The GAO report criticized the Nuclear Regulatory Commission for not requiring more stringent risk assessments for nuclear plants, especially in the aftermath of last year's magnitude-9.0 Fukushima quake. The report also noted that while both the Diablo Canyon and San Onofre plants can withstand a 7.0-plus-magnitude quake, an August 2011 5.8-magnitude earthquake in Virginia damaged a Dominion-operated plant after violent shaking exceeded industry standards.
The two California utilities aren't alone, the GAO said. Most of the 25 utilities that operate the 65 U.S. nuclear plants haven't used comprehensive risk analysis since getting their licenses to operate, in some cases as much as 40 years ago, the report said.
Since 1986, the Nuclear Regulatory Commission has urged operators around the country to use what it calls probabilistic risk assessment, a technique using advanced computer modeling to test a specific design to all potential risk factors, sometimes examining what would happen if two or three hazards occured at the same time, a scenario encountered by the Fukushima plant, which suffered an earthquake and a crippling flood that breached its seawall. The commission hasn't done an analysis to determine whether its method is superior to the current industry standard, deterministic risk analysis, which generally uses "over-engineering" and redundant systems to mitigate risk.
"Bottom line is, the probabilistic risk analysis is costly to implement but may save money in design and implementation by focusing efforts more efficiently on the most critical safety issues," said Frank Rusco, author of the GAO's report, wrote in an e-mail to California Watch.
The report also noted that many nuclear operators, including PG&E, are in the process of renewing their licenses for another 20 years, and the regulatory commission still hasn't ruled whether comprehensive risk analysis should be part of the renewal application.
“There is simply no excuse for the NRC's failure to require the most up-to-date methods to assess the threat posed by natural disasters, such as earthquakes, to our nuclear power plants,” said U.S. Sen. Barbara Boxer, D-Calif., who leads the Senate Environment and Public Works Committee and called for the report in February. “While the NRC has agreed to study the issue, action is needed now to ensure that standards are in place that best protect the health and safety of the American public.”
PG&E announced last year that it has asked the commission to delay its renewal of its operating license for Diablo Canyon until it conducts more seismic tests.
The report comes as the commission is already reeling from the resignation of Chairman Gregory Jaczko, who announced he was stepping down last week amid turmoil at the nuclear agency and poor relations with his own staff and Congress.
This story was produced by The Bay Citizen, a project of the Center for Investigative Reporting. Learn more at www.baycitizen.org.
The report, which looked at more than 100 operating nuclear reactors in the U.S., also found that the two companies have never done an assessment using the most up-to-date technology to determine what might happen in case of a tsunami or hurricane.