with its spent fuel pond but only one helicopter able to go back, zero or one helicopter able to go by because of radiation readings. so, instead, the helicopters focused on the reactor pool at reactor number three. so, again, there is this problem. you have to solve the problem. if you don't solve the problem, the radioactivity increases and able to do less about it going forward. that is the dilemma japanese officials face right now. >> thank you for the perspective. in a few minutes jim will come back to answer a question what is the best outcome we can hope for now. his answer just ahead. tens of thousands of americans live in japan and evacuations are finally under way for some of them. the u.s. is chartering flights for the families of its diplomatic staff there and washington is vowing to help other americans as well. cnn foreign affairs correspondent jill dougherty is following this development and joins us from the white house. what exactly are americans being told, jill? >> reporter: you have a couple of situations with who, among