press in a lithoprint edition reproduced from a typed manuscript (the xerographic copier had not yet been invented) on August 11, 1945. Six copies of that first edition went to Tass, the Soviet news agency, in mid-August. Tass immediately passed this compendium of valuable information about the US bomb program to Soviet intelligence.
Princeton University Press then published a typeset, hardbound edition of the Smyth Report titled
In spite of a great deal of preliminary study of fission products, an unforeseen poisoning effect of this kind very nearly prevents operation of the Hanford piles, as we shall see later.
The sentence refers to the near-disaster the plutonium-production complex at Hanford, Washington, faced on September 27, 1944, when its first big production reactor, the B pile, started up successfully, ran for about twelve hours, mysteriously died, started up again spontaneously after a delay and twelve hours later began another decline. Princeton theoretician John Archibald Wheeler, on hand for the start-up, worked out the problem in an all- night marathon review of fission physics. Uranium (92) does not always break up into barium (56) and krypton (36) (56 + 36 = 92) when it fissions. It frequently breaks up into other fragment sizes instead — iodine (53) and yttrium (39), for example. Wheeler realized that the high neutron flux of the B pile, the first large reactor built anywhere in the world, was creating a fission product that was poisoning the chain reaction by soaking up needed neutrons. After working through the possibilities he decided on iodine135, a radioactive isotope of iodine, and calculated that it would decay with a half-life of about six hours into a previously unknown daughter product, xenon135, which had a nine-hour half-life. Wheeler estimated that Xe135 had an appetite for pile neutrons that was a whopping 150 times as great as the most absorptive element previously known, cadmium, the metal of which the pile's control rods were made. The big production pile, it seemed, would start up normally and chain-react; fission would produce increasing quantities of iodine135; the iodine would decay to Xe135; as the Xe135 built up, its atoms would absorb neutrons one for one; and slowly the pile would be poisoned until there were not enough free neutrons left circulating to sustain the chain reaction. The Xe135 would then decay into a nonabsorptive daughter product; the flux of free neutrons would build until finally the pile had enough neutrons circulating to begin chain reacting again, at which time the cycle would repeat. “Xenon,” Wheeler writes, “had thrust itself in as an unexpected and unwanted extra control rod.”
The solution to the problem at Hanford was to increase the pile's reactivity by adding more uranium slugs until the sheer number of free neutrons available from fission overrode the poisoning effect. But that solution was only possible because the pile had been designed deliberately with a third again as many uranium channels drilled through its massive graphite block as calculations had indicated it needed. And such a generous margin of error had been possible in turn only because the United States had acquired ample supplies of uranium ore by 1944 and had mastered the production in quantity of highly purified graphite and of uranium metal. Had the B pile been designed with minimal tolerances, as someone might design a production reactor whose supplies of graphite and uranium were limited, it would have had to be completely rebuilt, delaying plutonium production by months or even years.
All this science, engineering and industry lay hidden behind that one fugitive sentence of Henry Smyth's report. And Groves's deletion of the sentence from the typeset Princeton edition highlighted its importance as surely as if the general had waved a red flag. Yuli Khariton and Yakov Zeldovich had warned presciently, in their March 7, 1940, paper on chain-reaction kinetics, that just such a problem might occur. (“As examples of such factors [affecting criticality] which need investigation we may note… the appearance of new nuclei capable of capturing neutrons in decay… ”) Obviously fission-product poisoning of the Hanford reactor was a phenomenon Kurchatov needed to know more about as he began to design the first Soviet production reactor destined for Chelyabinsk-40. Which product caused the poisoning effect? At what stage of operation did it occur? How did the US overcome it? On all these vital questions, the Smyth Report was silent.
At some point during autumn 1945, someone within the Soviet atomic-bomb establishment noticed the discrepancy. Evidently he or she did so prior to Sudoplatov's Bohr caper. Department S was responsible for translating the Smyth Report; its technical editor, comparing the two American editions sentence by sentence, was probably the first to notice the discrepancy. In his 1994 memoir, Sudoplatov remembered the issue of reactor poisoning in garbled form. “A pivotal moment in the Soviet nuclear program occurred in November 1945,” he writes. “The first Soviet nuclear reactor had been built [sic], but all attempts to put it into operation ended in failure [sic], and there had been an accident with plutonium [sic]. How to solve the problem?”
Shortly after the end of the war, Bohr had publicly expressed his hope that the scientific knowledge developed in the United States during the Manhattan Project years would be shared internationally as part of an agreement to forestall an atomic arms race. Superficially, Bohr's position on secrecy sounded like the argument that NKVD agents had used to prospect successfully for espionage in Britain and America during the war. To people of Beria's and Sudoplatov's mentality, Bohr's vision of an open world pioneered by scientific sharing seemed an appeal for collaboration. “We decided to turn to Bohr,” Sudoplatov recalls. “We took a young worker from my Department S… a young theoretical physicist, and we sent him to Bohr. Denmark, at the time, had recently been liberated from the Germans by the Red Army [sic: Denmark was still under German occupation on V-E Day], and attitudes in general to Soviet Russians were especially warm.” The young Soviet physicist, Yakov Petrovich Terletsky, had been drafted into service with the NKVD from outside the Soviet atomic-bomb program.
As Terletsky tells the story, Sudoplatov drafted him with Beria's approval to review translations of the voluminous intelligence materials the NKVD had collected and to brief Kurchatov's scientists. It was Terletsky who learned, on his first day on the job, October 11,1945, that some ten thousand pages of espionage materials lay on hand at the Lubyanka. These “were photocopies of scientific reports typed on a typewriter,” he writes. “At the top of every report was a standard stamp from the American state security agencies, warning that the report was secret.” After only four days of reviewing this unfamiliar material — Terletsky's specialty was statistical physics, not nuclear physics — the young scientist was ordered to report to the bomb project technical council on what he had learned. He was warned not to reveal the source of his information; he was to say it came from a fictitious “Bureau No. 2,” implying a parallel bomb program. Most of the scientists and managers who were members of the technical council knew at least informally of the extensive NKVD collections, however; few would have been fooled.
The Bohr caper followed a week after Terletsky's technical council report, when a messenger rousted him from sleep on a Saturday night and drove him to the Lubyanka for a meeting with Beria that never materialized. Sudoplatov turned up instead and asked Terletsky if he knew Niels Bohr. “What physicist didn't know Bohr!” Terletsky writes with literal-minded incredulity. “From further hints it became clear that a meeting was to take place with Niels Bohr… I was sent home and warned that I should maintain readiness and not leave town, even on Sunday. But where would I have gone at that time anyway?” The following week, Sudoplatov briefed Terletsky in detail. He would meet with Bohr in Copenhagen and ask him questions about the American project. Sudoplatov imagined that Bohr “was inclined against the Americans, and it could be expected that he would help us.” Kapitza would supply a letter of introduction. Terletsky met with Kapitza, who pointedly advised him not to ask Bohr many questions but to listen to what Bohr had to say.
Before he left for Copenhagen, Terletsky had his worn-out wartime clothes replaced with NKVD tailoring, “starting with underwear… at some top-secret tailor's shop” and met with Lavrenti Beria. To get to Beria's office, Terletsky remembers, he had to pass through a room “filled with armed officers who carefully looked us over” and then wait in an outer office “which reminded me of nothing so much as the dressing room adjoining a public bath,” with Sudoplatov and other Department S representatives already at hand and a four-hundred-pound torture specialist and Beria confidant named Bogdan Kabul — “egg-shaped,” Terletsky calls him. The gang filled the time joking about the hot Scandinavian girls Terletsky was likely to meet. Finally Beria received them:
When we entered, Beria got up from behind his desk, which was deep within an enormous room, and went up to a large conference table… Then I was introduced to the People's Commissar. He was of average height,
