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In spite of the continuing nuclear power plant catastrophes following the March 11 earthquake and tsunami in Japan, U.S. nuclear regulatory staff continues to insist it has found no inadequacies in the nation’s nuclear fleet. “We have not [identified] anything requiring immediate reaction,” Bill Borchardt, Nuclear Regulatory Commission executive director of operations, said April 28. He added that changing requirements for what nuclear plant owners should do in event of an electrical blackout may be subject to investigation. The NRC held a briefing on the status of the commission’s “response to events in Japan.” Commissioners’ primary concern was nuclear plants’ emergency backup power. Their meeting came a day after the Browns Ferry nuclear facility shut down all three reactors in the wake of thunderstorms and tornadoes. The power to the Tennessee Valley Authority-owned facility went down, and one line was restored as of April 28, according to NRC chair Greg Jaczko. While nuclear plants provide electricity through fission, the generation process requires outside power sources in order to operate. “For most things, you need water, and you need to pump it,” said Borchardt. Water supplies must be pumped by electricity, or the rare gravity feed, to keep radioactive components from overheating. The first line of backup power on site for nuclear plants when the grid goes out is diesel generators. In the case of the reactors at Fukushima Daiichi, the tsunami knocked out the grid and backup generators. At the Japanese plants, there also are battery backups, but they are only rated to last for a few hours. California’s operating nukes have a higher threshold. For San Onofre Nuclear Generating Station, it’s a six-hour battery life; for Diablo Canyon, the batteries are supposed to last 5.5 hours, according to Victor Dricks, NRC spokesperson. Batteries for most nuclear plants across the U.S. are rated for four hours. “Four hours doesn’t seem like a reasonable time to restore offsite power,” said Jaczko. The NRC uses the four-hour backup battery window because it estimates it takes one-half hour to three hours to restore offsite power, according to George Wilson, NRC radiation safety officer. Batteries are expected to be required from 0.9 hours to 2 hours. “Based on that, we doubled that to have a safety margin,” he added. “Four hours only applies to routine events,” commented commissioner George ApostoLakis. Underground electric cables could mitigate some weather effects noted the NRC, but there are no requirements for such, said Wilson. Commissioner Kristine Svinicki questioned whether the grid can continue to supply power to nuclear plants as the grid changes to adopt renewable resources. Staff said it’s working with regional grid operators, like the California Independent System Operator, and the North American Electric Reliability Corporation, to ensure transmission to reactors. Staff noted that when there are power outages, the first lines to be restored on an independent system operator basis are one connected to reactors.

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