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NuclearPlantJournal.com Nuclear Plant Journal, September-October 2013
Ultrasonic Leak...
(Continued from page 43)
was conceived by Phillip Twaddle and
a patent application was submitted in
2012. The shear wave energy (SWE)
values predict leak performance after
installation into the nuclear power plant.
I have discovered the acceptance range
for Target Rock 3-stage SRVs – the
pilot, the 2nd stage, and the main seats
have different ranges of acceptability.
This technology has also been used
successfully on Crosby pressurizer safety
valves (PSVs), Dresser Electromatic
relief valves (ERVs), and Dresser power
operated relief valves (PORVs). These
valves have slightly different acceptance
ranges than the Target Rock 3-stage
SRVs. Since the SWE data results
have been collected on ninety-six main
steam valves during as-left certification
over the last 18 months, the test results
are conclusive that the Scientech test
results are an effective tool to specify
a statistically based acceptance limit
called the Upper Control Limit (UCL),
which means that valves that are as-left
certified with Scientech values below the
UCL should perform leak free for two
operating cycles.
Productivity/Efficiency
The productivity performance was
seen through not requiring a shutdown
due to poor valve performance. The
Scientech SWE test results are the best
available technology for predicting leak-
free valve performance for the next two
2-year refuel cycles. There is a direct
correlation between a steam leak rate and
the quantity (range covers two orders of
magnitude) of the Scientech SWE values
recorded.
Transferability
The use of Scientech SWE values
to determine valve acceptance following
refurbishment or fabrication of new
valves is applicable throughout the
nuclear industry. Exelon has tested 96
main steam valves after refurbishment:
Crosby PSVs – Byron Station Units 1 & 2
(BY), and Braidwood Station Units 1 & 2 (BR);
Electromatic Relief Valves (ERVs) – Quad
Cities Station Units 1 & 2 (QC) , Dresden
Station Units 2 & 3 (DR), PB, and LGS;
Dresser PORVs and PSVs – TMI; and
Target Rock 3-stage SRVs – DR, QC, PB,
and LGS. The technology is transferable
to other nuclear companies, valve
rebuilders, and valve manufacturers.
Contact: Phillip Twaddle, Exelon
Generation, telephone: (630) 657-3866,
email:
Reference Chart -Ultrasonic Sensor photograph and 4 Ultrasonic Sensor
s.
lead-times being built into the schedule.
Another hidden cost that at times may
be overlooked is the FOB point. Can the
suppliers deliver on their own trucks or
do they contract with a common carrier?
Can customers get quoted a delivered
price and if so is the delivered cost
competitive? If a supplier has its own
fleet of trucks, a customer can often count
on a more reliable delivery schedule and
competitive cost structure.
It is critical that the “Total Cost of
Ownership” be recognized and logistics
is one of the key levers. The final
consideration in terms of logistics that
needs to be considered is the potential
damage to materials when products
are shipped via common carrier. When
materials are received in a damaged,
non-conforming condition, the lead-time
automatically expands as replacement
material is prepared for reshipment and
costs begin to escalate. Proper packaging
to assure that materials arrive in the
desired condition is critical, but it’s hard
to win a battle with a fork lift truck at
a freight terminal. If a supplier delivers
material on their own equipment there
is a benefit to be realized from a Quality
standpoint.
Ultimately, when looking to qualify
companies for anApproved Supplier List,
Purchasing Managers need to be sure
to consider the effects of sourcing and
logistics as they relate to supply chain
costs. Each link that can be eliminated
in the Supply Chain will have a positive
effect on quality, lead-times and overall
costs.
Contact: Chris White, Chatham Steel
Corporation, 2702 Cheek Road, Durham,
North Carolina 27704; telephone: (919)
Understanding the...
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