05000387/LER-2010-001
| Susquehanna Steam Electric Station | |
| Event date: | 03-15-2010 |
|---|---|
| Report date: | 0-0-5000 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded |
| 3872010001R00 - NRC Website | |
EVENT DESCRIPTION
On March 15, 2010 during the Susquehanna Unit 1 16th Refueling and Inspection Outage, it was determined that the as-found minimum pathway Secondary Containment Bypass Leakage (SCBL) Technical Specification (TS) limit has been exceeded during regularly scheduled Local Leak Rate Testing (LLRT). At the time the limit was surpassed, a LLRT was being performed on the Unit 1 'B' Residual Heat Removal Containment Spray penetration. The tested containment isolation valve (HV151F016B) was leaking 4,515 sccm. When the 4,515 sccm leakage through HV151F016B was added to the combined as-found minimum pathway SCBL calculation it equaled 7,977 sccm (16.9 scfh). This total as-found minimum pathway leakage exceed the Technical Specification limit of 7,079 sccm (15 scfh).
CAUSE OF THE EVENT
The higher than desired leak rate experienced at the Unit 1 'B' Residual Heat Removal Containment Spray penetration can be attributed to the design of the isolation valves and PPL's maintenance practices. In addition, the SCBL TS limit is difficult to meet based on the number of penetrations and sizes of valves, requiring very low leakage rates to be maintained.
ANALYSIS/SAFETY SIGNIFICANCE
This event was determined to be reportable in accordance with 10 CFR 50.73(a)(2)(ii)(A) in that the total as-found minimum pathway SCBL leakage rate exceeded the Technical Specification limit.
Actual Consequences The purpose of the primary containment isolation valves is to limit fission product release during and following postulated Design Basis Accidents. The SCBL TS value is established to limit the release of radioactive materials outside of secondary containment.
to ensure offsite and main control room doses remain within regulatory limits. No event occurred during the SCBL testing or during any other plant condition over the past operating cycle to challenge the regulatory limits. As such, there were no actual safety consequences resulting from this event.
Potential Consequences:
Analysis has concluded that, during a postulated design basis accident, the increase in dose related to the elevated SCBL leak rate would not have exceeded regulatory limits.
CORRECTIVE ACTIONS
The following corrective action has been completed:
- Valve maintenance was performed and the as-left SCBL value meets the Technical Specifications limit.
The following corrective action is planned:
- Evaluate design of the Emergency Core Cooling Systems (ECCS) SCBL penetrations including valve design and configuration to determine methods to reduce the leakage.
- Perform a training needs analysis for maintenance personnel for valve rework on specific valves.
- Evaluate and submit, if appropriate, a Technical Specification amendment to raise the SCBL limit.
No regulatory commitments are associated with this report.
ADDITIONAL INFORMATION
Failed Component Information:
Component:WHV151F016B; 12 inch globe valve Model:WW8522332B Manufacturer: Anchor Darling Valve Co.
Previous Similar Events:
- LER 96-002-00, Docket No. 387/License No. NPF-14
- LER 96-011-00, Docket No. 387/License No. NPF-14
- LER 99-002-00, Docket No. 388/License No. NPF-22
- LER 01-003-00, Docket No. 388/License No. NPF-22
- LER 07-001-00, Docket No. 388/License No. NPF-22