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Simulating Nuclear Explosions under the Comprehensive Test Ban Treaty

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While the April-May 1995 Nonproliferation Treaty Review Conference decided to extend the treaty indefinitely and without conditions, many delegations from non-nuclear weapon states expressed strong skepticism that the United States and other nuclear weapon states would ever take seriously their obligations under Article VI of the treaty to pursue negotiations "in good faith" on nuclear disarmament. For example, in support of this skepticism, Minister Mohamed Hacène Echarif of Algeria reportedly stated:

Although the efforts within the Conference on Disarmament to conclude a comprehensive nuclear-test-ban-treaty were commendable, the new treaty would prohibit only the use of explosions to test nuclear weapons, and not their improvement or the development of new types of weapons not requiring such testing. It seemed that "good faith" was lacking in an approach designed to prevent new nuclear states from emerging, but [which] did not prohibit current nuclear Powers from preserving and improving their nuclear capability. [24]

A member of the Indonesian delegation noted during the review of Article VI that "in order to retain the technological edge in military systems, one major nuclear weapon state had embarked upon a more sophisticated programme to refine its nuclear-weapons design using state-of-the-art technology."

His delegation was "very much concerned about that discouraging development, as it could trigger a renewed nuclear arms race among nuclear-weapon states. [25]

As the Conference on Disarmament in Geneva was laboring to complete negotiations on the CTBT in 1996, ACDA Director John Holum sought to assuage such concerns by describing the limitations on nuclear weapons design and development activities that the U.S. government would be constrained to observe under a "zero yield" CTBT:

Consider the extent of that limitation. It is true that the CTBT is not a back-door way to ban nuclear weapons….But the safe maintenance of existing weapons designs is a far cry from the confident development of new ones. The latter requires nuclear explosive tests, which the CTBT would preclude (emphasis added).

. . . . So let there be no mistake -- the CTBT will help impede the spread of nuclear weapons. But its great practical impact will also be for arms control -- to end development of advanced new weapons and keep new military applications from emerging (emphasis added).

This basic reality also lays to rest the claim that the CTBT will somehow help codify a discriminatory regime, dividing the world betwen nuclear "haves" and "have nots." In truth, it is and will remain possible to make simple nuclear weapons without nuclear explosive testing. So the CTB's' fundamental effect is less to preclude the acquisition of nuclear weapons as such, which the NPT [Nuclear Nonproliferation Treaty] addresses, than to constrain the advancement of nuclear weapons capabilities by any country (underscoring in original). [26]

Leaving aside the difficulty of verifying such constraints [on non-explosive experiments and simulations involving nuclear warheads], the United States has made clear that steps to maintain the safety and reliability of remaining weapons, not involving nuclear explosions, must continue. But we have also made it crystal clear, as long ago as President Clinton's message to this Conference in January 1994, that this Treaty will stop new generations of nuclear weapons as well as constraining [sic] the spread of nuclear explosive capabilities to other states.

This is sometimes referred to as halting both vertical and horizontal proliferation. Let me repeat: United States stockpile stewardship activities will not give us the means in the absence of nuclear testing to frustrate the comprehensive test ban, to discover technological alternatives, or to build new types of nuclear weapons. [27]

Some of the planned or already ongoing initiatives within the SSM Program are at variance with these statements and assurances. For example, while a ban on nuclear explosive tests would have the effect, over the next decade at least, of preventing "[full scale engineering] development of advanced new weapons," -- a bomb-pumped x-ray laser, for example -- that the U.S. has already elected not to pursue in any case, the current test moratorium has not served -- as in the case of the B61-Mod 11 earth-penetrating bomb -- to "keep new [U.S.] military applications from emerging."

Moreover, under the policies and programs clearly laid out in the DOE's 1996 SSM Program Plan, which have not changed substantially over the past year, the United States government will expend tens of billions of dollars over the next decade precisely for the purpose of "advancing its nuclear weapons capabilities" under a CTBT, even if no nuclear weapons of new design are actually produced for the stockpile. In fact, as documented in section III of this report, the U.S. is currently working on new warhead designs to replace the current W76 and W88 SLBM warheads by the middle of the next decade.

As the CTB negotiations entered a final stage in late July, 1996, perhaps the most definitive assurance regarding SSMP activities was provided during a press briefing by Robert Bell, Senior Director of Defense Policy and Arms Control at the National Security Council, on the occasion of DOE's announcement of contracts to acquire new supercomputers for its nuclear weapons laboratories:

Q: She [Israel] has never announced that she has a nuclear stockpile or anything else. And we've never acknowledged it, in deference to Israel.

MR. BELL: Well, the objective of the treaty is to stop the proliferation of nuclear weapons, both horizontally and vertically, in terms of improvements by the declared states. So there are a number of states that are required for entering the [into] force of this treaty and, as I said, Israel is on that list.

Q: Just to kind of complete the loop here, is the idea then, of announcing this [supercomputing contract] at this particular point to say, okay, come on board, because now the technology exists that you can actually simulate weapons without testing them? Is that one of the -

MR. BELL: Well, let me be very clear. We addressed this here on August 11th, when the President announced the zero yield decision. But the purpose of the U.S. Stockpile Stewardship program is to allow us to maintain the safety and the reliability of our existing stockpile, absent nuclear testing. We are not seeking through our technology to acquire the means to frustrate the CTB or to find technological alternatives to build new weapons types, absent testing. We accept that the effect of the treaty will be to rule out opportunities to create new weapon types, absent nuclear testing. In other words, it will halt the vertical proliferation of nuclear weaponry.[28]

But as a careful reading of DOE and DOD program plans reveal, the United States is spending billions of dollars on new experimental and computer modeling capabilities specifically to offset the loss of data formerly gained through nuclear testing. Indeed, an explicit goal of the program is to replace nuclear testing, to the maximum extent achievable by modern technology, with a combination of advanced nuclear and non-nuclear experimental capabilities and three-dimensional computer simulations based on a comprehensive, accurate "first principles" understanding of the underlying physics. The intent is to free nuclear weapon designers from their historical reliance on empirical "fudge" factors, derived from adjusting (calibrating) nuclear code predictions in order to match the results of past underground tests.

The current program is premised on the expectation that, with major public investment in new facilities and experiments, and with significant scientific and technical assistance from the academic community and the computer industry, the U.S. government will be able within a 10-15 year period to develop a capability to certify without explosive testing at least some types of new weapon designs for entry into the U.S. nuclear weapons stockpile, particularly those with nuclear performance characteristics that lie within or close to the design parameters established by previous nuclear test experience.


24. Final Document, Part III, Summary and Verbatim Records, NPT CONF.1995/32, New York, 1996, p. 267.

25. Final Document, Part III, p. 274.

26. Statement by The Honorable John D. Holum, Director, U.S. Arms Control and Disarmament Agency (ACDA), to the Conference on Disarmament, Geneva, January 23, 1996 (as delivered), p. 2 - 3.

27. Arms Control Text, The Honorable John D. Holum, Director, U.S. ACDA, Statement to the Conference on Disarmament, Geneva, Switzerland (as delivered), August 1, 1996, p. 2-3.

28. Press Briefing by Robert Bell, Senior Director of Deense Policy and Arms Control at the National Security Council, The White House, Office of the Press Secretary, July 26, 1996, p. 4 (emphasis added).

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