U.S. Nuclear Plants Not Fully Equipped to Handle Extreme Events: Scientific American

U.S. nuclear plants should be hardened to better withstand earthquakes and other extreme emergencies that could lead to a radioactive release, the Nuclear Regulatory Commission’s Japan Task Force has recommended.

The task force’s 90-page report on the implications of Japan’s nuclear disaster said that an accident involving damage to reactor cores and uncontrolled escape of radioactivity was “inherently unacceptable.” It called for a dozen actions to improve plant safety and redefine NRC regulations governing severe emergencies. The report was delivered to commission members and key congressional committees yesterday and will be released to the public today.

“Continued operation and continued licensing activities do not pose an imminent risk to public health and safety,” the task force of NRC experts said. “However, the Task Force also concludes that a more balanced application of the Commission’s defense-in-depth philosophy using risk insights would provide an enhanced regulatory framework that is logical, systematic, coherent and better understood,” according to a summary released by the NRC last night.

The dozen recommendations include:

Requiring that equipment and procedures are in place to keep reactor cores and spent fuel pools cool for at least 72 hours after an emergency, and that backup power is available to run cooling systems for at least eight hours if power from the outside grid or emergency generators is lost in a “station blackout” emergency. Some U.S. plants have a four-hour backup power capability. The 72-hour requirement would be new.

Requiring that emergency plans address accidents involving multiple reactors on the same site. Current regulations generally center on single-reactor emergencies.

Adding seismically protected systems and instrumentation to assure continued cooling of spent fuel pools, including at least one source of electric power that can operate cooling pumps and instruments at all times.

Requiring hardened vent designs for Mark I and Mark II reactors, the models at Japan’s Fukushima Daiichi reactor complex where three units suffered explosions tentatively blamed on hydrogen that leaked from vent systems.

Strengthening regulatory oversight of plant safety “by focusing more attention on defense-in-depth requirements.”

The Japan task force headed by NRC veteran Charles Miller will meet with NRC commissioners July 19 to review the report, and will hold a public meeting on its recommendations July 28.

via U.S. Nuclear Plants Not Fully Equipped to Handle Extreme Events: Scientific American.