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

76. Aide-Mémoire From the Department of State to the Soviet Embassy¹

Washington, May 18, 1965.

The United States Government has carefully considered the Soviet Government’s Aide-Mémoire of April 29, 1965,² concerning the April 14, 1965, experiment conducted by the United States Atomic Energy Commission as part of a program for developing peaceful uses of nuclear explosions.³

In planning the experiment of April 14, the United States took numerous precautions to avoid violation of the Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and Underwater. In fact, the purpose of the experiment was to obtain data on a method to enhance the containment of radioactive debris from underground nuclear excavation explosions.

The explosion had a yield of about four kilotons and was buried at a depth of 280 feet in hard rock. The depth was specifically chosen to be the same, scaled for the size of the explosion, as a previous test which did not produce a crater. As in the case of the previous test, the experiment was permitted to take place only under meteorological conditions carefully chosen to avoid the escape of radioactive debris from the territory of the United States.

As has been announced, the experiment did produce a crater and small amounts of radioactive debris were projected into the atmosphere. Most of this debris was deposited in the vicinity of the site of the experiment. In accordance with meteorological predictions, the small quantity of radioactive debris which went further was blown northward within the United States for several hundred miles from the Nevada test site and then southeastward over the central United States. During this time, the airborne concentrations of radioactive debris were determined by measurement to have been diluted by fallout, radioactive decay, and dispersion to extremely low levels.

The United States Government will continue to take the greatest care in the conduct of nuclear detonations including its program for peaceful uses of nuclear explosions. The United States Government affirms its commitment to the preservation of the Treaty with unimpaired authority.

In this connection the Government of the United States believes it necessary to revert to consideration of a very much larger nuclear explosion conducted in the Soviet Union on January 15, 1965,⁴ seemingly directed at a similar application as that of the United States on April 14, 1965, but which resulted in many times as much radioactive debris being released to the atmosphere.

The United States Government has studied Ambassador Dobrynin’s oral statements of January 25⁵ and March 9, 1965,⁶ and has examined all other available data on the Soviet underground nuclear explosion. As was pointed out in the United States Government’s Aide-Mémoire of February 15, 1965,⁷ radioactive debris from that Soviet explosion was detected on the ground by the Radioactivity Countermeasures Headquarters of the Government of Japan in concentration from as much as 10 to 100 times the levels on previous days.

If the Soviet Government were more forthcoming in response to the request of the United States Government for further information concerning the January 15 Soviet test, the United States Government might be better able to conclude that there was no intention on the part of the Soviet Government to violate the terms of the Treaty. A nuclear explosion such as that of January 15, which causes such large amounts of radioactive debris to be present outside the borders of the USSR, causes grave concern. Repetition of such a release of debris outside the borders of the USSR as occurred after January 15 could jeopardize the very existence of the Treaty, a consequence which the United States would view as extremely serious. The United States Government considers the maintenance of the obligations of this Treaty to be of utmost importance and trusts that the Soviet Government will take every precaution to ensure that the Treaty will be observed.

1. Source: Department of State,S/AL Files: Lot 67 D 2. No classification marking. Drafted by Thompson. The draft memorandum was considered at the meeting of the Committee of Principals on May 13; for a brief summary of the meeting, see Seaborg, Journal, Vol. 10, p. 478. A May 14 memorandum from Foster to the members of the committee transmitting the final version stated that it would be delivered to Ambassador Dobrynin at an early date. (Washington National Records Center, RG 330, OSD Files: Lot 70 A 1266, 388.3 (2 Feb. 65) May-June 1965)
2. Document 75.
3. See footnote 2, Document 75.
4. Regarding this Soviet test, see Document 62.
5. Document 66.
6. Ambassador Dobrynin’s oral statement of March 9, 1965, has not been found.
7. Not found, but see the draft aide-mémoire of February 9, attached to Document 70.