TNAG-0836-FCO40-1044-Comprehensive-Test-Ban-Treaty-national-seismic-stations-on-U-1979 — Page 56

CONFIDENTIAL

discrepancy and in principle enable the nature of all detected events to be identified.

7.

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In

Such an improvement in technical capability is far less important for a 3 year treaty than for a test ban of longer duration. The full network of 10 NSS would not become operational until 2 years after entry into force. any case, if the Soviet Union decided to cheat it would be imprudent for them to do so at yield levels above the detection capability of the improved AEDS. By testing up to this level, the Russians would be able to develop new sub-kiloton tactical weapons and might be able to develop new kiloton fission tactical weapons. But they would be unable to develop new thermonuclear weapons for either tactical or strategic purposes. While a continuing development programme for such weapons must seem desirable to the Soviet defence authorities, they would probably schedule the nuclear tests before and after, but not during, a 3 year ban.

8.

However, the longer the test ban lasts, the greater may be the temptation for the Soviet Union to carry out clandestine nuclear tests; and the more serious the consequences for the West if the Russians alone were able to increase their weapons design knowledge and conduct tests for stockpile maintenance purposes. Therefore the longer the test ban, the more important the verification role of NSS: and the more desirable will become the reduction of the seismic detection level as far as possible by installing a more extensive NSS network (with arrays replacing single borehole stations at a number of locations).

9.

There is nevertheless advantage in securing agreement on NSS of the necessary quality, rather than hoping to do so after 3 years when there might be pressures for extension on the basis of current arrangements irrespective of their suitability for a longer-lasting test ban. It will also be an advantage to have some experience of operating NSS in the

ourselves first 3 years, before committing analyses to a longer test ban.

B:: POLITICAL

10.

There is a relatively strong political case for NSS in a 3 year treaty:

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(a) the West has often expressed its unwillingness to rely on national technical means (NTM) alone and the installation of NSS in the Soviet Union would be a breakthrough in the verification of a CTB;

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