05000237/FIN-2010005-04
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Finding | |
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| Title | Adequacy of High Pressure Core Injection System Low Pressure Testing |
| Description | The inspectors identified an unresolved item regarding the low pressure testing of the HPCI system. The Technical Specifications require the testing of the HPCI system during reactor startup from a refueling outage prior to exceeding 150 psig. On November 26, 2010, during the post Unit 3 refueling outage low pressure testing of the HPCI system, the system experienced abnormal parameters. System flow cycled between about 4000 gpm to about 7000 gallons per minute (gpm). System discharge pressure cycled between 300 psig to about 500 psig. These oscillations resulted in a severe shaking of the system discharge piping. The operator in the control room did not observe the severity of these oscillations. The inspectors interviewed the control room operator performing the surveillance test. The control room operator stated that HPCI flow was observed in the control room to oscillate between 5000 and 5600 gpm. The more severe oscillations were observed by the system manager monitoring a computer point outside the control room. The licensee documented the flow oscillations in IR 1145149, Abnormal U3 HPCI Pump Parameters During Low Pressure Run. In this IR the licensee stated that the oscillations appeared to be the result of pump runout. Centrifugal pump runout is a condition where the pump flow is beyond the point where net positive suction head (NPSH) required exceeds NPSH available and the pump starts to cavitate. Prolonged operation in this condition can cause damage to the pump and the piping. The inspectors observed that IR 1145149 required no actions to attempt to determine why or if the pump ran out. The licensee accepted the test results because in the control room a flow rate of 5000 gpm was observed. The inspectors interviewed the control room operator who performed the test. The test procedure stated that HPCI test return flow to the condensate storage tank shall be throttled such that discharge pressure shall be maintained greater than 98 psig above reactor pressure. The operator stated that he thought this meant to get discharge as close to 98 psig above reactor pressure as possible. This would have made pump discharge pressure close to 250 psig. That was why he fully opened the test return valve. The inspectors determined through interviews that in previous performances of this surveillance test operators did not normally open the test control valve fully and maintained pump discharge pressure greater than 600 psig. The inspectors questioned licensee engineering management that if a HPCI injection occurred at a reactor pressure of 150 psig and then the HPCI injection valve fully opened without throttling, would the HPCI pump also runout? Licensee engineering management did not know the answer to this question. The licensee felt the problem was with the flow characteristics of the test valve but did not know if the injection valve would have significantly different flow characteristics. The licensee felt that the valve vendor would have to be consulted to get an assessment of the flow characteristics of the valves. If the HPCI pump would runout during injection at a discharge pressure of 150 psig, then the testing performed would be inadequate to determine HPCI operability. The licensee evaluation of system performance at low discharge pressure is an unresolved item pending inspector review for adequacy. |
| Site: | Dresden  |
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| Report | IR 05000237/2010005 Section 1R22 |
| Date counted | Dec 31, 2010 (2010Q4) |
| Type: | URI: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.22 |
| Inspectors (proximate) | E Sanchez F Nestor R Jickling T Bilik D Melendez-Colon W Slawinski C Phillips M Ring T Go J Draper D Sandr Langstafft Briley T Go A Shaikh B Kemker C Phillips D Lords D Melendez Colon F Ramirez J Cameron J Corujo Sandin M Bielby P Smagacz R Jickling |
| INPO aspect | |
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Finding - Dresden - IR 05000237/2010005 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Dresden) @ 2010Q4
Self-Identified List (Dresden)
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