05000348/LER-2010-001
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. 05000 | |
| Event date: | 01-26-2010 |
|---|---|
| Report date: | 03-26-2010 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3482010001R00 - NRC Website | |
Westinghouse -- Pressurized Water Reactor Energy Industry Identification Codes are identified in the text as [XX]
Description of Event
Containment (CTMT) Purge Exhaust Penetration Number 13 [JM] inoperable due to excessive leakage during the quarterly Leakage Rate Test. The outside CTMT Mini-Purge valve was identified as leaking past the seat. Technical Specification (TS) 3.6.3, "Containment Isolation Valves," was entered and the inside CTMT Mini-Purge Valve was closed and deactivated in accordance with TS 3.6.3. The Main Purge Valves are normally maintained in a closed and deactivated position. This established the penetration boundary as the inside CTMT valves.
Testing and adjustments to the outside CTMT Mini-Purge valve were conducted. Subsequently, it was determined that the outside Mini-Purge valve was not leaking. On January 26, 2010 SNC determined that the inside CTMT Purge Valve was actually the valve that was leaking. At this point the CTMT isolation for Penetration Number 13 was shifted to the outside CTMT valves. During the time the inside CTMT isolation valves were closed and deactivated, the outside CTMT Mini-Purge valve was not deactivated. This was a failure to meet the requirements of TS 3.6.3 to isolate the affected penetration flow path by use of at least one closed and de-activated automatic valve within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of detection of excessive penetration leakage.
During the eleven day period that the TS Boundary was established inside CTMT, SNC performed minor adjustments to the outside CTMT Mini-Purge valve to assess if the valve was seating correctly. At no time was this valve open for more than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> thus meeting the Required Action Time of TS 3.6.1 "Containment" for an inoperable boundary.
Repairs to the CTMT Purge Valve were completed and the penetration returned to service on February 8, 2010.
Cause of Event
During the initial testing with the penetration at 48 psig, SNC mistakenly determined that the air flow coming from the penetration test vent line was leakage past the seat of the outside CTMT Mini purge valve. When this test was being performed the Penetration Room Filtration (PRF) system was in operation which lowered the pressure in the room where the vent valve is located. SNC later determined that with the PRF system secured, no air flow was detected coming from the test vent valve. SNC adjusted the outside CTMT mini-purge valve off its seat and air flow from the pressurized penetration was detected. To confirm the observations, SNC aligned the outside CTMT mini-purge valve back on its seat, which stopped the air flow, and started the PRF system.
Air flow once again was detected coming from the test vent valve. The negative pressure created by the PRF system in the penetration room resulted in air being drawn out the vent valve from downstream of the Outside CTMT penetration isolation valve.
� Safety Assessment The Shutdown CTMT Purge System operates to supply outside air into the containment for ventilation and cooling or heating and may also be used to reduce the concentration of noble gases within containment prior to and during personnel access. The supply and exhaust lines each contain two isolation valves which are normally maintained closed and deactivated in MODES 1, 2, 3, and 4 to ensure the containment boundary is maintained.
The CTMT Mini-Purge System operates to maintain radioactivity levels in the containment consistent with occupancy requirements, and to equalize internal and external pressures with continuous system operation or batch releases. Since the valves used in the CTMT Mini-Purge System are designed to meet the requirements for automatic containment isolation valves, these valves may be opened as needed in MODES 1, 2, 3, and 4.
The CTMT Purge Exhaust penetration consists of a 48 inch isolation valve inside CTMT and a 48 inch isolation valve outside CTMT in the Penetration Room which are normally closed and deactivated. Between each of these isolation valves and the CTMT wall is a connection for Mini- Purge which has 8 inch isolation valves located inside CTMT and in the Penetration Room.
The valve that was determined to be leaking was the 48 inch valve inside CTMT. The initial isolation and deactivation of the penetration was established using the valves inside CTMT. During the time that the isolation boundary was established inside CTMT, the isolation valves outside CTMT were closed with the 48 inch valve being deactivated. The 8 inch valve was closed but not deactivated. This 8 inch valve was manually modulated to assess for leakage. At no time was this valve opened for more than one hour in accordance with TS 3.6.1, "Containment." Therefore, the safety and health of the public was not adversely affected during the limited time the outside CTMT mini-Purge valve was not deactivated.
Corrective Action The leaking Penetration Isolation Valve was correctly identified as the Main Purge valve inside CTMT, and the penetration isolation valves outside CTMT were verified closed and deactivated.
Repairs to the CTMT Purge Valve were completed and the penetration returned to service on February 8, 2010.
Plant procedures have been updated to clearly require the isolation and deactivation of all four CTMT Purge Penetration Isolation valves when the integrity of a CTMT Purge penetration is in question.
'NRC FORM 366A (9-2007)� PRINTED ON RECYCLED PAPER)
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