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NRC
inspectors Robert Krsek, Annie Kammerer and Steve Campbell (L to R)
conduct seismic walkdowns of the emergency diesel generators at the
Kewaunee nuclear power plant.
In
response to the lessons learned from last year’s nuclear accident in
Fukushima, the NRC has required every nuclear power plant in the U.S. to
take a number of actions. One of the highest-priority actions involves
re-examining earthquake and flooding issues. In the short term, both
plant personnel and NRC inspectors (shown in the photo) are walking
through the plants, ensuring the systems and components can withstand
the hazards that were analyzed when the reactors were built. There are
separate “walkdowns” for earthquakes and flooding.
Before
the earthquake walkdowns start, the plants compile a list of reactor
and spent fuel pool systems that must work after a quake. The plants
also assemble teams of employees, both people familiar with plant
systems and mechanical or civil/structural engineers with experience
working on nuclear plant earthquake issues.
The
teams walk through the plant, examining how systems and components are
anchored or supported to ride out a quake. They also look for issues
such as whether a quake might lead to a fire or cause something to fall
on an important component.
For
the flooding walkdown, the plants compile the features (such as
watertight doors or barriers) that protect the site, and take into
account any site changes (new buildings, for instance) that could change
flooding effects. The plant personnel doing the work would again
include engineers in relevant specialties, as well as staff familiar
with flood response procedures.
As
these teams do their work, they’ll ensure the protective features are
in place and able to deal with floods. They’ll also examine how much
extra physical margin is available beyond what’s expected. For example,
consider a watertight door protecting against a flood to the top of the
door as called for in the plant design. If a window two feet above the
door could allow floodwaters in, the site has two feet of available
physical margin.
The
plants will use their corrective action programs to deal with any
issues identified during both walkdowns. The plants must correct any
situation that challenges their ability to withstand quakes or floods
previously analyzed.
The
NRC’s part of the walkdowns combines earthquake and flooding
specialists from our headquarters with the resident inspectors who work
every day at the plants. They will examine the plants’ walkdown
documentation and perform independent inspections to ensure the plants
have done the walkdowns appropriately. The NRC’s resident inspectors
will also follow up on the plants’ actions to address whatever issues
they identify.
The
walkdowns will also provide information for the other part of the
earthquake/flooding reanalysis, which will ensure the plants understand
the current hazards at every site. This additional work will continue
for several years, with flooding work completed by 2015 and earthquake
work continuing into 2016 for plants needing the most extensive
reanalysis.
These
walkdowns are just one part of the many actions we’re taking in
response to what we’ve learned from the events at Fukushima. More
details are available on our
website.
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