ML23010A011
| ML23010A011 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 02/01/2023 |
| From: | Hipolito Gonzalez Plant Licensing Branch 1 |
| To: | Rhoades D Constellation Energy Generation, Constellation Nuclear |
| Sreenivas V, NRR/DORL/LPL1, 415-2596 | |
| References | |
| EPID L-2022-LLR-0044 | |
| Download: ML23010A011 (1) | |
Text
February 1, 2023
Mr. David P. Rhoades Senior Vice President Constellation Energy Generation, LLC President and Chief Nuclear Officer Constellation Nuclear 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
R. E. GINNA NUCLEAR POWER PLANT - PROPOSED ALTERNATIVE TO THE REQUIREMENTS ASSOCIATED WITH INSERVICE TESTING OF REFUELING WATER STORAGE TANK OUTLET VALVE (EPID L-2022-LLR-0044)
Dear Mr. Rhoades:
By letter dated April 11, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22101A095), Constellat ion Energy Generation, LLC (the licensee) proposed an alternative (Request for Relief VR-03) to the U.S. Nuclear Regulatory Commission for the use of an alternative to specific inservice testing (IST) requirements in the 2012 Edition of the American Society of Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants, Division 1, OM Code: Section IST (OM Code) at the R. E. Ginna Nuclear Power Plant (Ginna) for the Sixth 10-Year IST Program interval.
Specifically, pursuant to subparagraph (2) in paragraph (z), Alternatives to codes and standards requirements, of Section 55a, Codes and standards, in Part 50, Domestic Licensing of Production and Utilization Facilities, to Title 10, Energy, of the Code of Federal Regulations (10 CFR), the licensee requested to implement an alternative for the testing of Refueling Water Storage Tank Outlet Valve 896B at Ginna on the basis that compliance with the applicable ASME OM Code r equirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The NRC staff reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that the proposed alternative request VR-03 for the leak testing of RWST Outlet Valve 896B at Ginna as described in the licensees submittal dated April 11, 2022, is acceptable in that compliance with the specified requirement in the ASME OM Code, Subsection ISTC, paragraph ISTC-3630, subparagraph (b), would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC staff authorizes the proposed alternative request VR-03 for the Sixth 10-Year IST Program interval at Ginna, which began on January 1, 2020, and is scheduled to end on December 31, 2029.
D. Rhoades
All other ASME OM Code requirements for which an alternative was not specifically requested and approved remain applicable.
If you have any questions, please contact the Project Manager, V. Sreenivas, at 301-415-2597 or V.Sreenivas@nrc.gov.
Sincerely,
Hipólito J. González, Chief Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
Docket No. 50-244
Enclosure:
Safety Evaluation
cc: Listserv
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION
RELATED TO
RENEWED FACILITY OPERATING LICENSE NO. DPR-18
CONSTELLATION GENERATION COMPANY, LLC
R. E. GINNA NUCLEAR POWER PLANT
DOCKET NO. 50-244
1.0 INTRODUCTION
By letter dated April 11, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22101A095), Constellat ion Energy Generation, LLC (the licensee) submitted a proposed alternative request VR-03 to the U.S. Nuclear Regulatory Commission (NRC) for an alternative to specific inservice testing (IST) requirements in the 2012 Edition of the American Society of Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants, Division 1, OM Code: Section IST (OM Code) at the R. E. Ginna Nuclear Power Plant (Ginna) for the Sixth 10-Year IST Program interval.
Specifically, pursuant to subparagraph (2) in paragraph (z), Alternatives to codes and standards requirements, of Section 55a, Codes and standards, in Part 50, Domestic Licensing of Production and Utilization Facilities, to Title 10, Energy, of the Code of Federal Regulations (10 CFR), the licensee requested to implement alternative request VR-03 for the testing of Refueling Water Storage Tank (RWST) Outlet Valve 896B at Ginna on the basis that compliance with the applicable ASME OM Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The Ginna Sixth 10-Year IST Program interval began on January 1, 2020, and is scheduled to end on December 31, 2029.
2.0 REGULATORY EVALUATION
The NRC regulations in 10 CFR 50.55a(f)(4), Inservice testing standards requirement for operating plants, state that throughout the service life of a boiling or pressurized water-cooled nuclear power facility, pumps and valves that are within the scope of the ASME OM Code must meet the IST requirements (except design and access provisions) set forth in the ASME OM Code and addenda that become effective subsequent to editions and addenda specified in 10 CFR 50.55a(f)(2) and (3) and that are incorporated by reference in 10 CFR 50.55a(a)(1)(iv),
to the extent practical within the limitations of design, geometry, and materials of construction of the components. The IST requirements for pumps and valves that are within the scope of the
Enclosure
ASME OM Code but are not classified as ASME Boiler and Pressure Vessel Code Class 1, Class 2, or Class 3 may be satisfied as an augmented IST program in accordance with 10 CFR 50.55a(f)(6)(ii) without requesting relief under 10 CFR 50.55a(f)(5) or alternatives under 10 CFR 50.55a(z). This use of an augmented IST program may be acceptable provided the basis for deviations from the ASME OM Code, as incorporated by reference in 10 CFR 50.55a, demonstrates an acceptable level of quality and safety, or that implementing the Code provisions would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety, where documented and available for NRC review.
In proposing an alternative to IST requirements in the applicable edition or addenda of the ASME OM Code as incorporated by reference in 10 CFR 50.55a, a licensee must demonstrate that (1) the proposed alternative provides an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1), or (2) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety in accordance with 10 CFR 50.55a(z)(2).
3.0 TECHNICAL EVALUATION
The information provided by the licensee in support of this request for an alternative to ASME OM Code requirements as incorporated by reference in 10 CFR 50.55a has been evaluated and the bases for disposition are documented below.
3.1 Licensees Alternative Request VR-03
Applicable Code Edition
The applicable OM Code of Record for the Sixth 10-Year IST Program interval at Ginna is the 2012 Edition of ASME OM Code as incorporated by reference in 10 CFR 50.55a.
ASME Code Components Affected
In its submittal, the licensee proposed alternative testing for the following valve:
Table 1
Component ID Class Category Description
896B 2 A RWST Outlet to Containment Spray and Safety Injection Pumps
The licensee provides additional information regarding RWST Outlet Valve 896B as follows:
The Refueling Water Storage Tank Outlet Valve provides a suction supply flow path to the Containment Spray and Safety Injection pumps when open for the injection phase and isolates the Refueling Water Storage Tank during Safety Injection in the recirculation phase.
When the Refueling Water Storage Tank inventory reaches a low level during the injection phase, the pumps suction is realigned from the Refueling Water Storage Tank to the containment sump via the Residual Heat Removal system for recirculation. When this transition occurs 896A and 896B are closed, isolating the Refueling Water Storage Tank and preventing the release of radioactivity to the atmosphere via the Refueling Water Storage Tank atmospheric vent.
=
Applicable Code Requirement===
The IST requirement in the ASME OM Code (2012 Edition), as incorporated by reference in 10 CFR 50.55a, related to this alternative request is as follows:
ASME OM Code, Subsection ISTC, Inservice Testing of Valves in Light-Water Reactor Nuclear Power Plants, paragraph ISTC-3630, Leakage Rate for Other Than Containment Isolation Valves, subparagraph (b), Differential Test Pressure, states in part:
Valve seat tests shall be made with the pressure differential in the same direction as when the valve is performing its function, with following exceptions:
In its alternative request, the licensee did not indicate the applicability of any exceptions listed in subparagraph (b) of ASME OM Code, Subsection ISTC, paragraph ISTC-3630.
=
Reason for Request===
In its alternative request, the licensee stated that pursuant to 10 CFR 50.55a(z)(2), an alternative to the requirement of ASME OM Code, ISTC-3630(b), is proposed. The licensees basis for the request is that compliance with the specified requirement results in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The licensee indicated that when aligning leak testing in the accident direction, 11 boundary valves must be used as a pressure barrier. The licensee stated that cumulative leakage from each of the 11 boundary valves can contribute to a false high leakage rate of this valve that must be investigated and resolved. This would involve increased time to perform the testing and unnecessary radiation exposure to test personnel and would result in a hardship without a compensating increase in the level of quality and safety.
Licensees Proposed Alternative and Basis for Use
The licensee describes the proposed alternative and the basis for its use as follows:
896B is an Active Motor Operated 10-inch Split Wedge Gate Valve. As such, this valve is included in [ASME OM Code] Mandatory Appendix III and has been previously evaluated and tested in the GL [Generic Letter] 89-10/96-05 MOV [Motor-Operated Valve] program.
The motor operated valve closes against minimal differential pressure and is required to be leak tight against a differential pressure of 158 psid [pounds per square inch differential].
The gate valve design inherently has two sealing surfaces (upstream and downstream disc faces) with both designed to provide shutoff; however, only one face needs to seal to provide leakage integrity. When closed, the motor operator provides sufficient seating thrust with margin to wedge the disc into the seat and prevent the system pressure from unseating the valve. Based on the gate valve design and adequate seating force, leakage will be the same across the disc when pressurized in either direction; therefore, leak testing this valve in the reverse direction at the required differential test pressure is an acceptable alternative and will provide equivalent results in the same direction as when the valve is performing its function. This alternative to the Code-required testing direction of the Refueling Water Storage Tank Outlet Valve (896B) is proposed pursuant to 10 CFR 50.55a(z)(2).
896B has passed its IST leakage, position indication, stroke open/close, and diagnostic testing since 2008. A search of the corrective action database, covering the last 20 years resulted in no events where 896B malfunctioned or failed to perform any of its required active open/close functions.
3.2 NRC Staff Evaluation
The NRC regulations in 10 CFR 50.55a require that RWST Outlet Valve 896B at Ginna be tested in accordance with the 2012 Edition of the ASME OM Code as incorporated by reference in 10 CFR 50.55a. For leakage rating testing of OM Category A valves other than containment isolation valves, ASME OM Code, Subsection ISTC, paragraph ISTC-3630, states in subparagraph (a) that tests shall be conducted at least once every 2 years; and states in part in subparagraph (b) that the valve seat test shall be made with the pressure differential in the same direction as when the valve is performing its function with specific exceptions. In Alternative Request VR-03, the licensee proposes to perform the valve seat leakage test for RWST Outlet Valve 896B in the reverse direction.
In its submittal, the licensee stated that RWST Outlet Valve 896B is an MOV with a 10-inch split-wedge gate valve design. This MOV is within the scope of ASME OM Code, Mandatory Appendix III, Preservice and Inservice Testing of Active Electric Motor Operated Valve Assemblies in Light-Water Reactor Power Plants, and was evaluated and tested as part of the GL 89-10/96-05 MOV program at Ginna. The licensee also reported that RWST Outlet Valve 896B has passed its IST leakage, position indication, stroke open and close, and diagnostic testing since 2008. The licensee did not identify any events where RWST Outlet Valve 896B malfunctioned or failed to perform its required active functions over the last 20 years. The licensee indicates that the MOV closes against a minimal differential pressure and must be leak tight against a differential pressure of 158 psid. The licensee stated that the motor operator provides sufficient seating thrust with margin to wedge the disk into the seat and prevent the system pressure from unseating the valve. Based on the gate valve design and adequate seating force, the licensee considers that leak testing of RWST Outlet Valve 896B in the reverse direction at the required differential test pressure is an acceptable alternative and will provide equivalent results in the same direction as when the valve is performing its function.
As referenced by the Ginna licensee in its submittal, the NRC staff addressed valve leakage testing in the reverse direction in its safety evaluations of IST requests submitted by the licensee of the Donald C. Cook Nuclear Plant, Units 1 and 2 (D.C. Cook). In particular, the NRC staff evaluated valve leakage testing in the reverse direction proposed by the D.C. Cook licensee in a safety evaluation (SE) dated December 8, 2006 (ML063340516) and in a SE dated March 4, 2016 (ML16054A572). As stated by the NRC staff in those evaluations, a leakage test in the reverse direction from the operating requirement direction must provide equivalent or more conservative results than a test in the accident direction to be considered adequate. In evaluating the adequacy of a licensees proposed test, the physical construction and arrangement of the valve seat and disk, as well as the pressure forces acting in the attached piping, must be considered. In the request by the D.C. Cook licensee, the subject valves were MOVs with an 8-inch flex-wedge gate valve design that were tested at 12 to 17 psid and would experience accident conditions from 122 to 195 psid. As reported by the Ginna licensee, RWST Outlet Valve 896B has a 10-inch split-wedge gate valve design and has a 158 psid leakage requirement. As with the D.C. Cook licensee for the applicable MOVs in its request, the Ginna licensee has set up RWST Outlet Valve 896B as part of the GL 89-10/96-05 program to meet its operating requirements under applicable differential pressure conditions. Similar to the
discussion of the flex-wedge gate valve design at D.C. Cook, the valve disks and seating surfaces in the split-wedge gate valve design in RWST Outlet Valve 896B at Ginna are symmetrical such that the thrust applied by the valves motor operator will tend to seat each wedge face equally. Additionally, the split-wedge gate valve design will not exhibit significant deformation at the relatively low line pressures (less than 200 psid) applied to the valve disks.
These design features provide confidence that both faces of the valve wedge will seat to limit overall seat leakage through the valve. With the low line pressures, the NRC staff considers that adequate leak tightness is assured by the mechanical wedging force provided by the motor actuator for RWST Outlet Valve 896B at Ginna.
Based on the description provided in Alternativ e Request VR-03, the NRC staff agrees with the licensee that aligning leak testing for RWST Outlet Valve 896B at Ginna in the accident direction would involve unnecessary radiation exposure to test personnel. Based on the motor-operated gate valve design and adequate seating force, the NRC staff finds the proposed alternative to the Code-required testing direction for RWST Outlet Valve 896B at Ginna to be acceptable in that compliance with the specified requirement in the subparagraph (b) of ASME OM Code, Subsection ISTC, paragraph ISTC-3630, would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety in accordance with 10 CFR50.55a(z)(2).
4.0 CONCLUSION
As indicated above, the NRC staff concludes th at the proposed alternative request VR-03 for the leak testing of RWST Outlet Valve 896B at Ginna as described in the licensees submittal dated April 11, 2022, is acceptable in that compliance with the specified requirement in the ASME OM Code, Subsection ISTC, paragraph ISTC-3630, subparagraph (b), would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Accordingly, the NRC staff concludes that t he licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC staff authorizes the proposed alternative for the Sixth 10-Year IST Program interval at Ginna, which began on January 1, 2020, and is scheduled to end on December 31, 2029.
All other ASME OM Code requirements for which an alternative was not specifically requested and approved remain applicable.
Principal Contributors: K. Hsu, NRR G. Scarbrough, NRR
Date: February 1, 2023
ML23010A011 *by memorandum OFFICE NRR/DORL/LPL1/PM NRR/DORL/LPL1/LA NRR/DEX/EMIB/BC NAME VSreenivas KEntz SBailey DATE 1/9/2023 1/12/2023 7/15/2022 OFFICE NRR/DORL/LPL1/PM NRR/DORL/LPL1/BC NAME VSreenivas HGonzalez DATE 02/01/2023 02/01/2023