05000255/FIN-2014008-12
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Finding | |
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| Title | Component Cooling Water System Licensing Bases |
| Description | The inspectors identified an Unresolved Item (URI) regarding the licensing bases for the Component Cooling Water (CCW) system. Specifically, the inspectors require clarification as to what failures of the CCW system the licensee needs to postulate and evaluate. The NRC will conduct further inspection to determine when these changes to the licensing bases occurred. As part of the 2014 Component Design Bases Inspection (CDBI), the inspectors selected CCW pump P-52B and relief valve RV-0956 for review. Both of these components were part of the CCW system. The CCW system was designed as a closed cycle system, where both trains share a common suction and common discharge header. This means that although there were redundant pumps and heat exchangers, the system's piping was not designed to be redundant and a single pipe break or failure of the pressure boundary could result in the complete loss of CCW. One of CCW's safety functions was to transfer heat from the reactor and containment (post-Design Bases Events/Accidents) to the ultimate heat sink. Another important safety function for CCW was to provide cooling to the Engineered Safeguard Systems' (ESS) and containment spray (CS) pumps. Per the licensees design bases, cooling to the ESS pumps was required to maintain their operability. When reviewing the licensing bases for the plant, it was not clear what type of failures needed to postulated for the CCW system under post-accident conditions. The licensee's position was postulating a passive failure of CCW concurrent with a design bases accident (DBA) was not within their licensing bases. The licensee's position was that no active single failure, according to their definition in FSAR Section 1.4.16, would render CCW inoperable. They also considered a postulated failure of the non-safetyrelated portion of the CCW system inside containment as beyond design bases, except as result of a seismic event which was not postulated to occur in conjunction with an accident. Currently, the licensee credits post-accident heat being removed from containment by a combination of containment air coolers (CAC) and the containment spray (CS) system. The CAC are supplied by service water and are independent of the CCW system. Per the current design, the licensee needs either two CS pumps or one CS pump and three CACs. Both alternatives require the CCW system to remove heat from the CS system. However, the original design took credit for the CS and the CAC as independent and redundant in their capability to remove heat from the containment. In other words, originally the licensee needed either two CS pumps or three CACs. Additionally, the original design allowed for the capability to swap cooling water to the ESS pumps from CCW to service water remotely from the main control room (MCR). Both of these design flexibilities have been either lost or eliminated due to subsequent design changes. The inspectors noted the agency staff had previously evaluated the susceptibility of CCW to loss of function following certain assumed CCW pipe breaks during the Systematic Evaluation Program(SEP). This was documented on SEP Topic IX-3, Station Service and Cooling Water Systems Palisades, February 22, 1982. The agency staff had concluded the CCW design was not in conformance with GDC 44, regarding capability and redundancy of essential functions of the system. However, the staff noted the essential functions of CCW could be performed by other systems under all operating conditions. The SEP evaluation explicitly addressed a passive failure of the CCW system under post-accident conditions and concluded that the CACs would be capable of removing heat from containment. The inspectors were concerned that if the CCW system became inoperable as the result of non-safety-related component failures, the plant would no longer have the redundant capability to remove heat from the containment during a DBA, or provide alternate cooling to the ESS pumps from the MCR. In addition, the inspectors needed to clarify the licensing bases regarding a postulated loss of CCW concurrent with a design bases accident. This issue is unresolved pending further inspection to determine when these changes to the licensing bases occurred. |
| Site: | Palisades  |
|---|---|
| Report | IR 05000255/2014008 Section 1R21 |
| Date counted | Dec 31, 2014 (2014Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | A Stone C Baron C Brown C Zoia H Leake J Corujo-Sandin L Rodriguez S Sheldona Armstronga Nguyen C Hunt G Hansen G O'Dwyer J Boettcher J Cassidy J Coroju-Sandin J Jandovitz J Lennartz J Rutkowski L Rodriguez M Domke M Holmberg M Keefe T Taylor V Myers |
| INPO aspect | |
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Finding - Palisades - IR 05000255/2014008 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Palisades) @ 2014Q4
Self-Identified List (Palisades)
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