U.S. non-proliferation policy and programs regarding use of high-enriched uranium in research reactors

Uranium enriched to 90-93%, supplied by the U.S., is now used in 141 research and test reactors in 35 countries around the world with a cumulative power of 1714 MW. Since of the order of 3 kg of 235-U is involved annually in fuel fabrication, fresh fuel transport and storage, reactor operation, and spent fuel cooling and return per megawatt of research reactor power, it is estimated that more than 5000 kg of very high-enriched uranium is handled each year to operate these reactors. Recent U.S. assessments have led to the tentative conclusion that in only approximately 11 of these reactors, generally those of highest power or power density, is the use of 90-93% enriched uranium currently a technical necessity. Universal use of the best state-of-the-art fuel technology would permit an estimated 90 of these reactors to use 20% enriched fuel, and estimated 40 others to use 45% enriched fuel, without significant performance degradation. If advanced research reactor fuel development programs currently under way in the U.S. and elsewhere are successful, it may, in fact, be possible to operate virtually all of these reactors on less than 20% enriched uranium in the longer term. The physical and economic practicality of these developmental fuels must, of course, await future assessments. The wide-spread use of 90-93% enriched uranium today is a result of fuel technology limitations prevailing 15 years ago, the ready availability of uranium of this enrichment from the U.S. in the past, and the costs involved in introduction of new fuel technologies and enrichments into existing fuel fabrication facilities and reactors. Because of the limited reactor fuel market and the substantial costs involved in gaining safety and operating approvals for changes to reactor designs there is great pressure on fuel fabricators and reactor operators to standardize on well-proven fuel designs, and not to adopt marginal technological improvements--particularly in the absence of apparent economic benefits. Generally, these pressures have led to standardization of U-Al alloy and U-ZrH fuel technologies developed in the 1950's which, if 90-93% enriched uranium is available, are adequate for all but the highest power, highest performance, research reactors