Foreign Relations of the United States, 1969–1976, Volume E–14, Part 2, Documents on Arms Control and Nonproliferation, 1973–1976

181. National Security Decision Memorandum 321¹

Washington, March 11, 1976.

TO

• The Secretary of State
• The Secretary of Defense
• The Director, Arms Control and Disarmament Agency
• The Administrator, Energy Research and Development Administration

SUBJECT

• Instructions for the U.S. Delegation to the PNE Negotiations, Moscow, March 10, 1976

The President has approved the following instructions for the negotiations on underground nuclear explosions for peaceful purposes (PNEs) in Moscow. These instructions supplement those contained in NSDM 297 and NSDM 304.

1. For individual PNE events above 100 KT, observers should be permitted as needed for the purpose of verifying local geology, at the discretion of the side verifying the explosion.

2. The Delegation should take the position that the PNE agreement should have the same five-year duration provision as the Threshold Test Ban Treaty (TTBT), with a provision for renewal for an additional period, and a provision for consultations; the TTBT provides the model to be followed.

3. The Delegation should inform the Soviets that we continue to prefer an aggregate yield limit of 1000 KT for PNE salvos and that the ad referendum agreement on SLIFER emplacement is adequate for verification at that level. However, the Delegation is authorized, at its discretion, to inform the Soviets that if they are unwilling to agree to a 1000 KT limit, we would be willing to consider a somewhat higher limit but only in exchange for improved SLIFER yield determination through the following modified emplacement rule:

a. For individual PNE yields up to 50 KT the canister length, L (in meters), should be limited to a value given by the formula L = 5+W/20, where W is the stated PNE yield in kilotons; and the lower end of the SLIFER sensor should be a constant distance of one meter from the top of the device canister.

b. For individual PNE yields between 50 and 150 KT, the ad referendum agreement is acceptable—e.g., the canister should be limited to a maximum length of 10 meters and the lower end of the SLIFER sensor should be at a distance of 3W1/3 meters from the bottom of the canister.

Should the Soviet Delegation accept the principle of negotiating the modified SLIFER emplacement rule, the Delegation is authorized to accept an aggregate yield limit higher than 1000 KT but not exceeding 1500 KT for PNE salvos.

4. The Delegation is also authorized to propose a 500 KT threshold for deployment of an on-site seismometer network.

5. The Delegation should take the position that the U.S. will not submit the TTBT for ratification until a satisfactory PNE agreement is concluded. If this is not achieved by March 31, 1976 the U.S. cannot put the TTBT into effect; the Delegation is authorized to discuss how the two sides might proceed as of March 31, but without committing the U.S. to a suspension of weapons tests above 150 KT unless instructions are received from Washington.

6. The Delegation should proceed to complete the PNE negotiations as soon as possible, but without considering March 31, 1976 as a deadline.

Brent Scowcroft

1. Summary: Scowcroft communicated President Ford’s approval of a set of instructions for the U.S. delegation to the sixth round of PNE negotiations in Moscow.

   Source: Ford Library, National Security Council, Institutional Files—NSDMs, Box 69, Originals—NSDM 316 to NSDM 330. Secret. Copies were sent to Brown and Bush. NSDM 297 is Document 150; NSDM 304 is Document 161. The sixth round of negotiations began on January 27 and ended on April 8. See Document 192.