May 18, 2011

By MATTHEW L. WALD
New York Times

WASHINGTON — Five years before the crucial emergency vents at the Fukushima Daiichi nuclear plant were disabled by an accident they were supposed to help handle, engineers at a reactor in Minnesota warned American regulators about that very problem.

One of the two engineers, Anthony Sarrack, notified staff members at the Nuclear Regulatory Commission that the design of venting systems at his reactor and others in the United States, similar to the ones in Japan, was seriously flawed. He later left the industry in frustration because managers and regulators did not agree.

Mr. Sarrack said that the vents, which are supposed to relieve pressure at crippled plants and keep containment structures intact, should not be dependent on electric power and workers’ ability to operate critical valves because power might be cut in an emergency and workers might be incapacitated. Part of the reason the venting system in Japan failed — allowing disastrous hydrogen explosions — is that power to the plant was knocked out by a tsunami that followed a major earthquake.

Mr. Sarrack’s memo was found in the archives of the Nuclear Regulatory Commission by David Lochbaum, a boiling-water-reactor expert who works for the Union of Concerned Scientists, a nonprofit group based in Cambridge, Mass., that is generally hostile to nuclear power.

"The Nuclear Regulatory Commission cannot claim ignorance about this one," he said.

Plant managers and nuclear regulators are warned about far more problems each year than actually occur, but in this case, the cautionary note was eerily prescient and could rekindle debate over whether automatic venting systems are safer alternatives.

While staff members at the Nuclear Regulatory Commission considered Mr. Sarrack’s suggestion, they decided against it.

On Wednesday, a commission spokesman, Scott Burnell, said the commission still believed that existing venting systems were a "reasonable and appropriate means" of dealing with a rise in pressure after an accident. But he has also said that the commission’s staff members are studying the events at Fukushima for "lessons learned," and that they had identified means of "reducing risk even further" by making the vents "more passive." He said the staff had not yet chosen a way to do that.

Read more at the New York Times website…