The Nuclear Regulatory Commission is asking for more information on the earthquake risk of the nuclear power plant near Richland after the three western U.S. nuclear power reactors submitted updated seismic information this spring.
“This information shows us how the plants’ new earthquake hazard compares to the ground movement considered in the plants’ original designs,” Bill Dean, director of the NRC’s Office of Nuclear Reactor Regulation, said in a statement.
“The evidence we’ve seen so far leaves us confident the plants are safe to continue operating while they do more analysis,” he said.
However, it characterized Energy Northwest’s plant near Richland and the Diablo Canyon reactor in California, among plants nationwide with the highest priority for more risk analysis.
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That decision is based on the plant’s original seismic design, as well as the potential for ground energy to be transmitted at frequencies that can affect a plant’s structures, pipes, pumps and safety systems.
The closer look at earthquake hazard was triggered by the 2011 Japanese nuclear accident. Among the information each plant operator analyzed was where quakes are generated, how the country’s overall geology transmits quake energy and how an individual site’s geology can affect quake energy before it reaches the reactor building.
Seismic hazard screening and priority reviews for nuclear power plants in the central and eastern U.S. were completed last year. The detailed re-analysis for the three western plants was last because the West has more complex seismic information, according to the NRC.
Energy Northwest’s Columbia Generating Station and Diablo Canyon have until June 2017 to conduct an in-depth analysis of their updated earthquake risks. The third western plant, Palo Verde in Arizona, has been grouped with lower priority facilities.
The information submitted by Energy Northwest and the operators of the other two western plants shows their original engineering and construction methods added safety margins beyond their original designs’ anticipated hazards, according to the NRC.
“If a plant’s new hazard exceeds the original design, that additional analysis will determine if there are any changes in accident risk from an earthquake,” Dean said.
Plants also must do some shorter-term work to see if they should enhance key safety equipment while more substantial analysis is being done. Energy Northwest will complete its review of potential short-term enhancements by January, according to the NRC.
Energy Northwest is continuing to make other improvements required by the NRC in response to the Fukushima accident. It has purchased more backup equipment, including a fifth back-up diesel generator and portable pumps.
It also is doing work in its current refueling outage to prepare to install a robust vent system to safely relieve pressure if an accident happens. The system would be installed in the 2017 refueling outage.
The anti-nuclear group Physicians for Social Responsibility has called for the Columbia Generating Station not to be restarted after the current refueling outage until it can be shown not to pose a danger to Washington state residents.
Physicians for Social Responsibility and No Nukes Northwest also are questioning the safety of the reactor because of a possible crack in one of several pipes used to help force water through the reactor core.
Energy Northwest noticed a mark slightly more than an inch long on one of several 19-foot-tall pipes that might be a crack in 2011. It checked older video then and concluded it may have been there since 2001, according to Energy Northwest spokesman John Dobken.
The system is contained within the reactor pressure vessel and continues to perform its intended function, according to Energy Northwest.