05000315/FIN-2012007-05
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Finding | |
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| Title | |
| Description | The inspectors identified an issue related to the definition of operability of the SG PORVs as specified by the TS. The most limiting design bases accident for the SG PORVs, is a tube rupture event. During this accident, the operators prevent overfill of the ruptured steam generator using the SG PORVs. Assuming a coincident loss of offsite power (LOOP) to the station (affecting both units), the only readily available source of pneumatic motive force for the SG PORVs is the unit-specific CAC, which has the capability of being powered from onsite emergency power (EDGs). The TS bases for the SG PORVs (B 3.7.4) states the Control Air System (the system composed of the CAC) provides the normal air supply for pneumatic control. Each unit-specific CAC is not safety-related and is not subject to a TS limiting condition for operation. Therefore, these compressors could be unavailable (i.e., for maintenance) for an indeterminate length of time, consistent with the performance goals established for the maintenance rule, regardless of the units current mode of operation. With the exception of emergent repair maintenance, all preventive maintenance is performed on the CACs when the units are online, in Mode 1. As defined in the facilitys Unit 1 and Unit 2 TS, A system, subsystem, train, component, or device shall be OPERABLE or have OPERABILITY when it is capable of performing its specified safety function(s) and when all necessary attendant instrumentation, controls, normal or emergency electrical power, cooling and seal water, lubrication and other auxiliary equipment that are required for the system, subsystem, train, component, or device to perform its specified safety function are also capable of performing their related support function(s). The electrical and control air appurtenances for the SG PORVs are non-safety grade and do not have an associated TS operability requirement. However, since the electrical control power and control air system are credited to ensure the SG PORVs will operate to perform the mitigating function of cooling the RCS during the SGTR accident with a LOOP, the inspectors concluded this equipment is required to be functional for the SG PORVs to be considered OPERABLE. The inspectors indentified several occasions when the CAC was non-functional; however, the licensee did not declare the PORVs inoperable. Specifically, a review of the facilitys unavailability records for the Unit 1 and Unit 2 CACs from January 1, 2000 to August 20, 2012 identified 13 instances (5 associated with Unit 1 and 8 associated Unit 2) when the units CAC was unavailable for greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the TS allowed outage time for two or more SG PORVs being inoperable. In three of those instances for Unit 1 (April 18, 2001, for 79.8 hrs, November 23, 2003, for 133.2 hrs, and April 7, 2008, for 108.9 hrs) and two of those instances for Unit 2 (February 12, 2003, for 71.8 hrs and January 16, 2006, for 103.5 hrs) the unavailability time of the CAC was in excess of the total TS allowed outage times of 54 hours6.25e-4 days <br />0.015 hours <br />8.928571e-5 weeks <br />2.0547e-5 months <br /> to place the unit in a mode where the limiting condition of operation does not apply. As stated in Section 1R21.6(b)(1), the licensee disagreed with the inspectors initial assumption with respect to the initial conditions of a LOOP affecting both units. The licensee believes their licensing basis for a SGTR is a concurrent LOOP in the affected unit and the unaffected unit maintains an intact source of offsite power. In the licensees scenario, the affected units SG PORVs would still have a source of immediate remote. |
| Site: | Cook  |
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| Report | IR 05000315/2012007 Section 1R21 |
| Date counted | Dec 31, 2012 (2012Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | A Stone C Brown C Tilton G Skinner J Corujo Sandin R Baker W Sherbinr Bakerb Jose C Tilton |
| INPO aspect | |
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Finding - Cook - IR 05000315/2012007 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Cook) @ 2012Q4
Self-Identified List (Cook)
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