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147. Letter From the Acting Administrator of the Energy Research and Development Administration (Fri) to the President’s Assistant for National Security Affairs (Brzezinski)1

Dear Dr. Brzezinski:

Subject: Accommodating PNEs Under a Weapon Test Ban

This is to confirm ERDA’s position on identifying the dangers to national security of a comprehensive test ban which accommodates PNEs. The original request to Heads of Agencies in PRM–162 included a preliminary review of the major problems of verifying a complete ban on all testing; weapons, as well as peaceful nuclear explosions. Since that time, the possibility of accommodating Soviet interest in using PNEs in the Pechora-Kama River Project has become a factor in the PRM–16 test ban review.

It has been established in technical reviews within ERDA and its weapon design laboratories that there is no known way to prevent the Soviet Union from gaining military benefits from a comprehensive test ban through low yield clandestine testing if a PNE accommodation is permitted. In addition, it will increase significantly both the opportunities and the yield ranges available for the Soviet Union to exploit for military advantage. Even under the situation of maximum use of U.S. nuclear explosives for PNEs in the Soviet Union, it would still be possible under a CTB for the Soviets to mask their own weapon tests as collateral explosions which would not necessarily be detected and identified.

As presently described, the Pechora-Kama Project is estimated to require 5–10 years for completion. In analyses conducted by the Lawrence Livermore Laboratory prior to the PNET, it was estimated that 250 to 300 separate explosions with salvo yields up to 3 megatons would be required. Bilateral treaty constraints on individual explosions to 150 kt and 1500 kt for salvo yield in accordance with the PNET would increase the numbers significantly, providing ample opportunity for Soviet weapon testing and technology acquisition under the guise of PNE.

In the past, the Soviets have made it clear that they are interested in a comprehensive test ban which accommodates PNEs. They have [Page 344]stated in recent exchanges that they view the PNET as a basis for establishing a PNE accommodation under a CTB. The PNET threshold is tied directly to the 150 kt limit of the threshold test ban, with the understanding that the PNET threshold will be reduced with any reductions in the TTBT limit and that PNEs will not be allowed under a CTB. It is essential that this view of TTBT and PNET relationships be maintained.

It should be anticipated that the Soviets could continue to endorse a general PNE accommodation. Under this condition, which involves both low fission, relatively clean nuclear devices used for excavation and fission devices for contained explosions, the Soviets could have access to the full spectrum of weapon design and effects otherwise banned in a CTB. Under conditions of general accommodation of PNEs, it becomes even more difficult to deny military benefits.

ERDA strongly recommends that any accommodation of PNEs under a comprehensive test ban be thoroughly analyzed for its adverse impact on the treaty, our ability to verify that military benefits are not being obtained from PNEs, and the relative impacts on U.S. and Soviet national security.


Robert W. Fri 3 Acting Administrator
  1. Source: Library of Congress, Manuscript Division, Harold Brown Papers, Box 82, Comprehensive Test Ban Treaty 1977. Secret. Copies were sent to Harold Brown, Vance, George Brown, Sloss, and Turner.
  2. See Document 141.
  3. Printed from a copy that indicates Fri signed the original.