ENS 51028
ENS Event | |
|---|---|
04:44 May 1, 2015 | |
| Title | |
| Event Description | River Bend Station personnel declared the High Pressure Core Spray (HPCS) system inoperable at 2344 CDT on 4/30/2015.
The HPCS system at River Bend Station includes a test return line to the Condensate Storage Tank (CST). The test return line is isolated by two motor operated valves (E22-MOVF010 and E22-MOVF011), with both having a safety function to close on an ECCS initiation signal to ensure that injection flow is directed to the reactor vessel. There is currently a blind flange installed downstream of these two valves. While the HPCS pump is normally aligned to the CST, the credited source of water for the pump is the suppression pool. Accordingly, the pump suction is realigned to the suppression pool on low level in the CST or when suppression pool level rises to a certain point. While performing maintenance on the downstream test return valve (E22-MOVF011), station personnel identified leakage past the upstream test return valve (E22-MOVF010) which was being used as an isolation boundary. In evaluating this condition, engineering personnel noted that the observed leakage past the upstream isolation MOV might be sufficient to deplete suppression pool inventory such that it would not be capable of performing its specified function for the duration of the 30-day mission time. The issue of concern is that once HPCS is aligned to the suppression pool post-LOCA, pool inventory would be lost due to the leaking upstream isolation valve (E22-MOVF010) and out the disassembled downstream isolation valve (E22-MOVF011). Based on that concern, the HPCS pump suction valve from the suppression pool was disabled in the closed position to preserve pool inventory. This action caused the HPCS system to be declared inoperable at 2344 CDT. This action results in a 14 day shutdown LCO and is reportable to the NRC in accordance with 10CFR50.72(b)(3)(v)D. The HPCS pump remained available with its suction aligned to the CST. Message has been left with NRC Senior Resident Inspector.
The licensee is retracting the report for Event No. 51028. On April 28, the High Pressure Core Spray System (HPCS) was inoperable to support planned maintenance. During repairs on the HPCS pump test return valves, leakage through the upstream isolation valve was observed when the downstream valve was disassembled. At 2315 [CDT] on April 30, it was conservatively determined that the leakage represented a potential challenge to the 30-day inventory of the suppression pool, and the pool was declared inoperable. At 2344 [CDT] on April 30, the HPCS pump suction valve to the suppression pool was closed to isolate that potential leakage path until the maintenance could be completed. This action returned the suppression pool to an operable status. On June 24, a quantitative leak rate test was performed on the upstream isolation valve (E22-MOVF010). That test determined that the leakage through the valve was not of such magnitude to have had the potential to deplete the 30-day inventory of the suppression pool during post-accident operation of the HPCS system. Additionally, when the HPCS pump suction valve on the suppression pool was closed on April 30, the system was already in a planned outage that commenced on April 28. As such, this condition need not have been reported. The licensee notified the NRC Resident Inspector. Notified the R4DO (Campbell). |
| Where | |
|---|---|
River Bend  Louisiana (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+3.87 h0.161 days <br />0.023 weeks <br />0.0053 months <br />) | |
| Opened: | Robert Melton 08:36 May 1, 2015 |
| NRC Officer: | Donald Norwood |
| Last Updated: | Jun 29, 2015 |
| 51028 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |