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'A Smell of Nuclear Powder'
Early in January 1939, nine months before the outbreak of the Second World War, a letter from Paris alerted physicists in the Soviet Union to the startling news that German radiochemists had discovered a fundamental new nuclear reaction. Bombarding uranium with neutrons, French physicist Frédéric Joliot-Curie wrote his Leningrad colleague Abram Fedorovich Ioffe, caused that heaviest of natural elements to disintegrate into two or more fragments that repelled each other with prodigious energy. It was fitting that the first report of a discovery that would challenge the dominant political system of the world should reach the Soviet Union from France, a nation to which Czarist Russia had looked for culture and technology. Joliot-Curie's letter to the grand old man of Russian physics "got a frenzied going-over" in a seminar at Ioffe's institute in Leningrad, a protégé of one of the participants reports. "The first communications about the discovery of fission...astounded us," Soviet physicist Georgi Flerov remembered in old age. "...There was a smell of nuclear powder in the air."
Reports in the British scientific journal Nature soon confirmed the German discovery and research on nuclear fission started up everywhere. The news fell on fertile ground in the Soviet Union. Russian interest in radioactivity extended back to the time of its discovery at the turn of the century. Vladimir I. Vernadski, a Russian mineralogist, told the Russian Academy of Sciences in 1910 that radioactivity opened up "new sources of atomic energy...exceeding by millions of times all the sources of energy that the human imagination has envisaged." Academy geologists located a rich vein of uranium ore in the Fergana Valley in Uzbekistan in 1910; a private company mined pitchblende there at Tiuia-Muiun ("Camel's Neck") until 1914. After the First World War, the Red Army seized the residues of the company's extraction of uranium and vanadium. The residues contained valuable radium, which transmutes naturally from uranium by radioactive decay. The Soviet radiochemist Vitali Grigorievich Khlopin extracted several grams of radium for medical use in 1921.
There were only about a thousand physicists in the world in 1895. Work in the new scientific discipline was centered in Western Europe in the early years of the twentieth century. A number of Russian scientists studied there. Abram Ioffe's career preparation included research in Germany with Nobel laureate Wilhelm Roentgen, the discoverer of X rays; Vernadski worked at the Curie Institute in Paris. The outstanding Viennese theoretical physicist Paul Ehrenfest taught in St. Petersburg for five years before the First World War. In 1918, in the midst of the Russian Revolution, Ioffe founded a new Institute of Physics and Technology in Petrograd. Despite difficult conditions the chemist N. N. Semenov describes "hunger and ruin everywhere, no instruments or equipment" as late as 1921 "Fiztekh" quickly became a national center for physics research. "The Institute was the most attractive place of employment for all the young scientists looking to contribute to the new physics," Soviet physicist Sergei E. Frish recalls. "...Ioffe was known for his up-to-date ideas and tolerant views. He willingly took on, as staff members, beginning physicists whom he judged talented....Dedication to science was all that mattered to him." The crew Ioffe assembled was so young and eager that older hands nicknamed Fiztekh "the kindergarten."
During its first decade, Fiztekh specialized in the study of high-voltage electrical effects, practical research to support the new Communist state's drive for national electrification the success of socialism, Lenin had proclaimed more than once, would come through electrical power. After 1928, having ousted his rivals and consolidated his rule, Josef Stalin promulgated the first of a brutal series of Five-Year Plans that set ragged peasants on short rations building monumental hydroelectric clams to harness Russia's wild rivers. "Stalin's realism was harsh and unillusioned," comments C. P. Snow. "He said, after the first two years of industrialization, when people were pleading with him to go slower because the country couldn't stand it:
To slacken the pace would mean to lag behind; and those who lag behind are beaten. We do not want to be beaten. No, we don't want to be. Old Russia was ceaselessly beaten for her backwardness. She was beaten by the Mongol khans, she was beaten by Turkish beys, she was beaten by the Swedish feudal lords, she was beaten by Polish-Lithuanian pans, she was beaten by Anglo-French capitalists, she was beaten by Japanese barons, she was beaten by all for her backwardness. For military backwardness, for cultural backwardness, for agricultural backwardness. She was beaten because to beat her was profitable and went unpunished. You remember the words of the pre-revolutionary poet: "Thou art poor and thou art plentiful, thou art mighty, and thou art helpless, Mother Russia."
We are fifty or a hundred years behind the advanced countries. We must make good the lag in ten years. Either we do it or they crush us.
Soviet scientists felt a special burden of responsibility in the midst of such desperate struggle; the heat and light that radioactive materials such as radium generate for centuries without stint mocked their positions of privilege. Vernadski, who founded the State Radium Institute in Petrograd in 1922, wrote hopefully that year that "it will not be long before man will receive atomic energy for his disposal, a source of energy which will make it possible for him to build his life as he pleases." World leaders such as England's Ernest Rutherford, who discovered the atomic nucleus, and Albert Einstein, who quantified the energy latent in matter in his formula E = mc2, disputed such optimistic assessments. The nuclei of atoms held latent far more energy than all the falling water of the world, but the benchtop processes then known for releasing it consumed much more energy than they produced. Fiztekh had spun off provincial institutes in 1931, most notably at Kharkov and Sverdlovsk; in 1932, when the discovery of the neutron and of artificial radioactivity increased the pace of research into the secrets of the atomic nucleus, Ioffe decided to divert part of Fiztekh's effort specifically to nuclear physics. The government shared his enthusiasm. "I went to Sergei Ordzhonikidze," Ioffe wrote many years later, "who was chairman of the Supreme Council of National Economy, put the matter before him, and in literally ten minutes left his office with an order signed by him to assign the sum I had requested to the Institute."
To direct the new program, Ioffe chose Igor Vasilievich Kurchatov, an exceptional twenty-nine-year-old physicist, the son of a surveyor and a teacher, born in the pine-forested Chelyabinsk region of the southern Urals in 1903. Kurchatov was young for the job, but he was a natural leader, vigorous and self-confident. One of his contemporaries, Anatoli P. Alexandrov, remembers his characteristic tenacity:
I was always struck by his great sense of responsibility, for whatever problem he was working on, whatever its dimensions may have been. A lot of us, after all, take a careless, haphazard attitude toward many aspects of life that seem secondary to us. There wasn't a bit of that attitude in Igor vasilievich....[He] would sink his teeth into us and drink our blood until we'd fulfilled [our obligations]. At the same time, there was nothing pedantic about him. He would throw himself into things with such evident joy and conviction that finally we, too, would get caught up in his energetic style....
We'd already nicknamed him "General."...
Within a year, justifying Ioffe's confidence in him, Kurchatov had organized and headed the First All-Union (i.e., nationwide) Conference on Nuclear Physics, with international attendance. With Abram I. Alikhanov, he built a small cyclotron that became, in 1934, the first cyclotron operating outside the Berkeley, California, laboratory, of the instrument's inventor, Ernest O. Lawrence. He directed research at Fiztekh in 1934 and 1935 that resulted in twenty-four published scientific papers.
Kurchatov was "the liveliest of men," Alexandrov comments, "witty, cheerful, always ready for a joke." He had been a "lanky stripling," his student and biographer Igor N. Golovin writes, but by the 1930s, after recovering from tuberculosis, he had developed "a powerful physique, broad shoulders and ever-rosy cheeks." "Such a nice soul," an Englishwoman who knew him wrote home, "like a teddy bear, no one could ever be cross with him." He was handsome, Sergei Frish says "a young, clean-shaven man with a strong, resolute chin and dark hair standing straight up over his forehead." Golovin mentions lively black eyes as well, and notes that Kurchatov "worked harder than anyone else....He never gave himself airs, never let his accomplishments go to his head."
When Igor was six, his father, a senior surveyor in government service, took a cut in pay to move west over the Urals from the rural Chelyabinsk area to Ulyanovsk, on the Volga, where the three Kurchatov children could attend a proper academic gymnasium. Three years later, in 1912, Igor's older sister Antonina sickened with tuberculosis. For her health the family moved again, to the balmier climate of Simferopol on the Crimean Peninsula. The relocation proved to be a forlorn hope; Antonina died within six months.
The two surviving Kurchatov children Igor and his brother Boris, two years younger thrived in the Crimea. Both boys did well in gymnasium, played soccer, traveled into the country with their father during the summer on surveying expeditions. Igor ran a steam threshing machine harvesting wheat the summer he was fourteen. Another summer he worked as a laborer on the railroad.
A chance encounter with Orso Corbino's Accomplishments of Modern Engineering encouraged the young gymnasium student to dream of becoming an engineer. The Italian physicist would influence Kurchatov's career again indirectly in the 1930s when Corbino sponsored Enrico Fermi's Rome group that explored the newly discovered phenomenon of artificial radioactivity. The discoveries of the Rome group would inspire and challenge Kurchatov's Fiztekh research.
The Great War impoverished the Kurchatov family. Igor added night vocational school to his heavy schedule, qualified as a machinist and worked part-time in a machine shop while taking nothing but 5's straight A's during his final two years of gymnasium.
After the Revolution, in 1920, when he was seventeen years old, Kurchatov matriculated in physics and mathematics at Crimean State, one of about seventy students at the struggling, recently nationalized university. None of the foreign physics literature in the university library dated past 1913 and there were no textbooks, but the rector of the school was a distinguished chemist and managed to bring in scientists of national reputation for courses of lectures, among them Abram Ioffe, theoretical physicist Yakov I. Frenkel and future physics Nobel laureate Igor E. Tamm.
In the wake of war and revolution there was barely enough to eat. After midday lectures, students at Crimean State got a free meal of fish soup thickened with barley so flinty they nicknamed it "shrapnel." The distinction of an assistantship in the physics laboratory in the summer of 1921 gratified Kurcnatov in part because it won him an additional ration of 150 grams about five ounces of daily bread.
Kurchatov finished the four-year university course in three years. He chose, to prepare a thesis in theoretical physics because the university laboratory was not adequately equipped for original experimental work; he defended his dissertation in the summer of 1923. His physics professor, who was leaving for work at an institute in Baku, invited the new graduate to join him. Drawn from childhood to ships and the sea, Kurchatov chose instead to enroll in a program in nautical engineering in Petrograd. He suffered through a winter short on resources in the bitter northern cold, eking out a living as a supervisor in the physics department of a weather station, sleeping on a table in the unheated instrument building in a huge black fur coat. "This is no life I'm living," he wrote a friend that winter, uncharacteristically depressed, "but a rusted-out tin can with a hole in it." But the station director gave him real problems to solve, including measuring the alpha-radioactivity of freshly fallen snow, and the work finally won him for physics. He returned to the Crimea in 1924 to help his family his father had been sentenced to three years of internal exile and later joined his former teacher in Baku.
In the meantime, one of Kurchatov's physics classmates, his future brother-in-law Kirill Sinelnikov, had caught Ioffe's eye and accepted his invitation to work at Fiztekh. Sinelnikov told the institute director about his talented friend. Off went another invitation. Kurchatov returned to Leningrad, this time to take up his life's work. (He married Sinelnikov's sister Marina in 1927.)
Kurchatov quickly impressed Ioffe. "It was almost routine to chase him out of the laboratory at midnight," the senior physicist recalls. In the interwar years Ioffe sent twenty of his protégés abroad "to the best foreign laboratories where [they] could meet new people and familiarize [themselves] with new scientific techniques." Like a young entrepreneur too busy to bother going to college, Kurchatov never found time for foreign study. "He kept putting off taking advantage of [this opportunity]," Ioffe adds. "Everytime it was time to leave he was on an interesting experiment that he preferred to the trip."
Others left and won international reputations. Peter Kapitza explored cryogenics and strong magnetic fields at Cambridge University and became a favorite of Ernest Rutherford, the New Zealand-born Nobel laureate who directed the Cavendish Laboratory. there; Kapitza would earn a Nobel in his turn. So would theoretician Lev Landau, who worked in Germany during this period with his young Hungarian counterpart Edward Teller. The German emigré physicist Rudolf Peierls remembers a walking tour of the Caucasus with Landau after Landau had returned home when the Soviet theoretician pointed out that a nuclear reaction that produced secondary neutrons, if it could be found, would make possible the release of atomic energy "remarkably clear vision in 1934," comments Peierls, "just two years after the discovery of the neutron." Less conspicuously, but with more enduring influence on Soviet history, Yuli Borisovich Khariton, the youngest son of a St. Petersburg journalist and an actress in the Moscow Art Theater "compact, ascetically slight and very sprightly," a friend describes him worked at Fiztekh on chemical chain reactions with Semenov, their discoverer, before earning a doctorate in theoretical physics at the Cavendish in 1927. Alarmed by the growing mood of fascism he found in Germany on his return passage, Khariton at twenty-four organized an explosives laboratory in the new Institute of Physical Chemistry, a Fiztekh spinoff. These were only a few of Ioffe's talented protégés.
Their talents barely protected them from the Great Terror that began in the Soviet Union after the assassination of Central Committee member Sergei Mironovich Kirov in December 1934 as Stalin moved to eliminate all those m power whose authority preceded his imposition of one-man rule. "Stalin killed off the founders of the Soviet state," writes the high-level Soviet defector Victor Kravchenko. "This crime was only a small part of the larger blood-letting in which hundreds of thousands of innocent men and women perished." According to a Soviet official, the slaughter claimed not hundreds of thousands but millions: "From 1 January 1935 to 22 June 1941, 19,840,000 enemies of the people were arrested. Of these 7 million were shot in prison, and a majority of the others died in camp." Exiled Soviet geneticist Zhores Medvedev notes that "the full list of arrested scientists and technical experts certainly runs into many thousands." Kharkov, where Kirill Sinelnikov had moved to direct the high-voltage laboratory after studying at Cambridge, lost most of its leaders, though Kurchatov's brother-in-law himself was spared.
The British Royal Society had funded an expensive laboratory in its own dedicated building in the courtyard outside the Cavendish for Peter Kapitza. Perhaps suspecting that he intended to defect, the Soviet government detained him during a visit home in the summer of 1934 and barred him from returning abroad. His detention shocked the British, and for a time he was too depressed to work, but the Soviet government bought his Cambridge laboratory equipment and built a new institute for him in Moscow. (A frustrated Kapitza had to order such unavailable consumer goods as wall clocks, extension telephones and door locks from England.) Eventually he went back to work, as he wrote People's Commissar Vyacheslav Molotov, "for the glory of the USSR and for the use of all the people." Niels Bohr, the Danish physicist, after visiting him in Moscow in 1937, observed that "by his enthusiastic and powerful personality, Kapitza soon obtained the respect and confidence of Russian official circles, and from the first Stalin showed a warm personal interest for Kapitza's endeavors."
Kapitza's golden captivity was not yet terror, but he needed all his connections when Lev Landau was arrested in April 1938, convicted of being a "German spy" and sent to prison, where he languished for a year and became ill. Landau had been working at Kapitza's Institute for Physical Problems. Kapitza determined to save him, writes Medvedev:
After a short meeting with Landau in prison, Kapitza took a desperate step. He presented Molotov and Stalin with an ultimatum: if Landau was not released immediately, he, Kapitza, would resign from all his positions and leave the institute....It was clear that Kapitza meant business. After a short time Landau was cleared of all charges and released.
In old age, Edward Teller would cite his friend's arrest and imprisonment as one of three important early influences on his militant anti-Communism (the other two, Teller said, were the Great Terror itself and Arthur Koestler's novel Darkness at Noon): "Lev Landau, with whom I published a paper, was an ardent Communist. Shortly after he returned to Russia, he went to prison. After that he was no longer a Communist." Communist or not, Landau continued to work at Kapitza's institute in Moscow.
Not even Ioffe escaped the general harrowing. "Although the majority of [Soviet] scientists realized the importance of work in the field of nuclear physics," writes Alexandrov, "the leadership of the Soviet Academy of Sciences and of the Council of People's Commissars believed that this work had no practical value. Fiztekh and Ioffe himself were heavily criticized at the 1936 general assembly of the Academy of Sciences for 'loss of touch with practice.'" With the Great Terror destroying lives all around them, Soviet physicists understandably learned caution from such charges. "In those years," writes Stalin's daughter Svetlana Alliluyeva, "never a month went by in peace. Everything was in constant turmoil. People vanished like shadows in the night." Her father brooded over it all, reports the historian Robert Conquest: "Stalin personally ordered, inspired and organized the operation. He received weekly reports of...not only steel production and crop figures, but also of the numbers annihilated." Shot in the back of the head at Lubyanka prison, truckloads of bodies to the crematorium at the Donskoi Monastery, smoking ashes bulked into open pits and the pits paved over. That was the era when Osip Mandelstam suffered three years' exile and then five years in a gulag camp five years that killed him for writing a poem, "The Stalin Epigram," the most ferocious portrait of the dictator anyone ever devised:
Our lives no longer feel ground under them.
At ten paces you can't hear our words.
But whenever there's a snatch of talk
it turns to the Kremlin mountaineer,
the ten thick worms his fingers,
his words like measures of weight,
the huge laughing cockroaches on his top lip,
the glitter of his boot-rims.
Ringed with a scum of chicken-necked bosses
he toys with the tributes of half-men.
One whistles, another meows, a third snivels.
He pokes out his finger and he alone goes boom.
He forges decrees in a line like horseshoes,
one for the groin, one the forehead, temple, eye.
He rolls the executions on his tongue like berries.
He wishes he could hug them like big friends from home.
Igor Kurchatov organized the initial Soviet study of nuclear fission at Fiztekh in the early months of 1939, following Joliot-Curie's letter to Ioffe and confirmation of the discovery in scientific journals. Landau's remark to Peierls in 1934 about secondary neutrons points to one universal line of inquiry: examining whether the fission reaction, which a single neutron could initiate, would release not only hot fission fragments but additional neutrons as well. If so, then some of those secondary neutrons might go on to fission other uranium atoms, which might fission yet others in their turn. If there were enough secondary neutrons, the chain reaction might grow to be self-sustaining. Joliot-Curie's team in Paris set up an experiment to look for secondary neutrons in late February; in April the French reported 3.5 secondary neutrons per fission and predicted that uranium would probably chain-react. Enrico Fermi, now at Columbia University in flight from anti-Semitic persecution (his wife Laura was Jewish), and emigré Hungarian physicist Leo Szilard, also temporarily working at Columbia, soon independently confirmed fission's production of secondary neutrons. At a Fiztekh seminar in April, two young members of Kurchatov's Fiztekh team, Georgi Flerov and Lev Rusinov, reported similar results between two and four secondary neutrons per fission. (In 1940, Flerov and Konstantin A. Petrzhak would make a world-class discovery, the spontaneous fission of uranium, a consequence of uranium's natural instability and a phenomenon that would prove crucial to regulating controlled chain reactions in nuclear reactors. Before the young Russians succeeded, the American radiochemist Willard F. Libby, later a Nobel laureate, had tried two different ways unsuccessfully to demonstrate spontaneous fission.)
Down the street at the Institute of Physical Chemistry, Yuli Khariton and an outstanding younger colleague, theoretician Yakov B. Zeldovich, began exploring fission theory. "Yuli Borisovich notes a curious detail," Zeldovich recalled: "we considered the work on the theory of uranium fission to be apart from the official plan of the Institute and we worked on it in the evenings, sometimes until very late." Zeldovich was a brilliant original "not a university graduate," comments Andrei Sakharov; "...in a sense, self-educated" who had earned a master's degree and a doctorate "without his ever bothering about a bachelor's degree." "We immediately made calculations of nuclear chain-reactions," Khariton remembers, "and we soon understood that on paper, at least, a chain-reaction was possible, a reaction which could release unlimited amounts of energy without burning coal or oil. Then we took it very seriously. We also understood that a bomb was possible." Khariton and Zeldovich reported their first calculations in a seminar at Fiztekh in the summer of 1939, describing the conditions necessary for a nuclear explosion and estimating its tremendous destructive capacity one atomic bomb, they told their colleagues, could destroy Moscow.
Theoretical physicist J. Robert Oppenheimer at Berkeley, Fermi, Szilard, Peierls in England, all quickly came to similar conclusions. "These possibilities were immediately obvious to any good physicist," comments Robert Serber. But it was also soon obvious from work by Niels Bohr that a formidable obstacle stood in the way of making bombs: only one isotope of uranium, U235, would sustain a chain reaction, and U235 constituted only 0.7 percent of natural uranium; the other 99.3 percent, chemically identical, was U238, which captured secondary neutrons and effectively poisoned the reaction. There were then two difficult technical questions that needed to be resolved by any nation that proposed to explore building an atomic bomb: whether it might be possible to achieve a controlled chain reaction to build a nuclear reactor using natural uranium in combination with some suitable moderator, or whether the U235 content of the uranium would have to be laboriously enriched; and how to separate U235 from U238 on an industrial scale for bomb fuel when the only exploitable distinction between the two isotopes was a slight difference in mass. Enrichment and separation were essentially identical processes ("separated" bomb-grade uranium is natural uranium enriched to above 80 percent U235) and would use the same massive, expensive machinery that no one yet knew how to build; while a reactor fueled with natural uranium, if such would work, might be a straightforward enterprise.
Khariton and Zeldovich approached these questions from first principles, as it were, carefully calculating what was not possible as well as what might be. In the first of three pioneering papers they published in the Russian Journal of Experimental and Theoretical Physics in 1939 and 1940 (papers that went unnoticed outside the Soviet Union) they demonstrated that a fast-neutron chain reaction was not possible in natural uranium. Isotope separation would therefore be necessary to build a uranium bomb.
A second, longer paper, delivered a few weeks later on October 22, 1939, developed important basic principles of reactor physics. Khariton and Zeldovich correctly identified the crucial bottleneck that experimenters would have to bypass to build a natural-uranium reactor that worked. Visualize a stray neutron in a mass of natural uranium finding a U235 nucleus, entering it and causing it to fission. The two resulting fission fragments fly apart; a fraction of a second later they eject two or three secondary neutrons. If these fast secondary neutrons encounter other U235 nuclei they will continue and enlarge the chain of fissions. But there is much more U238 than U235 in the mass of natural uranium, making an encounter with a U238 nucleus more likely, and U238 tends to capture fast neutrons. It is particularly sensitive to neutrons moving at a critical energy, twenty-five electron volts (eV), a sensitivity which physicists call a "resonance." On the other hand, U238 is opaque to slow neutrons. To make a reactor, then, Khariton and Zeldovich realized, it would be necessary to slow the fast secondary neutrons from U235 fission quickly below U238's twenty-five eV resonance. The way to do that, they proposed, was to make the neutrons give up some of their energy by bouncing them off the nuclei of light atoms such as hydrogen. "In order to accomplish [a chain] reaction [in natural uranium]," they wrote, "strong slowing of the neutrons is necessary, which may be practically accomplished by the addition of a significant amount of hydrogen."
The simplest way to mix uranium with hydrogen would be to make a slurry a homogeneous mixture of natural uranium and ordinary water. But Khariton and Zeldovich demonstrated in this second paper that such a mixture would not sustain a chain reaction, because hydrogen and oxygen also capture slow neutrons, and in a reactor fueled with natural uranium such capture would subtract too many neutrons from the mix. Important consequences followed from this conclusion. One was that instead of hydrogen in ordinary water it would apparently be necessary to use heavy hydrogen deuterium, H2 or D, an isotope of hydrogen with a smaller appetite for neutrons than ordinary hydrogen perhaps in the form of rare and expensive heavy water. (In a review article published in 1940, Khariton and Zeldovich proposed carbon and helium as other possible moderators, both materials that later proved to work.) Alternatively, wrote the two Soviet physicists, "another possibility lies in the enrichment of uranium with the isotope 235." They calculated that natural uranium enriched from 0.7 percent U235 to 1.3 percent U235 would work in a homogeneous solution with ordinary water.
In a third paper submitted in March 1940, Khariton and Zeldovich identified two natural processes that would make it easy and "completely safe" to initiate and control a chain reaction in a nuclear reactor. The fissioning process would heat the mass of uranium and cause it to expand, which in turn would increase the distance the neutrons would have to travel to cause additional fissioning and would therefore slow down the chain reaction, allowing the mass of uranium to cool and the chain reaction to accelerate. This natural oscillation could be controlled by increasing or decreasing the volume of uranium. Another natural process delayed neutrons released in fission which would "significantly increase" the oscillation period subsequently proved more significant for reactor control. (Apparently critics within the Soviet scientific community had made safety a point of attack; in this third paper Khariton and Zeldovich vigorously disputed what they called "hasty conclusions...on the extreme danger of experiments with large masses of uranium and the catastrophic consequences of such experiments." Because of the natural processes they had identified, they scoffed, such conclusions "do not correspond to reality.")
Khariton and Zeldovich summarized these early and remarkable insights in the introduction to their third paper:
It would appear (the lack of experimental data precludes any categorical assertions) that by applying some technique, creating a large mass of metallic uranium either by mixing uranium with substances possessing a small capture cross-section (e.g., with heavy water) or by enriching the uranium with the U235 isotope...it will be possible to establish conditions for the chain decay of uranium by branching chains in which an arbitrarily weak radiation by neutrons will lead to powerful development of a nuclear reaction and macroscopic effects. Such a process would be of much interest since the molar heat of the nuclear fission reaction of uranium exceeds by 5 · 107 [i.e., 5,000,000] times the heating capacity of coal. The abundance and cost of uranium would certainly allow the realization of some applications of uranium.
Therefore, despite the difficulties and unreliability of the directions indicated, we may expect in the near future attempts to realize the process.
At the annual All-Union Conference on Nuclear Physics, held in 1939 in November at Kharkov in the Ukraine, Khariton and Zeldovich reported their conclusion that carbon (graphite) and heavy water were possible neutron moderators. They also reported that a controlled chain reaction even with heavy water would be possible in a homogeneous reactor only with uranium enriched in U235. Since uranium enrichment was notoriously difficult, and would require the development of an entirely new industry, their conclusion made the possibility of building a working nuclear reactor within a reasonable period of time and for a reasonable amount of money appear remote. But there are other possible arrangements of natural uranium and graphite or heavy water that they overlooked, even though their second 1939 paper had offered an important clue. Why two such outstanding theoreticians should have overlooked more promising alternative arrangements is a question worth exploring.
The effectiveness of a moderator such as graphite or heavy water is limited crucially by its probability of capturing rather than reflecting neutrons. That probability, called a "cross section," can only be determined by experiment. Physicists quantify capture cross sections (and other such probabilities) in extremely small fractions of a square centimeter, as if a cross section were the surface area of a target the incoming neutron might hit. The two theoreticians had calculated that to achieve a chain reaction in a mixture of ordinary uranium and heavy water, the cross section of deuterium for neutron capture must not be larger than 3 · 10-27 cm2. They lacked the laboratory equipment they needed a powerful cyclotron and a large quantity of heavy water to measure the actual capture cross section of deuterium (the entire Soviet supply of heavy water at that time amounted to no more than two to three kilograms). For the 1939 All-Union Conference they must have offered an approximation drawn from the international physics literature.
Apparently they continued to search the literature to see if someone had determined a more accurate value for the deuterium capture cross section. They found an estimate in a letter to the editor of the American journal Physical Review published in April 1940. In that letter, University of Chicago physicists L. B. Borst and William D. Harkins noted a "quantitative estimate" of 3 · 10-26 cm2, a full order of magnitude too large (-26 rather than -27). "Thus," Igor Kurchatov would explain in 1943 in a top secret report, "we came to the conclusion that it is impossible to achieve a chain reaction in a mixture of [ordinary] uranium and heavy water." And if not in heavy water without investing expensively in isotope enrichment, then also not in carbon, where tolerances were even closer. "Contrary to the opinion of a small group of enthusiasts," Khariton would comment late in life, "the dominant opinion in our country was that a technical solution to the uranium problem was a matter for the remote future, and that success would require fifteen to twenty years." Khariton and Zeldovich's disappointing conclusion must certainly have contributed to that conservative assessment. But the "small group of enthusiasts," which included Khariton, Zeldovich, Kurchatov and Flerov, was not deterred. "In the case of a homogeneous reactor, the enterprise looked doomed," Khariton would note, "but there was still some hope that a loophole was possible. The cross sections were not very reliable and we felt that we had to dig through the material."
Believing that a nuclear reactor as well as a bomb Would require increasing the U235 content of natural uranium, Kurchatov's group examined various methods of uranium enrichment. Gaseous diffusion pumping a gaseous form of uranium against a porous barrier through which the lighter U235 isotope would diffuse faster than the heavier U238, selectively enriching the product the physicists discounted as impractical. Instead they recommended separating U235 from U238 in gaseous form in a high-speed centrifuge, a method Khariton had studied in detail in 1937 but one for which the technology had not yet been developed.
These early discussions caught the attention of Leonid Kvasnikov, the head of the science and technology department of the state security organization, the People's Commissariat of Internal Affairs, known by its Russian initials NKVD. The NKVD, which had orchestrated the Great Terror (which then swallowed up some 28,000 of its own), had been headed since 1938 by Stalin's brutally efficient fellow Georgian Lavrenti Pavlovich Beria. It maintained a network of spies throughout the world run by NKVD rezidents stationed in Soviet consulates and embassies. One important field of rezidency work was industrial espionage stealing industrial processes and formulas to save the Soviet Union the expense of licensing these technologies legitimately from their developers. The American industrial chemist Harry Gold, who began a long career of espionage for the Soviet Union in 1935, mentions among such information "the various industrial solvents used in the manufacture of lacquers and varnishes...,such specialized products as ethyl chloride (used as a local anesthetic) and in particular, absolute (100%) alcohol (used to blend, i.e., 'extend,' motor fuels)." These commonplace products, Gold understood, "would be a tremendous boon to a country [that was] back in the 18th century, industrially speaking (in spite of some localized advances)." They "could go toward making the harsh life of those who lived in the Soviet Union a little more bearable."
Early in 1940, Kvasnikov alerted the rezidency network to collect information on uranium research. According to Georgi Flerov, the early focus of Soviet concern was on German more than on Anglo-American work, just as it was in England and America:
It seemed to us that if someone could make a nuclear bomb, it would be neither Americans, English or French but Germans. The Germans had brilliant chemistry; they had technology for the production of metallic uranium; they were involved in experiments on the centrifugal separation of uranium isotopes. And, finally, the Germans possessed heavy water and reserves of uranium. Our first impression was that Germans were capable of making the thing. It was obvious what the consequences would be if they succeeded.
Espionage, then, accompanied the Soviet development of nuclear energy from its earliest days.
In the spring of 1940, George Vernadsky, who taught history at Yale University, sent his father, V. I. Vernadski, an article about atomic energy published in the New York Times. Vernadski wrote a letter to the Soviet Academy of Sciences about the article, following which the academy created a Special Committee for the Problem of Uranium. Khlopin, who had succeeded Vernadski as director of the State Radium Institute, was appointed to head the Uranium Committee, which also included Vernadski, Ioffe, the distinguished geologist A. Y. Fersman, Kapitza, Kurchatov and Khariton as well as a number of senior Soviet scientists. The committee was directed to prepare a scientific research program and assign it to the necessary institutes, to oversee the development of methods of isotope separation and to organize efforts toward achieving a controlled chain reaction that is, building a nuclear reactor. The decree that established the committee also ordered the construction, completion or improvement of no fewer than three Soviet cyclotrons, two already at hand in Leningrad and one to be built in Moscow; set up a fund for the acquisition of uranium metal, which Soviet industry at that time did not have the technology to produce; and appointed Fersman to lead an expedition into Central Asia to prospect for uranium. ("Uranium has acquired significance as a source of atomic energy," Vernadski wrote a colleague in July. "With us uranium is a scarce metal; we extract radium from deep brine [pumped from oil wells], and any quantity can be obtained. There is no uranium in these waters.")
Kurchatov was disappointed with the committee's plan, which the Academy of Sciences approved in October 1940. He believed it to be unduly conservative. Despite the expectation that uranium would have to be enriched, he wanted to move directly to building a nuclear reactor. At the Fifth All-Union Conference on Nuclear Physics in Moscow in late November, he analyzed fission studies published throughout the world to demonstrate that a controlled chain reaction was possible and listed the equipment and materials he would need. Asked if a uranium bomb could be built, he said confidently that it could and estimated that a bomb program would cost about as much as the largest hydroelectric plant that had been built in the Soviet Union up to that time an estimate low by several orders of magnitude, but comparable to one Rudolf Peierls and Austrian emigré physicist Otto Robert Frisch had prepared in England eight months earlier for the British government. In any case, as Frisch commented later, the cost of a plant for separating U235 "would be insignificant compared with the cost of the war."
Golovin was an excited eyewitness to the November debate:
The situation...during Kurchatov's talk was rather dramatic. The workshop took place at the Communist Academy on Volkhonka Street, in a large hall with an amphitheater overcrowded by numerous participants. In the course of the presentation the excitement of the audience kept growing and by the end of it the general feeling was that we were on the eve of a great event. When Kurchatov finished his talk, and, together with the chairman of the meeting, Khlopin, went to the adjacent room from the rostrum, Ioffe, Semenov, [A.I.] Leipunski, Khariton and others started to move there one after the other. Meanwhile, the discussion over Kurchatov's talk was continued in the hall....The break was delayed. Instead of the ordinary five or ten minutes between talks, the chairman, Khlopin, didn't return even in twenty minutes....A noisy discussion was taking place [in the adjacent room].
The Great Terror had taught its survivors wary circumspection. In the fifteen months since the beginning of the Second World War on September 1, 1939, Germany had overrun Europe. To buy time, Stalin had concluded a nonaggression pact with Hitler, but the Soviet Union was gearing up for the war with Germany that Stalin understood was coming; in May 1941 he would tell his inner circle, "The conflict is inevitable, perhaps in May next year." The Soviet leadership had made clear its suspicion of "impractical" science, and Stalin had ordered the scientists in no uncertain terms to roll up their sleeves and get down to practical work. Nor had Khariton and Zeldovich's calculations encouraged optimism in an older generation still suspicious of the new physics. Surprisingly, even Ioffe was skeptical. He was not a nuclear physicist, and after the discovery of fission he had taken a long view of its potential, predicting that "if the mastering of rocket technology is a matter of the next fifty years, then the utilization of nuclear energy is a matter of the next century." All these factors would have influenced the noisy discussion going on in the adjacent room at the Communist Academy. Golovin:
A quarter of an hour later, Khlopin returned to the rostrum and declared that he had come to the conclusion that it was too early to ask the government for large grants since the war was going on in Europe and the money was needed for other purposes. He said that it was necessary to work a year more and then make the decision whether there would be some grounds to involve the government....The audience was disappointed.
The development of a capacity to build atomic bombs required a massive commitment of government funds, funds that would have to be diverted from the conventional prosecution of the war. If atomic bombs could be built in time they would be decisive, in which case no belligerent could afford not to pursue them. But making that judgment depended critically on how much scientists trusted their governments and how much governments trusted their scientists.
Trust would not be a defining issue later, after the secret, the one and only secret that the weapon worked became known. This first time around, however, it was crucial, as the Russian physicist Victor Adamsky emphasizes in a discussion of why Nazi Germany never developed an atomic bomb:
The tension [between scientists and their governments] stemmed from the fact that there existed no a priori certainty of the possibility of creating an atomic bomb, and merely for clarification of the matter it was necessary to get through an interim stage: to create a device (the nuclear reactor) in order to perform a controlled chain reaction instead of the explosive kind. But the implementation of this stage requires tremendous expenses, incomparable to any of those previously spared for the benefit of scientific research. And it was necessary to tell this straight to your government, making it clear that the expenses may turn out to be in vain an atomic bomb may not result.....
Scientists and their governments developed confidence and mutual understanding in England and the United States, Adamsky concludes, but not in Germany. At the end of 1940, such confidence and mutual understanding had not yet developed in the USSR.
The overwhelming German surprise attack along the entire western border of the Soviet Union at dawn on June 22, 1941, one month after Stalin's prediction that a shooting war would not begin for another year, mooted the issue of how large an effort should be devoted to what Soviet physicists called the "uranium problem." Stalin met with military and other leaders for eleven hours that first day and almost continuously for several days thereafter, Beria at his side. The Wehrmacht decimated the Soviet Air Force, rolled over Belorussia and the Ukraine and thrust up through the Baltic states toward Leningrad. Once the magnitude of the disaster sank in, says Stalin biographer and General of the Soviet Army Dmitri Volkogonov, the dictator "simply lost control of himself and went into deep psychological shock. Between 28 and 30 June, according to eyewitnesses, Stalin was so depressed and shaken that he ceased to be a leader. On 29 June, as he was leaving the defense commissariat with Molotov, [Kliment] Voroshilov, [Andrei] Zhdanov and Beria, he burst out loudly, 'Lenin left us a great inheritance and we, his heirs, have fucked it all up!'" Stalin retreated to his dacha at Kuntsevo; it took a visit from the Politburo, led by Molotov, to mobilize him. "We got to Stalin's dacha," Anastas Mikoyan recalled in his memoirs. "We found him in an armchair in the small dining room. He looked up and said, 'What have you come for?' He had the strangest look on his face...."
By the time the Soviet dictator rallied, the Germans were bombing Moscow. Volkogonov chronicles the debacle:
Soviet losses were colossal. Something like thirty divisions had been virtually wiped out, while seventy had lost more than half of their numbers; nearly 3,500 planes had been destroyed, together with more than half the fuel and ammunition dumps....Of course, the Germans too had paid a price, namely about 150,000 officers and men, more than 950 aircraft and several hundred tanks....The [Red] army was fighting. It was retreating, but it was fighting.
Stalin finally rallied the Soviet people on July 3. Molotov and Mikoyan had written the speech and they almost had to drag Stalin to the microphone. The Soviet writer Konstantin Simonov, a front-line correspondent throughout the war, recalled the momentous occasion in his postwar novel The Living and the Dead:
Stalin spoke in a toneless, slow voice, with a strong Georgian accent. Once or twice, during his speech, you could hear a glass click as he drank water. His voice was low and soft, and might have seemed perfectly calm, but for his heavy, tired breathing, and that water he kept drinking during the speech....
Stalin did not describe the situation as tragic; such a word would have been hard to imagine as coming from him; but the things of which he spoke opolcheniye [i.e., civilian reserves], partisans, occupied territories, meant the end of illusions....The truth he told was a bitter truth, but at last it was uttered, and people now at least knew where they stood....
"It was an extraordinary performance," reports the Russian-born journalist and historian Alexander Werth, who covered the war in the USSR for the London Times, "and not the least impressive thing about it were these opening words: 'Comrades, citizens, brothers and sisters, fighters of our Army and Navy! I am speaking to you, my friends!' This was something new. Stalin had never spoken like this before."
But Stalin's secret police had surprises in store for any of his newfound "friends" whose loyalty might be suspect, particularly if their background was German. "In every village, town and city," notes Victor Kravchenko, "long blacklists were ready: hundreds of thousands would be taken into custody....The liquidation of 'internal enemies' was, in sober fact, the only part of the war effort that worked quickly and efficiently in the first terrible phase of the struggle. It was a purge in the rear in accordance with an elaborate advance plan, as ordered by Stalin himself...." Half a million people the entire population of the Volga German Republic were transported to internal exile in Siberia. "In Moscow alone thousands of citizens were shot under martial law in the first six months," Kravchenko concludes. "...The magnitude of the terror inside Russia cannot be overstated. It amounted to a war within the war."
In the course of his July 3 speech, Stalin announced the formation of a State Defense Committee (GKO), in which he vested "all the power and authority of the State." He appointed himself chairman of the five-man committee, Molotov deputy chairman, and as members Red Army Marshal Kliment Voroshilov ("an utterly mindless executive with no opinion of his own," scoffs Volkogonov), the assiduous bureaucrat Georgi Malenkov and Beria.
Thus Lavrenti Beria came into his own. Born in the Sukhumi district of Georgia in 1899, he had worked his way to power first as police chief and then party chief of Georgia and the Transcaucasus (where he had personally organized the terrible purges) and now at the center in Moscow. Stalin had summoned him from Georgia in 1938 to purge the NKVD itself. "By early 1939," according to a biographer, "Beria had succeeded in arresting most of the top and middle-level hierarchy of [his predecessor's] apparatus...."He inherited a gulag slave-labor force of several million souls. "Camp dust," he liked to call them. "A magnificent modern specimen of the artful courtier," Svetlana Alliluyeva mocks; she blamed Beria for her father's excesses. The Yugoslavian diplomat Milovan Djilas met Beria in the course of the war: a short man, Djilas says, "somewhat plump, greenish pale, and with soft damp hands," with a "square-cut mouth and bulging eyes behind his pince-nez" and an expression of "a certain self-satisfaction and irony mingled with a clerk's obsequiousness and solicitude." Beria's brutality extended to casual rape of teenage girls plucked off the street and delivered to his Lubyanka office and official torture and murder. He was nevertheless an exceptional administrator. Stalin gave him huge responsibilities: for evacuating wartime industry eastward over the Urals, for mobilizing gulag labor, for overseeing industrial conversion and for moving troops and matériel to the front. "Beria was a most clever man," Molotov testified, "inhumanly energetic and industrious. He could work for a week without sleep." In the early months of the war he almost certainly did.
"Beria was no engineer," observes Victor Kravchenko, a factory manager in those days. "He was placed in control for the precise purpose of inspiring deadly fear. I often asked myself as others assuredly did in their secret hearts why Stalin had decided to take this step. I could find only one plausible answer. It was that he lacked faith in the patriotism and national honor of the Russian people and was therefore compelled to rely primarily on the whip. Beria was his whip."
According to Marshal K. S. Moskalenko, who told a group of senior military officers in 1957 that he heard it from Beria himself, Stalin colluded with Beria and Molotov in late July to offer a surrender, "agreeing to hand over to Hitler the Soviet Baltic republics, Moldavia, a large part of the Ukraine and Belorussia. They tried to make contact with Hitler through the Bulgarian ambassador. No Russian czar had ever done such a thing. It is interesting that the Bulgarian ambassador was of a higher caliber than these leaders and told them that Hitler would never beat the Russians and that Stalin shouldn't worry about it."
The war emptied out the Leningrad institutes. The scientists crated up their movable equipment and shipped it on tracks crowded with troop trains to the other side of the Urals, out of range of German bombers. Fiztekh went to Kazan, four hundred kilometers east of Moscow on the Volga. Whole factories moved east, reports Sergei Kaftanov, minister of higher education and deputy for science and technology to the State Defense Committee:
How long would it take today to move a big industrial enterprise to a new site? Two years? Three years? During the war it took only months for plants that had been moved a thousand kilometers to start up again. The regular order of construction is: walls roof machines. We were doing it this way: machines roof walls. War pressed us for quick solutions.
Quick solutions meant solutions, including scientific solutions, that contributed immediately to the defense of the beleaguered country. In the late summer of 1941, Kurchatov and Alexandrov set up a laboratory together in the Crimean port of Sevastopol, on the Black Sea, organized a test site for demagnetizing ships to protect them against magnetic mines and trained Navy crews in the lifesaving technology until September, when the Germans began bombing Streletskaya Bay. Alexandrov went north then to work with the Northern Fleet; Kurchatov stayed on in Sevastopol demagnetizing submarines.
Boris Pasternak compacted the mood that terrible autumn into a shudder of dread:
Do you remember that dryness in your throat
When rattling their naked power of evil
They were barging ahead and bellowing
And autumn was advancing in steps of calamity?
In October there was panic in Moscow. The Germans had advanced to within a hundred kilometers of the city and it seemed they might succeed in seizing it. A young Red Army cipher clerk stationed in training nearby, Igor Gouzenko, had been given a pass into Moscow on October 16 and witnessed the debacle. "The street was crowded with people carrying bundles, sacks and suitcases," Gouzenko recalled after the war. "They were scurrying in all directions. No one seemed to know where they were fleeing. Everyone was just fleeing. Most astounding of all was the strange silence hanging over the scene. Only the stamp of hurrying feet created an undertone of frantic rhythm." Andrei Sakharov, who was then a young university student, remembered that "as office after office set fire to their files, clouds of soot swirled through streets clogged with trucks, carts, and people on foot carrying household possessions, baggage, and young children....I went with a few others to the [university] Party committee office, where we found the Party secretary at his desk; when we asked whether there was anything useful we could do, he stared at us wildly and blurted out: 'It's every man for himself!'"
At the Scientific Research Institute where Igor Gouzenko's sister had been working, a notice had been posted on the door on the authority of the chairman of the Moscow Soviet: "The situation at the front is critical. All citizens of the City of Moscow, whose presence is not needed, are hereby ordered to leave the city. The enemy is at the gates."
Gouzenko thought the notice qualified as "the most panicky document of World War II." Warranted or not, Moscow emptied out; by the end of October, more than two million people had been evacuated officially and many more had simply fled. Stalin stayed. The counterattack outside Moscow, the first major Soviet offensive, began early in December and saved the city. "West of Moscow," observes Alexander Werth, "...miles and miles of road were littered with abandoned guns, lorries and tanks, deeply embedded in the snow. The comic 'Winter Fritz,' wrapped up in women's shawls and feather boas stolen from the local population, and with icicles hanging from his red nose, made his first appearance in Russian folklore." But the siege of Leningrad had begun, and that winter nearly half the population of the city, a million people, died of starvation.
Georgi Flerov had been drafted into the Soviet Air Force at the beginning of the war and assigned to the Air Force Academy in Ioshkar-Ola to train as an engineer. He was a stubborn man; he suspected that other nations, including the fascist enemy, were working on a uranium bomb; he believed passionately that his country should develop such a weapon first. He said as much in a letter to the State Defense Committee in November, but the letter went unanswered.
That month German bombs and artillery barrages finally drove the Soviet Navy from the Sevastopol harbor. Kurchatov left ruined Sevastopol then, evacuating first by boat to Poti, south of Sukhumi on the eastern shore of the Black Sea, then beginning the long journey by train to Kazan, seven hundred kilometers east of Moscow, to resume work at the temporary Fiztekh installation there. On his way, the Soviet physicist spent a night on a below-zero station platform and caught cold. Suzanne Rosenberg, a daughter of Canadian Communists who had returned to the Soviet Union to support the Revolution, describes a similar railroad ordeal evacuating Moscow during the October panic:
So crammed with evacuees was the train that we spent the first twenty-four hours standing on the wind-swept platform between the carriages. Later we took brief turns sitting down on the benches inside. Our journey lasted nineteen days: normally it took forty-six or fifty hours. We learned to sleep standing up, like horses, to do without water and with little food for whole days. The German Messerschmitts were on our trail. Hearing their approach we would jump off the train, tumbling over one another, and scurry off in all directions. If there were woods we made a dash for their cover. If not, we fled into the open fields and stretched out in the frozen grass, faces buried in the icy ground.
In December Flerov won leave to present a seminar on the uranium problem to the Academy of Sciences, which, like Fiztekh, had been evacuated to nearby Kazan. He missed Kurchatov, who was still in transit, but wrote him a long letter in a school notebook that repeated the gist of his report. One of the participants remembers:
Flerov's report was well-argued. As usual, he was vivid and enthusiastic. We listened to him attentively. Ioffe and Kapitza were present....The seminar left the impression that everything was very serious and fundamental, that work on the uranium project should be renewed. But the war was going on. And I don't know what the outcome would have been if we'd had to decide whether to start work immediately or to delay beginning for another year or two.
Flerov was proposing work on a fast-neutron chain reaction: a bomb. He argued that an atomic bomb was possible and that 2.5 kilograms of pure U235 would yield 100,000 tons of TNT equivalent. "He suggested developing a 'cannon' design," reports Khariton, "that is, quickly driving together two hemispheres made of U235. He also expressed the important idea of the use of 'compression of the active material.'" The record is silent on how Flerov proposed to achieve such compression in a uranium gun, which assembles but does not compress. Flerov's 2.5 kilograms was at best a rough approximation, far below the minimum quantity of U235 necessary to sustain a chain reaction, but it compares with the 1 kg that Rudolf Peierls and Otto Frisch in England had first roughly estimated and was probably derived similarly from the known cross section of uranium for neutron capture, the geometric cross section, 10-23 cm2.
By the time Kurchatov arrived behind the Urals, at the end of December 1941, his cold had turned to pneumonia. He took to his bed. His wife Marina Dmitrievna joined him in Kazan and nursed him. Abram Ioffe nursed him. During his illness he chose not to shave. When he recovered, early in 1942, he emerged into Russian winter with a full-blown beard, "which," says Golovin, "he declared no scissors would touch till after victory." It was unusual in those days for a young Russian to wear a beard. Kurchatov would make his famous.
Khariton says Kurchatov cherished Flerov's report, saving it in his desk to the end of his life. Admiring Flerov's enthusiasm was not the same as trusting his judgment, however. "Kurchatov knew," comments Golovin, "that Flerov did not and indeed could not have proofs; he only had a passion for experimentation and would not back down from his ideas....Cares of the day distracted Kurchatov. He was recalled to fleet duty and left for Murmansk."
"Scientific work which is not completed and produces no results during the war," Peter Kapitza explained in a lecture in 1943, "may even be harmful if it diverts our forces from work which is more urgently required." With ships to demagnetize, tank armor to harden and radar to invent, the Soviet scientific establishment concluded once again, that hard winter of 1941, that it would be imprudent to undertake expensive, problematic and long-term nuclear-fission research in the midst of war.
Copyright © 1995 by Richard Rhodes