493. Memorandum of Conversation1

[Facsimile Page 1]


  • U.S.
    • The President
    • The Secretary
    • Mr. Gates
    • Mr. Merchant
    • Mr. Irwin
    • Mr. Farley
  • U.K.
    • The Prime Minister
    • Foreign Secretary Lloyd
    • Sir Patrick Dean
    • Lord Plowden
    • Sir Richard Powell
    • Sir Norman Brook


  • Nuclear Test Negotiations

There was discussion of current technical assessments of our present and future ability to monitor nuclear test suspension. It was noted that the theoretical possibility of decoupling the signal from underground nuclear tests by a factor of hundreds had been called to the Soviets’ attention at Geneva, but that the “large hole” technique for achieving this decoupling, and the implications as to the feasibility of a ban on underground tests, had not been presented.

Mr. Herter referred to the urgency of underground experiments to resolve questions of “one point safety” of United States weapons. Necessary tests might be conducted with only a high explosive detonation, but a small nuclear yield might be produced in some cases. Should they result in a detectable atomic explosion, the public explanation could attribute this occurrence to “an accident”.

Both the Prime Minister and Foreign Secretary Lloyd expressed the belief that the United States would be fully justified in conducting safety tests. The President indicated his acquiescence in making the underground safety tests. The talks left unresolved the question as to whether the necessary preparations at the testing site might arouse public suspicion and what might be said publicly.

  1. Source: Monitoring nuclear testing, U.S. need for safety testing. Secret; Limit Distribution. 1 p. NARA, RG 59, Conference Files: Lot 64 D 560, CF 1449. Drafted September 2.