ML11325A003
| ML11325A003 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 11/18/2011 |
| From: | Anthony Mcmurtray Component Performance and Testing Branch |
| To: | Nancy Salgado Plant Licensing Branch 1 |
| McMurtray A | |
| References | |
| TAC ME5749, TAC ME5750, TAC ME5752 | |
| Download: ML11325A003 (4) | |
Text
ENCLOSURE SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ALTERNATIVE REQUEST NO. VRR4 RELATED TO THE INSERVICE TESTING PROGRAM, BEAVER VALLEY POWER STATION UNIT 2, THIRD 10-YEAR INTERVAL FIRSTENERGY NUCLEAR OPERATING COMPANY DOCKET NO. 50-412
1.0 INTRODUCTION
By letter dated February 21, 2011 (Accession No. ML110560014), FirstEnergy Nuclear Operating Company (FENOC), the licensee, submitted request VRR4 to the Nuclear Regulatory Commission (NRC) for the third ten-year inservice testing (IST) program interval for Beaver Valley Power Station (BVPS) Unit 2. The licensee requested authorization to perform relief valve testing on three BVPS Unit 2 pressurizer relief valves on a different test frequency than the five year interval required by the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code), Appendix I, paragraph I-1320. By letter dated August 22, 2011 (Accession No. ML1123107376), the NRC requested additional information for request VRR4. The licensee provided the additional information in a letter dated September 14, 2011 (Accession No. ML11262A0450).
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Section 50.55a(a)(3)(i), the licensee requested to use the proposed alternative in VRR4, on the basis that the alternative provides an acceptable level of quality and safety.
2.0 REGULATORY EVALUATION
10 CFR 50.55a(f), "Inservice Testing Requirements," requires, in part, that IST of certain ASME Class 1, 2, and 3 components must meet the requirements of the ASME OM Code and applicable addenda, except where alternatives have been authorized pursuant to paragraphs (a)(3)(i) or (a)(3)(ii).
In proposing alternatives, a licensee must demonstrate that the proposed alternatives provide an acceptable level of quality and safety (10 CFR 50.55a(a)(3)(i)), or compliance would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety (10 CFR 50.55a(a)(3)(ii)). Section 50.55a allows the NRC to authorize alternatives to ASME OM Code requirements upon making the necessary findings.
The 2001 Edition of the ASME OM Code with Addenda through OMb-2003 is the code of record for the BVPS Unit 2 third ten-year IST program interval.
The NRCs findings with respect to authorization of the requested alternative, VRR4, are given below:
3.0 TECHNICAL EVALUATION
3.1 Licensees Alternative Request VRR4 Appendix I, Paragraph I-1320, "Test Frequencies, Class 1 Pressure Relief Valves,"
subparagraph (a), "5-Year Test Interval," states, Class 1 pressure relief valves shall be tested at least once every 5 years, starting with initial electric power generation. No maximum limit is specified for the number of valves to be tested within each interval; however, a minimum of 20%
of the valves from each valve group shall be tested within any 24-month interval. This 20%
shall consist of valves that have not been tested during the current 5-year interval, if they exist.
The test interval for any individual valve shall not exceed 5 years.
ASME OM Code Case OMN-17, "Alternate Rules for Testing ASME Class 1 Pressure Relief/Safety Valves" from the 2009 Edition of ASME OM Code, allows a six-year test interval plus an additional six months grace period coinciding with a refueling outage, in order to accommodate extended shutdown periods.
Alternative testing is requested for the following Class 1, Category C valves:
2RCS*RV551A Pressurizer Safety Valve 2RCS*RV551B Pressurizer Safety Valve 2RCS*RV551C Pressurizer Safety Valve The licensee notes the following in their submittal:
Beaver Valley Power Station Unit No. 2 (BVPS-2) has three (3) pressurizer safety valves installed to protect the reactor coolant system from overpressure. Since BVPS Unit 2 operates on an 18-month fuel cycle, one valve can be tested each refueling outage such that each valve is tested over a four and a half year period. In order to avoid outage delays due to valve testing, a pressurizer safety valve is replaced during each refueling outage with a spare valve that has been tested. The removed valve is refurbished and tested for installation during the following refueling outage. In order to ensure the spare replacement valve does not exceed the five-year test interval limit from test to test, it must be tested within six months prior to installation.
Extending the maximum test interval to six years with a six month grace period would allow BVPS Unit 2 to continue to rotate in a spare pressurizer safety valve without the need to test the spare valve within six months of installation.
As an alternative to the ASME OM Code-2001 Edition, Appendix I, Paragraph 1-1320(a) test interval for pressurizer relief valve testing, of at least once every five years, the licensee proposes to test pressurizer safety valves at least once every six years plus a six month grace period, if required, in accordance with the periodicity and other requirements of ASME OM Code Case OMN-17. Code Case OMN-17 provisions will not be applied to a valve until the valve is disassembled and inspected as described in paragraph (e) of Code Case OMN-17.
Paragraph (d) of Code Case OMN-17 requires disassembly and inspection of each valve after as-found set pressure testing is performed in order to verify that parts are free of defects resulting from time related degradation or service induced wear. Paragraph (e) of Code Case OMN-17 requires each valve to be disassembled and inspected in accordance with Paragraph (d) prior to the start of the 72 month test interval.
When the proposed alternative is applied to a valve, the valve will be disassembled and inspected, after as-found set pressure testing is performed in accordance with Code Case OMN-17 paragraphs (d) and (e). The initial inspection and ongoing inspections will verify that valve parts are free of defects resulting from time-related degradation or service-induced wear.
These inspections will provide additional assurance that the pressurizer safety valves will perform their intended function.
The longer test interval will eliminate the need for a valve test within six months of installation during each refueling outage. Eliminating the test will in turn remove the risk of any return shipping damage to the valve from the offsite testing facility and reduce wear on metal valve seats due to steam testing.
The as-found set-pressure acceptance criteria is plus or minus three percent of valve nameplate set pressure in accordance with Paragraph I-1320(c)(1) of ASME OM Code-2001 Edition, Appendix I for the purpose of determining the need to test additional valves. The as-found set-pressure acceptance criteria is plus 1.6 percent or minus three percent of valve nameplate set pressure in accordance with BVPS Technical Specification (TS) Limiting Condition for Operability (LCO) 3.4.10 for the purpose of determining pressurizer safety valve operability.
Since 1989, 18 as-found set pressure tests have been performed for the four Crosby Model HB-86-BP pressurizer safety valves (including the spare valve). These tests have been performed at an offsite test facility using saturated steam. The majority of the tests were performed after the valve was installed for three operating cycles. As-found tests were within plus or minus three percent of the valve set pressure with the exception of valve 2RCS*RV551 C, which lifted low (minus 5.6 percent) in 1989 due to excessive seat leakage. BPVS TS Surveillance Requirement 3.4.10.1 requires that following testing, lift settings shall be within plus or minus one percent. For 12 of the 18 tests, the valves were found within the as-left tolerance of plus or minus one percent. These test results show limited time-related degradation or set point drift and demonstrate that it is acceptable to extend the test interval from four and a half years (three fuel cycles) to six years with a six-month grace period (four fuel cycles).
The ability to detect degradation and ensure the operational readiness of the pressurizer safety valves to perform their intended function is assured based on the valve test history and by performing the required inspection and testing initially and at the proposed alternative frequency. Therefore, test and inspection of the valves in accordance with the proposed alternative demonstrates an acceptable level of quality and safety.
3.2
NRC Staff Evaluation
ASME OM Code, Mandatory Appendix I does not require that safety relief valves (SRVs) be disassembled and inspected prior to the start of the five year test interval. The ASME developed Code Case OMN-17, which was published in the 2009 Edition of OM Code. Code Case OMN-17 allows extension of the test interval for SRVs from five years to six years plus a six month grace period. The code case imposes a special maintenance requirement to disassemble and inspect each SRV to verify that parts are free from defects resulting from time-related degradation or maintenance-induced wear prior to the start of the extended test interval.
The licensee has provided test data to show that the subject valves have historically exhibited very limited susceptibility to time related degradation or set point drift. And they have committed to implement a disassembly and inspection program in conjunction with the extended test interval, as required by ASME OM Code Case OMN-17, in order to detect and control defects resulting from time-related degradation or service-induced wear going forward.
Based on the historical performance of the set-point testing of BVPS Unit 2 pressurizer safety valves and the licensees commitments to disassemble and inspect the SRVs prior to use, the NRC staff finds that implementation of the ASME OM Code Case, OMN-17, for the testing of the designated pressurizer safety valves, in lieu of the requirements of ASME OM Code 2001 Edition with Addenda through OMb-2003, Mandatory Appendix I, Section I-1320 of OM Code, provides an acceptable level of quality and safety.
4.0 CONCLUSION
As set forth above, the NRC staff has concluded that the proposed alternative in request VRR4 provides an acceptable level of quality and safety for pressurizer safety valves 2RCS*RV551A, 2RCS*RV551B, and 2RCS*RV551C. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(a)(3)(i),
and is in compliance with the ASME OM Code requirements. All other ASME OM Code requirements for which relief was not specifically requested and approved in the subject request for relief remain applicable.
Therefore, the NRC staff authorizes the alternative in request VRR4 for the remainder of the Beaver Valley Unit 2 third 10-year IST interval which commenced on November 18, 2007.
Principal Contributor: J. Billerbeck, NRR/DE/EPTB