05000324/LER-2003-001, For Brunswick Unit 2 Main Steam Line Drain Isolation Valve Local Leak Rate Test Failures
| ML031410491 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 05/15/2003 |
| From: | Noll W Progress Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BSEP 03-0077 LER 03-001-00 | |
| Download: ML031410491 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| 3242003001R00 - NRC Website | |
text
ta Progress Energy May 15, 2003 SERIAL: BSEP 03-0077 10 CFR 50.73 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-324/LICENSE NO. DPR-62 LICENSEE EVENT REPORT 2-03-001 Ladies and Gentlemen:
In accordance with the Code of Federal Regulations, Title 10, Part 50.73, Progress Energy Carolinas, Inc. submits the enclosed Licensee Event Report. This report fulfills the requirement for a written report within sixty (60) days of a reportable occurrence.
Please refer any questions regarding this submittal to Mr. Edward T. O'Neil, Manager - Support Services, at (910) 457-3512.
Sincerely, W. G Noll Plant General Manager Brunswick Steam Electric Plant SFT/sft Enclosure: Licensee Event Report Progress Energy Carolinas, Inc.
Brunswick Nuclear Plant P.O. Box 10429 Southport, NC 28461
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Document Control Desk BSEP 03-0077 / Page 2 cc (with enclosure):
U. S. Nuclear Regulatory Commission, Region II ATIN: Mr. Luis A. Reyes, Regional Administrator Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, GA 30303-8931 U. S. Nuclear Regulatory Commission ATIN: NRC Resident Inspector 8470 River Road Southport, NC 28461-8869 U. S. Nuclear Regulatory Commission ATTN: Ms. Brenda L. Mozafari (Mail Stop OWFN 8G9) (Electronic Copy Only) 11555 Rockville Pike Rockville, MD 20852-2738 Ms. Jo A. Sanford Chair - North Carolina Utilities Commission P.O. Box 29510 Raleigh, NC 27626-051
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Abstract
to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On March 21, 2003, during the Unit 2 B216R1 refueling outage, the results of local leak rate testing of the main steam line drain inboard and outboard isolation valves, 2-B21-F016 and 2-B21-F019, determined that the valves would not pressurize and consequently, the Technical Specification primary containment leakage rate limit was exceeded. Following the performance of valve maintenance activities and prior to restart of the unit, post-maintenance leakage rate tests were performed which verified valve leakage rates were within allowable limits. The failure of the valves to minimize leakage rates within allowable limits is attributed to a less than optimum valve design. Corrective actions include future replacement of the valves with a valve design which is more suited for the valve application. Review of Licensee Event Reports within the past three years identified no similar events.
NHU FORM SbO (7-2001)
(If more space is required, use additional copies of (If more space is required, use additional copies of NfRC Form 366A) (17)
Darling. This valve type was considered to be the best design available for containment isolation valves in high temperature service at that time. However, subsequent leak rate test performance did not significantly improve. To improve valve performance, the valves were changed from torque seated to limit seated in 1995. Although limit seating has improved performance, the current configuration is considered less than optimum for the long term.
CORRECTIVE ACTIONS
- 1. The 2-B21-F016 and 2-B21-F019 valves were repaired and post-maintenance LLRTs performed prior to unit startup.
The post-maintenance LLRTs confirmed leakage rates within the allowable limit.
- 2. A team will be assembled for the purpose of reviewing applicable industry experience on similar valve applications to determine an optimum valve design. This team will develop a comprehensive valve improvement plan including the consideration of new valve design. The plan will incorporate improvements for the Unit 1 MSL drain valves which are also double-disc gate valves of similar design and have experienced previous leak rate performance concerns.
The valve improvement plan will be implemented in accordance with the Maintenance Rule action plan.
SAFETY ASSESSMENT
The actual safety significance of this condition is considered minimal in that the main steam line drain piping inside primary containment, the reactor building, and extending through the turbine building to the condenser was not ruptured during the last operating cycle. The potential safety significance of this condition is considered minimal based on the physical evidence obtained during valve repair activities. During the post LLRT maintenance that was performed on each of the valves, no evidence of major valve internal wear or degradation was identified. The relatively minor defects that were identified are not considered the result of a total failure of either of the valves to isolate or the expected damage that would most likely occur from a 1000 psi differential pressure being applied across the valve seats during an operating cycle. Consequently, based on the evidence, although the valves were not leak tight, the valves were capable of closing and reducing the release of radioactive gases.
PREVIOUS SIMILAR EVENTS
A review of reportable events for the past three years did not identify any previous similar events.
COMMITMENTS
Those actions committed to by Progress Energy Carolinas, Inc. in this document are identified below. Any other actions discussed in this submittal represent intended or planned actions by Progress Energy Carolinas, Inc. They are described for the NRC's information and are not regulatory commitments. Please notify the Manager - Support Services at BSEP of any questions regarding this document or any associated regulatory commitments.
A team will be assembled for the purpose of reviewing applicable industry experience on similar valve applications to determine an optimum valve design. This team will develop a comprehensive improvement plan, including the consideration of a new valve design, by July 30, 2003.
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