ENS 40451
ENS Event | |
|---|---|
23:50 Jan 15, 2004 | |
| Title | Potential Gas Binding of Centrifugal Charging Pump |
| Event Description | The following information was obtained from the licensee via facsimile:
During routine 31-day ECCS [Emergency Core Cooling System] venting per SR [Surveillance Requirement] 3.5.2.3 on January 7, 2004, a higher than normal amount of gas was vented from a location on a line off the common suction line for both charging pumps (NV pumps) for Unit 1. The amount of gas vented was not initially considered to be an operability concern. As a conservative measure the frequency of venting was increased from monthly to weekly. Follow-up venting on January 14 indicated the amount of gas vented from this location had increased. Gas was also collecting at a second location at a high point in the NV system. The second location was near the normally-closed valve 1ND-28A. 1ND-28A completes the lineup for 'piggy-back' flow from the Train 'A' decay heat removal system (ND) into the NV system. The type of gas from both locations was determined to be hydrogen. The increased presence of gas was considered a potential operability concern and an operability evaluation was initiated. Venting was increased to once per shift. The source of the hydrogen gas intrusion is unknown and is being investigated. On January 15 at 1850 [EST] it was determined that the amount of gas discovered on January 14 at both locations was greater than what is bounded by current analysis to ensure gas binding of both NV pumps would not have occurred. Since January 14, subsequent venting at the first location (NV pump common suction line) has resulted in gas volumes within the analysis limits. The amount of gas at the second location (Train 'A' piggy-back tie in) initially decreased but increased again on January 15. As a result, the power was removed from 1ND-28A to prevent the transfer of gas into the NV pump suction line. This action results in Unit 1 Train 'A' of ECCS being inoperable and entry into TS [Technical Specification] 3.5.2 Action A1 on January 15 at 1857[hrs]. Train 'B' of ECCS is considered currently operable with 1ND-28A closed and continued increased venting. Licensee notified the NRC Resident Inspector. This places Unit 1 in a 72-hr Limiting Condition for Operation [LCO]. Unit 2 is not affected.
UPDATE ON POTENTIAL FOR GAS BINDING CENTRIFUGAL CHARGING PUMPS On January 15, 2004, Catawba reported potential for gas binding Unit 1 centrifugal charging pumps (Refer to Event Number 40451). Normally-closed valve 1ND-28A completes the lineup for 'piggy-back' flow from the Train 'A' decay heat removal system (ND) for Train 'A' of ECCS. Gas accumulation near 1ND-28A became an operability concern on January 15 for both centrifugal charging pumps. On January 15, 1ND-28A was deenergized (power removed) to prevent the potential transfer of gas into ECCS suction piping. Deenergizing this valve placed Unit 1 into the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action statement of TS 3.5.2 (ECCS) and 3.6.6 (containment spray). Subsequent ultrasonic testing (UT) of several ECCS vent locations, including the one at 1ND-28A, revealed the piping to be essentially full of water. Based on the UT results, Catawba concluded the gas intrusion was a discrete event and that a current gas production mechanism did not exist. Based on the ECCS piping remaining essentially full of water over a period of approximately 60 hours6.944444e-4 days <br />0.0167 hours <br />9.920635e-5 weeks <br />2.283e-5 months <br />, power was restored to 1ND28A and Catawba exited TS 3.5.2 and 3.6.6 at 1725 on January 18. Catawba continued with UT a several ECCS locations every six hours as a prudent measure. At 0350 on January 19, UT revealed a void at the 1ND-28A location that was larger than the currently established acceptance criteria. The gas was vented and water solid conditions established at 0506. TS 3.0.3 was entered from 0350 until 0506 due to the discovery of the gas at 1ND-28A. The cause of the gas intrusion into the ECCS piping continues to be investigated. Frequent UT and venting (if necessary) continues while the root cause evaluation is in progress. Power was removed from 1ND-28A and the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action statements of TS 3.5.2 and 3.6.6 entered at 0715 on January 19. Licensee notified the NRC Resident inspector. The Reg 2 RDO(Haag) was informed |
| Where | |
|---|---|
Catawba  South Carolina (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+-0.18 h-0.0075 days <br />-0.00107 weeks <br />-2.46564e-4 months <br />) | |
| Opened: | Jeff Bradley 23:39 Jan 15, 2004 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Jan 19, 2004 |
| 40451 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |