The Nuclear Regulatory Commission will increase oversight of Energy Northwest's nuclear power plant near Richland after investigating an emergency preparedness issue.
The NRC confirmed Thursday that two inspection findings for the Columbia Generating Station's emergency preparedness program were "white," meaning they had a low to moderate safety significance. The findings were reported as preliminary earlier in the year.
At issue were faulty calculations made in the 1990s, said Mark Reddemann, Energy Northwest chief executive, at a board meeting Thursday in Kennewick.
The inputs into the calculations were incorrect, and the problem compounded for several years, said Brad Sawatzke, chief nuclear officer for the plant.
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That resulted in the Quick Emergency Dose Projection System including values that would have overestimated or underestimated the potential radiation offsite in an emergency, according to the NRC.
The inaccurate data would have caused a delay by Columbia Generating Station in recognizing an emergency requiring precautionary actions to protect the public or a more serious emergency with conditions that threatened the public, according to an NRC report.
The conditions existed between 2000 and 2011.
Last year, the problem was found by Energy Northwest during a self-assessment and fixed, according to Energy Northwest.
During that time, there was no emergency, Reddemann said.
Energy Northwest also has other methods it would rely on in an emergency to determine the emergency level and the protective actions needed, Sawatzke said. That includes direct readings from monitors, he said.
But when a piece of the emergency preparedness program "is not working appropriately, it is taken seriously," he said.
The NRC "white" inspection findings were for failure to maintain the plan to appropriately characterize emergency action levels, and failure to maintain adequate methods for assessing and monitoring actual or potential offsite radiation releases.
The NRC evaluates regulatory performance at commercial nuclear power plants with a color-coded process that classifies findings as either green, white, yellow or red in order of increasing safety significance.
The two white findings move the nuclear plant into the "degraded cornerstone" column of the NRC's action matrix, resulting in a higher level of NRC scrutiny. It's the third-highest level of NRC oversight, and the Energy Northwest plant joins seven other nuclear plants in that category.
Energy Northwest will remain at that oversight level until at least spring.
Energy Northwest has investigated and found no similar issues. It also has taken steps to prevent a recurrence, Sawatzke said.
A more rigorous review of calculations for emergency preparedness are done now with an additional level of oversight, he said.