05000369/FIN-2007005-03
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Finding | |
|---|---|
| Title | Failure to Take Adequate Corrective Action for Implementations of SAFETY-RELATED Rn Strainer Backwash |
| Description | On August 6, 2007, the licensee identified that the procedures for performing a manual backwash of the nuclear service water strainers directed operators to use a nonseismically qualified, non-safety related air system to manipulate the valves required for the manual backwash function. This unqualified air system cannot be relied upon to function during a DBA. These backwash procedures were written as part of a 2003 plant modification (MGMM-14403) to upgrade and reclassify the manual RN filtering and backwash functions to safety-related, in response to NRC concerns (PIP M-02-2427). The concerns were that the changed environment of Lake Norman had caused seasonal macro-fouling of the strainers from increased concentrations of Alewife fish during late July and early August. The basis for reclassification was to ensure proper operation of the strainer in the event that significant fouling from these fish occurred. This modification also failed to identify reliance on other non-safety instrumentation and components for performing safety-related backwashes, including the UFSAR-credited differential pressure instrument. The reliance on non-safety-related systems to perform the safety-related manual backwash function was not recognized during the modification. The inspectors found that the licensee has continued to evaluate this issue after the LER was submitted. These continuing evaluations address such aspects as what happens inside the strainer, at what point does flow become less than what is needed as identified in design calculations, and what actions would operators take that might impact when the minimum flow point is reached. This finding involves the inability to perform a safety-related manual backwash of nuclear service water strainers due to reliance on non-safety systems and motive force to provide the backwash function. Without manual backwash capability during macrofouling season, these strainers could become permanently fouled, which could prevent the nuclear service water system from performing its intended safety function. This issue is more than minor because it affects the availability, reliability, and capability of the nuclear service water system and is related to the design control, protection from external factors (loss of heat sink), and procedure quality attributes of the mitigating systems cornerstone. This issue is unresolved pending NRC review of the licensees evaluations of past strainer operability, including the licensees classification of significant fouling periods and the engineering analyses of the fish clogging effects on the strainer. This item is identified as Unresolved Item (URI) 05000369,370/2007005-03 Failure to Take Adequate Corrective Action for Implementation of Safety-Related RN Strainer Backwash. This issue is in the licensees corrective action program as PIP M- 07-4313. |
| Site: | McGuire  |
|---|---|
| Report | IR 05000369/2007005 Section 4OA3 |
| Date counted | Dec 31, 2007 (2007Q4) |
| Type: | Other: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | S Rose V Mccree C Evans J Moorman J Wray R Bernhardh Gepfordj Brady J Diaz J Moorman R Eul R Hamilton R Taylor S Walker W Looc Evansr Bernhard S Rose |
| INPO aspect | |
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