Foreign Relations of the United States, 1964–1968, Volume XI, Arms Control and Disarmament

200. Letter from the Chairman of the Atomic Energy Commission (Seaborg) to Secretary of State Rusk¹

Washington, August 4, 1967.

Dear Dean:

Bill Foster’s reply to Mrs. Myrdal at the ENDC meeting of July 11, 1967 on the subject of our attitude toward a comprehensive test ban was quite appropriate in the light of our stated policy.² On the other hand I am concerned that our present commitments to our defense requirements may be in conflict with the interpretation made by some that given adequate inspection we are prepared to accept immediately a comprehensive test ban treaty.

You will recall that at a Meeting of the Principals about a year ago,³ we discussed our policy regarding a possible threshold test ban treaty of a comprehensive test ban treaty. At that time certain estimates were made regarding the period of underground testing that might be required in order to complete the accelerated testing of nuclear weapons that then might be regarded as indispensable for future security.

Since that time our requirements for these new weapons have been further clarified and our careful and detailed analysis of possible accelerated weapons development and test programs has given us sufficient additional information to indicate that the time estimates of a year ago cannot now be considered to be realistic. Therefore, the Atomic Energy Commission believes that it might be useful to give you a brief assessment of the situation as it now exists.

As you know, the DOD and AEC are currently developing a complete new generation of weapons for the strategic offensive forces. Both development and proof tests are required for these high priority systems. Additionally, since these new systems will constitute the major U.S. response to the Soviet ABM deployment, it is vitally important that there be assessments of their vulnerability to nuclear attack. This requires exposure of components and assemblies to large fluxes of neutrons, gamma and X-rays that can only be provided by nuclear detonations. The development of the techniques for carrying out these nuclear effects tests within the constraints of the limited test ban treaty has been an important achievement of recent time.

The requirement for continued underground testing is further emphasized by the Spartan 6 MT, “hot” X-ray ABM warhead. Development and confirmation testing of this warhead by underground techniques involves efforts at least through 1970 because a capability to test at this yield must also be developed.

The need to test has not been and presumably will not be entirely dependent on developments for the future stockpile. There have been instances in which nuclear testing was the only solution or that which offered the highest degree of confidence with respect to the urgent correction of defects found in stockpile weapons affecting either operational reliability or safety.

I had personally hoped that the necessary underground testing associated with the development of the DOD weapons systems could be accelerated so that the results would be available at an earlier time; however, I cannot find a way, despite a great deal of personal attention to the problem. I realize the advantages of taking steps beyond the present limited test ban treaty as soon as it is feasible and I continue to be hopeful that we can reach some broader agreements with the Soviets.

I thought that this information might be useful to you, and I would be pleased to discuss it further with you if you believe that this would be helpful.

Cordially,

Glenn

1. Source: Washington National Records Center, RG 383, Central Policy File: FRC 85 A 83, Committee of Principals Record Book, January-December, 1967. Secret; Restricted Data. The source text was sent to Rusk under cover of an August 14 memorandum from Kohler requesting Rusk’s approval to circulate the source text to the members of the Committee of Principals. Rusk indicated his approval with a checkmark on the covering memorandum with the date “8/15/67” next to it.
2. For Foster’s reply, see Documents on Disarmament, 1967, pp. 294-298. On June 29 Mrs. Myrdal, the Swedish Representative to the ENDC, delivered a statement to the ENDC in which she urged that a ban on underground nuclear weapon tests be considered in any discussion of a comprehensive test ban. (Ibid., pp. 272-278) Several days later Charles Johnson informed Walt Rostow in a July 7 memorandum of the views of several agencies on Foster’s proposed draft response to Mrs. Myrdal’s statement. In his memorandum, Johnson emphasized to Rostow that “ACDA believes strongly that we must rebut Mrs. Myrdal’s charge that we have lost interest in the CTB because failure to do so would have a very adverse effect on our position on the NPT negotiations.” (Johnson Library, National Security File, Agency File, ACDA, Vol. III, Box 6)
3. Regarding this meeting, see Seaborg, Journal, Vol. 26, pp. 312-316.