ENS 44287
ENS Event | |
---|---|
21:05 Jun 11, 2008 | |
Title | Identification of a Potential Issue with Accumulator Drain Valves |
Event Description | On June 11, 2008 at 1405 PDT, licensed plant operators entered Technical Specification (TS) 3.0.3 on Units 1 and 2 due to identification of a potential ASCO solenoid valve failure that could initiate draining if the safety injection system accumulators following a small break Loss-of-Coolant-Accident (LOCA).
ASCO Model 8316 and 8321 pilot-operated solenoid valves over 12 years old are susceptible to a potential shuttle ('insert' per vendor documentation) malfunction. The malfunction is that with greater than 12 years of service and a loss of minimum operating pressure differential (MPOD), the shuttle (or insert) could reposition and fail to return to the desired position. This MPOD related reposition could result following instrument air pressure loss and subsequent restoration to containment following a postulated small break LOCA. Diablo Canyon Power Plant (DCPP) Units 1 and 2 each have four susceptible ASCO solenoid valve locations used as drain valves for each of the four safety injection system accumulators per unit. DCPP is reviewing the performance of the ASCO solenoids based on a plant problem report and subsequent discussion with the vendor. The safety significance of this event is low as there was no actual accumulator drain valve failure. Although PG&E is still evaluating the potential degradation mechanism and failure mode of these valves, TS 3.03 was conservatively entered base on the potential for malfunction of these valves. On June 11, 2008, at 1610 PDT licensed plant operators exited TS 3.0.3 following isolation of the suspect accumulator drain lines. A licensee event report will be issued for this event. The NRC Resident Inspector has been notified. |
Where | |
---|---|
Diablo Canyon California (NRC Region 4) | |
Reporting | |
10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
LER: | 05000275/LER-2008-001 |
Time - Person (Reporting Time:+2.72 h0.113 days <br />0.0162 weeks <br />0.00373 months <br />) | |
Opened: | Ken Johnston 23:48 Jun 11, 2008 |
NRC Officer: | Pete Snyder |
Last Updated: | Jun 12, 2008 |
44287 - NRC Website
Loading map... {"minzoom":false,"maxzoom":false,"mappingservice":"leaflet","width":"350px","height":"250px","centre":false,"title":"","label":"","icon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"zoom":6,"defzoom":14,"layers":["OpenStreetMap"],"image layers":[],"overlays":[],"resizable":false,"fullscreen":false,"scrollwheelzoom":true,"cluster":false,"clustermaxzoom":20,"clusterzoomonclick":true,"clustermaxradius":80,"clusterspiderfy":true,"geojson":"","clicktarget":"","imageLayers":[],"locations":[{"text":"\u003Cb\u003E\u003Cdiv class=\"mw-parser-output\"\u003E\u003Cp\u003E\u003Ca class=\"mw-selflink selflink\"\u003EENS 44287\u003C/a\u003E - \u003Ca href=\"/Diablo_Canyon\" title=\"Diablo Canyon\"\u003EDiablo Canyon\u003C/a\u003E\n\u003C/p\u003E\u003C/div\u003E\u003C/b\u003E\u003Cdiv class=\"mw-parser-output\"\u003E\u003Cp\u003EIdentification of a Potential Issue with Accumulator Drain Valves\n\u003C/p\u003E\u003C/div\u003E","title":"ENS 44287 - Diablo Canyon\n","link":"","lat":35.21169166666667,"lon":-120.85504166666666,"icon":"/w/images/f/ff/Pacific_Gas_%26_Electric_icon.png"}],"imageoverlays":null} | |
Unit 1 | |
---|---|
Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |
Unit 2 | |
---|---|
Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |