65 Flood
Evaluations
by Spring
2015
By Patrick T. Brunette, ENERCON.
Patrick T. Brunette
Patrick T. Brunette, P.E., is a National
Engineering Lead with ENERCON and
has over thirty years’ experience as
an environmental
professional with
extensive experience
in risk/cost control,
project management,
design/build for
engineering projects
and regulatory
compliance. Mr.
Brunette specializes
in Risk/Cost Control,
project management,
Quality Assurance/
Quality Control (QA/
QC), and design
build for engineering,
consulting, and
construction projects.
He has provided
hydrologic engineering support for
U.S. Nuclear Regulatory Commission
(NRC) projects, including Probable
Maximum Flood (PMF), Probable
Maximum Precipitation (PMP) and
hydrologic modeling. He is active
in Nuclear Industry Institute (NEI)
Flooding Task Force that interacts with
the NRC Staff. He is currently providing
overall engineering management
oversight on NRC related “Flooding
Analysis.” Mr. Brunette holds a B.S.
in Mechanical Engineering from
the University of Oklahoma and is a
Registered Professional Engineer in
over 20 states. He is a Corrective Action
Project Manager as well as a Certified
Remediation Consultant.
Industry Response
to Flood Hazard
Re-Evaluations
The NRC issued a 10 CFR 50.54(f),
Requirements for Renewal of Operating
Licenses for Nuclear Power Plants
information request letter on March
12, 2012, to all nuclear power reactor
licensees asking them to perform a re-
evaluation of the flooding hazards for
each of their facilities. This request came
as a result of the events that occurred in
Japan following the 2011 tsunami that
crippled the Fukushima Daiichi nuclear
facility.
In response to the NRC’s request,
re-evaluated flooding hazard results are
being compared to
the plants’ current
licensing basis. Im-
portantly, the NRC’s
current guidance for
flooding hazard re-
evaluation is different
than that used prior to
2011, often produc-
ing modeled flood el-
evations above design
basis flooding events.
Among the signifi-
cant differences from
older methodologies
are the use of updated
Hydro-Meteorologi-
cal Reports (HMRs)
as inputs to the models and the modeling
of river floods resulting from collapse of
all
upstream dams. It should also be not-
ed that the NRC-approved re-evaluation
methodologies do not include a method
to report return periods (i.e. flood fre-
quency) – providing no information for
use in probabilistic risk assessment of the
modeled flooding events.
For cases in which the re-evaluated
model results are found not to be bounded
by a plant’s Current Licensing Basis
(CLB), the NRC requires the licensee to
develop an Integrated Assessment of the
plant’s response to flooding hazards. The
Integrated Assessment must consider all
modes of plant operation that could be
affected by a flood, including shutdown,
and take into account other events that
could reasonably be expected to occur at
the same time as a flood. When licensees
report the results of these assessments to
the NRC, they must outline the measures
that have been taken, or are planned,
to deal with the re-evaluated flooding
hazard.
For an Integrated Assessment, the
upgraded protection systems must be
able to withstand the flood event with
margin. If any Structures, Systems and
Components (SSC) important to safety
are compromised, the licensee must
have mitigation capabilities in place.
Mitigating strategies acceptance criteria
are to maintain or restore capabilities for
core cooling, containment and spent fuel
pool cooling.
The Integrated Assessment uses
many methods, including design features,
structures, and procedures, to address
protection of nuclear plant safety
functions against flooding. Depending on
the site, these elements have included:
•
Mitigation Strategies, such as
switching plant’s cooling, power,
and controlling operations to planned
temporary systems such as are used
in Diverse and Flexible Coping
Strategies referred to as FLEX.
•
Placement of essential systems and
structures at elevated levels.
•
Exterior barriers that protect safety
equipment from flooding and the
various dynamic forces created
by wave run-up and current. Such
barriers include levees, seawalls,
bulkheads, and breakwaters. In some
cases existing barriers are upgraded.
•
Plant designs that incorporate sealed
engineered
barriers,
including
reinforced concrete walls and
watertight access openings for
personnel and equipment to keep
water from penetrating into areas
containing safety-related equipment.
•
Site grading designed to cause water
to flow away from buildings and
equipment.
•
Site procedures and training to guide
plant staff in their response to a flood.
To estimate the level of effort taken
to comply with the NRC information
42
NuclearPlantJournal.com Nuclear Plant Journal, September-October 2014
