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Pressure Boundary Integrity Issues for Pressurized Water Reactors
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Pressurizer Issues
Operating experience, both domestic and foreign, has demonstrated that
Alloy 82/182/600 materials connected to a pressurized water reactor (PWR)
pressurizer are susceptible to primary water stress corrosion cracking
(PWSCC). Most recent leakage events were the result of axially-oriented
PWSCC of the pressure boundary portion of pressurizer heater sleeves.
Recent non-destructive examination results on heater sleeves have demonstrated
that circumferentially-oriented PWSCC can occur in the non-pressure boundary
portion of these components.
Extensive operational experience with PWSCC in Alloy 82/182/600 materials
used in the fabrication of pressurizer penetrations and steam space piping
connections is not surprising. The initiation and growth of PWSCC flaws
is known to be strongly dependent on the temperature of the primary system
water to which the Alloy 82/182/600 materials are exposed. Given the fact
that at the pressurizer, the reactor coolant system environment attains
a temperature of about 650°F (343°C), PWSCC should be expected
to occur in these materials and an effective degradation management program
is warranted. The following links include information on the NRC and nuclear
industries activities on reactor coolant pressure boundary integrity of
the pressurizer.
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