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THE CHALLENGE:
For safety, spent or
exhausted nuclear fuel is usually stored under forty feet of water in specially
designed “fuel pools”. Water over the used fuel rods is an effective barrier to
the intense radiation escaping the rods. At a domestic USA nuclear power plant,
an aging spent fuel pool had to be prepared for decommissioning after many years
of service. In order for this process to be safely accomplished, it was first
necessary to fully encapsulate the radioactive isotopes that had escaped the
submerged fuel rods and attached themselves to the walls of the pool. Failure
to perform this task makes it possible for radioactive isotopes becoming
airborne and posing a health risk.
THE SOLUTION:
Working closely
with nuclear divers from Underwater Construction Corporation of Essex,
Connecticut, TFT produced a version of BIO-DUR 560 that could be applied by
pressure rollers under water to allow encapsulation of the pool walls before
draining.
BIO-DUR
560 is a lower viscosity version of BIO-DUR 561 which has become an industry
standard for underwater nuclear-related projects. To provide materials tailored
for specific applications, several variants of the BIO-DUR 561 formula have been
created with differences in viscosity and cure rate. BIO-DUR 561 itself is also
available in a “Nuclear” version approved by EPRI as an underwater applied
coating suitable for Service Level 1 applications within the primary containment
of a nuclear plant.
Working
under the nuclear conditions of a spent fuel pool meant careful attention must
be paid to the condition of the divers’ equipment because submerged working time
was limited and equipment reliability critical.
Operational aspects of this project were managed with the extensive experience
of Underwater Construction Corporation while the reliability and
“field-friendliness” of the BIO-DUR 560 assured optimum application rates.
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Specialized plural component equipment delivered proportioned
and pressurized coating components through 100’ of heated hose to a high
pressure mixing block. Exiting from the mixing block was a 10’ insulated “whip”
hose that was comfortable for a diver to handle. Consequently, divers had a
continuous supply of properly mixed coating material at the touch of a trigger.
Applications were made from the waterline down to a depth of 10–15 feet as the
water level was lowered. Utilizing this procedure, the contaminated surfaces
were never directly exposed to air.
THE RESULT:
The coating cured to a
“firm”, condition within 3 hours and was fully hard and tightly adhered after 12
hours. The operation proceeded on schedule and has set the standard for similar
future projects.
Reports to TFT indicated
that the work went very smoothly and totally successfully.
(Similar Case
Histories: 32 & 40)
(Underwater
Construction Corporation link)
(News Article from "Inside Nuclear" Magazine)
For more information regarding this project contact:
Jeff Longmore, Technical Director
Thin Film Technology, Inc.
P.O. Box 580669
Houston TX 77258-0669
(713) 910-6200
FAX: (713) 910-6210
E-mail: jeff@thinfilmtech.net
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