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Safety issues at the
Columbia Generating Station (WPPSS Nuclear Plant 2)

Columbia Generating Station: NRC's Special Inspection of Self-Inflicted Safety Woes By Dave Lochbaum, Union of Concerned Scientists, April 13, 2017
Self-inflicted problems turned a fairly routine incident into a near-miss on December 18, 2016, when the plant stopped generating electricity and started generating problems. Luck stopped it from progressing further. The problem started offsite due to causes outside the control of the plant’s owner. Those uncontrollable causes resulted in the main generator output breakers opening as designed.
By procedure, the operators were supposed to trip the main generator. Failing to do so resulted in the unnecessary closure of the MSIVs and the loss of the normal makeup cooling flow to the reactor vessel.
By procedure, the operators were supposed to manually start the RCIC system to provide backup cooling water flow to the reactor vessel. But they failed to properly start the system and it immediately tripped. Procedures are like recipes—positive outcomes are achieved only when they are followed.
The operators resorted to using the HPCS system. It took about a minute for the HPCS system to recover the reactor vessel water level—the operators left it running in “idle” for the next three hours and 42 minutes during which time about 5 gallons per minute leaked into the reactor building. The leak was through eroded gasket material that had been identified as improper for this application nearly a decade earlier, but never replaced.
Defense-in-depth is a nuclear safety hallmark. That hallmark works best when operators don’t bypass barriers and when workers patch known holes in barriers. Luckily, other barriers remained effective to thwart this near-miss from becoming a disaster. But luck is a fickle factor that needs to be minimized whenever possible.  


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