08/31/2009 - 09:47

Reprocessing is the answer

George S. StanfordGerald E. MarshWilliam Hannum

William Hannum

Hannum, a physicist, is retired from Argonne National Laboratory. He has served in various high-level positions at the Energy Department,...

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Gerald E. Marsh

Marsh, a physicist, is retired from Argonne National Laboratory. He was a consultant to the...

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George S. Stanford

Stanford, a reactor physicist, is retired from Argonne National Laboratory. He is a member of the American Nuclear Society, a past member of...

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When you combine the country's addiction to oil to its mounting concern over global warming you have a clear-cut case for expanded nuclear power. The issue has been clouded, however, by the recent decision to stop work on the Yucca Mountain permanent spent fuel repository in Nevada, so far the only real solution the United States has for its accumulating spent fuel from its 104 light water reactors (LWR).

Some argue that instead of building more nuclear reactors, the country should invest in renewable energy such as solar or wind power that could provide all of the electricity it needs--but that notion is hopelessly unrealistic. Even the most optimistic projections don't foresee more than a few percent of our electricity generation coming from these sources by 2030. Anyway, neither solar nor wind can eliminate our dependence on fossil fuels, since they must be backed up by reliable, rapid-response generators when the sun doesn't shine or the wind doesn't blow. Renewables absolutely have a role to play, but only in niche applications for the foreseeable future.

A technology that's much closer to being fully realized is advanced nuclear power. To solve the spent-fuel dilemma, what's needed is to finish the nearly complete fast reactor, which can recycle spent nuclear fuel. (For further information, see "Smarter Use of Nuclear Waste".) By the mid-1990s, this work was well advanced and technical feasibility had been demonstrated, but the program was terminated for political reasons. If we're serious about finding a solution to the energy crisis, such research must be continued.

From the very earliest days of nuclear power, we've known that fast reactors in concert with recycling of spent fuel--also known as reprocessing--are the key to efficient utilization of the energy locked inside uranium. Such a system converts the common uranium 238 isotope into plutonium, which can then be recycled to make even more plutonium to fuel additional power plants. The value for long-term energy security is obvious: The current once-through cycle (where spent fuel is removed from reactors for eventual burial) uses less than 1 percent of the energy in the original uranium, but with recycling, utilization exceeds 99 percent. As a result, enough uranium is already mined and in storage—partly as used fuel, but mainly as depleted uranium left over from the enrichment process—to support a massive nuclear power industry for hundreds of years to come. Further mining will be required only to support the current fleet of LWRs over their lifetime, perhaps 100 years, and the known ore reserves are adequate for this task.

For complete use of the uranium, the fuel must be refreshed periodically to replace the built-up fission products with fresh uranium. A reprocessing method called PUREX (for plutonium uranium extraction) was developed early in the Manhattan Project to extract chemically pure plutonium for weapons, and that process was carried over to the civilian power sector. In the 1970s, however, due to proliferation concerns, the broad deployment of PUREX technology was stopped in the United States and put under high security in other countries. In any event, PUREX is very expensive and far from optimal for recycling in fast reactors.

Specifically to address the need to recycle spent fuel without producing weapons-usable plutonium, pyroprocessing was developed in the 1980s and 1990s to recover, recycle, and consume the long-lived hazardous materials. The process is so efficient that the waste becomes essentially harmless within a few hundred years, as opposed to tens of thousands of years as is the case now. The dilemma of what to do with used spent fuel is thus resolved. It's no longer a waste--it's a valuable resource. Freed from the apparently intractable challenge of proving that direct disposal into a permanent repository is safe, the deployment of LWRs would become much more politically tractable.

The new technology provides an even greater proliferation-prevention benefit as well. Consider this: A nuclear weapon can be made either with high-quality plutonium or with enriched uranium. To get the plutonium, one has to irradiate special fuel elements in a reactor and then put them through a complex chemical separation process. For the uranium, one has to separate uranium 235 from the far more common uranium 238. In a mature fast-reactor economy, however, there will be no legitimate reason either to enrich uranium or to use the PUREX-type process that extracts pure, weapons-usable plutonium. Any such effort would be prima facie evidence of an attempt to build nuclear weapons, making it easy to monitor and stop would-be proliferators.

Aggressive governmental implementation of a fast-reactor recycling program, coupled with massive deployment of additional LWRs will put us on the path toward energy independence, while dramatically reducing the burning of fossil fuels.