As of midday Thursday, the country's Nuclear and Industrial Safety Agency spokesperson Yoshitaka Nagayama, noted that "because we have been unable to go to the scene, we cannot confirm whether there is water left or not in the spent fuel pool at reactor No. 4," The New York Times reported. As of March 16, there had been at least two fires suspected at that reactor.
If the burning-hot fuel is not covered by adequate water, the heat from the ongoing nuclear reactions can cause the water to boil off. "Water in the pool serves as shielding and cooling, and when that water is gone, that direct gamma radiation is very high," Resnikoff said.
Resnikoff was skeptical at the briefing that helicopters would be an effective way to stave off overheating in the spent-fuel pools. "Part of the roof still remains, and they cannot just dump water into the fuel pools" from the air, he said.
In a congressional testimony yesterday, Gregory Jaczko, chairman of the U.S. Nuclear Regulatory Commission (NRC) said of the conditions at the plant: "We believe that radiation levels are extremely high."
In any case, the NRC recommended Wednesday that U.S. residents in Japan within 80 kilometers of the facility should evacuate. American military personnel were being kept at least at this distance from the site. The Japanese government had evacuated residents within a 20-kilometer radius (and recommended those 20 to 30 kilometers away to remain indoors).
Yukio Edano, Japan's chief cabinet secretary, said that the U.S.'s "more conservative decision" to move U.S. residents farther away from the plant is "understandable," CNN reported.
Governments, agencies and many in the public have complained about the paucity of data being made available by the Japanese government and Tokyo Electric Power, the company that owns and operates the facility. But as Resnikoff pointed out, many of the radiation sensors are located on the nuclear plant's site and may well have been damaged during or since the March 11 magnitude 9.0 earthquake. "So it's not surprising that we're not getting the numbers we want."
And whether or not the 50 tons of water dumped on reactor No. 3 was enough to temporarily cool the spent fuel pool, the efforts will need to continue to avoid a significant release of radiation. "This is a several-months problem," Resnikoff said. "The heat values will be high for months—high enough to cause an exothermic reaction. So this is going to be a continual problem."
At least, the threat of radioactive release in Japan seems to be contained to the Fukushima Daiichi facility (Japan has a total of 54 nuclear reactors at various facilities). "Other nuclear power plants in Japan are in normal operations or safely shutdown," the JAIF reported Thursday.