leakage. the navy has repositioned u.s. ships away from that site after discovering low levels of radiation on 17 helicopter crew members, all have been treated and declared contamination free. we're breaking out our coverage into a couple of conversation. more on the search-and-rescue efforts but first i want to focus on another threat which is the nuclear one. joining us now two experts in nuclear matters, david albright, a former nuclear inspector with the institute for science and international security. also with us from washington, robert alvarez. he advises secretary of energy who is in charge of our nation's nuclear complex and david, what is the worst case scenario right now? >> it's very hard to know. of course you worry that if there's a lot of fuel melting and perhaps a very serious steam