prospect of a hydrogen explosion. what's also worrying is that that contained a pool and in that pool was spent fuel rods. what they're concerned about is that the water may have evaporated and those spent fuel rods may have caught on fire. now, that also led to a spike in radiation around about the same time within the plant. it went to level that we haven't seen before throughout the crisis, levels that the authorities said posed a risk to humans. that was contained within the plant. in the hours since then, the levels have come down when measured just outside the perimeter of the plant. the prime minister naoto kan is warning we could see the radiation levels rise again in the coming days, now there is an exclusion zone of 20 kill meters, 200,000 people have been moved away from there. the prime minister saying people within a 30-kilometer radius