ML17059C561
| ML17059C561 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 02/17/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML17059C559 | List: |
| References | |
| NUDOCS 9902230145 | |
| Download: ML17059C561 (6) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATIONBYTHE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO INSERVICE TESTING PROGRAM RELIEF RE VEST GVRR-01 NINE MILEPOINT NUCLEAR STATION UNIT NO. 2 DOCKET NO. 50-410
1.0 INTRODUCTION
The Code ofFederal Regulations, 10 CFR 50.55a, requires that inservice testing (IST) of certain American Society of Mechanical Engineers (ASME) Code Class 1, 2, and 3 pumps and valves be performed in accordance. with Section XI of the ASME Boilerand Pressure Vessel Code (the ASME Code) and applicable addenda, except where alternatives have been authorized or relief has been requested by the licensee and granted by the Commission pursuant to Sections (a)(3)(i), (a)(3)(ii), or (f)(6)(i) of 10 CFR 50.55a.
In proposing alternatives or requesting relief, the licensee must'demonstrate that: (1) the proposed alternatives provide an acceptable level of quality and s'afety; (2) compliance would result in hardship or unusual difficultywithout a compens'ating increase in the level of quality and safety; or (3) conformance is impractical for its facility. Section 50.55a authorizes the Commission to approve alternatives and to grant relief from ASME Code requirements upon making the necessary findings.
Guidance related to the development and implementation of inservice testing (IST) programs is given in Generic Letter (GL) 89-04, "Guidance on Developing Acceptable Inservice Testing Programs," issued April 3, 1989, and its Supplement 1, issued April4, 1995. Also see NUREG-1482, "Guidelines for Inservice Testing at Nuclear Power Plants," and NUREG/CR-6396, "Examples, Clarifications, and Guidance on Preparing Requests for Relief from Pump and Valve Inservice Testing Requirements."
The 1989 Edition of the ASME Code is the latest edition incorporated by reference in Para'graph (b) of Section 50.55a.
Subsection IWVof the 1989 Edition, which gives the requirements for IST of valves, references Part 10 of the American National Standards Institute/ASME Operations and Maintenance Standards (OM-10) as the rules for IST of valves.
OM-10 replaces specific requirements in previous editions of Section XI, Subsection IWV, of the ASME Code.
Subsection IWP of the 1989 Edition, which gives the requirements for IST of pumps, references Part 6 of the American. National Standards Institute/ASME Operations and Maintenance Standards (OM-6) as the rules for.lST of pumps.
OM-6 replaces specific requirements in previous editions of Section XI, Subsection IWP, of the ASME Code.
In a letter dated June 16, 1998, Niagara Mohawk Power Corporation, (NMPC and the licensee) submitted the second ten-year interval IST Program for Pumps and Valves for Nine Mile Point Nuclear Station, Unit 2 (NMP2). The submittal included one general valve relief request (GVRR) and no pump relief request.
The second ten-year IST interval for NMP2 began on April5, 1998.
99'02230%45 99'02i7 PDR ADQCK 050004i0 P
PDR Enclosure
The scope of the NMP2.IST program should include pumps and valves that are ASME Code Class 1, 2, or 3 or are required to perform a specific function in shutting down the reactor to the cold shutdown condition, maintaining the cold shutdown condition, or necessary to mitigate the consequences of an accident, in accordance with ASME Code requirements.
2.0 GENERAL VALVERELIEF RE UEST-01 In its submittal dated June 16, 1998, for GVRR-01, NMPC requests relief from the requirements of Section 4.3.2.2 of OM-10 which states that each check valve shall be exercised or examined in a manner which verifies obturator travel to the closed, full-open or partially-open position required to fulfillits function. The IST Category C, ASME Code Class 2, system pressure pump discharge check valves prevent diversion of emergency core cooling system (ECCS) flow by preventing reserve flowfrom the ECCS discharge path into the associated press'ure pumps discharge piping for the following systems: High Pressure Core Spray S'stem (CSH), Low Pressure Core Spray System(CSL), and the Residual Heat Removal System (RHS). The applic'able valves for these systems are 2CSH*P2 to CSH Header 2CSH*V17, *V55; 2CSL *P2 to CSL Header 2CSL'V14, *V21; 2RHS *V47, *V48; 2RHS*P2 to valves 2RHS*V60, *V61, and *V17, *V18.
2.1 Licensee's Basis For Request NMPC provided the following basis for the relief request:
These check valves close on the initiation of the associated ECCS system to prevent the diversion of ECCS pump discharge flow.via the pressure pump piping. In each case above, two check valves are in series without any means provided for individual reverse flowverification. NMPC contacted General Electric who designed the system to determine the need for both check valves.
GE said that only one check valve was needed and that the second was placed there for added reliability. NMPC considered removing the internals from one valve; however, NMPC determined that a more conservative approach would be to test the valves as a unit. The test results of each set shall be applied to each valve of the set individually.
Consistent with NUREG-1482, Section 4.1.1, Closure Verification forSeries Check Valves without Intermediate Test Connections, relief is sought on the following basis:
a) None of these check valve is in the reactor coolant pressure boundary (RCPB) ~
b) The configuration does not require two check valves. The system designer confirmed that only one was needed, and that the second was added for reliability.
c) These check valve pairs have no seat leakage requirement, either individually or as a pair. Checking reverse flow is sufficient demonstration of their ability to provide their required safety function.
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f) Ifthe performance of a pair of check valves becomes questionable, both valves shall be declared inoperable, and corrective action consistent with OM-10 shall be taken before the valves are returned to service.
2.2 Proposed Alternate Testing NMPC plans to apply the quarterly reverse flowtesting requirement of each valve to the valve pairs.
Ifthe reverse flowtest of the pair of valves should fail, then NMPC's corrective action willbe applied to both valves prior to returning the system to operability, in accordance with NUREG-1482.
NMPC proposes the following:
[NMPC will] test each pair of series check valves quarterly as a unit for reverse flow closure.
2.3 Evaluation These check valves are located in series without intermediate test locations to test the valves individually. They are pump discharge check valves that are not equipped with position indication or external operators.
Their function is to close to prevent diversion of ECCS flow by preventing reserve flowfrom the ECCS discharge path into the discharge piping of the associated pressure pumps.
NMPC is unable to individually verify closure of these valves.
Requiring installation of instrumentation to verify valve position would involve system redesign and modifications.
These modifications would be burdensome to NMPC. However, the closure capability of this valve pair in series could be verified by reverse flow leak testing. Testing the pair for reverse flowwhile closed would give reasonable assurance of operational readiness and supply a reasonable alternative to the ASME Code test method since both valves willbe declared inoperable and repaired or replaced ifexcessive leakage is noted. This alternative is consistent with the guidance provided in Section 4.1.1 of NUREG-1482.
3.0 CONCLUSION
The proposed alternative described in GVRR-01 is authorized pursuant to 10 CFR 50.55a(a)(3)(ii), because of operational readiness.
Imposition of the ASME Code requirements would result in hardship without a compensating increase in the level of quality and safety giving that the alternative provides reasonable assurance of operational readiness.
This NRC staff approval applies to the second ten-year IST interval for the NMP2 valves named in Section 2.0 above.
Principal Reviewer:
T. Cerovski Date:
February 17, 1ggg
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