05000254/FIN-2014008-03
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Finding | |
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| Title | Testing of MSIVs with Instrument Air or Drywell Pneumatic System Aligned to Actuators |
| Description | The inspectors identified an unresolved issue (URI) regarding the testing of the MSIVs. Specifically, the inspectors identified the MSIV closure timing surveillance tests were performed with non-safety related instrument air or the drywell pneumatic system aligned to the actuators. The inspectors were concerned that the surveillance test acceptance criteria could be non-conservative. The inspectors reviewed surveillance test Procedure QCOS 0250-04, MSIV Closure Timing, and noted the MSIV fast closure testing (required by TS surveillance requirement (SR) 3.6.1.3.6 and the IST Program) was performed with non-safety-related instrument air or the drywell pneumatic system aligned to the actuators. The MSIVs were designed with safety-related accumulators to provide pressure to assist in closing the valves; however these air accumulators would be expected to provide less pressure than the non-safety-related instrument air or drywell pneumatic systems. Technical Specification SR 3.6.1.3.6 required verification that the isolation time of each MSIV will be 3 seconds and 5 seconds. The inspectors observed test Procedure QCOS 0250-04 included separate closure time acceptance criteria for hot and cold conditions, but did not include any acceptance criteria adjustments for the use of non-safety-related instrument air or the drywell pneumatic system. The inspectors were concerned the surveillance test maximum closing time acceptance criteria ( 5 seconds for cold valves) could be non-conservative. This concern was previously addressed by NRC IN 85-84, Inadequate Inservice Testing of Main Steam Isolation Valves. At that time, the licensees review of IN 85-84 stated the MSIV air supply isolation valve was closed during testing. On February 22, 1989, 13 General Electric Nuclear Services Information Letter (SIL) No. 482 was issued to address the effect of non-safety related air on the closure time testing of some MSIVs. The SIL indicated that testing of two Boiling Water Reactor MSIVs equipped with hydraulic self-compensation mechanisms resulted in a time increase of about 0.1 seconds when the non-safety-related air supply was disconnected. The installed MSIVs were also equipped with hydraulic self-compensation mechanisms. The SIL No. 482 also recommended testing to verify the effect of removing non-safety related air supplies. The SIL stated that if the closure time with the air disconnected increased less than 0.3 seconds, it would be acceptable to leave the non-safety-related air connected during closure time testing. The 0.3 second criterion was based on a typical total allowable variation of 0.5 seconds. This 0.5 margin was based on an historical practice of setting MSIV closure times between 3.5 and 4.5 seconds (light to light). In addition, the historical accident analyses were based on the MSIVs closing in less than 10 seconds (plus an additional 0.5 second allowance for instrument/control response). The current alternate source term accident analysis was based on the MSIVs closing within 5 seconds (plus an additional 0.5 second allowance for instrument/control response) under accident conditions (UFSAR Section 15.6.4.5.1). Based on the current alternate source term analysis, there was no allowance for margin between the as-found surveillance test acceptance criterion, the TS limit, and the analytical limit. It was unclear to the inspectors whether the licensees basis to revise the test methodology to having non-safety air un-isolated was based on the SIL. The licensees evaluation of SIL No. 482, dated June 27, 1989, stated the MSIVs were tested with the non-safety-related instrument air or drywell pneumatic system aligned to the actuators. The evaluation also stated a special test was required to determine the effect of air pressure on MSIV closure time. The licensee determined the special test was performed with acceptable results to justify continued closure time testing with the non-safety related instrument air or the drywell pneumatic system aligned to the actuators. However, the actual test results were lost in the late 1980s due to a computer records failure. The licensee initiated AR02420923 on December 4, 2014, to address this issue. The licensee was able to obtain MSIV closure time special test results for eight similar MSIVs from Dresden Station, performed in May 1992. The results indicated an average closure time increase of less than 0.1 seconds with non-safety related air disconnected. However, there was considerable variation in the individual MSIV test results. Based on the Dresden special test results, the records indicating that a special test was performed successfully, the most recent as-left MSIV closure time test results, and documentation from General Electric, the licensee determined the MSIVs remained operable. Resolution of this issue will be based on additional analysis and/or testing by the licensee. This analysis/testing will determine if additional surveillance test acceptance criteria margin and/or a change in testing methodology will be required to ensure the MSIVs will close in the required time under the most limiting conditions. Specifically, the inspectors were concerned the current testing methodology (with the non-safety-related instrument air or drywell pneumatic system aligned to the actuators) could result in the MSIVs stroking faster than the most limiting accident conditions, with only safety-related accumulators available, which appeared to be a change from the testing methodology prior to IN 85-84. The inspectors were also concerned the recommendations of SIL No. 482 were not applicable to the current licensing/design basis because those recommendations were based on an assumed total allowable variation of 0.5 seconds. As discussed above, the alternate source term analysis 14 (performed after the SIL was issued) did not include any closure time margin beyond the as-found surveillance test acceptance criterion and the upper TS time limit. It appeared that any non-conservatism in the test methodology would be unacceptable unless the test acceptance criteria included explicit allowances for the difference between the test conditions and the most limiting accident conditions. Pending resolution, this item will be tracked as an unresolved item. |
| Site: | Quad Cities  |
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| Report | IR 05000254/2014008 Section 1R21 |
| Date counted | Dec 31, 2014 (2014Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | A Dunlop A Stone B Jose C Baron G O'Dwyer M Jeffers R Walton S Kobylarz |
| INPO aspect | |
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Finding - Quad Cities - IR 05000254/2014008 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Quad Cities) @ 2014Q4
Self-Identified List (Quad Cities)
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