General Leslie Groves, the project began in earnest on December 2, 1942, the day that Fermi’s pile became a self-sustaining fission engine, which liberated energy at a steady rate. In the jargon, the pile became “critical.” The development of nuclear reactors was the strand of the Tube Alloys project to which Bruno Pontecorvo would soon be co-opted.

  The project was of course top secret, and its members were thoroughly vetted. The fact that Halban’s operation was known as the Anglo-Canadian project is ironic as its genesis was in France, and its early members more French than English. The senior team consisted almost exclusively of émigrés from France and central Europe, who had been working together at Cambridge University with Halban and Kowarski. When Halban proposed that Bruno Pontecorvo join the project, Edward Appleton, the secretary of the British Department of Scientific and Industrial Research (DSIR), initially objected that he did not want to “add to the number of non-British nationals” working on this secret project.1 In light of later events, this objection was ironic: the sole British member of the team borrowed from Cambridge was Alan Nunn May, later imprisoned for passing secrets to the Soviets. It is not clear how the Czech George Placzek and French Pierre Auger, who were already deeply involved in the project, felt about Appleton’s insular attitude. In any event, they argued successfully that “the brilliant physicist Pontecorvo” should be included.2

  Bruno had worked with neutrons for nearly a decade, and had been trained by Fermi in both experiment and theory. A further attraction was that Bruno would be able to consult his mentor in Chicago, to the obvious advantage of the Anglo-Canadian project. Bruno’s work in Tulsa had taught him how neutrons behave in a range of minerals, which would be key issues in designing a working reactor. At the time, the judgment was that there was “no specialist of the same character [as Bruno Pontecorvo] available in North America.”3

  On November 4, 1942, the DSIR asked the British embassy in Washington, DC, to make “discreet enquiries [about Pontecorvo] before any direct approach to employ him.” On November 30 the embassy’s reply deemed him “quite satisfactory from point of view of security for employment by any British agency.” It added, rather patronizingly, that Pontecorvo is “Italian by birth and Hebrew by race, but his record makes it quite clear that he is entirely in sympathy with the Allied Cause.”4

  On December 9, the British security authorities gave Bruno “an unusually enthusiastic report.” The recommendation described him as follows: “One of the ablest of the younger Nuclear Physicists and is acknowledged to be an expert on slow neutron physics—a subject on which he was doing research before the Atomic Energy project was started.”5

  BRUNO RESIGNED FROM THE OIL BUSINESS, AND MADE PREPARATIONS to move to Canada. On January 7, 1943, he traveled from Tulsa to Kansas to obtain a passport, returned home the next day, and then went to New York on the fifteenth to be formally appointed to Tube Alloys. He spent the rest of January in the city, where he was briefed about the project, and finally transferred to Montreal with his family on February 7.6 He would work on secret nuclear physics programs for the Allies and the British for the next seven years.

  Unknown to the security authorities in Canada, a fortnight after Pontecorvo’s appointment three letters were exchanged between the FBI and the British Security Coordination in Washington. The FBI was concerned about Pontecorvo’s sympathies with communism. The origin of this concern was the visit by the two agents to his home in Tulsa a few months earlier, when they had quizzed Marianne in Bruno’s absence. Although the letters were exchanged after Bruno’s initial appointment to Tube Alloys, he was still only a probationer, and his final approval had yet to take place. Inexplicably, “by some organizational error,”7 these letters were not available to the relevant authorities, and on March 3, 1943, his security clearance was approved.8

  Canada would be strategically important for the Allies. There were vast deposits of uranium at Great Bear Lake in the Northwest Territories, and a uranium refinery at Port Hope, Ontario. Bruno’s skill in locating minerals underground would be put to good use. The objective of the reactor program was to complete the Nuclear Reactor X (NRX), the most powerful source of neutrons in the Western world, and a groundbreaking source of nuclear power. The Chalk River reactor in Canada would be the experimental facility from which Britain’s postwar nuclear program would grow, and it would also serve as a means to produce plutonium, as a “second string to the nuclear bow.”9 As a result, Chalk River would become a key target for Soviet agents.10 Whereas overt communists, such as Frédéric Joliot-Curie, had been excluded from the Manhattan Project for security reasons, Bruno Pontecorvo had hidden his enthusiasm and slipped through the net.

  IMAGE 7.1. Bruno Pontecorvo’s security clearance, issued March 3, 1943. (AUTHOR, THE NATIONAL ARCHIVES.)

  ARRIVING IN MONTREAL

  Bruno Pontecorvo’s move from Oklahoma to Montreal was a shock. Having grown up in the warmth of Italy and lived for six years in France and Tulsa, where winters were mild, Montreal was brutally cold, dipping below zero even on the Fahrenheit scale.11 Bruno’s breath turned to icicles in front of his face, as the deep freeze continued for several weeks. There were a couple of days in February when the temperature peaked at the freezing point before plummeting once more, to –20 degrees Fahrenheit.

  The Pontecorvos rented an apartment at the south end of Mount Royal, in a side street off Chemin de la Côte-des-Neiges, about two miles from the city center. The family home was not large by North American standards, but was comfortable nonetheless, with a good view of Saint Joseph’s Oratory, an imposing landmark that was reached by ascending a large number of steps. Bruno liked to entertain guests by taking them out on the balcony to watch the worshippers who mounted the stone staircase on their knees.

  For Europeans, who constituted much of the membership of the Anglo-Canadian project, 1940s Quebec was a cultural backwater, dominated by religious divisions. The French Catholic province had backed the fascists in the Spanish Civil War, and was now supporting Marshall Pétain’s collaboration with the Nazis in France. This contrasted with the local English-speaking community, who had favored the Spanish Republicans and now supported the French Resistance. There was little science being practiced at the University of Montreal, and faculty membership was restricted to practicing members of the Roman Catholic Church. This astonished the newcomers, who found it hard to believe the immense control that the Church exercised. It censored books and films. It also banned drive-in movie theaters, which it regarded as dens of immorality.

  On the plus side, downtown Montreal was cosmopolitan, with a large selection of restaurants: French, Chinese, and especially Jewish. This area was located some distance from the university laboratory, so although downtown was a popular dinner destination, midday lunch tended to consist of sandwiches eaten in the university common room. Over lunch, conversation thrived. The members of the team came from around the world, and had a wide range of backgrounds. Chatter initially centered on world affairs, but soon more formal lunch-hour discussions were organized on a range of issues.

  It was at these gatherings that Bruno began to make his mark. They not only informed him about all aspects of the project and physics at large, but also made Bruno Pontecorvo known to everyone in the laboratory. In this way, he managed to cut through some of the bureaucracy. The formal pattern of work was divided between senior and junior members. Bruno was in the former class, even though he was barely thirty years old. The senior scientists tended to work closely with one another, whereas the junior staff was assigned specialized tasks, subject to the “need to know” principle, with little interaction between members of different groups. In the memory of one junior scientist: “Hierarchy prevailed. The atmosphere was more military than academic.”12

  And there, in a nutshell, is the tension, common among scientists throughout the war years. Science
advances through free-ranging discussion, the sharing of half-baked ideas, from which unexpected synergies emerge. Military administrators such as General Groves were obsessed with security, however, and wanted to create firewalls to keep pockets of knowledge contained within small groups. For them, the ideal was that information should be compartmentalized, so that only a handful of bosses would have the complete picture. This was anathema for scientists, who were reared on skepticism and imbued, then as now, with a distrust of “the suits.” Stories of how these rules were bypassed at Los Alamos are legion; in Canada the same was true. Scientists talk together; it’s a fact of life. It’s great for making progress, but a nightmare for security during wartime.

  One member of the theoretical physics group recalled that Bruno had a broad interest in physics, science, and philosophy.13 Although his primary role in the project was that of an experimentalist, theory remained close to his heart. He began to seek out the theoretical group’s members in order to have discussions about physics that went beyond the project’s immediate problems.

  The theoretical team consisted mainly of young mathematicians with limited knowledge of nuclear physics. Bruno’s interaction with them was a two-way street. His expertise in neutrons gave them the background they needed to apply theory to problems in nuclear physics; in return, these regular contacts brought his own talents in theoretical physics to life.

  Several of these discussions touched on the fundamental ideas underlying radioactivity and nuclear transmutations. It was these talks that led Bruno to appreciate the singular role and importance of the still-hypothetical neutrino, the ghostly particle that had briefly interested his mentor Fermi years before, when Bruno was a student. After the war’s end, the neutrino would become a lifelong interest for Bruno.

  HALBANIA

  Bruno’s first task was to catch up with the progress that had been made on fission. In Paris he had been party to the experiments with heavy water, and he knew that his colleagues believed that each act of fission liberated two or three neutrons. Now he learned that, during his interregnum, Halban and Kowarski’s experiments at Cambridge had convinced them that a chain reaction should be feasible.

  Unlike Enrico Fermi, whose uranium-and-graphite pile had become critical on December 2, Halban’s team had not established this fact. Yet the aggressive and arrogant Halban appeared to believe that his “proof,” achieved in Paris and Cambridge, that a chain reaction could be produced using uranium and heavy water gave him a patent claim over all future work. The Americans were not impressed, questioned the French patents’ validity, and even doubted the results on which they were based. In their opinion, the fact that Enrico Fermi (who distrusted Halban’s results) had produced a chain reaction in practice moved the question far beyond mere theoretical possibility. Any collaboration between the British and the Americans would be under Fermi’s scientific control, something that the autocratic and prickly Halban could not accept.

  Thus Bruno found himself at a laboratory where stimulating research had yet to blossom. Even before his arrival, heated arguments had developed in the higher echelons of politics about the respective national interests of the US and UK.14 The atomic bomb had been conceived in Europe and was being developed in America; who would control it postwar? For the US administration and General Groves, the answer was obvious: the United States, on whose soil the bomb would be built, and whose taxpayers were funding most of the work. The British, however, regarded the bomb as their invention. Their scientists had conceived the possibility, developed the early ideas, demonstrated that U-235 could be separated in principle, and were prominent in North America.15

  Another goal of the Allied collaboration was the development of nuclear power, potentially the solution to the world’s energy needs, and perhaps the most valuable prize of all. It did not sit well with the United States that ICI, who was managing Tube Alloys, had a clear commercial interest in developing nuclear power. The British, on the other hand, suspected that the official US agenda was hegemony in nuclear technology after the war. So, despite being united in fighting a common enemy, the two nations’ divergent long-term political agendas created the need for firewalls, which held back sensitive data. Fermi’s breakthrough, in December 1942, changed the politics considerably, and from that moment the American policy was to severely limit information exchange with the Anglo-Canadian project in Montreal.

  The fact that the Montreal team was unhappy is no surprise, but there was also strong dissatisfaction among the American team of scientists with the policy of restricting access to data.16 Ultimately, members of both teams found ways around this imposition.17 In February 1943, for example, Pierre Auger—head of the Montreal experimental physics program, and Bruno’s immediate boss—visited Fermi’s team in Chicago, along with chemist Bertrand Goldschmidt. The pair had been consultants at Fermi’s laboratory and still retained their security passes, so they simply walked in the front door. They found the American scientists welcoming and helpful. Auger and Goldschmidt returned to Montreal the same evening, having persuaded the Americans to give Auger the basic details of the pile, and to give Goldschmidt two tubes, one containing a portion of fission products, the other containing four micrograms of plutonium.18

  When a reactor is operating, the uranium inside is flooded with neutrons. Those that cause fission liberate energy, which is the goal, but many are captured and lost. The result of adding two neutrons to uranium is that, after a few days, natural radioactivity produces plutonium in the residue. By 1943, physicists knew that plutonium was a better fuel for chain reactions than U-235, and, by implication, a better fuel for weapons as well. Thus, although a reactor physicist might be driven by the goal of producing power for the good of society, and not wish to be party to weapons research, the reactor itself makes no such distinction. Plutonium is plutonium. To make use of plutonium, however, you have to remove it from the reactor by some chemical means, as tons of uranium lead to the creation of mere grams of plutonium per day. As a result of Goldschmidt’s success in Chicago, the radiochemists in Montreal now had enough material to learn how to extract the element.

  Bruno, meanwhile, set out to establish the facts about heavy water and fission. During his first weeks in Montreal, he had “many discussions on the Halban-Kowarski papers” with the head of the theoretical physics group, George Placzek, and with experimentalist Alan Nunn May. Nunn May, who boasted pince-nez spectacles and a small mustache, was a caricature of the 1940s egghead scientist, in marked contrast to the film star glamour of Bruno Pontecorvo. A nuclear physicist from Cambridge University, Nunn May was an expert in making precision measurements of nuclear processes.19 He was also a communist, a fact that seems to have escaped notice when he was vetted for the Anglo-Canadian team, even though his views were well known to his colleagues in Canada.20

  Halban as director was a mixed blessing. True, he had been intimately involved with fission from the outset, but many viewed him as having more ostentation than substance. His self-confident arrogance was pithily summarized by a remark in his obituary: “He moved easily from the laboratory, through the ministerial office, into the board room.”21 Halban’s style and chutzpa were on full display at a meeting of the British and American teams in New York. On a Saturday morning he phoned his colleagues in Montreal, demanding that they take some documents from the Top Secret drawer and courier them immediately under diplomatic cover to New York. A call came back from Montreal, checking which papers he needed. “Any will do,” Halban replied. “It doesn’t matter which.”22 The purpose, in Nunn May’s opinion, was simply to make grand theater, to impress the Americans. The feeling among some members of the Anglo-Canadian team was that the purpose of the heavy-water work was less to further scientific knowledge than to bolster Halban’s and ICI’s commercial visions. Nunn May in particular felt that the scientists in Montreal were “pawns in a game between the British and Americans”23 and living in a state of “Halbanian politics.”24

  SPENDING ONE’S TIME EVA
LUATING THE RELIABILITY OF HALBAN’S DATA on fission and chain reactions is a poor substitute for real experimental work. In 1943, the only immediate source of heavy water in Montreal was the batch that Halban and Kowarski had rescued, but these 185 kilograms were still in Cambridge in the United Kingdom. Even if this batch made it overseas, the team would still face problems: this limited amount of heavy water would be enough for the initial research process, but was utterly inadequate for a large-scale reactor, in which more than a ton of the liquid would be needed. The Anglo-Canadian project was in danger of being stillborn. Many found these early months frustrating, with Alan Nunn May later recalling, “The purpose of [going to Canada] seemed to have evaporated. [We] had no equipment, no laboratory, and no prospect of obtaining any materials, and the Americans were cut off [from us].”25

  At last, in the spring of 1943, the heavy water arrived from Cambridge by air. Serious investigations could now begin. One of the first tasks was to repeat the Halban-Kowarski experiments with more sensitive detection equipment. The original findings—that fission released neutrons, capable of initiating a chain reaction—were confirmed, to great relief. Morale slowly declined, however, as the British and American authorities continued to argue over the control of the whole atomic project.

  In August 1943, Prime Minister Winston Churchill and President Franklin D. Roosevelt met in Quebec. Part of the agreement they came to called for greater cooperation between the two teams. This raised the Anglo-Canadians’ hopes. They eagerly anticipated the arrival of sufficient uranium and heavy water to start their project in earnest. The Americans, however, were slow to respond to the agreement, and it was not until December that preparations began for the first conference between the two teams, held in Chicago in January 1944.