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| Entered date | Event description | |
|---|---|---|
| ENS 40632 | 1 April 2004 00:44:00 | A new worst case single failure was identified on 03-31-04 for the small break LOCA analysis of record due to a postulated loss of a DC power bus. This condition may result in the analysis of record exceeding 10 CFR 50.46 acceptance criterion of 2200 F when a small break LOCA with this failure is postulated. The current small break LOCA analysis of record assumes a single failure of one Emergency Diesel Generator (EDG) and credits flow from one charging pump. The peak cladding temperature for the analysis of record is 1929 F compared to the acceptance criteria of less than or equal to 2200 F. Half of the flow from a charging pump is assumed to go to the RCS and half is assumed to flow out the break. It was identified on 03-31-04 that a single failure of a DC power bus would be more limiting than the currently assumed single failure of an EDG. The DC bus failure will result in the EDG failure to start and also cause a charging loop isolation valve to the RCS to fail closed on loss of DC power. The other charging flow path to the RCS is on the assumed broken RCS leg so it is assumed to be spilled to the containment resulting in no charging flow to the RCS. Therefore, no charging flow would be delivered to the RCS as assumed in the current small break LOCA analysis of record. This condition has not been analyzed. Engineering judgment indicates that in the event of a small break accident the 10 CFR 50.46 acceptance criterion of 2200 F may be exceeded if the charging flow is not credited in the analysis of record. Therefore, this condition is reportable pursuant to 10 CFR 50.46 and 10 CFR 50.72(b)(3)(ii)(B). The current conservatism in the analysis of record and previous Westinghouse SBLOCA non-design basis scoping analyses using the NOTRUMP code provide assurance the plant is operating in a safe manner and is operable. The NOTRUMP analyses included cases with no changing flow. The peak clad temperature for these analyses were significantly below the acceptance criteria of 2200 F by more than 200 F. Thus, if an analysis were performed for Waterford 3 with the NOTRUMP code there is reasonable assurance due to the large margins that acceptable results would be achieved without any charging flow. This report is based on conservative judgment and available information. This report may be retracted based on the results of further evaluation. The licensee notified the NRC Resident Inspector. |
| ENS 40278 | 27 October 2003 00:21:00 | Inspection of the pressurizer bottom nozzles in accordance with the Alloy 600 Program during Refuel 12 identified a wet stain on heater sleeve C1, and a nozzle with a white substance extruding from a portion of the penetration on heater sleeve C3. The substance could not be verified at the time, and further investigation is required to determine if the substance is boron on heater sleeve C3. This condition constitutes a degradation of the RCS Pressure Boundary and is reportable pursuant to 10 CFR 50.72(b)(3)(ii)(A). The NRC Resident Inspector will be notified of this event by the licensee. |