05000424/FIN-2007006-04
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Finding | |
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| Title | Capability of Auxiliary Feedwater System to Meet Design and Licensing Requirements. |
| Description | 520.5 gpm and the MDAFW pumps could deliver a flow of 547 gpm. For faulted steam generator cases this calculation predicted a maximum flow of 1038.5 gpm. This review identified the following concerns: The accuracy of the AFW system resistance values obtained from plant testing did not evaluate the effect of accuracy of the instrumentation used on the calculation results. Information provided in the calculation states: In view of the scattered test data, it is obvious that the inaccuracy and uncertainty were involved in pressure / flow measurements. To minimize the effect, the representative orifice dP (i.e., the average dP) is used for new orifice sizing. In addition to the data averaging, one set of data points was completely discarded because it was not consistent with the other data without any analysis of the reasons for the differences. Considering the fact that a typical instrument error associated with just the flow measurement office is 2 percent and the very small system margins, it is not clear that this analysis can demonstrate the systems ability to satisfy the intended safety function by providing above the total minimum flow of 510 gpm to intact steam generators while not exceeding the value of 1050 gpm used in the containment analysis for a faulted steam generator. The inspectors reviewed surveillance procedure 28210-C, Main Steam Line Code Safety Valve Setpoint Verification, Revs. 15, 16, 17, and 18 for the steam generator safety relief valves (SRVs) 1PSV3001, 1PSV3011, 1PSV3021, 1PSV3031, 2PSV3001, 2PSV3011, 2PSV3021, and 2PSV3031 completed from March 2003 through March 2005. This review identified that this procedure established the as-found acceptance criteria for these valves to be a range 1149 to 1209 psig (1185 +3%, -2%) and the as-left 1173 to 1197 psig (1185 +1%, -1%). This allowable band for SRV settings was not applied to the analysis to determine the worst case acceptable high and low steam generator back pressure which could further decrease the available margin for the minimum flow cases for the higher SRV setpoints, while decreasing the available margin for the faulted steam generator case for the lower SRV setpoints. The inspectors reviewed modification MDD-91-V1M016, Auxiliary Feedwater Rated Speed Change, dated April 4, 1991, and LDCR 2003034, Revise FSAR to Show Values for AFW System Performance Based on Calculation X4C1302S12, dated November 26, 2003. The review identified that in 1991, the TDAFWP speed setting was changed from 4200 to 4230 rpm by modification MDD-91-V1M016, which did not evaluate the effect of the speed increase on the AFW systems margin for the faulted steam generator containment analysis. In 2003, the UFSAR was changed to reflect the results of calculation X4C1302S12 by LDCR 2003034, which did not evaluate the effects of the cumulative margin reduction changes, lack of the instrument uncertainty considerations by the calculations, effects of the allowable speed variations, and potential negative effects of the allowable SRV set point acceptance criteria. The inspectors reviewed minor design change MDC-00-V1M036, 1A AFW Pump Rotating Element Replacement and Thrust Bearing Change, dated September 11, 2000, and identified that when the 1A MDAFW pump rotating element was replaced, the pump characteristics were changed. The effect of the pumps higher TDH and flows on the AFW system margin for the faulted steam generator ccontainment analysis was not evaluated. CR 2007105979 was generated to address this concern. |
| Site: | Vogtle  |
|---|---|
| Report | IR 05000424/2007006 Section 1R21 |
| Date counted | Jun 30, 2007 (2007Q2) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | R Berryman B Collins T Chandler S Shaeffer L Lake G Mccoy C Peabodym Shlyambergs Rose D Mas-Penaranda J Chiloyan R Berryman |
| INPO aspect | |
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Finding - Vogtle - IR 05000424/2007006 | |||||||||||||||||
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Finding List (Vogtle) @ 2007Q2
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