05000237/FIN-2010004-02
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Finding | |
|---|---|
| Title | Failure to Seal Holes in the Floor Above the Emergency Core Cooling System (ECCS) Corner Rooms |
| Description | During a walkdown of the Unit 2 and Unit 3 reactor buildings the inspectors identified: That there were holes in the floor on both units, which would allow flood water to bypass the berms around the stairways to the ECCS corner rooms. The holes in the floor could also potentially result in a loss of all ECCS pumps. In regard to the first observation, the inspectors reviewed a letter from the NRC to Commonwealth Edison (the licensee) dated August 20, 1982. The subject was, SEP [Systematic Evaluation Program] Topic III-5.B, Pipe Break Outside Containment - Dresden Nuclear Power Station Unit 2. The enclosure to the letter was the NRCs Safety Evaluation Report (SER) for SEP Topic III-5.B. In the safety evaluation, the NRC reviewed the licensees response to a previous NRC concern about the failure of the RBCCW piping above the 23-1 and 24-1 switchgear on Unit 2. The licensee responded that there were several holes in the floor inside the bermed area around busses 23-1 and 24-1. The largest hole had a one and one-half inch lip around it. The licensee stated that the lip would be notched and that the holes would be sufficient to let the water drain before it could get high enough to impact the safety-related busses. There was no mention of Unit 3 in the safety evaluation
In regard to the second observation, the inspectors reviewed DR PSA-012, Internal Flood Evaluation Summary and Notebook, dated May 2009. This document supported the licensees probabilistic risk assessment, but was not part of the licensing basis. This document stated that the berms around the ECCS corner room stairs were credited in the internal flooding analysis. A review of the licensing basis to determine the design requirements of the ECCS corner room stairway berms was an unresolved item. (URI 05000237/2010004-02; 05000249/2010004-02) |
| Site: | Dresden  |
|---|---|
| Report | IR 05000237/2010004 Section 1R06 |
| Date counted | Sep 30, 2010 (2010Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.06 |
| Inspectors (proximate) | G Roach D Melendez-Colon C Phillips T Go J Cameron M Learn R Edwardsd Melendez-Colonc Phillips M Ring T Go E Coffman J Draper D Sand |
| INPO aspect | |
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Finding - Dresden - IR 05000237/2010004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Dresden) @ 2010Q3
Self-Identified List (Dresden)
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