05000397/FIN-2008002-03
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Finding | |
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| Title | Operability of RHR-P-2C During the Suppression Pool Mixing Mode of Operation |
| Description | \\\"An unresolved item (URI) was identified pending Energy Northwests evaluation of Pump RHR-P-2C, in the suppression pool mixing mode of operation. On February 6, 2008, Energy Northwest took the Division 2 Emergency Core Cooling System Keepfill Pump, RHR-P-3, out of service for planned maintenance. Pump RHR-P-3, a nonsafety related pump, normally operates continuously and discharges to both of the Division 2 RHR Pumps RHR-P-2B and RHR-P-2C to assure that the respective pump injection lines are filled and pressurized. Keeping the injection lines filled and pressurized assures that, when Pumps RHR-P-2B or RHR-P-2C are started, that a water hammer event does not occur potentially damaging safety-related piping and supports. As an alternative to Pump RHR-P-3 keeping the system piping filled, in preparation for taking Pump RHR-P-3 out of service, Energy Northwest started Pump RHR-P-2B in the suppression pool cooling mode of operation and Pump RHR-P-2C in the suppression pool mixing mode of operation to keep their respective injection lines pressurized and filled while Pump RHR-P-3 was out of service. During an accident, the systems automatically re-align to their reactor vessel injection lineup for accident mitigation. The inspectors noted that while Pumps RHR-P-2B and RHR-P-2C were in the alternate lineups, that Energy Northwest considered both pumps available and operable. The inspectors requested the basis for operability because under design basis accident conditions of a coincident LOOP with a LOCA that a water hammer event may occur. Specifically, upon the LOOP, the main system pumps Pumps RHR-P-2B and RHR-P-2C would stop upon the loss of electrical power. As a result of the pump stopping and the piping configuration with the system return lineups to the suppression pool, the injection piping would immediately drain to the suppression pool depressurizing the system injection piping. Following the LOOP, the emergency diesel generators automatically start and in response to a LOCA the emergency safety-related systems, including Pumps RHR-P-2B and RHR-P-2C, automatically start. Upon pump start, a water hammer event would most likely occur due to the depressurized injection piping. Similar water hammer events associated with RHR systems were also provided in NRC Information Notice 87-10, Potential for Water Hammer During Restart of Residual Heat Removal Pumps, dated February 11, 1987. Energy Northwest provided a basis of operability for Pump RHR-P-2B while in the suppression pool cooling mode of operation. To summarize, the basis for operability of both Pump RHR-P-2B (as well as the Division 1 RHR Pump, RHR-P-2A) was
predicated on Energy Northwests response to an apparent violation (AV) (See AV 05000397/1993029-01 and Inspection Reports 05000397/1993029 and 05000397/1995029 for more details). The AV was identified during an NRC review of Licensee Event Report (LER) 93-01, Inoperable Suppression Pool Cooling Due to Potential Water Hammer, Revisions 0 and 1. The LER provided that water hammer could fail a train of RHR in suppression pool cooling mode due to a LOOP coincident with a LOCA. Subsequent analysis by Energy Northwest, as provided in an enforcement conference documented in Enforcement Conference and Management Meeting Report 05000397/1993037, and in LER 93-01, Revision 2, determined that Pumps RHR-P-A and RHR-P-2B were operable while operating in the suppression pool cooling mode of operation even with a LOOP coincident with a LOCA. The analysis determined that an accident sequence of a LOOP coincident with a LOCA, occurring while an RHR loop was in the suppression pool cooling (or suppression pool spray) mode of operation was not in the original design basis for the facility. Energy Northwest also provided that General Electric, the plant designer, supported the position, and that limited use of RHR in these operating modes during a LOOP and LOCA resulting in a water hammer event was not sufficiently credible to be included in the design basis accident analysis. Energy Northwest also provided in LER 93-01 that with adherence to limits on duration of RHR operation in the suppression pool cooling (or suppression pool spray) mode of operation that an RHR loop in that lineup would not be declared inoperable. Energy Northwest established the operational limits of Pumps RHR-P-2A and RHR-P-2B to less than an average of 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> per week in the suppression pool cooling (or suppression pool spray) mode of operation. Energy Northwest implemented procedure revisions to track and assure that the operational limit was maintained. Although the inspectors conceded that Energy Northwest established an operability basis for Pump RHR-P-2B, the inspectors noted that Energy Northwest did not have a similar basis for Pump RHR-P-2C while it was operating in the suppression pool mixing mode. Specifically, Energy Northwests basis for operability for Pump RHR-P-2B was based partly on the reliance of not exceeding a prescribed number of average hours per week. The inspectors questioned the basis for operability of Pump RHR-P-2C if the time operating in the suppression pool mixing mode of operation wasnt similarly tracked and limited. Energy Northwest documented the issue in AR/CR 177222. The inspectors noted that in addition to Pump RHR-P-2C that the low pressure core spray and the high pressure core spray systems were also subject to the same concerns when their respective keep fill pumps were out of service with the pumps operating in a test return lineup mode to the suppression pool. The licensee was still evaluating the condition at the end of the inspection period as provided in Action Request 179672. Consequently, a URI was opened pending an NRC review of Energy Northwests final evaluation of the acceptability of considering Pump RHR-P-2C operable while in the suppression pool mixing mode of operation (URI 05000397/2008002-03; Operability of RHR-P-2C During the Suppression Pool Mixing Mode of Operation). Energy Northwest issued Operations Department Night Order 915 to document the pending evaluation and to direct the control room staff to declare RHR-P-2C, low pressure core spray, and high pressure core spray systems inoperable with the systems lined up to return to the suppression pool pending a completion of the analysis |
| Site: | Columbia  |
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| Report | IR 05000397/2008002 Section 1R15 |
| Date counted | Mar 31, 2008 (2008Q1) |
| Type: | URI: |
| cornerstone | No Cornerstone |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.15 |
| Inspectors (proximate) | R Cohen Z Dunham C Johnsonb Hendersonr Cohen T Mckernon L Carson G Replogle W Sifre M Hayes M Bloodgood T Pate |
| INPO aspect | |
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Finding - Columbia - IR 05000397/2008002 | |||||||||||||||||||||||||||||
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Finding List (Columbia) @ 2008Q1
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