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NuclearPlantJournal.com Nuclear Plant Journal, July-August 2014
Ensuring
Nuclear
Plant
Safety
During
Power
Loss
By Ken Price, AREVA Inc.
Ken Price
Ken Price serves as Product
Development Manager in the Reactors
& Services Business of AREVA Inc. Ken
moved into this position in 2012 after
working 24 years as
Technical Support for
AREVA and previous
iterations of the
company.
Ken began his
career in 1975
in procurement
engineering
at Babcock &
Wilcox (B&W)
while completing
an engineering
administration
program at George
Washington
University. He
was transferred to
AREVA’s Old Forest
Road Nuclear Parts Center in 1984
and held the role of business manager
through 1988. He has been working with
Jeumont reactor coolant pump (RCP)
products since 1999.
A graduate of North Carolina State, Ken
holds a bachelor’s degree in Engineering
Operations.
In the relentless quest to make plants
continually safer and more reliable, one
issue in particular has garnered a lot of
attention – from the industry, the U.S.
Nuclear Regulatory Commission (NRC),
the public and the media: what happens
when a plant loses power during a natural
disaster or another extreme event? The
nuclear industry is working tirelessly to
address this question by developing new
tools and products to ensure the safety
of nuclear plants during natural disasters
and other extreme conditions.
AREVA Inc. is working to help
utilities ensure the safety of their plants
during both normal operating conditions
and extreme events. In fact, through its
subsidiary AREVA JEUMONT, AREVA
completed an exten-
sive
development
and qualification pro-
gram for its new Pas-
sive Shut Down Seal
(PSDS), which limits
reactor coolant sys-
tem leakage through
the reactor coolant
pumps (RCP) during
post-accident event
conditions with loss
of all sources of seal
cooling. Under these
conditions, a typi-
cal current RCP hy-
drostatic seal design
could allow leakage
through the seal of
approximately
21
gallons per minute. With AREVA’s PSDS
installed, the leakage through the RCP
seal is limited to less than one gallon per
minute for up to seven days after the loss
of cooling. As a result, this robust mecha-
nism improves plant safety because the
controlled low leakage gives the plant op-
erator time to focus on reducing the pres-
sures and temperatures, and mitigating
any other post-accident impacts.
The PSDS is simple, with only four
operating parts and a single triggering
mechanism, which adds reliability.
This triggering mechanism, known as
the fuse spacer, is made from a high-
temperature polymer that keeps the
energizing component, known as the
wave spring, compressed. This keeps the
PSDS components under compression in
normal plant operation.
The RCP shaft with the driver motor
on one end and the impeller on the other
must pass through the reactor coolant
system (RCS) boundary to immerse the
impeller in the RCS water. The RCPs
utilize a three-stage hydrostatic seal that
is designed to control the leakage through
the seal and break down the RCS pressures
from full system pressure to ambient
pressure. This pressure breakdown is
accomplished via the RCS water passing
through the three stages with each stage
designed to break down a portion of
the pressure. The first stage seal breaks
down roughly 96% of the pressure while
Passive Shut Down Seal.
