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
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.