http://www.bikiniatoll.com/divetour3.html
Found a page that says:
"Despite what you might think, the radiation is not dangerous. A recent study showed that the radiological dose while swimming in the lagoon is essentially zero and the radiological dose for a two week diving visit is estimated at about 1/10 that of living in a US city for two weeks. "
( http://www.pacificislandtravel.com/micronesia/diving/bikini_wrecks.html )
Thanks for the link.:)