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

172. Addendum to December 20 Report of NSAM 205 Committee, February 27¹

February 27, 1963

ADDENDUM TO THE 20 DECEMBER 1962 REPORT OF THE NSAM 205 COMMITTEE

CONCLUSIONS

On 14 and 15 February 1963, the Foreign Weapons Evaluation Group (Bethe Panel) reported on the analysis of Soviet 1962 tests in the 100 to approximately 1,000 KT range and of the two high-yield devices tested in December 1962. After review of this information, the NSAM 205 Committee has concluded that while the Soviets have somewhat extended their capabilities in the sub-megaton yield range, the advances made are not of major significance in terms of their military capabilities. The analyses on the whole do not appear to alter the basic conclusions in the 20 December 1962 report of the NSAM 205 Committee.

DISCUSSION

I. The 1962 Soviet Test Series

From 20 December to 25 December 1962, the Soviets conducted 9 additional tests at the Novaya Zemlya site (see Table I). Five of these tests had yields of less than 100 KT, two were between 1 and 2 MT, one was about 6 MT and one was 26 MT. The very low yield events previously reported as JOEs 121, 122 and 123 (27, 28 and 31 July 1962) are now no longer considered by the Joint Atomic Energy Intelligence Committee to have been definitely of nuclear origin.² The totals of confirmed nuclear tests for the Soviet 1962 series from 1 August to 25 December 1962 are: 66 tests of which 35 were less than 100 KT, 11 were between 100 and 1,000 KT, 14 were between 1,000 and 10,000 KT and 6 larger than 10,000 KT. (This may be compared with the Soviet test series of 1961 which consisted of 44 tests: 24 small-yield tests, 6 thermonuclear tests between 100 and 1,000 KT, 12 between 1,000 and 10,000 KT and 2 larger than 10,000 KT.)

TABLE I

1962 SOVIET NUCLEAR TESTS

20 December–25 December 1962

DATE	NAME	YIELD (KT)	ENVIRONMENT	LOCATION
20 Dec.	JOE 1783	10	Atmosphere	Novaya Zemlya
22 Dec.	JOE 179	30	Atmosphere	Novaya Zemlya
23 Dec.	JOE 180	—	Atmosphere	Novaya Zemlya
23 Dec.	JOE 181	—	Atmosphere	Novaya Zemlya
23 Dec.	JOE 182	1,200	Atmosphere	Novaya Zemlya
24 Dec.	JOE 183	1,900	5,000 ft.	Novaya Zemlya
24 Dec.	JOE 184	26,000	11,500 ft.	Novaya Zemlya
25 Dec.	JOE 185	Prob. <40	Atmosphere	Novaya Zemlya
25 Dec.	JOE 186	5,800	5,000–10,000 ft.	Novaya Zemlya

II. Soviet 1962 Tests in the Sub-megaton Yield Range

Evaluation of Soviet tests in the 400 to 1,200 KT range indicates considerable progress in thermonuclear technology. In JOE 163 the Soviets, for the first time, tested a device [text not declassified] previous Soviet devices in this weight class. However, analysis of all the sub-megaton tests points to a reluctance on the part of the Soviets [text not declassified].

In tests around 200 KT the Soviets still show no evidence of attempts [text not declassified] though these 200 KT devices may have had slightly lower weights than were seen in previous Soviet thermonuclear tests [text not declassified] they do not appear to represent important technological advances.

Yield-to-weight ratios for the sub-megaton yield tests are shown in Table II.

III. High-Yield Tests on 24 and 25 December 1962

The two high-yield tests which have been carried out since previous analyses appear to be somewhat different in design than previous devices in the same yield classes. The analysis of the 26 MT device is particularly difficult since it contained appreciable amounts of unburned themonuclear fuel and does not permit any precise reconstruction of the design of the device. However, neither it nor the 6 MT device appear to involve any radical advances in weapon technology.

TABLE II

YIELD-TO-WEIGHT RATIOS DEMONSTRATED IN SOVIET

1962 LOW-YIELD THERMONUCLEAR TESTS

JOBNUMBER		YIELD(KT)	WEIGHT(lb)	YIELD/WEIGHT(KT/lb)
139 167 176 177		150–220	[text not declassified]	[text not declassified]
126 150 159		400–500	[text not declassified]	[text not declassified]
163		Alt. A. 750	[text not declassified]	[text not declassified]
		Alt. B. 650	[text not declassified]	[text not declassified]
169		1,100	[text not declassified]	[text not declassified]
182		Alt. A. 1,200	[text not declassified]	[text not declassified]
		Alt. B. 1,200	[text not declassified]	[text not declassified]

1. Concludes that Soviet advances in sub-megaton yield range are not of major military capability significance. Two attached tables provide a listing of additional December Soviet tests and yield-to-weight ratios on the sub-megaton yield tests. Top Secret. 4 pp. Kennedy Library, National Security Files, Meetings and Memoranda Series, NSAM 205, Box 339.
2. As the result of dropping these three events, JOE numbers listed in the 20 December report (from JOE 124 on) should be re-numbered; JOE 124 becomes JOE 121, JOE 125 becomes JOE 122, etc.
3. Revised JOE numbers which resulted from dropping of events on 27, 28 and 31 July 1962 as nuclear tests.