ENS 43885
ENS Event | |
|---|---|
15:40 Jan 8, 2008 | |
| Title | Rcic Inoperable Due to Min Flow Valve Inability to Reposition |
| Event Description | This report is being made in accordance with 10 CFR 50.72 (b) (3) (v) due to the Reactor Core Injection Cooling (RCIC) system being determined to be inoperable on 01/08/08 at 1040 EST. During a planned RCIC system outage, an instrument calibration surveillance identified a flow switch failure that would have prevented automatic closure of the pump minimum flow valve. Insufficient data is immediately available to assess the ability to achieve design basis flow rates with the minimum flow valve open. This event is an eight-hour notification. The RCIC instrument is currently under repair and will be completed prior to return to service.
Plant is in a stable condition. Investigation is continuing. The resident NRC inspector has been notified of this event. This event places them in a 14-day LCO per ACT-1-08-002. HPCI verified operable.
BASIS FOR RETRACTION: Event Notification 43885 was conservatively made to ensure that the Eight-Hour Non Emergency reporting requirements of 10 CFR 50.72 were satisfied pending the evaluation of RCIC System operability. On 1/8/08, during performance of Attachment 5 to 8.E.13, 'RCIC System Instruments Calibration', RCIC flow switch FS-1360-7, contact number 2 failed to close as expected on increasing test pressure. This switch is expected to close while increasing test pressure between 13.7 to 14.3 inWC [inches of Water Column]. Contact number 2 closes when RCIC flow exceeds 100 gpm signaling [minimum] flow valve MO-1301-60 to close. Failure of the switch to close prevents automatic closure of the [minimum] flow valve on a system flow of 100 gpm increasing. Failure of the [minimum] flow valve to close during RCIC system operation would allow about 70 gpm to 170 gpm of RCIC pump discharge flow to go directly to the torus bypassing the reactor vessel. The switch was replaced and the flow switch was returned to service. The defective switch was evaluated and the cause of the failure was determined to be carbon buildup on the switch contacts. A functional failure review was performed to assess the impact of the flow switch failure on the RCIC System design basis functions. The RCIC System is required to automatically provide makeup water to the reactor vessel following vessel isolation. This review identifies that 400 gpm is adequate to meet reactor vessel makeup requirements. With the flow controller in 'AUTO' and the minimum flow valve open, the flow controller would increase turbine speed until the flow rate setpoint of 400 gpm is achieved. Based on evaluation of the RCIC System flow controller configuration, turbine speed limits, and hydraulic modeling, it was determined that the required 400 gpm flow rate could have been delivered under worst case conditions with a failed open minimum flow valve. These evaluations concluded that the RCIC System was capable of performing its intended safety functions during the time when FS-1360-7 failure prevented automatic closure of the pump minimum flow valve. The RCIC System would have started and supplied design basis flow to reactor vessel under design basis conditions. Thus there would have [been] no impact on nuclear safety. Therefore, this event was not reportable pursuant to 10 CFR 50.72(b)(3)(v). Event Number 43885, made on 01/08/2008, is being retracted. The licensee will be notifying the NRC Resident Inspector. Notified R1DO (Caruso). |
| Where | |
|---|---|
| Pilgrim Massachusetts (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+1.12 h0.0467 days <br />0.00667 weeks <br />0.00153 months <br />) | |
| Opened: | Frank Clifford 16:47 Jan 8, 2008 |
| NRC Officer: | Steve Sandin |
| Last Updated: | Mar 6, 2008 |
| 43885 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |