ML16148B143
| ML16148B143 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/07/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML16148B142 | List: |
| References | |
| NUDOCS 9205260088 | |
| Download: ML16148B143 (5) | |
Text
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aNUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2065 SAFETY EVALUATION REPORT BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF FROM ASME SECTION XI REQUIREMENTS DUKE POWER COMPANY OCONEE NUCLEAR STATION, UNIT 1 DOCKET NO. 50-269 I.
BACKGROUND INFORMATION The Technical Specifications for the Oconee Nuclear Station, Unit 1, states that inservice examination of ASME Code Class 1, 2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable Addenda as required by 10 CFR 50.55a(g)(4), to the extent practical within the limitations of design, geometry, and materials of construction, except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). In addition, alternatives to the requirements of the ASME Code may be authorized pursuant to 10 CFR 50.55a(a)(3).
Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance with an examination requirement of Section XI of the ASME Code is not practical for his facility, information shall be submitted to the Commission in support of that determination and a request made for relief from the ASME Code requirement. After evaluation of the determination, relief may be granted, and alternative requirements may be imposed that are determined to be authorized by law, and will not endanger life or property or the common defense and security, and are otherwise in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed.
By letters dated August 20 and September 6, 1991, Duke Power Company (licensee) requested relief from requirements of the 1980 Edition though Winter 1980 Addenda of Section XI for Oconee Unit 1. The information provided by the licensee in support of the request is evaluated herein to determine if the necessary findings can be made to grant the relief requested.
9205260088 920507 PDR ADOCK 05000269 PPR
-2 II. REQUEST AND SUPPORTING INFORMATION A. Relief Request No. 91-03, Volumetric Examination of Pump Casing Welds and Visual Examination of Pump Casing Internal Surfaces Relief from the volumetric examination of pump casing welds and visual examination of pump casing interior surfaces requirements for Class 1 reactor coolant pumps of the 80W80 Code,Section XI.
- 1.
Reference Code Requirement that has been determined to be impractical:
Table IWB-2500-1, Examination Category B-L-1, Item 812.10, Pump Casing Welds - Volumetric examination of essentially 100% of all welds in at least one pump in each group of pumps performing similar functions in the system. The examinations shall be performed during each inspection interval, and may be performed at or near the end of the inspection interval.
Table IWB-2500-1, Category B-L-2, Item B12.20, Pump Casing Internal Surfaces - Visual examination of the internal surfaces of at least one pump in each group of pumps performing similar functions in the system. The examinations shall be performed during each inspection interval, and may be performed at or near the end of the inspection interval.
IWB-2420(a) requires that the sequence of component examinations established during the first inspection interval shall be repeated during each successive interval to the extent practical.
- 2.
Component for which relief is requested:
(a) Name and Number:
Unit 1 Reactor Coolant Pump 1A2 (Duke System No. 50)
(b) Function: The reactor Coolant Pump recirculates primary (borated) coolant water from the Once Through Steam Generator (OTSG) in its respective loop to the reactor vessel.
(c) ASME Code Class:
1
-3
- 3.
Basis for requesting relief:
During the first inspection interval, the Reactor Coolant Pump 1A2, Casing Welds and Casing, were examined during the third period. In order to comply with the Code, it is necessary to examine these components during the third period of the second inspection interval.
This examination will require approximately 10,304 man-hours and approximately 30 person-rem to disassemble, inspect, and reassemble the reactor coolant pump.
- 4.
Alternative Examination:
Volumetric and visual examinations on the Pump Casing Welds and Pump Casing on Reactor Coolant Pump 1A2 that are required by the ASME Boiler & Pressure Vessel Code will be deferred to when maintenance activities require disassembly of the Reactor Coolant Pump.
- 5.
Staff Evaluation:
The material used (Type 316 stainless steel castings), has had an excellent performance history, as have these pump casings. There have been no reported instances of pump casing weld or interior surface degradations in nuclear power plant service.
The volumetric examination of the materials of construction (thick, welded cast stainless steel) is very difficult to inspect and would not provide adequate, meaningful inspection results. Because of the man-rem exposure associated with performing the required examinations and the excellent service record of the-pump casting welds and casing interior surfaces, the staff finds that disassembly of a pump for the sole purpose of inspections required by Section XI of the ASME Code would result in a hardship without a compensating increase in the level of quality and safety. The alternative examinations proposed by the licensee will provide adequate assurance of pressure boundary integrity. If this pump, or one of similar design and purpose, has not been disassembled, the licensee should report such fact in the ISI Summary Report at the end of the interval.
B.
Relief Request No. 91-04, System Hydrostatic Test after Weld Repairs Relief from the system hydrostatic test after weld repair requirements of the 80W80 Code,Section XI.
-4
- 1.
Reference Code Requirement that has been determined to be impractical:
IWA-4400(a)
"After repairs by welding on the system pressure retaining boundary, a system hydrostatic test shall be performed in accordance with IAW-5000."
- 2.
Component for which relief is requested:
(a) Name and Number:
Low Pressure Service Water pipe between LPSW-117 and 1LPSW-356.
(b) Function:
Directs water from the outlet of Unit 1 Reactor Building Component Coolers to the CCW pipe.
(c) ASME Code Class:
2, Duke Class F
- 3.
Basis for requesting relief:
This particular section of pipe is located in the Turbine Building. Repairs were necessary for 1LPSW-356. A mechanical plug, a Marbo plug, was installed in the pipe between 1LPSW-356 and 1LPSW-117 in order to restrict the flow from Unit 2 Component Cooler for the system pressure test. When it was attempted to remove the plug, it could not be dislodged.
In order to remove the Marbo plug, a rod needed to be inserted through a hole in the pressure boundary. After removal of the plug, the hole through which the rod was inserted was weld repaired. A Section XI hydrostatic test of the repair is impossible to perform with the Marbo plug installed since it is unidirectional and could not withstand the pressure of a hydrostatic test on the back side of the plug. After the Marbo plug is removed, a hydrostatic test is impossible to perform since this section of pipe cannot be isolated from Unit 2 due to system configuration.
- 4.
Alternative Examination:
A visual examination (VT-2) performed once the system is placed back in service.
- 5.
Staff Evaluation:
To require a system hydrotest of the section of piping with the weld repair of the hole, Unit 2 would have to be shut down. Extensive redesign and reconstruction would be required to allow for the system hydrotest of this particular repair to be accomplished. Therefore, the Code requirement is impractical.
-5 This piping system has a very low design pressure and temperature, and the water supply capability is very large (27 inch diameter supply line) compared to the the leakage that would occur if a crack developed in the weld repair.
The required surface examination of the thin wall pipe repair and the VT-2 examination when the system goes into service should provide adequate assurance of the repair's integrity.
III.
CONCLUSIONS Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee has determined that conformance with certain Code requirements is impractical for its facility and submitted supporting information. The staff reviewed the licensee's submittals, and concluded, pursuant to 10 CFR 50.55a(a)(3)(ii), that the proposed alternative to the required inservice inspections of the reactor coolant pump casing and welds is acceptable, and pursuant to 10 CFR 50.55a(g)(6)(i), that the system hydrotest of a weld repair in the low pressure service water pipe is impractical to perform to the extent required by Section XI of the ASME Code.
The public health and safety will not be endangered by allowing the proposed alternative examinations to be performed in lieu of the Code requirements. Therefore, pursuant to 10 CFR 50.55a(g)(6)(i), relief is granted for Relief Request RR-91-04. Pursuant to 10 CFR 50.55a(a)(3)(ii), relief is granted for RR-91-03. Such relief is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest. This relief has been granted giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.