U.S., Japan to research uranium fuel swaps

Labs team up on safeguarding reactors used for research


Laboratories in Japan and the United States will soon launch a joint study on how to run a test reactor in Osaka by using low enriched uranium fuel (LEU) instead of highly enriched uranium fuel (HEU), which can be diverted for weapons use, a researcher involved in the project says.

Hironobu Unesaki, professor at Kyoto University Research Reactor Institute, said Saturday the research will be conducted by the institute and the U.S. Department of Energy’s Argonne National Laboratory.

The move, which comes amid heightened concerns that HEU fuel used for research could be diverted for use in terrorism, is expected to find ways to overcome technical problems involving switching to LEU fuel.

In a related development, leaders from around the world are scheduled to meet Monday and Tuesday in Seoul for the Nuclear Security Summit, where they are likely to agree on minimizing the use of HEU to prevent it from getting into the hands of terrorist groups via research laboratories.

Unesaki said there have been few reported cases of switching from HEU fuel to LEU fuel to operate an experimental critical assembly device used for basic research.

The joint study will seek to make the switch at the Kyoto University Critical Assembly, a small research reactor established in 1974 that runs on HEU fuel imported from the United States. The facility conducts basic research in fields such as radiation physics and nuclear reactor physics.

While there is no telling whether the study will be successful, due to the technical difficulties and financial burdens involved, Unesaki said any success will pave the way for a pioneering international contribution in antiterrorism measures.

Since the end of the Cold War, the U.S. has reinforced its activities to recover HEU from various places around the globe because it sees nuclear terrorism as a major threat and has strongly promoted the switch to LEU fuel for research reactors.

As part of the move, a total of 600 kg of HEU — equivalent to 20 or more nuclear bombs based on simple calculations — has been recovered in Japan and returned to the United States since 1996.

Unesaki and his colleagues, together with U.S. researchers, have conducted preparatory research on the possibility of switching from HEU to LEU fuel. As a result, they determined that a full-fledged study into the matter is necessary.

HEU contains 20 percent or more of uranium 235, an isotope that is key to sustaining nuclear chain reactions that is found at a rate of only 0.7 percent in natural uranium ore, and LEU fuel contains less than 20 percent of the isotope. Weapons-grade HEU must be further enriched to 90 percent or more.