very carefully at how much risk power plants might face, those near earthquake fault lines. what s happening in japan could be a major wake-up call for us. you hear people, my god, if the big one hits california or something like that. certainly, this is another example of what we have to fear in this country as well. considering nuclear power, that s right. coming up later, the difficulty many americans had getting out of japan after surviving such an ordeal. it s a story told at many u.s. airports all weekend long. people there reconnecting. you can imagine the relief to get home. the lucky few. first, the unfolding nuclear crisis in japan. there has been a second hydrogen explosion at stricken fukushima daiichi nuclear power plant. the japanese authority say radiation levels have exploded and within legal limits, however. diana alvear has the latest. from narita, japan. good morning. reporter: good morning. what happened earlier today is just a sign of how fluid and how