U.S. Nuke Design Could Help Japan

Wednesday, March 16, 2011 @ 08:03 PM gHale

By Bob Felton
Though designed to withstand a 7.9 (Richter scale) earthquake, Japan’s Daiichi nuclear power plant survived a 9.0 earthquake – a once every 300-years event – and backup diesel power performed as expected, until the tsunami mixed seawater with the diesel fuel, said North Carolina State University Nuclear Engineering Professor Paul Turinsky.

The earthquake and tsunami exceeded the design basis of the plant, he said.

Boiling water reactor process.

Boiling water reactor process.

Because the earthquake disabled the electrical grid to which the plant would ordinarily have turned for backup power, it switched to diesel generators; those were disabled when the tsunami caused seawater to mix with the fuel. The plant then turned to batteries. The battery run-down disabled the water pumps and triggered overheating of the reactors, with confirmed melting of fuel in #2 and probable melting in #1 and #3.

Though natural disasters are “acts of God” not susceptible of reliable prediction, Turinsky noted American design requirements might have mitigated the severity of the problems caused at the Daiichi plant. First, facilities have been hardened since 9/11, and there is more redundancy in critical systems. Second, all American plants are designed to handle a comprehensive, 8-hour blackout. Even so, he said, “That’s what the NRC is going to be looking at, the robustness of our designs, and what changes would have to be made for a higher design basis.”

Though the Daiichi plant withstood the earthquake, American diplomatic cables from 2008 unearthed by London’s Telegraph among the Wikileaks files indicate the International Atomic Energy Agency (IAEA) alerted Japan then the design basis for some Japanese plants might be inadequate. From the cable:

“On earthquakes and nuclear safety, the IAEA presenter noted the Agency has officials in Japan to learn from Japan’s recent experience dealing with earthquakes and described several areas of IAEA focus. First, he explained that safety guides for seismic safety have only been revised three times in the last 35 years and that the IAEA is now reexamining them. Also, the presenter noted recent earthquakes in some cases have exceeded the design basis for some nuclear plants, and that this a serious problem that is now driving seismic safety work. The IAEA is issuing a new guide on seismic evaluation to accompany existing guidelines on seismic hazard and design.”

Japan subsequently built an emergency response center at the plant.

Bob Felton is a freelance writer based in Wake Forest, NC.