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  • Dan is a deputy news editor for Science.
 

No Technical Reason to Avoid a Test Ban, NRC Panel Says

30 March 2012 6:04 pm
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The United States' nuclear deterrent will remain safe and reliable without nuclear testing as long as the government keeps its weapons up to date with the so-called Stockpile Stewardship Program and fosters a scientific workforce capable of running the SSP, says a report from the U.S. National Academies released today. The report investigated technical issues surrounding the Comprehensive Nuclear-Test-Ban Treaty (CTBT) and also concluded that the treaty's monitoring system, along with America's own intelligence resources, have made huge strides in recent years in their ability to detect clandestine tests that could pose a military threat to the United States. The CTBT Organization's International Monitoring System (IMS) "has created a capability so that any potential tester would have to be concerned about being detected," says Ellen D. Williams, committee chair and chief scientist of the oil company BP.

President Barack Obama said in a speech in Prague in the first months of his presidency that his Administration would aggressively pursue U.S. ratification of the CTBT. The CTBT was created in 1996 and has now been signed by 182 nations, of which 157 have ratified it. But the treaty only comes into full force when all 44 countries that had either nuclear weapons or reactors in 1996 have ratified it. Eight of those--including the United States--still have not done so.

The U.S. Senate debated the treaty in 1999 but failed to endorse it. Opponents argued that the U.S. nuclear stockpile might grow unreliable if it could not be tested; they also warned that verification technology wasn't strong enough to ensure that other countries were not cheating and carrying out secret tests. If others continued developing and testing new weapons while the United States honored the ban, CTBT opponents said, the U.S. would be at a military disadvantage.

The White House commissioned the National Academies in 2009 to review a 2002 study on this topic and investigate whether technical capabilities have changed over the past decade in a way that might influence the debate over ratification. Williams said at a briefing at the National Academies today that the SSP was still quite young in 2002, and since then there has been enormous progress. "They've overhauled and refurbished two complete weapon classes," she says. Part of the program involves understanding the physics and chemistry of the materials that make up the weapons and understanding how they decay and degrade. In some cases, replacement parts can be manufactured. "We understand these weapons today even better than we did while testing," committee member Marvin Adams, a nuclear engineer at Texas A&M University in College Station, said at the briefing. "We've done it. We've reset the clock on these weapons."

A large part of the program also involves developing computer simulations of the action of nuclear explosives. To test the validity of the simulations, national laboratories have built facilities that can reproduce parts of a nuclear explosion without creating an actual blast. These facilities include the National Ignition Facility at Lawrence Livermore National Laboratory, the Microsystems and Engineering Sciences Applications facility (MESA) at Sandia National Laboratories, and Dual-Axis Radiographic Hydrodynamic Test Facility (DARHT) at Los Alamos National Laboratory. "It's very crucial for researchers to establish a close coupling between [these facilities] and scientific computing so that they can test and stress the computer codes essential to the health of the program," Williams says.

The committee's main concern was about the government's future commitment to this program and its workforce. "The technical ability to maintain the stockpile exists; our concern is about the political will to maintain those capabilities," Williams says. Committee member Lynn Sykes of the Lamont-Doherty Earth Observatory at Columbia University says, "There's one golden bullet: a high quality workforce. I can't stress that too strongly."

The committee also saw improvements in verification through CTBT Organization's IMS, which was in its infancy in 2002. The IMS plan is to build a network of 337 monitoring stations across the entire globe-from Spitsbergen to Antarctica. The network, about 80% complete now, is made up of seismic stations to detect underground tests, radionuclide detectors to sniff out radioactive fission products in the air, and hydrophones and infrasound detectors to listen for acoustic signals in the oceans and atmosphere. Some techniques in use now weren't even considered in 2002, including sensing radioactive xenon gas and a regional seismology method that detects shock waves traveling along shallow paths through Earth's crust and upper mantle.

The committee did not take a position on whether the United States should ratify the CTBT, but it said the IMS is an important tool. "The technical capability of the IMS is extremely valuable for our ability to monitor tests, and we should support that going forward," Williams says. The committee was confident that the IMS could detect any test of 1 kiloton or greater; much smaller explosions are detectable in some parts of the world. Surreptitious tests small enough to be concealed would only be useful for making weapons of the type that the U.S. already has in its armory. "Advances achieved by evasive testing would not require the U.S. to resume testing to counter them," Williams said at the briefing.

Developing a new, threatening type of strategic weapon, the committee asserts, would require tests large enough to be easily detectable. In that eventuality, the United States could invoke the CTBT's get-out clause: Signatories can withdraw from the treaty in situations of "supreme national interest." And the United States could then quickly develop a deterrent weapon of its own, assuming it has maintained the workforce and technical expertise to do so.

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