05000483/FIN-2012002-01
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Finding | |
|---|---|
| Title | Failure to Properly Evaluate the Design of Steam Generator Drain Plugs |
| Description | The inspectors reviewed a non-cited violation of 10 CFR Part 50, Appendix B, Criterion III, Design Control, after the licensee failed to ensure that testing used to verify the adequacy of a steam generator drain plug was conducted under expected design conditions. On November 1, 2011, containment workers noticed reactor coolant system leakage out of the steam generator B manway onto the floor. Reactor coolant system water from the reactor cavity was draining past a dislodged tube plug out the steam generator manway onto the floor below. Plant operators verified the spent fuel pool isolation to the reactor cavity was intact and pumped the approximately 400,000 gallons of reactor cavity water to the refueling water storage tank. This stopped the leak and left the reactor coolant system at a midloop condition. The licensee\\\'s root cause analysis determined that criteria for the drain plug design and installation specifications were inadequate. Specifically, the plug had not been tested under expected conditions such as a slick environment due to boron in the water. Testing with a simulated boric acid solution revealed that slippage occurred at much lower loads than the 70 psi assumed in the original design review. The possibility of side loads being applied to the plug during eddy current maintenance had also not been properly considered. Callaway Action Request 201109257 was generated with actions to address the causes of the plug becoming dislodged. This finding is more than minor because it is associated with the reactor coolant system equipment and barrier performance attribute of the Barrier Integrity Cornerstone and affects the associated cornerstone objective to provide reasonable assurance that physical design barriers (fuel cladding, reactor coolant system, and containment) protect the public from radionuclide releases caused by accidents or events. A senior reactor analyst performed a bounding significance determination using NRC Inspection Manual 0609, Appendix G, Shutdown Operations Significance Determination Process. |
| Site: | Callaway  |
|---|---|
| Report | IR 05000483/2012002 Section 4OA3 |
| Date counted | Mar 31, 2012 (2012Q1) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | D Dumbacher N O'Keefe Z Hollcraft |
| INPO aspect | |
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Finding - Callaway - IR 05000483/2012002 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Callaway) @ 2012Q1
Self-Identified List (Callaway)
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