During Callaway refueling outage 19 on 5/8/13 at approximately
1900 hour0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> CDT, water was observed dripping from piping insulation in the overhead by
RCS loop 4. Further investigation determined it was near Safety Injection (
EP) vent valve EPV0109. A scaffold was built and insulation was removed to perform an inspection. At approximately
0509 hours0.00589 days <br />0.141 hours <br />8.416005e-4 weeks <br />1.936745e-4 months <br /> CDT on 5/9/13, engineering inspected the piping and determined there was a crack in the socket weld where 3/4 inch vent valve EPV0109 is connected to the 'B' train injection piping to
RCS loop 4 Cold Leg. The estimated leakage rate through the crack is 6 (six) drops per minute. The configuration of this vent valve is a 3/8 inch flow restrictor socket welded to the six inch piping and a 3/4 inch vent valve socket welded to the flow restrictor. The crack is in the socket weld between the
ASME code class 1 flow restrictor socket and the
ASME code class 2 vent piping.
Callaway plant was in mode 6 with refueling pool level greater than 23 feet above the reactor vessel flange at the time of the discovery. The 'A' RHR train which discharges to RCS loops 1 and 3 Cold Legs is the currently operable RHR train. 'B' RHR train was declared inoperable when the weld crack was identified. Only one RHR train is required to be operable at the present plant Mode of applicability. Repair plans are being developed.
Basis for Reportability: This condition constitutes abnormal degradation of a principle safety barrier due to unacceptable welding defects within the primary coolant system.
There is a check valve between this leak and the reactor coolant system. Therefore, this is considered unisolable and pressure boundary leakage.
The licensee notified the NRC Resident Inspector.
