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05/21/93

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Los Alamos scientists plan waste cleanup experiments at SLAC

STANFORD -- Researchers soon will begin using intense beams of X-rays generated by the Stanford Linear Accelerator Center (SLAC) to seek ways of cleaning up the nation's nuclear wastes.

Experiments to be performed at SLAC this summer by scientists from the Los Alamos National Laboratory in New Mexico should provide a deeper understanding of how the radioactive elements neptunium and plutonium can be extracted from nuclear wastes and safely stored for extended periods of time. Such information will be crucial in the massive cleanup efforts being coordinated by the U.S. Department of Energy, which funds both laboratories.

Led by Dr. Steven Conradson, the Los Alamos group will direct X- ray beams onto small experimental samples containing tiny amounts of neptunium and plutonium. Analysis of the way these elements absorb X- rays provides detailed information about how their atoms are bound in complex molecules or dissolve in solutions. This information will aid in developing improved techniques to extract these elements from nuclear wastes and to minimize the risks involved in storing them.

The specialized X-ray beams that allow these experiments to be performed with very small samples are available at only a few facilities around the world - including the Stanford Synchrotron Radiation Laboratory (SSRL) at SLAC. Generated by high-energy electrons that circulate in a particle accelerator called a storage ring, they can be supplied at a wide range of energies and intensities.

"We are anxious to provide whatever help we can offer in alleviating the serious nuclear waste disposal problems of this country," said SLAC Associate Director Arthur Bienenstock, head of the SSRL Division.

"There are many tons of plutonium already in existence, much of it in nuclear weapons that we will soon have to decommission," noted Conradson. "We need to develop better and safer ways to process, treat and store this material." The experiments he plans, which are unclassified and will be published openly, should help scientists and engineers better understand how this element behaves in the company of other elements and compounds.

The experiments on neptunium will help scientists to understand how it behaves in soils and groundwater. This information should allow engineers to design more effective containment systems and strategies.

Only tiny amounts of plutonium and neptunium, less than one- hundredth of an ounce, will be brought to SLAC and used in these experiments, Conradson said. The total amount of plutonium to be brought on site weighs substantially less than a common paper clip.

After the experiments are completed, all radioactive materials will be returned immediately to Los Alamos; they will be at SLAC for less than a month.

The SLAC management has required that a stringent set of safety measures be followed by the Los Alamos researchers in the handling of these elements and during their experiments. A detailed, comprehensive safety plan, whose goal is to prevent any possible release of radioactive material, has been reviewed and approved at both laboratories by safety committees that included outside experts.

Safeguards include three containment walls isolating the radioactive material from the environment at all times, as well as storage in fireproof, impact-proof containers. Personnel experienced in handling this material will be present at all times during the experiment. These and other measures are designed to prevent the release of any radioactive substance to the environment- even in the event of an earthquake or fire.

"Our safety review has convinced me that with these precautions, this experiment poses no significant hazards for our employees and the general public," Bienenstock said.

SLAC is a national laboratory operated by Stanford University under contract with the Department of Energy, which has approved the experimental plans.

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