In September 1996, when President Clinton signed the "zero-yield" comprehensive test ban-a treaty outlawing all nuclear explosions-he managed to win over the treaty's strongest opponents. But this support did not come for free. The Pentagon, the Joint Chiefs of Staff, and the weapons labs conditioned their approval of a test ban on a number of "safeguards." As part of the agreement, Clinton declared that if ever a high level of confidence in a certain type of nuclear weapon could no longer be certified, he would be prepared to invoke the supreme national interest clause under the test ban and conduct whatever nuclear testing may be required. "Exercising this right, however, is a decision I believe I or any future president will not have to make," Clinton's official statement read. His optimism may have been connected with another condition imposed by the military and the labs: full funding for the Department of Energy's Stockpile Stewardship and Management Program "over the next decade and beyond." The program is slated to receive about $40 billion over the next 10 years.

The stewardship program is supposed to help maintain the safety, reliability, and performance of the nuclear arsenal so that no U.S. president has to resume nuclear testing. It would achieve this goal by keeping three separate nuclear weapons laboratories in operation-Los Alamos and Sandia in New Mexico, and Lawrence Livermore in California-and by spending $3 billion to build a variety of new experimental facilities to simulate different aspects of a nuclear explosion. Some facilities would address the primary stage of a warhead and some the secondary stage (in thermonuclear weapons, a primary, or fission, stage produces x-rays to implode the secondary, which releases energy through fusion); other facilities would simulate the effects of nuclear explosions on military hardware. About a third of this funding would be spent on new supercomputers to make the most use of the new facilities and to tie the three labs together into one "superlab."