The head of the Nuclear Regulatory Commission's Fukushima inquiry task force said yesterday his panel is concerned that the severe threats that Japan's massive earthquake and tsunami posed to the Fukushima Daiichi nuclear complex reveal gaps in the voluntary guidelines that protect U.S. plants against incidents deemed unlikely.
Task force leader Charles Miller, who briefed NRC commissioners yesterday, said the panel is also considering whether older nuclear plants should be held to more demanding standards that have been applied to newer reactors, based on evolving safety insights.
Miller did not disclose how the task force will come down on these issues. It is scheduled to make its final report to the commission on July 12, with a public release of its recommendations on July 19.
NRC Chairman Gregory Jaczko and Commissioner George Apostolakis also pointed to potential weaknesses in the commission's voluntary policy toward low-probability but extreme threats to nuclear plants.
"As we look at this event," Jaczko said of the Fukushima plant catastrophe, "it's been a moment of reflection, because I think deep down there was a belief that you would never see an event like this, that we had done everything to basically take this type of event completely off the table. And obviously, we haven't."
"And we have over the years done things maybe halfway, and not all the way, to try to address these things," Jackzo said.
Jaczko suggested the differences in safety standards applied to older and newer plants might need to be addressed when nuclear plant owners ask the NRC to renew the initial 40-year operating licenses.
"Obviously, at license extension time we have an opportunity -- although the commission has not availed itself of that opportunity -- to in a sense re-baseline everybody ... so that everybody at that point kind of has a consistent understanding and basis for what is the definition of safety, what is the definition of external hazard," Jaczko said.
A focus on older plants
Miller said the task force had not looked at that. "We can't go back and rebuild" older plants, but this is an opportunity to consider reasonable actions to cover vulnerabilities, he said.
NRC's executive director for operations, Bill Borchardt, stepped into the discussion at that point to advise that changing the current requirements for license renewal "would clearly be a major policy decision." He said that the NRC had acted too hastily in making some ill-advised regulatory changes following the Three Mile Island nuclear accident in 1979, and that the agency should move deliberately this time.
Apostolakis, a former professor at the Massachusetts Institute of Technology, said he was puzzled by the line between mandatory regulation and voluntary guidance. "I'm wondering, what does voluntary mean?" he said.
Miller said that at some plants, the operators' attention to voluntary guidelines falls below its level of compliance with mandatory regulation. "I think the industry has come to those same conclusions, also," Miller said.
NRC policy has not considered the risk that a natural disaster could cause an extended loss of outside electric power from the grid, and also backup power within a plant, shutting down cooling systems that prevent core melting or exposure of spent fuel in storage pools, said Miller. He is a senior NRC official who delayed his retirement to head the short-term review of the Fukushima accident.
Extreme threats were considered so remote that they were covered by voluntary "severe accident management guidelines" (SAMGs) to plant operators, Miller noted. But NRC inspections since the Fukushima disaster in March revealed failures at some U.S. plants to keep the emergency guidelines and operators' training up-to-date.
"As a voluntary initiative, the SAMGs did not get rigorous oversight by many licensees. This was confirmed by our inspection results. The inspections revealed inconsistent implementation" by some of the licensees, Miller said.