Research Note: Soviet Thermonuclear Development

Research Note Soviet Thermonuclear Development David Holloway T h e development of thermonuclear weapons marked one of the major turning-points in the history of Soviet-Americanstrategic arms competition. In his book The Advisors Herbert York enhances our understanding of this turning-point by showing that the first Soviet thermonuclear test device (commonly known as "Joe4 "), which was exploded on 12 August 1953, was not a superbomb but had a different configuration and a substantially lower yield.' The first Soviet superbomb was tested in November 1955. York's analysis is important because it makes it possible to assess more accurately the progress of Soviet nuclear weapons development in the 1950s, and to understand more clearly the nature of Soviet-American strategic arms competition. The object of this note is to make public a document which gives more detailed information about Soviet nuclear weapons tests in the 1950s. The data given here support York's analysis, and indeed can be seen as a footnote to it; they also raise a question about Joe-4's place in Soviet nuclear weapons development. The document, which is available in the Joint Chiefs of Staff records in the National Archives, is quoted in its entirety at the end of this note.2It was prepared by the Nuclear Weapons Working Group of the Joint Technical Intelligence Subcommittee of the JCSJoint IntelligenceCommittee in response to a request from the Chief of Staff, Armed Forces Special Weapons Project for intelligence data on the 1955 Soviet nuclear test series. The document, which was classified "Top Secret," is dated 10February 1956; the version given below includes a correction made on 15 February. It was declassified on 16 November 1976. The first Soviet fission bomb test took place in August 1949, but Soviet work on thermonuclear weapons had already started in 1947-48. At that time the Soviet government asked Kurchatov, the scientificdirector of the nuclear 1. Herbert York, The Advisors. Oppenheimer, Teller and the Superbomb, W. H. Freeman and Co., San Francisco, 1976. 2. National Archives, Modern Military Branch, R G 218, Records of the U.S. Joint Chiefs of Staff, 1954-56, CCS 334 JIC(12-28-55)Section 3. The figures in this document are not of course as reliable as American figures for American test yields. It is possible that a change in assumptions would lead to a change in yield estimates. But in an area where little specific information is publicly available, the document reproduced below does have a scarcity value. David Holloway is Lecturer in Politics, University of Edinburgh. During 1978-1979 he was a Fellow of the International Security Studies Program, Woodrow Wilson International Center for Scholars, Washington , DC. 192 Research Note I 293 program, and other physicists whether there was any basis to reports from the West of a superbomb. They replied that there was, and a group was set up to study the theory of thermonuclear weapon^.^ The Soviet Union had been informed by Klaus Fuchs of the studies of thermonuclear weapons at Los Alamos up to 1946. He could have told them that in the spring of 1946 discussion had taken place of two possible types of thermonuclear bomb: one in which a relatively small amount of thermonuclear fuel is ignited by a relatively large fission explosion (later known as a boosted fission weapon) and the other in which a relatively smallfission explosion ignites a very large mass of thermonuclear fuel (the ~uperbomb).~ It is true that Fuchs’ account of these early discussions of the superbomb would have been misleading rather than helpful to Soviet scientists in a scientific sense, because the early ideas were later shown not to work. But it is possible that Fuchs’ report of the Los Alamos discussions of 1946served to spark the Soviet interest in thermonuclear weapons. He appears to have reported on these discussions to his Soviet contact early in 1947, and it was in 1947 that the Soviet government asked its scientists whether there was any basis for reports on a superbomb.5 By the time of the first Soviet fission bomb test on 29 August 1949 the work of the Soviet theoretical group had shown, in the words of one of Kurchatov...