Nuclear Plant Journal, May-June 2015 NuclearPlantJournal.com
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equipment. It buys you enough time to
connect portable equipment that’s on-site
– Phase 2. And then that equipment is run
until the off-site resources from the national
response center comes to bear – Phase
3. For whatever reason, if that all failed
and you’re now having the core starting
to melt because you don’t have active
decay removal, then the commission, on
top of that, said we want these particular
containments, Mark I and Mark IIs, to have
severe accident capable hardened venting
system. In other words you can operate in
that high pressure, high temperature, and
high radiation environment.
Jeremy Bowen:
The mitigating
strategies Order that was put in place to
mitigate the effects of a beyond-design-
basis external event, and it doesn’t say
anything more than that, it intentionally
was left undefined, very broad. There
was a specific event – it happened in
Fukushima – but it was an event that was
not predicted, it wasn’t designed for. So,
the agency didn’t want to try and predict
or design a specific external event. Taking
that information, the industry developed
some guidance to try and at least start to
think about how that event would look.
And Jack mentioned an ELAP. Basically,
as everybody started to look at this, we
recognized that regardless of what the
event would look like, whether it’s a
seismic event, a flooding, a tornado, a
snowstorm, high heat, whatever it was, it
would all result in an impact on the plant
such that the plant would lose off-site
power and it could potentially affect the
backup electrical systems and the diesels.
And that would result in the plant losing all
AC power for an extended period of time.
And then the strategies were developed
based on that situation. Regardless of
how you got there, the end result is all
essentially the same, an extended loss
of AC power, and then what would you
do? How would the plant respond based
on the installed equipment? And then
going from that equipment, you needed
to bring additional portable equipment to
bear, that’s your phase 2. And then bring
equipment from off-site. That’s phase 3.
The industry proposed guidance that
we endorsed. Basically took all these
starting assumptions, the extended loss of
AC power, well, assume that this happens,
during the back shift, on a holiday or on a
weekend, so you have a minimum amount
of staffing. And that was another part of
the 50.54(f) letter that was sent out, the
request for additional information. Can
licensees go back and look at their plants
to make sure that
you have sufficiently
evaluated that and
you have enough staff
on-site to deal with
an event at all units,
because most emer-
gency preparedness
activities to date had
looked at an event at
a single unit. So the
50.54(f) letter in ad-
dition to asking them
to reevaluate their
seismic and flooding
hazard information,
it also asked them to
reevaluate and ensure
that you have suf-
ficient staffing and
communication from an emergency pre-
paredness standpoint to deal with an event,
an undefined event, at multiple units at
any given time in the worst case scenario,
back shift, minimum staff on-site. The
plant staff can’t get access to the site for
a certain period of time. What would you
do, and how would that be accomplished?
The strategies were developed and we
simplified the actions as much as possible
across the industry. There was a kind of
standardization of connections, simplifi-
cation and standardization of operations.
So, you tried to make it as universal as
possible for all this portable equipment.
You didn’t have to overthink and over-
engineer something while you’re in the
middle of an incident. It was a simplified
action that the licensees could take.
2.
What is the current strategy to keep the
plant staffed in an emergency situation?
Jeremy Bowen:
The assumption is
that during an event, within the first six
hours there is no access to the plant. So,
it’s the bare minimum staff that would be
on-site. Then between 6 and 24 hours,
there is limited access restored to the
site, and that maybe through support
from local and state and federal agencies.
It could be helicopters, if necessary,
bringing in additional staff, but then
within 24 hours there’s additional access
restored to the site. So, it’s kind of a step,
tiered approach of no access, limited
access, and additional access at that point.
Jack Davis:
But it’s important to
recognize that the commission’s Order
said that you needed to cope indefinitely.
That’s the keyword. So, you have to be
able to cope indefinitely in that situation,
and which was one of the lessons learned,
obviously, from Fukushima. There you
weren’t able to do that.
Mitigation strategies are probably
one of the most significant safety margin
improvement. We made the determination
that U.S. plants are safe and continue
to be safe, but this is additional safety
on top of that. It’s real equipment, real
procedures, real people, improvements to
industry, probably the biggest since TMI.
3.
How has plant safety been enhanced
with portable and additional redundant
post-Fukushima equipment?
Jeremy Bowen:
The mitigating
strategies’ Phase 1 equipment, the
permanently installed equipment, has
to be shown to be protected against a
series of external events and beyond,
Jeremy Bowen
Jeremy Bowen is Associate Director
for Program Management, Policy, and
Support in the Office of Nuclear Reactor
Regulation’s (NRR’s)
Japan Lessons
Learned Division.
He joined the NRC
in 2007 as a Project
Manager in NRR’s
Division of Operating
Reactor Licensing
(DORL). Since then,
his positions included
Reactor Operations
Engineer, NRR’s
Technical Assistant for
Enforcement, DORL’s
Chief of Plant
Licensing Branch
III-2, and Chief of
the Projects Branch
in NRR’s Mitigating
Strategies Directorate. Prior to joining
the NRC, he served 8 years as a U.S.
Navy submarine officer. He received his
bachelor’s degree in Systems Engineering
from the U.S. Naval Academy.
