Beneath this concrete dome on Runit Island, part of Enewetak Atoll, built between 1977 and 1980 at a cost of about $239 million, lie 111,000 cubic yards or radioactive soil and debris from Bikini and Rongelap atolls. The dome covers the 30-foot deep, 350-foot wide crater created by the May 5, 1958, Cactus test.

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