Reprocessing Used Fuel

June 4, 2001

Reprocessing Used Fuel

By MATTHEW L. WALD

WASHINGTON, June 3 — Is it really waste? For years, nuclear engineers have argued that used fuel should be "reprocessed" to extract the uranium fuel that was not consumed and the plutonium that was produced in the reactor.

In the early days of nuclear power, when uranium was scarce and expensive, they argued (wrongly, it turns out) that this would save money. Now they say it would simplify disposal, by removing the elements that last the longest and feeding them back through a reactor, where they would be converted into shorter- lived radioactive materials.

The idea has surfaced again in the Bush-Cheney energy plan, which calls for research on a new form of reprocessing called pyroprocessing. Opponents say the idea was put in the report as a sop to the Nevadans who oppose Yucca Mountain as a burial ground for waste; supporters say it is a realistic option.

Pyroprocessing was tested at the Argonne National Laboratory's Idaho test station, where researchers chopped up used fuel and ran electric currents through the mixture. With the right electrode and the right voltage, uranium will migrate to the electrode, along with plutonium, neptunium and lawrencium, the so- called transuranic family of elements found at the bottom of the atomic chart.

The transuranics are created in reactors by adding neutrons to uranium. While they take thousands of years to lose radioactivity, most of the fission products, which are the fragments of split uranium atoms, take hundreds.

But the transuranics are not good fuel for the existing generation of reactors, because of the neutrons used to sustain a chain reaction in them. In existing designs, those neutrons are slowed to a speed where they are more likely to split uranium atoms, but that speed is too low to break up the transuranics. Pryroprocessing might be technically feasible, but experts say it would require hundreds of newly designed reactors to use the resulting fuel.

Copyright 2001 The New York Times Company