Foreign Relations of the United States, 1961–1963, Volumes VII, VIII, IX, Arms Control; National Security Policy; Foreign Economic Policy, Microfiche Supplement

76. Report of Foreign Weapons Evaluation Group, January 16¹

January 16, 1962

• Prof. H.A. Bethe, Chairman
• Dr. Hans A. Bethe, Cornell University
• Dr. John S. Foster, Lawrence Radiation Laboratory
• Dr. R.H. Goeckermann (last meeting only), Lawrence Radiation Laboratory
• Dr. Kenneth Street (last meeting only), Lawrence Radiation Laboratory
• Dr. J. Carson Mark, Los Alamos Scientific Laboratory
• Dr. R.W. Spence, Los Alamos Scientific Laboratory
• Dr. George A. Cowan, Los Alamos Scientific Laboratory
• Dr. Walter Goad, Los Alamos Scientific Laboratory

The group met three times (in November, December, and January) to consider AFTAC data and evaluation of the Soviet devices tested in their fall 1961 series.

The Soviet development tests showed a highly sophisticated nuclear weapons technology. [text not declassified]

1–5 Megatons

Twelve of the Soviet tests fall in the yield range from 1.5 to 5 MT while there are none between 6 and 25 MT. Thus their interest in the lower megaton range has continued but this yield range now corresponds to lower weight, [text not declassified]. Their interest may be connected with some missile development.

Of the 1–5 MT tests, JOE 96 (2.9 MT), 97 (4.6 MT), and 112 (5.1 MT) gave radiochemical data [text not declassified] and can be treated on this basis. JOE 87 (1.6 MT), 89 (2.3 MT), and 104 (2.7 MT) appear to be proof tests of 1958 devices. Also JOE 80 (4.7 MT) is very similar to JOE 70 of the 1958 series, and this test can be compared [text not declassified].

At least two other tests, i.e., JOE 86 (2.0 MT) and 91 (1.5 MT) appear to represent modest but significant improvements over Soviet 1958 tests of the same yield range. [text not declassified]

Still in the 1–5 MT class, JOE 96 (2.9 MT) and JOE 97 (4.6 MT) and 112 (5.1 MT) provided debris which markedly differs from that obtained from the shots, discussed above. In addition, the isotopic ratios for [text not declassified].

This series of Soviet devices is impressive also in other respects which do not depend on the weight estimate. [text not declassified]

25 Megatons

The 25-megaton test, JOE 106, presents similar difficulties to the [illegible in the original] as the series 96 (2.9 MT), 97 (4.6 MT) and 112 (5.1 MT). [text not declassified].

50–100 Megatons

The Soviet 58 megaton device (JOE 111) [text not declassified].

Sub-Megaton

Four of the Soviet tests, 93, 94, 108 and 116 were in the sub-megaton range with yields between about 0.3 MT and 0.85 MT. [text not declassified] Some part of this increase could probably be realized with confidence without full scale test, but it would seem unlikely that such a change would be made to the full extent indicated without additional tests. The 1961 Soviet series of tests does not include any devices with weights in the neighborhood of [text not declassified]. The Soviets would need additional tests if they want to match U.S. technology in this low weight range.

Fission Devices

The analysis of the small kiloton tests indicate that a substantial portion of these devices was boosted (over half of these tests for which debris was collected show evidence of boosting). This marks a considerably increased Soviet interest in boosting and from these tests a variety of boosted fission devices are now available to them. Several of the tested devices gave boosted yields of a few kilotons [text not declassified]. These may be associated with an interest in tactical weapons. In two instances the yield appears unusually high (75 KT). [text not declassified]

Summary

In summary, we find that the Soviet test series includes various impressive devices. Their advanced experimentation in the yield range from 1.5 to 5 MT should have given them very solid knowledge of the functioning of thermonuclear weapons. [text not declassified]

The panel commends the effort to obtain close-in diagnostic data on staging of Soviet devices from an aircraft. It is recognized that success in such a hazardous operation depends upon a combination of favorable weather conditions, accurate forecasts of shot location and time and faultless performance of complex airborne equipment. Nevertheless, staging information on future Soviet thermonuclear tests is of such importance that all possible effort should go into improving the quality of the measuring equipment, calibrating it on U.S. tests and operating it on possible future Soviet tests at Novaya Zemlya.

H.A. Bethe

Chairman, Foreign Weapons
Evaluation Group

1. Soviet development tests. Secret. 9 pp. Washington National Records Center, RG 330, OSD Files: FRC 69 A 2243, 58 AWT USSR Tests, 1961–1965.