Last week the Tokyo Electric Power Company (TEPCO) said it would need help from outside of Japan to stabilize and safely decommission damaged reactors at the Fukushima nuclear power station. That followed an announcement by the chairman of Japan's nuclear authority, who said that he feared there would be further leaks. The impact of the contamination on the environment remains unclear as the leakage spreads farther into the ocean. Ken Buesseler, a senior scientist at Woods Hole Oceanographic Institution, has examined the waters around Fukushima. He'll tell us about the risk factors. (Photo: AP Images).