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

192. Telegram 95986 From the Department of State to the Mission in Geneva and the Mission to the North Atlantic Treaty Organization¹

Washington, April 21, 1976, 0118Z.

95986. Subject: PNE Treaty.

1. For USNATO. Text of briefing paper on PNE treaty, protocol, and agreed statement is given below beginning para 3. Briefing paper should be circulated ASAP under cover of letter from U.S. Rep together with suggestion that any questions about paper could be raised at next NAC meeting.

2. For Geneva. U.S. Rep to CCD may draw on briefing paper to brief Western group (NATO allies and Japan) on classified basis.

3. United States and Soviet negotiators have completed an ad referendum text of an agreement governing underground nuclear explosions for peaceful purposes (PNEs). This agreement was mandated by the treaty on the limitation of underground nuclear weapon tests (the “Threshold” Test Ban Treaty, or TTBT) signed on July 3, 1974. The ad referendum text has been submitted to the respective governments for final approval before signature.

4. As negotiated, the agreement consists of a treaty, a protocol to the treaty, and an agreed statement which delineates certain important activities that are not contemplated by the term “peaceful application,” as used in the treaty.

5. The provisions of these three documents fully complement the provisions of the TTBT and thereby establish a comprehensive system of provisions governing underground nuclear explosions of the U.S. and the USSR. The TTBT will govern explosions at specified weapon test sites, and all such explosions are considered to be nuclear weapon tests. The PNE treaty governs all other underground nuclear explosions, which are permitted only for peaceful purposes, wherever conducted outside the weapon test sites.

6. The PNE treaty limits the yield of individual explosions to 150 kilotons. By specifying the same threshold as the TTBT, the PNE treaty recognizes the fact that it has not been possible to distinguish between nuclear explosive device technology as applied for weapons-related purposes and for peaceful purposes. The parties devoted considerable effort to an investigation of whether it would be possible to accommodate individual explosions with yields greater than 150 kilotons under the treaty, consistent with the agreed aim that weapons-related benefits precluded by the TTBT should not be derived from PNEs. The yield threshold for individual explosions is a recognition that no means of making such an accommodation has been discovered.

7. The treaty defines a category of explosions called “group” explosions; a group consists of several individual explosions in sufficiently close proximity in distance and time that teleseismic means cannot reliably distinguish and measure the yields of the individual explosions in the group. The aggregate yield of a group cannot exceed 1500 kilotons, and, of course, the yield of each individual explosion in the group must not exceed 150 kilotons.

8. For any group explosion whose planned aggregate yield exceeds 150 kilotons, in order to ensure that no individual explosion has a yield exceeding 150 kilotons, the treaty provides that observers of the verifying side will be permitted on-site, where they will have the unqualified right to measure the yield of each individual explosion in the group by means of electrical equipment that measures the velocity of propagation of the shock wave in the close vicinity of the explosion. Thus the PNE treaty introduces a singular breakthrough in arms control: For the first time the USSR has agreed to provisions allowing on-site observation on their own territory.

9. When the planned yield of a group explosion is between 500 and 1500 kilotons, the observers will in addition have the unqualified right to deploy a network of seismometers at the site to assist in detecting any undeclared explosion that might be detonated under the cover of the PNE. For explosions having yields between 100 and 150 kilotons, observers will be present if the need for their presence is mutually agreed to between the parties on the basis of available information. Under these circumstances, their functions will be to confirm geological and other information in order to assist in the teleseismic determination of the yield of the explosion. Observers will also confirm the geological and other information provided by the party carrying out the explosion at higher aggregate yields.

10. This scaling of functions with the aggregate yield of an explosion provides a level of verification proportional to the possibility of evasion of the 150 kiloton limit on the yield of the individual explosion, as well as a basic capability at all yields to confirm that the circumstances of the explosion are consistent with the stated peaceful purposes. For example, the possibility of a clandestinely emplaced explosive detonated under the cover of a group explosion with an aggregate yield of 500–1500 kilotons is greater than if the PNE is at a lower yield, and therefore, as noted above, a local network of seismometers is provided for to help confirm the absence of such explosion.

11. Below 100 kilotons, the PNE treaty makes no provision for observers, and verification will be on the basis of national technical means supplemented by detailed data supplied to the verifying side by the party carrying out the explosion. National technical means, assisted by such data, will provide adequate assurance that individual explosions having yields greater than 150 kilotons are not being conducted.

12. There are a number of other important features of the PNE treaty, including the following:

(A) For any PNE, regardless of yield, information is to be provided about the purpose, location, date, planned yield, depth of burial, geology, number of explosives and their relative locations, and about the specific features of the project which could influence the determination of the yield beforehand; and the results of the explosion must be provided afterwards. More extensive information provisions are established for explosions of higher yields;

(B) Any underground nuclear explosion for peaceful purposes must be carried out in a manner fully consistent with existing treaty obligations, in particular with the provisions of the Limited Test Ban Treaty, which prohibit underground nuclear explosions that cause radioactive debris to be present outside the boundaries of the state in which the explosion was carried out;

(C) A joint consultative commission is to be established to “promote the objectives and implementation of the provisions” of the agreement; it will provide a consultation forum where, for example, technical issues may be discussed;

(D) Consideration of the question of carrying out individual explosions with yields greater than 150 kilotons is expressly deferred to an unspecified future time. It should be emphasized that the PNE treaty (as noted above) prohibits such explosions and would require amendment to provide for them;

(E) The inseparability of the TTBT and the PNE treaty is further recognized by making identical the duration of five years for both agreements, and by the provision that neither party may withdraw from the PNE treaty while the TTBT remains in force;

(F) The treaty will govern all underground nuclear explosions for peaceful purposes that might be carried out by either the U.S. or the USSR not only on their own territories but also, consistent with Article V of the Non-Proliferation Treaty, on the territories of third countries in the future;

(G) The treaty provides for the development of mutually beneficial cooperation in various areas related to PNEs, although no specific form of such cooperation has either been discussed or agreed upon;

(H) Both parties have pledged to continue to fulfill their obligations under Article V of the NPT, to assist the IAEA with regard to the international agreements and procedures referred to in this article, and to keep the IAEA informed of the results of any cooperative efforts that they develop.

13. The agreed statement specifies that a “peaceful application” of an underground nuclear explosion does not include the development testing of nuclear explosives. Nor would associating test facilities, instrumentation or procedures with any explosion carried out under the treaty constitute a “peaceful application.”

Robinson

1. Summary: The Department transmitted the text of a briefing paper on the PNE treaty, protocol, and agreed statement, noting that the three documents “establish a comprehensive system of provisions governing underground nuclear explosions of the U.S. and the USSR.”

   Source: National Archives, RG 59, Central Foreign Policy File, D760150–0160. Secret; Priority. Drafted by Corden and Givan; cleared by Sloss, Marcum, Robert Martin, John Hawes (EUR/RPM), Kelly, and Jerome Hoganson (S/S); approved by Davies. Repeated for information to Moscow.