A hearing of the Nuclear Regulatory Commission (NRC) pointed to apparent weaknesses in the regulation of nuclear plants.
Japanese and US officials are proposing resin, a giant tarp, and even robots in efforts to slow the leak of radioactive material from Japan's damaged Fukushima Daiichi nuclear power plant.
Administration officials, in the first formal accounting to Congress on the Japan nuclear crisis, assured senators that US reactors are safe. But industry critics said much needs to be improved.
The power to operate cooling pumps, a challenge at the heart of the Japan nuclear crisis, is on the verge of being restored, and a detailed assessment by a US expert is notably upbeat.