05000341/FIN-2008002-01
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Finding | |
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| Title | Failure to Perform Adequate Evaluation for Penetrations in Reactor and Auxiliary Building Walls |
| Description | The inspectors identified an unresolved item (URI) for the licensees failure to perform an adequate 10 CFR 50.59 evaluation for approximately 55 penetrations in the reactor and auxiliary building walls. The licensee entered this issue into its corrective action program and initiated a review of the cumulative tornado missile damage probability calculations. On August 19, 1988, the licensee identified approximately 36 penetrations in the exterior walls of the reactor and auxiliary buildings that were sealed with foam. The licensee could not find any documentation to show that those penetration seals had been evaluated for their ability to protect safety-related equipment located within the buildings from the postulated effects of tornado-generated missiles. The licensee entered this issue into their corrective action program as Deviation Event Report (DER) 88-1528. The licensee later discovered an additional 19 penetrations that required a similar evaluation. The licensee contracted an engineering consultant to perform the required evaluation. This evaluation was documented as SAD-524, Probabilistic Analysis of Tornado Missile Hazard Due to Some Penetrations and Openings in Reactor/Auxiliary Building Walls, dated February 23, 1989. The evaluation concluded that the aggregate probability of damage to all 55 newly identified vulnerable areas was 1.15E-7 per year. The methodology used in estimating these probabilities utilized the TORMIS computer code NP-2005, Electric Power Research Institute, August 1981 edition. The licensee used the results of SAD-524 to justify a change to UFSAR Section 3.5.1.3, which discussed various analyses on tornado missile hazards, to include justification for not providing missile protection for the 55 newly identified penetrations. The licensee performed Safety Evaluation SE-89-0094 and concluded that prior NRC approval of the UFSAR change was not required because of a belief that the probability of damage was low enough not to be a design basis consideration. The licensee made this determination based on their review of NRC Standard Review Plan 3.5.1.4 and Regulatory Guide 1.117 which stated that additional missile protection was not required if the cumulative site-wide probability of damage was less than 1.0E-7. The licensee determined that the actual probability was likely less than 1.15E-7 and revised the UFSAR without seeking prior NRC approval. When the licensee performed this revision, 10 CFR 50.59 required, in part, prior NRC approval if the change either increased the probability of a malfunction of equipment important to safety previously evaluated in the UFSAR or if the change created the possibility of an equipment malfunction of a different type than any previously evaluated in the UFSAR. Because the UFSAR previously assumed the reactor and auxiliary building walls provided missile protection for safety-related equipment inside the respective buildings, tornado-induced missile damage of that equipment was not previously evaluated in the UFSAR. As such, the newly identified non-missile protected penetrations constituted both an increase in the probability of damage to safety-related equipment and the possibility of an equipment malfunction of a different type than any previously evaluated in the UFSAR. The inspectors reviewed SAD-524 and raised concerns with the licensee regarding the evaluation. First, the October 1983 NRC safety evaluation that approved TORMIS required the licensee to consider five specific points and to provide the relevant information, but the documentation was inadequate to assure that all five points were considered. Second, the licensee evaluated the cumulative probability of the newly discovered penetrations but not the cumulative probability of all susceptible targets. Consequently, the inspectors could not utilize the results of SAD-524 to determine the significance of the underlying issue. At the close of this inspection period, the licensee was revising the cumulative probability calculated in SAD-524. This issue will remain unresolved until the inspectors review the licensees final evaluation of the cumulative probability of site-wide damage from tornado-induced missiles: URI 05000341/2008002-01, Failure to Perform Adequate Evaluation for Penetrations in Reactor and Auxiliary Building Walls |
| Site: | Fermi  |
|---|---|
| Report | IR 05000341/2008002 Section 1R01 |
| Date counted | Mar 31, 2008 (2008Q1) |
| Type: | URI: |
| cornerstone | No Cornerstone |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.01 |
| Inspectors (proximate) | T Steadham M Phalen R Morris C Lipaa Dunlopj Cassidy T Steadham M Phalen D Jones R Morris A Wilson V Meghani F Tran |
| INPO aspect | |
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Finding - Fermi - IR 05000341/2008002 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Fermi) @ 2008Q1
Self-Identified List (Fermi)
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