US Nuclear Regulatory Commission chair Gregory Jaczko testified before Congress today on the growing nuclear crisis in Japan, and he didn't paint a pretty picture.

The chairman of the United States Nuclear Regulatory Commission gave a significantly bleaker appraisal of the threat posed by Japan’s nuclear crisis than the Japanese government, saying on Wednesday that the damage at one crippled reactor was much more serious than Japanese officials had acknowledged and advising to Americans to evacuate a wider area around the plant than the perimeter established by Japan.

[...] Gregory Jaczko, the chairman of the commission, said in Congressional testimony that the commission believed that all the water in the spent fuel pool at the No. 4 reactor of the Fukushima Daiichi Nuclear Power Station had boiled dry, leaving fuel rods stored there exposed and bleeding radiation. As a result, he said, “We believe that radiation levels are extremely high, which could possibly impact the ability to take corrective measures.”

Japanese officials are now facing a deadly Catch 22. Water in the fuel rod pools not only cools the rods, but shields workers from gamma radiation. With the pools dry, radiation has spiked to such dangerous levels that workers can't approach them to add water. Likewise, helicopters attempting to drop water from overhead would be exposed to equally dangerous radioactive plumes. But without water, the rods will meltdown, spewing more radiation, making it all the more difficult for workers to approach.

Suicide missions on the part of workers and pilots may be the only hope for bringing this crisis under control.

Meanwhile, the US Embassy has advised Americans in Japan to evacuate from a 50-mile radius around the Fukushima plant, as opposed to the 12-mile radius imposed by the Japanese government.