Soviet atomic bomb project

• 1. Introduction

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  On the 29th of August 1949, a device called RDS-1 detonated in secret at the Semipalatinsk Test Site in Kazakhstan. The Americans, who had been watching the skies with atmospheric fallout monitors, knew almost immediately what had happened. The Soviet Union had become a nuclear power. What had taken the United States years of open, lavishly resourced effort had been accomplished by a country still rebuilding from the most destructive war in human history. How did they do it? The answers reach back to a lone physicist noticing something strange in scientific journals, to spies threading classified blueprints out of American laboratories, to tens of thousands of Gulag prisoners digging uranium ore in Tajikistan, and to a closed city that did not officially exist. This is the story of the Soviet atomic bomb project.

• 2. The Physicist Who Noticed

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  Georgy Flyorov was serving as an officer in the Soviet Air Force when he made an observation that would change history. In 1940-1942, he noticed that German, British, and American scientists had all stopped publishing papers on nuclear science. In a field where progress had previously been shared openly across borders, the silence was conspicuous. Flyorov concluded the obvious: each country had classified its nuclear research. In April 1942, he sent two letters directly to Stalin. The second, co-written with Konstantin Petrzhak, was blunt: "it is essential to manufacture a uranium bomb without a delay." Stalin had largely disregarded the Soviet Union's atomic knowledge up to that point. Reading the Flyorov letters changed that. Stalin authorized a bomb project and named the young Igor Kurchatov as its technical director. Kurchatov had been chosen partly because Abram Ioffe, the more senior figure, had declined the role on account of his age and recommended his younger colleague. The new program was headquartered at Laboratory No. 2, established near Moscow.

• 3. Stolen Blueprints

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  In 1943, Foreign Minister Vyacheslav Molotov shared with Kurchatov a trove of intelligence accumulated through NKVD espionage. Kurchatov's reaction was immediate. He told Molotov: "The materials are magnificent. They add exactly what we have been missing." According to historian Richard Rhodes, what Kurchatov learned was enough to accelerate the Soviet program by a full two years. The spy network ran deep into the American Manhattan Project. Klaus Fuchs, a British physicist, passed detailed technical information to the courier Harry Gold, who was himself coordinated by Semyon Semyonov. Theodore Hall, an American theoretical physicist, also provided significant data. David Greenglass supplied detailed descriptions of the implosion-type Fat Man bomb. One of the most consequential pieces of intelligence was a cross-section measurement for D-T fusion, which Soviet officials obtained from Fuchs roughly three years before it was openly published in the Physical Review in 1949. This data would eventually shape the entire Soviet approach to thermonuclear weapons. The existence of the spy network was exposed by the U.S. Army's secretive Venona project, which began its work in 1943.

• 4. Uranium and Forced Labor

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  Before any bomb could be built, the Soviet Union faced a raw materials problem. The Americans had, with the help of Belgian businessman Edgar Sengier in 1940, already moved to block Soviet access to uranium sources in the Congo, South Africa, and Canada. The Soviets dated the beginning of their domestic uranium mining effort precisely: a State Defense Committee directive issued on the 27th of November 1942. The first Soviet uranium mine opened at Taboshar, in present-day Tajikistan, and by May 1943 it was producing at an annual rate of a few tons of uranium concentrate. Demand was far higher than supply. Lavrentiy Beria, who took personal control of the atomic project on the 22nd of August 1945, resolved the labor shortage in the manner characteristic of the NKVD: he filled the mines, processing plants, and construction sites with tens of thousands of Gulag prisoners. The Chelyabinsk province, where the plutonium production complex known as Mayak was being built about fifteen miles east of the small town of Kyshtym, already held at least twelve forced labor camps in the area. Additional uranium came from East Germany through a deceptively named entity called SAG Wismut, as well as from mines in Czechoslovakia, Bulgaria, Romania, and Poland.

• 5. The Closed Cities

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  To house the most sensitive work, the Soviet Union built cities that did not appear on any public map. During the Cold War, at least nine such places were created, collectively known as Atomgrads. Their code names were assigned by combining the name of the nearest large city with the last two digits of the local postcode. Arzamas-16, which corresponded to the city now known as Sarov, was established in 1946. It housed Design Bureau-11, where the first nuclear weapon was assembled under Yulii Khariton. Chelyabinsk-40, established in 1947 and later known as Ozyorsk, was the site of the Mayak Production Association, which handled plutonium production and component manufacturing. Sverdlovsk-44, now Novouralsk, opened in 1946 for uranium enrichment. After the Soviet Union dissolved, all the closed cities changed their names, but all remained legally closed. As of the writing of the source, three of them, Sarov, Snezhinsk, and Zheleznogorsk, had opened parts of themselves to foreign visitors who obtained special permits.

• 6. From Fission to Hydrogen

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  The test of RDS-1 in 1949 did not end Soviet ambitions; it redirected them. Even while the first fission bomb was being assembled, project scientists were developing conceptual thermonuclear weapons. Andrei Sakharov's study group at FIAN in 1948 proposed a layered fission-fusion-fission design: a shell of natural uranium surrounding the deuterium fuel, which they called the sloika, or layered cake. This design became the RDS-6S. On the 12th of August 1953, it was detonated with a yield of 400 kilotons, roughly ten times more powerful than any previous Soviet test. The Americans, who had detonated their own first thermonuclear device on the 1st of November 1952, code-named it Mike. Though the Mike yield was about twenty times greater than the RDS-6S, it was not a practical weapon. Sakharov then worked on a third concept: a two-stage design in which the radiation wave of a fission bomb, not merely heat and compression, ignited the fusion reaction. The KB-11 Scientific-Technical Council approved plans for this design on the 24th of December 1954, and technical specifications were completed on the 3rd of February 1955. The resulting weapon, the RDS-37, was tested successfully on the 22nd of November 1955, producing a yield of 1.6 megatons.

• 7. The Price of the Program

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  The Soviet Union tested 969 nuclear devices between 1949 and 1990, more than any other nation on the planet, according to records the Russian government released in 1991. Between 1949 and 1963, when the Partial Nuclear Test Ban Treaty came into effect, the Soviets set off 214 devices in the open atmosphere. The majority of these tests took place at the Semipalatinsk Test Site in Kazakhstan, and that testing alone exposed hundreds of thousands of Kazakh citizens to radioactive fallout. The test site was chosen, in part, because the Soviets were curious about the potential for lasting harm that their weapons held. Water contamination around the Mayak site became extreme. From the early 1950s, the Soviets pumped tens of millions of cubic meters of radioactive waste into the small Lake Karachay. By the 1990s, hundreds of millions of curies of waste remained in the lake. In 1967, the lake dried up and winds carried radioactive dust over thousands of square kilometers, exposing at least 500,000 citizens to health risks. Soviet scientists responded by piling concrete on top of the lake, but the weight of the concrete pushed radioactive materials into closer contact with underground groundwater. Cancer rates in affected regions, particularly thyroid and lung cancers linked to Iodine-131, remained elevated far above national averages for decades. The most significant legislative response was a bill authorizing the conversion of the already-contaminated Mayak complex into an international radioactive waste dump, accepting payments from other countries in exchange for storing their nuclear byproducts.

• 8. Tsar Bomba

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  On the 30th of October 1961, a three-stage hydrogen bomb was dropped over the Novaya Zemlya archipelago. The weapon, known as the Tsar Bomba, produced a yield of approximately 50 megatons; the device had been designed to reach 100 megatons but was deliberately reduced before the test. That yield was equivalent to ten times all the explosives used in World War II combined. At 100 kilometers of clear air, the heat of the blast was estimated to be sufficient to cause third-degree burns. The Tsar Bomba was never entered into operational service; it existed as a demonstration of Soviet capability rather than a practical military asset. Its detonation at Novaya Zemlya, a site the program had expanded into during the 1950s when testing outgrew Semipalatinsk, marked the outer limit of what the project that began with Flyorov's letters to Stalin in 1942 had achieved.