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Physics of High and Low Level Waste Management Explored

Published June 1, 1996

Public policy issues and concern over the management of disposal of high and low level radioactive waste were the featured topics at a Monday afternoon session on physical methods of waste management, sponsored by the APS Forum on Industrial and Applied Physics. Related physics and chemistry issues under discussion included criticality, plutonium loading in glass, leach rates, and diffusion, while public policy issues center on non-proliferation, states' rights, stakeholder participation, and nuclear power.

John Ahearne, a lecturer at Duke University and adjunct scholar for Resources for the Future, defines high level waste as used fuel from nuclear reactors and the most hazardous wastes from manufacturing nuclear weapons. Low level wastes include items such as contaminated rags, clothing, and tools from nuclear plants, hypodermic needles, and other medical wastes.

Most of these low level wastes cannot be safely incinerated without producing harmful toxins, and thus are sent to storage sites throughout the country. However, existing sites are rapidly reaching capacity, and no new waste site has been developed because of public opposition. Compaction can further reduce waste volume by as much as 75 percent, and Ahearne favors an omnibus regulation that would allow material below a certain level to be disposed of as regular waste.

A much bigger challenge is what to do about the growing stockpile of high level nuclear waste, according to Ahearne. Currently, such waste is stored on-site in pools of water, in which the water absorbs the radiation from the fuel and also cools it. The preferred option is dry storage, in which the fuel is placed in large casks, which are then placed upon concrete pads. However, state regulatory commissions are reluctant to approve expanded cask storage until there is some solution other than leaving the waste on the utility site for the indefinite future. Consequently, some plants are in danger of being shut down well before the end of their useful life.

Some alternatives include transmuting the fission products into other elements, which is technically possible but not economically feasible, and still may not eliminate the need for a repository. Attempts to liquefy high level waste and store it in glass rods face similar obstacles. Another option being explored for weapons plutonium is storing the waste in holes several miles deep, or in deep seabeds, which would require substantial changes in existing international law.

The problems of cleaning up the former defense facilities are even more complex. To that end, the DOE has recently issued a request for proposals to the research community for long-term research programs aimed at site remediation and decontamination. "First, we lack complete knowledge about what and where the wastes are," said Ahearne of the issue's complexity. "Also, the science and technology does not yet exist for handling many of the DOE's waste problems. Defense wastes are a problem for only a few countries. The difficulties are many, the solutions few, and the costs large."

In the same session, William Edelstein of General Electric's Corporate R&D Center in Schenectady, New York, and Tadeus W. Patzek (University of California, Berkeley) described a new method for destroying soil contaminants without removing or concentrating them first. The process uses the application of heat through thermal blankets or wells to vaporize contaminants, then draws them towards the surface with a vacuum. Temperatures continue to rise as contaminants draw nearer to the surface and the heat source itself, and the molecules are destroyed as they approach 600-700 degrees C. The process works well on any waste that can be volatized at 1,000 degrees C, including mercury, arsenic, lead compounds, and all hydrocarbon compounds.

Robert Frosch of Harvard University's John F. Kennedy School of Government closed the session with a description of Industrial Ecology, a systems view of material and energy flows in the industrial system, and between the industrial system and the environment. "Using fundamental physical and chemical principles, and some business experiences, industrial ecologists suggest that that the reuse of wastes, products, parts, components, and materials is likely to be an environmental and economically beneficial strategy," said Frosch, offering the waste management practices of U.S. steel mills as an example of efficient employment of the method. Although it presents some problems for industry, consumers, and public policymakers, he believes the strategy could be further improved with some technological and business developments.

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