05000237/FIN-2008002-01
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Finding | |
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| Title | LPCI Heat Exchangers Design Calculation Deficiencies and Discrepancies |
| Description | The inspectors identified an unresolved item (URI) regarding the ability of the Unit 2 and Unit 3 LPCI heat exchangers to perform their design safety functions after a design basis loss of coolant accident (Design Basis Accident (DBA)-LOCA). During a routine thermal performance test on March 21, 2008, the licensee determined that the 3B LPCI heat exchanger had degraded. Specifically, the heat removal capability was determined to be 70.586 MBtu/hr at design conditions which was below the design heat removal rate of 71 MBtu/hr as shown in UFSAR Table 6.2-3b. The licensee determined the heat exchanger was operable but degraded. On April 14, 2008, while completing actions associated with a concern raised during the NRC Component Design Bases Inspection (05000237/2007006; 05000249/2007006), the licensee discovered that the increased containment pressure expected as a result of extended power uprate (EPU) post-LOCA conditions was not considered in the containment analysis. The increased containment pressure would result in an increased LPCI system pressure which required an increase in the assumed containment cooling service water (CCSW) system pressure to ensure that the CCSW system pressure would always be 20 psid more than the LPCI system. This differential pressure was required to prevent radioactive water from leaking from the LPCI system into the CCSW system and discharging to the Kankakee River. The licensee determined that the required throttling of the CCSW system flow to maintain a higher pressure would reduce the CCSW system flowrate below the 5,000 gpm assumed in DBA-LOCA design calculations. The licensee determined that the CCSW system flowrate could be as low as 3,798 gpm. The inspectors were also concerned that the associated increase in containment temperature resulting from the increased pressure may not have been considered by the licensee in determining the maximum reactor building room temperatures assumed for the environmental qualification of equipment throughout the reactor building. This potential omission will be considered by the next URI. The licensee initiated Assignment Report (AR) 763663 and determined the heat exchangers were operable at a maximum river temperature of 85 degrees Fahrenheit. (Current temperature was about 75 degrees Fahrenheit.) This issue is considered unresolved (URI 05000237/2008002-01 (DRS) URI 05000249/2008002-01 (DRS)) pending the licensees completion of a past operability determination and inspectors review of the evaluation |
| Site: | Dresden  |
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| Report | IR 05000237/2008002 Section 1R07 |
| Date counted | Mar 31, 2008 (2008Q1) |
| Type: | URI: |
| cornerstone | No Cornerstone |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.07 |
| Inspectors (proximate) | T Bilik D Melendez-Colon W Slawinski C Phillips C Brown M Ring C Acosta Acevedoj Bozga J Draper R Murray E Sanchez-Santiago R Winter F Ramirezr Jicklingd Melendez-Colon W Slawinski C Phillips M Ring R Schulz J Tapp R Russell |
| INPO aspect | |
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Finding - Dresden - IR 05000237/2008002 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Dresden) @ 2008Q1
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