Until the late 1970s, most commercial power plant operators outside the United States adopted a spent fuel management policy of immediate reprocessing and recycling of recovered products. In response to rising reprocessing prices, decreasing values of re­ covered products, concerns over proliferation risks, and a belief in the favorable eco­ nomics of direct disposal, many utilities have since opted to store spent fuel on an in­ terim basis pending the availability of direct disposal facilities or a change in the eco­ nomic and/or political climate for reprocessing and recycling uranium and plutonium. Spent fuel has traditionally been stored in water-filled pools located in the reactor building