05000282/FIN-2012003-05
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Finding | |
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| Title | Impact of Outside Air Temperatures on D1 and D2 EDG Operability |
| Description | The inspectors identified an unresolved item (URI) regarding the licensees preparations to ensure that the Unit 1 EDGs were ready for operation during extreme outside air temperatures. On June 8, 2011, the licensee provided a 10 CFR 50.72 report to the NRC when both of the Unit 1 EDGs (D1 and D2) were declared inoperable due to extreme outside air temperatures. Specifically, the outside air temperature on June 8, 2011, was 101.4oF while the licensees maximum temperature to support EDG operability was 100.5oF. Several weeks later, the licensee retracted the 10 CFR 50.72 report based upon additional analysis which showed that D1 and D2 remained operable up to a maximum outside air temperature of 102.5oF. On February 29, 2012, the licensee initiated CAP 1327157 to document that the analysis used to support the 10 CFR 50.72 retraction discussed above was non-conservative. On April 15, 2012, the licensee completed an operability recommendation (OPR 1327157-01, Revision 0), to address the non-conservatisms. The results of the operability recommendation showed that the D1 and D2 EDGs were rendered inoperable when the outside air temperature exceeded 97oF. During the week of June 26, 2012, the inspectors performed a maintenance effectiveness inspection on the D1 EDG (see Section 1R12 of this inspection report). As part of this inspection, the inspectors discovered Engineering Change (EC) 20055 which was approved by the engineering department on approximately June 10, 2012. The purpose of this EC was to evaluate the operability of the D1 and D2 EDGs over the past three years based upon a maximum outside air temperature. The inspectors reviewed the contents of the EC and were concerned that the licensee had assessed the past operability of the EDGs using a maximum outside air temperature of 105oF even though the temperature limit stated in the operability recommendation remained at 97oF. As a result, the licensee may not have properly reported periods of past EDG inoperability to the NRC. The inspectors also found that the licensee had approved increasing the maximum EDG room temperature without adequately assessing the impact of critical EDG components such as the diesel engine, the generator, and three lube oil pressure switches. Specifically, the licensee had deemed the continued operation of these components acceptable based upon engineering judgment without providing an appropriate basis for the conclusion. The inspectors discussed their concerns, and the impending weather forecast which predicted temperatures in excess of 97oF, with engineering, operations, and licensee management personnel. Following these discussions, licensee management rescinded the results of EC 20055; performed an additional review of the critical components to determine whether other actions could be completed to gain additional operability margin; and reaffirmed that the D1 and D2 EDG outside air temperature operability limit was 97oF. At the conclusion of the inspection period, the licensee determined that additional margin could be gained by derating the EDG when outside air temperatures exceeded a specified temperature and by replacing the lube oil pressure switches with switches qualified for a higher operating temperature. The licensee replaced the D2 EDG lube oil pressure switches on June 30, 2012. The D1 EDG pressure switches were scheduled for replacement as soon as the weather conditions allowed. The licensee also planned to perform testing on the replaced temperature switches to determine their maximum operating temperature. These test results will be used to determine whether the D1 and D2 EDGs had been inoperable at any time during the past three years. Since the test results were not available for inspection and review at the conclusion of the inspection period, this issue will be documented as an unresolved item |
| Site: | Prairie Island  |
|---|---|
| Report | IR 05000282/2012003 Section 1R01 |
| Date counted | Jun 30, 2012 (2012Q2) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.01 |
| Inspectors (proximate) | C Moore C Zoia D Betancourt K Riemer K Stoedter P Cardona Morales P Voss P Zurawski S Shahb Kemkerk Riemer K Stoedter P Zurawski T Bilik A Shaikhd Mcneilk Riemer T Bilik C Moore M Phalen R Baker K Stoedter D Passehl J Laughlin K Barclay M Jones M Learn J Beavers D Oliver |
| INPO aspect | |
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Finding - Prairie Island - IR 05000282/2012003 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Prairie Island) @ 2012Q2
Self-Identified List (Prairie Island)
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