ENS 49371
ENS Event | |
|---|---|
22:00 Sep 9, 2013 | |
| Title | Unanalyzed Leakage of Containment System Isolation Valve Controlled Leakage Devices |
| Event Description | On September 9, 2013, during the A1R17 Braidwood Station Unit 1 refueling outage, the as-found leakage of the controlled leakage devices (1RH01SA and 1RH01SB) for the safety injection (SI) system ECCS sump containment isolation valves (1SI8811A and 1SI8811B) were determined to not be 'leak tight' as described in the UFSAR. Since there was only minor leakage from the isolation valves or the associated residual heat (RH) system piping (1-2 drops/month from 1SI8811A and no leakage from 1SI8811B), there was no actual impact on offsite dose or long-term ECCS operation. However, further evaluation has concluded that there was a potential to exceed the assumed leakage limits of the Alternate Source Term (AST) calculation.
The RH system is classified as a closed system outside containment meaning the system is designed to accommodate a single active failure (i.e., the failure of the 1SI8811B valve to close) and still maintain an adequate isolation barrier to release recirculation water outside containment. The encapsulation device is intended to capture and limit leakage from a potential leak in the 1SI8811A/B or piping. The controlled leakage device is built to the same standards as the remainder of the RH system recirculation water outside containment. The design function is to limit potential offsite dose due to leakage of recirculation water outside containment. This is not a specified safety function and there are no Technical Specification requirements for these devices. The encapsulation devices do not perform a containment function and are not a principle safety barrier. As there was only minor ECCS system leakage at the time of discovery, there was no impact on past offsite dose or long-term ECCS operation. This is reportable pursuant to 10 CFR 50.72(b)(3)(ii)(B) since the as-found leakage of the controlled leakage devices could have allowed RH leakage to exceed the calculated limits for ECCS systems outside containment. The NRC Resident Inspector has been informed.
Retraction of ENS 49371 dated 9/09/2013: The purpose of this report is to retract ENS report #49371 (September 9, 2013). This report was made during Braidwood's refueling outage (A1R17) for the as-found leakage on the controlled leakage devices (1RH01SA and 1RH01SB) for the safety injection (SI) system ECCS sump containment isolation valves (1SI8811A and 1SI8811B) that were determined not to be 'leak tight' as described in the UFSAR. When the ENS notification was made on 9/9/2013, the station determined that there was a potential to exceed the assumed leakage limits of the alternate source term (AST) calculation. The ENS notification was made under 10CFR50.72(b)(3)(ii)(B) as an unanalyzed condition that significantly degrades plant safety. At 1500 CDT on Thursday, October 17, 2013, the Braidwood Generating Station concluded that the prior ENS notification could be retracted based on the completion of Revision 2 of calculation BRW-13-0135-M, '1/2RH01SA/B Leak Rate Conversion and Test Pressure Determination'. The as-found pressure test results for the 1RH01SA and 1RH01SB valve containment assemblies would not have resulted in a total ECCS leakage outside containment in excess of that assumed in the AST dose calculation BRW-04-0038-M, 'Re-Analysis of Loss of Coolant Accident (LOCA) Using Alternate Source Terms (AST)'. The as-found valve containment assembly (VCA) pressure test results did not result in an unanalyzed condition that significantly degrades plant safety. The licensee has notified the NRC Resident Inspector. Notified R3DO (Daley). |
| Where | |
|---|---|
Braidwood  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+256.67 h10.695 days <br />1.528 weeks <br />0.352 months <br />) | |
| Opened: | Joe Klevorn 14:40 Sep 20, 2013 |
| NRC Officer: | Charles Teal |
| Last Updated: | Oct 31, 2013 |
| 49371 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |
WEEKMONTHYEARENS 519592016-05-25T19:15:00025 May 2016 19:15:00
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