05000498/LER-2006-004, Re Multiple Main Steam Safety Valves Found Outside Acceptance Criteria
| ML063250342 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 11/16/2006 |
| From: | Halpin E South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NOC-AE-06002083 LER 06-004-00 | |
| Download: ML063250342 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 4982006004R00 - NRC Website | |
text
Nuclear Operating Company South Tews Proiect £lectnc Gencratins Station PO. Box 289 Wadsworth, Texas 77483 A/v.
November 16, 2006 NOC-AE-06002083 10CFR50.73 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 South Texas Project Unit 1 Docket No. STN 50-498 Licensee Event Report 2006-04, Multiple Main Steam Safety Valves Found Outside Acceptance Criteria Pursuant to 10 CFR 50.73(a)(2)(i)(B), STP Nuclear Operating Company submits the attached Unit 1 Licensee Event Report 2006-04 regarding three Main Steam Safety Valves being found outside acceptance criteria on as-found surveillance testing, This event did not have an adverse effect on the health and safety of the public.
There are no commitments contained in this event report. Resulting corrective actions will be implemented in accordance with the Corrective Action Program.
If there are any questions regarding this submittal, please contact S. M. Head at (361) 972-7136 or me at (361) 972-7849.
E. D. Halpin Site Vice President/
Plant General Manager wem!
Attachment: South Texas Unit 1 LER 2006-04 STI: 32087507
NOC-AE-06002083 Page 2 of 2 cc:
(paper copy)
(electronic copy)
Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 Richard A. Ratliff Bureau of Radiation Control Texas Department of State Health Services 1100 West 49th Street Austin, TX 78756-3189 Senior Resident Inspector U. S. Nuclear Regulatory Commission P. 0. Box 289, Mail Code: MN1 16 Wadsworth, TX 77483 C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 A. H. Gutterman, Esquire Morgan, Lewis & Bockius LLP Mohan C. Thadani U. S. Nuclear Regulatory Commission Steve Winn Christine Jacobs Eddy Daniels NRG South Texas LP J. J. Nesrsta R. K. Temple E. Alarcon City Public Service Jon C. Wood Cox Smith Matthews C. Kirksey City of Austin
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007 (6-2004)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the digits/characters for each block) information collection.
- 3. PAGE South Texas, Unit 1 05000498 1 OF 5
- 4. TITLE Multiple Main Steam Safety Valves Found Outside Acceptance Criteria
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR 05000
_ I
_I_
FACILITY NAME DOCKET NUMBER 09 25 2006 2006 004 -
00 11 27 2006 05000
- 9. OPERATING MODE
- 11. THIS REPORTIS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
El 20.2201(b)
E] 20.2203(a)(3)(i)
[I 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii) 1 El 20.2201(d)
El 20.2203(a)(3)(ii)
[I 50.73(a)(2)(ii)(A)
[I 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
El 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
[I 50.73(a)(2)(viii)(B)
[I 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL [I 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
E] 50.73(a)(2)(x)
[E 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4)
[I 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71(a)(5) 87 C] 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
[I 50.73(a)(2)(v)(C)
El OTHER E] 20.2203(a)(2)(vi)
Z 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES A portion of the twenty MSSVs per unit are tested prior to each outage to meet the Technical Specifications requirements such that all valves get tested in a five year period. If a MSSV lifts outside of the +/- 3% band on the initial as found test, then the valve is declared inoperable.
The valve must be restored to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or else the Power Range Neutron Flux High Trip Setpoint must be reduced. In addition, if a valve fails the initial lift test, then additional valves in the same unit are required to be tested per ASME/ANSI OMa-1 988 Addenda to ASME/ANSI OM-1987, "Operation and Maintenance of Nuclear Power Plants." All valves are adjusted if necessary to be left at +/- 1% of their setpoints on the final as left lifts.
On 9/25/06 two of the six valves being tested in Unit 1 were greater than 3% above the setpoint on the initial lift (MSSVs 7440A and 7440B). Four additional valves were selected for Code sample expansion testing based upon the length of time since their last surveillance test and all four lifted within the +/- 3% acceptance band. After further evaluation showed that the two failed valves had been overhauled during the previous outage (1RE12), it was decided that we should test the other two valves that were overhauled in the last Unit 1 outage in an attempt to understand the cause of the two test failures. One of the two valves lifted high outside of the 3% band (7430C) and the other valve came within 1.5 psi of being 3% high (7430). All of the valves tested were adjusted so that they lifted within +/- 1% of their setpoints.
Because the three failures and the one near failure in Unit 1 were all valves that had been overhauled during the previous outage (1RE12), it was decided to also test the four valves in Unit 2 that had been overhauled during the previous outage based on generic implications.
One of the valves in Unit 2 lifted high outside of the 3% band. The other three valves in Unit 2 lifted high above their setpoints but they were within the 3% band. These valves were also
(If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17)
IV.
CAUSE OF THE EVENT
The event being reported is a condition prohibited by TS in that three MSSVs tested outside the allowable setpoint tolerance. The cause of the failure was stated in Section II.B above.
V.
CORRECTIVE ACTIONS
Based on the above conclusions and based on an evaluation of the maintenance and testing history of all 40 MSSVs, inservice disc and seat conditioning lifts will be performed on the Unit 1 and 2 valves that had been lapped during the previous outage and on Unit 1 MSSV 7420C that was lapped during 1 RE1 3. These inservice conditioning lifts will ensure that sufficiently thick oxide layers are formed on the nozzle seat and disc seat surfaces. Corrective action document 06-12124 is tracking these additional lifts.
A "decision tree" will be incorporated into procedure OPSP1 1-MS-0001, "Main Steam Safety Valve Inservice Test" to provide inservice seat conditioning lifts for MSSVs that are lapped in the future.
Corrective action document 06-12124 will track the revision to procedure OPSP1 1-MS-0001 that will incorporate this change.
VI.
PREVIOUS SIMILAR EVENTS
There have been no other MSSV failures in the past three years.