ML082950361
| ML082950361 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 11/12/2008 |
| From: | Melanie Wong Plant Licensing Branch II |
| To: | Baxter D Duke Energy Carolinas |
| Olshan L N, NRR/DORL, 415-1419 | |
| References | |
| TAC MD8605, TAC MD8606, TAC MD8607 | |
| Download: ML082950361 (7) | |
Text
November 12, 2008 Mr. Dave Baxter Vice President, Oconee Site Duke Energy Carolinas, LLC 7800 Rochester Highway Seneca, SC 29672
SUBJECT:
SAFETY EVALUATION FOR OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3, THIRD 10-YEAR INSERVICE INSPECTION INTERVAL REQUEST FOR RELIEF NO. 04-ON-012, REVISION 1, END OF INTERVAL SYSTEM PRESSURE TEST (TAC NOS. MD8605, MD8606, AND MD8607)
Dear Mr. Baxter:
By letter dated April 21, 2008, you submitted relief request No. 04-ON-012, Revision 1, for Oconee Nuclear Station, Units 1, 2, and 3 proposing an alternative to the requirement of American Society of Mechanical Engineers, Boiler and Pressure Vessel Code (ASME Code),
Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, 1989 Edition, for the duration of the third 10-year inservice inspection interval. You requested relief from performing the end of interval system hydrostatic test at the Code-required test pressure for certain ASME Code Class 1 components within the system boundary. You proposed to perform the pressure test and the visual examination for the affected Code Class 1 components at their nominal operating pressure.
We have evaluated your request for relief from the Code in the attached safety evaluation and authorize the proposed alternative pursuant to Title 10 of the Code of Federal Regulations, Part 50, Section 50.55a(a)(3)(ii) for the duration of the third 10-year inservice inspection interval of Oconee Nuclear Station, Units 1, 2 and 3.
Sincerely,
/RA/
Melanie C. Wong, Chief Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287
Enclosure:
Safety Evaluation cc w/encl: Distribution via List Serve
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION THIRD 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM REQUEST FOR RELIEF NO. 04-ON-012, REVISION 1 OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3 DUKE ENERGY CAROLINAS, LLC DOCKET NOS. 50-269, 50-270, AND 50-287
1.0 INTRODUCTION
By letter dated April 21, 2008, Duke Energy Carolinas, LLC (the licensee), submitted relief request No. 04-ON-012, Revision 1 for Oconee Nuclear Station, Units 1, 2, and 3 proposing an alternative to the requirement of American Society of Mechanical Engineers, Boiler and Pressure Vessel Code (ASME Code),Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, 1989 Edition, for the duration of the third 10-year inservice inspection interval. The licensee requested relief from performing the end of interval system hydrostatic test at the Code-required test pressure for certain ASME Code Class 1 components within the system boundary. The licensee proposed to perform the pressure test and the visual examination for the affected Code Class 1 components at their nominal operating pressure.
The licensees request for relief is based on 50.55(a)(3)(ii); it would be a hardship to perform off-normal activities in order to pressurize the portion of piping between the inboard and outboard isolation valves to Code Class 1 system hydrostatic test pressure. The NRC staff has evaluated the licensees request for relief pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Section 50.55a(a)(3)(ii) and determined that compliance to the Code requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
2.0 REGULATORY REQUIREMENTS Section 50.55a(g)(2) requires that inservice inspection (ISI) of ASME Code Class 1, 2, and 3 components be performed in accordance with Section XI of the ASME Code and applicable addenda, except where specific relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). According to 10 CFR 50.55a(a)(3), alternatives to the requirements of paragraph 50.55a(g) may be used, when authorized by the U.S. Nuclear Regulatory Commission, if an applicant demonstrates that the proposed alternatives would provide an acceptable level of quality and safety or if the specified requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, Rules for ISI of Nuclear Power Plant Components, to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that ISI of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) twelve months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein.
The ISI Code of Record for the third 10-year inspection interval for Oconee Units 1, 2, and 3 is the 1989 Edition of the ASME Code,Section XI.
3.0 TECHNICAL EVALUATION
System/Component(s) for Which Relief is Requested Reactor Coolant Pressure Boundary (RCPB)
(i)
Decay heat removal system between motor-operated valves LP-1 and LP-2 (ii)
Boron dilution system between gate valves LP-103 and LP-104 (iii)
Low pressure injection system between valves LP-47, CF-11, and CF-12 (iv)
Low pressure injection system between valves LP-48, CF-13, and CF-14 (v)
Alternate pressurizer spray supply line between check valves LP-46 and LP-131 ASME Code Requirements The 1989 Edition with no addendum to the ASME Code,Section XI, Table IWB-2500-1, Examination Category B-P, Item B15.51 Note (2) states that the pressure retaining boundary during the system hydrostatic test shall include all Class 1 components within the system boundary. Note (6) states that this test is to be conducted once during the 10-year interval either at or near the end of each inspection interval. Paragraph IWB-5222 System Hydrostatic Test states that the system hydrostatic test may be conducted at any test pressure specified in Table IWB-5222-1 corresponding to the selected test temperature, provided the requirements of IWB-5230 are met for all ferritic steel components within the boundary of the system (or portion of system) subject to the test pressure (see IWA-5245).
Licensees Request for Relief Relief is requested from performing the system hydrostatic test at the pressure prescribed under IWB-5222 of the ASME Code,Section XI, 1989 Edition, for the portion of Class 1 piping between the inboard and the outboard isolation valves including the check valves identified above in Section 3 under items (i), (ii), (iii), (iv), and (v).
Licensees Basis for Requesting Relief Applying reactor coolant system (RCS) pressure to piping sections in Section 3 items (i), (ii),
(iii), (iv), and (v) during a hydrostatic pressure test would result in a hardship by exposing station personnel to:
Safety Hazards - ranging from physical exposure to temporary connections with the piping segment pressurized to 2155 psig (and in some cases at 600 degree F) or pressurizing the segments to RCS pressure with single valve isolation.
Radiation Exposure - from activities in containment such as carrying, installing, performing test activities and removing hydro pump or temporary jumpers as needed. Further, activities to install and remove scaffold, removal/replacement of insulation and valve internals, as necessary, would expose personnel to high radiation exposure.
These off-normal configurations and challenges may also contribute to the risk of delaying normal plant start-up because of the critical path time and the effort required to ensure that system configuration is restored.
The piping subject to this request is outboard of the first isolation valve and is designed to RCPB conditions. However, its operations during normal conditions is typically not subject to RCPB operating conditions but to Class 2 system conditions of decay heat removal, auxiliary spray, or low pressure injection. While the subject piping is extremely difficult to test with the Class 1 leakage test, it is easily tested with the Class 2 system at Class 2 test conditions because of the check valve boundaries. Although Class 2 system pressure is lower than that of Class 1, it is representative of conditions for which the subject piping is exposed during both normal and accident conditions. Additionally, if the inboard valve leaked (thereby pressurizing the subject piping) and a through-wall flaw did exist that could only be detected at the higher pressure, the flaw would be discovered during the Class 1 leakage test which is performed during each refueling outage with the inboard valve closed.
Licensees Proposed Alternative In lieu of performing the system hydrostatic test at the Code-required RCS pressure at or near the end of the inspection interval of the Class 1 piping between the inboard and the outboard isolation valves including the isolation valves in the RCPB identified in Section 3, items (i), (ii)
(iii) (iv) and (v) of this safety evaluation, the licensee proposed a system inservice test conducted to perform VT-2 visual examination while the system is in service under operating pressure.
4.0 NRC STAFFS EVALUATION The ASME Code,Section XI of Record requires that all Class 1 components within the reactor coolant system (RCS) boundary undergo a system hydrostatic test at or near the end of each inspection interval. In relief request No. 04-ON-012, Revision 1 for Oconee Units 1, 2, and 3, the licensee proposed an alternative to test the Class 1 piping between the inboard and the outboard isolation valves including the isolation valves in the RCPB identified in Section 3, Items (i), (ii), (iii), (iv), and (v) of this safety evaluation that are within the system hydrostatic test boundary. The licensee proposed to perform VT-2 visual examination during a pressure test at a pressure corresponding to their operating pressure in lieu of the Code-required pressure which is slightly higher than the RCS pressure in accordance with Table IWB-5222-1.
The inboard and the outboard isolation valves in decay heat removal loops A and B, and pressurizer auxiliary spray system for which the licensee has requested the relief, are check valves which prevent flow from the RCS to the connecting system. The portion of piping between the check valves including the valves are Class 1. The nominal operating pressure for the components is that of its connecting system unless the inboard check valve leaks. In order to perform the Code-required system hydrostatic test for these components in the extended Class 1 pressure boundary, an alternative method of pressurizing it to the RCS operating pressure corresponding to 100-percent power would be required. The staff believes that the provision for pressurization for the system hydrostatic test would require considerable man-hour effort resulting in high radiological exposure to personnel. Furthermore, pressurization by this method would preclude the RCS double valve isolation and may cause safety concerns for the personnel performing the examination.
The licensee has proposed an alternative to the system hydrostatic test of the extended Class 1 boundary by a system inservice test of each connecting system which is Class 2 and to perform the VT-2 visual examination during the same inspection interval. This alternative, however, would expose the extended Class 1 boundary to a lower test pressure that corresponds to the operating pressure of each connecting system in lieu of the Code-required RCS pressure corresponding to 100-percent power. The staff believes that the lower pressure system leakage test of the components in the extended Class 1 boundary will also detect leakage in the pressure boundary with a lower leak rate than that of the Code-required test pressure.
Nevertheless, the components in the extended Class 1 boundary are exposed to a lower pressure than the RCS pressure during normal operation or accident condition. Additionally, if the inboard check valve would leak (thereby pressurizing the subject components) with a through-wall flaw existing in the subject component that could only be detected at the higher pressure than that of the normal operating pressure, the flaw would be detected during routine system leakage test of the RCS conducted prior to startup of the unit following each refueling outage. The NRC staff believes that the licensees proposed alternative provides reasonable assurance of structural integrity for the components in the extended Class 1 boundary while maintaining personnel radiation exposure to as low as reasonably achievable. The staff has further determined that compliance to the Code requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
5.0 CONCLUSION
Based on the NRC staffs evaluation of relief request No. 04-ON-012, Revision 1, the requirements of the 1989 Edition of the ASME Code,Section XI, Paragraph IWB-5222(a) for the portion of Class 1 piping between the inboard and the outboard isolation valves including the check valves identified under Section 3, Items (i), (ii), (iii), (iv), and (v) of this safety evaluation would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The licensees proposed alternative in the request for relief provides reasonable assurance of structural integrity. Therefore, pursuant to 10 CFR 50.55a(a)(3)(ii), the proposed alternative in relief request No. 04-ON-012, Revision 1 is authorized for the third 10-year ISI interval of Oconee Nuclear Station, Units 1, 2, and 3. All other requirements of the ASME Code,Section XI for which relief has not been specifically requested remain applicable, including a third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: P. Patniak, NRR/DCI/CSG
ML082950361 OFFICE NRR/LPL2-1/PM NRR/LPL2-1/LA NRR/CSGB/BC OGC NRR/LPL2-1/BC NAME LOlshan MOBrien AHiser EWilliams MWong DATE 10/ 27/08 10/27/08 10/31/08 11/3/08 11/12/08