296. Telegram 2322 From the Department of State to Embassy in the Soviet Union1 2


  • Soviet Statement re U.S. Underground Explosions

Ambassador Dobrynin, at his initiative, called on Assistant Secretary Hillenbrand on January 6 to present the following oral statement:


On December 16, 17 and 18, 1970, the United States carried out four underground nuclear explosions as a result of which there was a release of radioactive products into the atmosphere. According to reports, a noticeable increase in radiation occurred in the area of the explosion and at considerable distance from it.

The Soviet side could not but pay attention to the lack of an official evaluation of the possibility of the radioactive cloud going outside the national borders [Page 2] of the United States.

As is known, the Treaty banning nuclear weapon tests in the atmosphere, in outer space and under water prohibits a signatory from carrying out a nuclear test, “if such explosion causes radioactive debris to be present outside the territorial limits of the State.”

Drawing attention to the fact of release into the atmosphere of a large quantity of radioactive products as a result of a nuclear explosion on December 18, the Soviet side expects that necessary explanations will be given in the light of the Treaty which banned nuclear explosions causing radioactive debris to be present outside territorial limits.

Competent Soviet authorities will naturally watch the radioactive cloud that has developed and, if the analyses of the debris of this cloud reveal the presence of radioactive products, then the Soviet side reserves the right to return to this question. END QUOTE

Hillenbrand said that he had not received a full report of the tests to which Dobrynin referred. Any pertinent information relating to the matter raised in the Soviet statement would be brought to the attention of the Soviet Government.

Hillenbrand then said that he would like to call the Ambassador’s attention to Soviet nuclear explosions of October 14 and December 17, 1970 from which we had collected radioactive material outside the borders of the USSR. In this connection he handed Dobrynin a piece of paper containing the following statement:


The United States collected outside of the Soviet Union radioactive material directly associated with the Soviet nuclear explosions of October 14 and December 17, 1970.

In view of Paragraph 1(b) of Article I of the Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer [Page 4] Space, and Under Water, the Government of the United States wishes to draw the attention of the Government of the Soviet Union to this matter, and to the importance of due precautions to insure compliance with that Treaty. The United States Government would welcome any pertinent information the Soviet Government could make available about these events. END QUOTE

Hillenbrand added that both sides no doubt agree that it is in their interests to observe the Limited Test Ban Treaty as rigorously as possible. In this light, it is useful to exchange information when questions arise from either side. To the degree possible, of course, both should seek to avoid explosions which may raise questions, although it is recognized that these sometimes inadvertently and regrettably occur.

Dobrynin said he would pass the U.S. statement to his government and convey any information given to him in response to the U.S. request for any pertinent information.
FYI. As has been practice in past we do not intend to publicize nature of this exchange.


  1. Source: National Archives, RG 59, Central Files 1970–1973, DEF 18–8 US. Confidential; Limdis. It was repeated to AEC. Drafted by Dubs (EUR/SOV); cleared by Davies (EUR) and in PM, SCI, ACDA, and AEC; and approved by Hillenbrand.
  2. This telegram transmitted Dobrynin’s verbal statement criticizing the U.S. for the venting from recent underground nuclear explosions.