The National Academy of Sciences has issued a report concluding that the “main technical concerns raised about the Comprehensive Nuclear Test Ban Treaty (CTBT) … are all manageable.” Technical Issues Related to the Comprehensive Nuclear Test Ban Treaty was written over a two-year period by 11 members of the NAS committee on international security and arms control. The panel of scientists, arms control experts, and former national laboratory and industry executives was chaired by John Holdren of Harvard University. The report concludes that “verification capabilities for the treaty are better than generally supposed, adversaries could not significantly advance their nuclear weapons capabilities through tests below the threshold of detection, and the United States has the technical capabilities to maintain confidence in the safety and reliability of its existing weapons stockpile without periodic tests.” The State Department is currently evaluating the report, which is available at http://www.nap.edu/html/ctbt.
The report was commissioned by the Clinton administration to look at questions that arose when the US Senate refused to ratify the CTBT in October 1999. The US was among the first of 165 nations to sign the 1996 CTBT, which will come into force after ratification by the 44 countries that currently possess either nuclear weapons or nuclear reactors. To date, 31 of these countries have ratified the CTBT, including France, Russia, and the UK. The Bush administration, though, has made clear that it does not intend to push for ratification by the Senate. The current administration views the treaty as unverifiable and as constraining the US’s ability to develop and test new nuclear weapons, especially new low-yield tactical warheads that could destroy hardened targets such as underground bunkers. The Bush administration requested $15.5 million in the 2003 defense budget to analyze options for developing such weapons.
In addition to prohibiting nuclear test explosions in the atmosphere, underground, under the oceans, and in space, the CTBT would establish a network of several hundred monitoring stations using seismological, hydroacoustic, infrasound, and radionuclide sensors to help monitor compliance, and would provide for inspections of suspected test sites. The CTBT would permit R&D and design activities by the nuclear weapons states, but outlaw experiments that produce a nuclear explosion.
The report’s conclusion that the US can maintain the weapons stockpile without nuclear testing differs from the conclusion of the Bush administration’s nuclear posture review. That classified document asserts that the US may have to resume testing to maintain the reliability of its nuclear stockpile and calls for a reduction from years to months in the preparation time needed to resume testing. The US has not performed a nuclear test in 10 years, although it has conducted at least 17 subcritical tests—the most recent in August—which are allowed under the CTBT.
The solution to dealing with age-related defects in weapons, says the NAS report, is rigorous surveillance coupled with the remanufacture of warheads to their original specifications when problems are discovered. In fact, the safety and reliability of the stockpile are better now than when testing ceased, says the report, which calls for revamping the Department of Energy’s manufacturing capabilities and further strengthening evaluations of the warheads. If unforeseen problems should emerge in the stockpile that could not be resolved without nuclear tests, the US would still have the option of withdrawing from the treaty, the report notes.
The network of monitoring stations within the CTBT verification regime is the only system through which the US can confirm “with high confidence in all environments” that no tests with yields above 1–2 kilotons are being conducted anywhere. In some cases of particular potential concern, such as Russia’s Novaya Zemlya test site, even lower yields—down to 10 tons—could be “reliably detected,” according to the report.
The report concedes that highly experienced nuclear weapons states—the US, Russia, the UK, France, and the People’s Republic of China—might be able to use sophisticated masking techniques to hide a blast of 1 or 2 kilotons. But such constrained nuclear testing would not add significantly to the nuclear weapons capabilities those states already possess, the report says. Other nuclear weapons states—notably India and Pakistan—and those aspiring to develop nuclear weapons capabilities, such as Iraq, would not be able to reliably test below the detection threshold without the help of one of the more experienced states, the report says. The results of such tests alone would not be enough to enable such states to develop advanced nuclear weapons, the report adds. But, cautions the report, some types of simple and relatively heavy and inefficient fission weapons could be developed without any nuclear testing at all.
The report concludes that “the worst-case scenario under a no-CTBT regime poses far bigger threats to US security interests—sophisticated nuclear weapons systems in the hands of many more adversaries—than the worst-case scenario of clandestine testing in a CTBT regime, within the constraints posed by the monitoring system.”
The NAS panel was not asked to reach a conclusion as to whether the US should ratify the treaty. “Answering that question requires taking into account a wider array of issues—not just the technical ones we addressed but also military and political issues that were outside our mandate,” says Holdren. “But understanding of the technical issues is certainly an essential ingredient of the informed public and policymaker discussion that must precede a ratification decision, and we hope our report will help provide this.”
