Water used to cool radioactive waste at the stricken nuclear complex in Japan did not dry up, as earlier feared, U.S. regulators said Wednesday in a reversal of a claim that pitted U.S. officials against Japan in the days following that country's nuclear disaster.
U.S. officials, most notably Nuclear Regulatory Commission Chairman Gregory Jaczko, had warned that all the water was gone from one of the spent fuel pools at Japan's troubled nuclear plant, raising the possibility of widespread nuclear fallout. Loss of cooling water in the reactor core could have exposed highly radioactive spent fuel rods, increasing the threat of a complete fuel meltdown and a catastrophic release of radiation.
Japanese officials denied the pool was dry and reported that the plant's condition was stable.
On Wednesday, U.S. officials said newly obtained video shows that the spent fuel pool at Unit 4 at the Fukushima Dai-ichi complex probably did not go dry, as Jaczko had insisted in March.
Bill Borchardt, the NRC's executive director for operations, said U.S. officials welcomed the video evidence as "good news" and one indication that the meltdown at the Fukushima plant's Unit 4 reactor "may not have been as serious as was believed."
U.S. officials have never fully explained why Jaczko made the claim, but said it was based on information from NRC staff and other experts who went to Japan after the March 11 earthquake and tsunami.
Jaczko did not mention the spent fuel pool during a commission meeting Wednesday at NRC headquarters in Rockville, Md. He declined to comment afterward.
Jaczko, 40, has been under fire in recent days, as the NRC's inspector general released a report indicating that he repeatedly misled fellow commissioners about his efforts to stop work on a disputed dump for high-level radioactive waste. Inspector General Hubert T. Bell said Jaczko manipulated the panel's four other commissioners by selectively withholding information on a crucial safety review of the proposed Yucca Mountain nuclear waste dump in Nevada. Jaczko's actions allowed him to shut down the review last year without a vote of the full commission.
Bell told the House Energy and Commerce Committee that Jaczko's conduct was not criminal but added, "It's not an upfront way to do business."
Several agency scientists and a former NRC chairman also have questioned Jaczko's actions, and at least two GOP lawmakers have called for him to resign.
A spokesman for the NRC said Wednesday that the belief that the spent fuel pool may have gone dry played a role in Jaczko's controversial decision to recommend that U.S. citizens stay at least 50 miles away from the crippled Japanese plant. The Japanese authorities had ordered evacuations of people within about 12 miles of the plant.
NRC spokesman Scott Burnell said Jaczko and other U.S. officials made the recommendation based on the best information available at the time.
"The NRC felt and continues to feel that the 50-mile recommendation was appropriate," he said.
Meanwhile, Charles Miller, a senior NRC executive who is leading a 90-day safety review of U.S. nuclear plants, told commissioners that current safety rules do not adequately weigh the risk of a single event that could knock out power from the grid and from emergency generators, as the quake and tsunami did in Japan. Safety experts until now have focused on the risk of losing electricity from the grid or from emergency sources, but not both.
NRC officials have said they are studying whether the nation's 104 nuclear reactors can cope with such a "station blackout," which could go on for days.
Commissioner George Apostolakis questioned why current rules assume that electricity would be restored within four or eight hours. "Why do we still assume things that are now, in retrospect, unrealistic?" he asked.
Jaczko said the Japan disaster had caused everyone involved in nuclear power, from industry to regulators, to rethink their assumptions.
"I think deep-down there was a belief that you would never see an event like this, that just simply we had done everything to basically take this type of event completely off the table. And obviously, we haven't," Jaczko said.
A final report from the task force is due in mid-July.