(GDR) Pushing Limits at Lab? Weapons test plan sparks BNL
Date: 9/4/00 11:52:07 AM Pacific Daylight Time
Pushing Limits at Lab? Weapons test plan sparks BNL debate
by Earl Lane
Washington - As part of an effort to ensure the reliability of the nation's nuclear arsenal, weapons scientists want to use a particle accelerator at Brookhaven National Laboratory to help develop better ways to "photograph" small-scale implosions that mimic the triggering of a nuclear warhead.
Los Alamos National Laboratory in New Mexico is expected to submit a proposal to use Brookhaven facilities for the studies, which some senior Brookhaven scientists have questioned as going beyond the lab's traditional mission of open, non-weapons-related research.
John Marburger, Brookhaven's director, stressed yesterday that Brookhaven is not a weapons lab, but said it has no bar against doing work related to national security, including classified research.
"If this lab has a technology that is valuable for another federal mission, then, in general, it is reasonable to expect that we would make that technology available," Marburger said.
Since 1996, Brookhaven has allowed Los Alamos researchers to use a proton beam from the lab's Alternating Gradient Synchrotron to do static tests on a variety of classified and non-classified metallic objects. The proton beam can be used like an X-ray to reveal density, structure and composition of stationary materials.
Such proton radiography, as it is called, also can be used to create a "movie" of how materials change under the impact of a shock wave from an explosive detonation.
The Los Alamos researchers have done more than 50 such dynamic tests, as they are called, with a less powerful proton beam at their home laboratory. The Brookhaven beam-about 30 times more powerful -allows studies of thicker objects at fine resolution. So the scientists are eager to use the Brookhaven beam for the first time in dynamic tests involving small-scale explosions in a chamber.
No nuclear materials would be involved.
The ultimate goal is to develop technology that could be adapted to a next-generation test facility at Los Alamos, perhaps using protons rather than conventional X-rays, to obtain high-resolution pictures of imploding mock warheads in which the nuclear material has been replaced by surrogates.
In a warhead, conventional explosives surrounding a nuclear trigger create a spherical shock wave that compresses the material to such density that a runaway chain reaction creates a nuclear explosion.
Marburger said proton radiography also has applications in non-weapons fields such as metallurgy. But the prospect of more active tests at Brookhaven involving small amounts of explosive for the first time has prompted some internal debate at the lab. On Friday, about 100 people attended a departmental seminar on the proposed tests at which several Brookhaven scientists spoke against them.
"I think there are issues about doing this kind of research at Brookhaven, and I wanted to raise them," said Alan Carroll, an accelerator specialist at Brookhaven who gave a presentation at the seminar. He declined to elaborate.
A senior Brookhaven physicist who asked not to be named said: "Los Alamos would say this is guaranteeing the stockpile. The line between guaranteeing the stockpile and actually developing triggers [for nuclear warheads] is a fuzzy one. From our point of view, this is not appropriate for the lab." "No one is proposing to make Brookhaven a weapons lab," said Alessandro Ruggiero, a Brookhaven accelerator physicist who is not involved with the Los Alamos-sponsored effort. He worked on a competing proposal with a team at the Lawrence Livermore National Laboratory in California. The team wanted to build a small proton accelerator at the Department of Energy's Nevada test site to do the same sort of dynamic tests being considered for Brookhaven.
Ruggiero said proton radiography is a promising method for assessing the safety and reliability of warheads in the absence of periodic underground tests. The United States has adhered to a self-imposed moratorium on such tests since 1992.
The decision on whether to proceed with the Brookhaven tests is months away. John McClelland, deputy director of the physics division at Los Alamos, said no formal proposal has been made and no funding set aside. Any proposal would include evaluation of any environmental hazards, he said. The dynamic tests done at Los Alamos typically involve less than two pounds of explosive.
McClelland said the containment vessels for the possible Brookhaven tests are designed to hold up to 40 pounds of high explosives. "We have experience with these vessels," McClelland said. "We know they are safe." Brookhaven has been criticized by local residents for past environmental problems and, more recently, a leak of radioactive tritium. Scott Cullen, an attorney with STAR (Standing for Truth About Radiation), a local environmental group, said, "They should be careful to involve the community and get people's thoughts on [the tests] before they do it."