219. Addendum to December 20, 1962, Report of the NSAM 205 Committee, August 151

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On 27 June 1963, the Foreign Weapons Evaluation Group (Bethe Panel) reported on the analysis of the Soviet fission weapon tests conducted during 1962. After reviewing this information, the NSAM 205 Committee has concluded that while the Soviets have improved their capabilities in small, lightweight boosted fission weapons, the advances made do not significantly alter their military capabilities nor does this new information appear to alter the basic conclusions in the 20 December 1962 report of the NSAM 205 Committee.

In summary, as a result of Soviet fission weapons testing in the last 2 years, they have available improved nuclear warheads for tactical and defensive purposes. Although it is not possible to determine which warhead may be designed for use in their anti-ballistic missile system, a suitable low yield fission warhead is undoubtedly available to them if required. However, none of the warheads on which we have information [text not declassified]. Furthermore, we have seen no evidence of low-yield clean devices which might minimize self blackout or which might be used as radiation kill weapons in tactical situations, but such developments might be difficult to identify from debris analyses. Although the Soviets now probably have warheads for tactical or possible ABM use of the order of 100 lbs. weight, there is no evidence that they have very small devices, i.e., [text not declassified] less than about 13″ diameter, although such tests could have escaped detection. Finally, with the possible exception of JOE 85 which was apparently a rather poor design, we have no evidence of the Soviet development of small implosion devices using very little or no plutonium equivalent. Such devices could be particularly useful to the Soviets in light of their estimated relative shortage of plutonium.

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Thirty-five Soviet fission weapon tests were detected between 1 August and 25 December 1962, 26 at Semipalatinsk and 8 at Novaya Zemlya. Of these fission tests, 9 events had yields between 15 and 35 KT and 26 events were of 10 KT or less.

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Of the 35 low yield tests, debris has been collected and analyzed from 30 of these events. For several of these, the debris sample is so poor that no reliable evaluation can be made. For the remainder of these events, the samples are of sufficient quality to permit a reasonably reliable appraisal of the performance and character of the test devices.

Eight of the fission tests involved low efficiency, unboosted fission devices, with tuballoy tampers. The large number of unboosted tests is surprising since such devices hardly seem worthy of development at this stage of the Soviet weapons program. Some of these devices may have been used in effects or operational tests. Three other unboosted devices were without tuballoy tampers and appear to be an extension of similar tests in previous series to lower core efficiencies and thereby possibly to smaller dimensions.

Seven of the 1962 tests were of boosted, composite devices without tuballoy tampers. Four of these closely resemble devices tested in the 1961 Soviet series. The other three devices had indications of a very small boost, but the interpretation of these three tests remains somewhat obscure.

The most significant development in fission weapons was a set of very small, boosted weapons without tuballoy tampers. [text not declassified] In this family of fission weapons, the yield has been varied from about 2 KT to 15 KT. Without boosting, an even lower yield could be obtained. This series of tests has provided the Soviets with a very flexible and useful, lightweight fission weapon [text not declassified].

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Finally, five of the 1962 low yield tests appear to have involved thermonuclear failures or, perhaps, in one or two cases, thermonuclear mockups. That they were intended to be thermonuclear tests is indicated by the excess [text not declassified] Li–6 found in the debris. In two of these tests the cause of the failure was probably in the secondary stage.

  1. Implications of Soviet fission weapons testing. Top Secret. 3 pp. Kennedy Library, National Security Files, Meetings and Memoranda Series, NSAM 205, Box 339.