by CKR
According to the 2 December Science magazine (subscription only; article reproduced here), the Department of Energy’s fiscal year 2006 budget contains $50 million toward a goal of beginning construction on an engineering-scale plant for reprocessing of nuclear fuel by 2010. A summary from the Office of Management and Budget presents a timeline and a suggestive sentence:
The Budget also continues research on advanced, proliferation-resistant nuclear fuel cycles, which would allow the Nation to extract the energy potential from spent nuclear fuel and dramatically reduce the quantity and toxicity of the remaining waste.
The word reprocessing is not used, but that’s what “extracting the energy potential from spent nuclear fuel” has to mean.
This represents a significant change in United States policy.
The current policy has been in force since 1977. On April 7 of that year, Jimmy Carter announced that the United States would no longer reprocess spent nuclear fuel. The rationale was that if plutonium and uranium were not separated via reprocessing, proliferation would be more difficult. Carter expected that other countries would follow.
The world has not followed the United States. Russia, France, Britain, and Japan all reprocess nuclear fuel. What the ban on reprocessing has done is lost the United States capability in this area and required that enormous, heavily protected volumes be developed for storage or disposal of spent nuclear fuel rods, primarily Yucca Mountain, although the Waste Isolation Pilot Plant in Carlsbad, New Mexico, has also been mentioned as a possibility.
What is Reprocessing?
The uranium in the fuel of most commercial nuclear reactors is enriched to about 3.5% U-235 from its natural level of 0.7%. The U-235 fissions in those reactors, providing the heat that makes steam that drives the turbines to make electrical power. The rest of the uranium, U-238, picks up neutrons to become plutonium-239. Both the U-238 and the plutonium fission and provide some of the energy, too.
Fission literally breaks the atoms of uranium and plutonium apart into smaller atoms, called fission products, which are highly radioactive for relatively short times. The longest-lived fission products are strontium-90 and cesium-137, with half-lives of 25 and 33 years, respectively. After most of the U-235 has fissioned, the reactor no longer produces heat effectively, and the fuel must be replaced. The old fuel is called spent fuel. In the United States, it is also called nuclear waste, along with a wide variety of other materials, most of which are not so difficult to handle nor potentially valuable.
It was the plutonium and the possibility it could be diverted to use in nuclear weapons that bothered Jimmy Carter. The Indians had tested their first nuclear device in 1974. But that plutonium, along with the leftover uranium, can be reused as reactor fuel. Other countries see the plutonium and uranium as resources that shouldn’t be wasted. Petroleum is becoming more expensive, and concerns about greenhouse gases are increasing.
Reprocessing has been a messy business. The PUREX process (Plutonium-Uranium Extraction) was developed during World War II and has been the mainstay ever since. Although separating the plutonium and uranium for further use can decrease the volumes of waste that must be stored, past development and use of PUREX gave us the notorious underground tanks at Hanford, Washington, and Savannah River, South Carolina. Better methods for dealing with PUREX wastes are now available.
In the 1970s, a PUREX plant was being built at Barnwell, South Carolina. It was almost completed at about the time Carter changed US policy. It was never used for reprocessing.
There are other methods of reprocessing. Bill Hannum, Gerald Marsh, and George Stanford have an article on one of them in the December Scientific American. Here’s a similar article outside the subscription barrier.
Other methods of reprocessing haven’t been developed and used to the same extent as PUREX. They would require additional research and development, which presumably is the purpose of the new appropriations.
Security and resistance of reprocessing to diversion of nuclear materials is a concern. A number of innovations have been suggested to improve security. They range from the obvious step of locating reprocessing facilities near reactors, to decrease the necessity for transporting the materials, to technical fixes of the various processes. Again, some research and development will be necessary.
Removing reprocessing from development in the US has not achieved Carter’s goals. It has removed the US from the international discussion of how, when, and why to reprocess. Dealing with differences in policy on this subject has occupied probably thousands of hours of scientists’ and diplomats’ time and has slowed the progress of safeguarding Russian nuclear materials.
Nuclear power will be needed in the future; we must develop safer and more secure methods for its utilization. Those methods will take years to develop. We need to start now.