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6.  Sig Hecker, director, Los Alamos National Laboratory,

Letter to Sen. Jon Kyl, September 24, 1997, as entered

into the record of a hearing before the Subcommittee on

International Security, Proliferation, and Federal Services

of the Senate Committee on Governmental Affairs, October

27, 1997 (S. Hrg. 105-267), p. 81.

7.  Vic Reis, assistant secretary, U.S. Department of

Energy, Written responses to questions for the record from

Sen. Thad Cochran, April 1998.

8.

Ibid.

9.  The number of weapons production plants has fallen

from 14 to 8, and the personnel have been reduced from

57,935 in 1990 to 24,384 in 1997.  See Medalia, pp. 7-8.

10. Senator Kyl asked, "What yield of testing would be the

lowest possible to accomplish new designs as well as safe-

ty and reliability?"  Bruce Tarter, director of Lawrence

Livermore National Laboratory, replied, "If we were to

resume testing, the lowest useful test for safety issues

would be a few pounds, and for a reliability test around

500 tons."  Tarter, p. 27.  Sig Hecker, in answer to the

same question, replied, "I believe that most designs could

be tested at yields between 1 and 10 kilotons."  Hecker,

p. 84.

11. An argument could be made that yields even smaller

than 500 tons could be militarily significant in some sce-

narios.  For example, some nations testing a device with

an extremely low yield might be satisfied simply because

they demonstrated that their warhead designs worked.

12. The effects of "decoupling" are well documented.  For

example, the United States conducted two nuclear tests in

the Tatum salt dome located at Chilton, Mississippi.

Sterling, the test conducted on December 3, 1966, had a

yield of 380 tons.  The apparent seismic yield was only

5.3 tons, a reduction by a factor of 71.7.

13. Experts' opinions vary on the size of the largest

explosion that could be easily decoupled.  Ten kilotons is

probably the upper limit.

14. Testing with a few pounds of yield is useful for

ascertaining nuclear weapon safety.  Testing the reliabili-

ty of complex U.S. nuclear designs can be done at subkilo-

ton levels.  However, other nations, such as Russia, may

use different types of designs whose reliability could be