ML20236X494

Safety Evaluation Granting Util 860617 Relief Request from Performing Volumetric & Visual Exam Requirements of ASME Section XI for Reactor Coolant Pumps Casing Welds & Internal Surfaces

ML20236X494
Person / Time
Site:	Beaver Valley
Issue date:	11/09/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20236X490	List: ML20236X489 ML20236X494
References
NUDOCS 8712090244
Download: ML20236X494 (4)

Text

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ENCLOSURE 1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION OF REQUESTS FOR RELIEF FROM EXAMINATION OF REACTOR COOLANT PUMP CASING WELDS AND INTERNAL SURFACES AND VALVE INTERNAL SURFACES DUQUESNE LIGHT BEAVER VALLEY POWER STATION, UNIT NO. 1 DOCKET NO. 50-344 1

I. EACKGROUND INFORMATION 10 CFR 50.55a(g)(4) requires that inservice examination of ASME Code Class 1, 2, and 3 components be performed in accordance with Section XI of the ASME Code except where specific written reliefs from those requirements have been granted by the Comission. By letter dated June 17, 1986, Duquesne Light (the licensee) requested relief from the examination requirements of the 1974 Edition through Sumer 1975 Addenda of Section XI for a reactor coolant pump and certain valves at Beaver Valley Power Station, Unit No.1. Following a telephone conference on February 26, 1987, between NRC and Duquesne Light staff members concerning the requests, a revision of the supporting information was submitted by letter dated June 1, 1987. Based on the revised information, the staff has determined that the requirements of the Code are impractical to perform and that the necessary findings can be made to grant ,

the reliefs as requested. The bases for our conclusions are presented below.

II. RELIEF REQUESTS} CODE REQUIREMENTS,' SUPPORTING INFORMATION, KRD3TA^FF_EVALUATIOM A. Relief Request Relief is requested from performing the volumetric and visual examination requirements of Section XI for the reactor coolant pumps' casing welds and internal surfaces.

Co_mponents Affected Reactor Coolant Pumps (RC-P-1A, IB, IC)

Sec_ tion XI Requirements (74S75)

Table IWB-2500, B-L-1 (Pump Casing Welds) and B-L-2 (Pump Casing) l examinations - The pump casing weld and pump casing of one reactor coolant pump (RCP) will be examined volumetrically and visually, respectively, by the end of the inspection interval.

I 8712090244 871130 PDR ADOCK 05000334 G PDR l

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l _B_ asis for Reli_ef The examinations of the RCP casing weld and casing internal pressure boundary require the complete disassembly cf the RCP.

Complete disassembly of an RCP would result in large expenditures of manpower and a substantial increase in radiation exposure. Also, possible damage to the pump could occur since these pumps were'not designed for ease of disassembly in the field.

The volumetric examination of the casing weld is extremely technically difficult. The inherent coarse gain structure of ASTM

, A351-65 Grade CF8 material precludes meaningful ultrasonic examination with present technology. The combination of surface radiation levels and material thickness (5" -6" minimum) preclude conventional radiographic techniques, leaving only high-curie Cobalt 60 or MINAC as possible alternatives.

RCP casing examinations performed by other plants have shown no evidence of cracks or surface degradation.

Potential or significant pump degradation would be detected by abnormalities in pump parameters, i.e., pump vibration, bearing temperature, seal flow and by RCS leakage.

Considering the technical difficulty, radiation exposure, cost, and possible damage resulting from pump disassembly, along with past industry results of RCP casing examination and the continuously monitored pump parameters that would detect pump degradation, it is concluded that the required examination will not provide a .

compensating increase in the level of safety to justify such examinations.

Alternate, Examination As an alternative to the B-L-1 examination, the exterior of the pump casing will be visually examined during pressure tests as required by IWB-5000 and a surface examination will be performed on the weld of one Reactor Coolant Pump.

The B-L-2 examination will be performed only when the pump is disassembled for maintenance.

Staff Evaluation and Conclusion Considering the pump design, materials of construction of the pump casing, and the radiation levels associated with performing the required examinations, the staff finds the examinations impractical to perfonn.

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In lieu of the volumetric examination of the pump casing weld and visual inspection of the internal surfaces, the licensee has committed to perform a surface examination of the welds. In addition to the surface examination , a visual inspection of the casing exterior surface will be performed during the hydrostatic test of the reactor coolant system. In the event that the pump has to be disassembled for operational or maintenance purposes, the required visual inspection of the internal surfaces will be performed.

We conclude that the surface and visual examinations which will be performed on the pump casing will provide adequate assurance of its structural integrity and that relief from the volumetric examination of the casing weld and visual inspection of the internal surfaces may be granted.

B. RELIEF REQUEST Relief is requested from performing the visual examination requirements for the internal surfaces of valves exceeding four-inch nominal pipe size.

COMPONENTS AFFECTED Velan, Check SI-10 6" SI-23 6" SI-11 6" SI-24 6" SI-12 6" SI-25 6" SI-15 6" SI-48 12" SI-16 6" SI-49 12" SI-17 6" SI-50 12" SI'-20 6" SI-51 12" SI-21 ;w 6" SI-52 12" -

SI-22 6" SI-53 12" Westinghouse, Gate Target Rock, Relief Valve -

MOV-RC-590 29" RV-RC-551A 6" MOV-RC-592 29" RV-RC-552B 6" M0V-RC-594 29" RV-RC-551C 6" MOV-RC-591 27 1/2" MOV-RC-593 27 1/2" MOV-RC-595 27 1/2" Darlina, Gate Rockwell, Gate M0V-RH-720A 10" MOV-RC-585 8" MOV-RH-720B 10" MOV-RC-586 8" MOV-RC-587 8" Copes / Vulcan, Gate l

MOV-RH-700 14" M0V-RH-701 14" C

Section_XIRequirement(745,751 Table 2500, B-M-2, requires a visual examination of the internal pressure boundary surfaces on selected valves exceeding 4-in.

nominal pipe size each inspection interval.

Basis for Relief The design of the valves is such that disassembly is required to perform the examination. Based on past performance of these valves and the service history of stainless steel valves, the requirement to disassemble one valve of each design type for the purpose of visual examination has a small probability of identifying service-induced flaws or degradation. The required examination would result in unnecessary exposure and cost and is therefore not justified.

Alternate Examination Proposed By Licensee The B-M-2 visual examination, will be deferred until valve disassembly is required for maintenance purposes.

Staff Evaluation and Conclusion The visual examination of the internal surfaces of Class 1 valves exceeding four-inch nominal pipe size necessitates complete disassembly of the valves and, in many cases, drainage of the reactor coolant and associated sy.ctems in which the valves are located. The valves for which reliefefrom the requirement has been requested have cast bodies without welds. Disassembly of these valves and drainage of systems to accomplish the visual _ examination requirement represent an undue hardship without a compensating increase in plant safety.

The licensee has proposed performing the visual examination of the internal surfaces of the valves when disassembly is required for maintenance purposes. The valve bodies are subjected to pressure tests (including hydrostatic) during which visual examinations (VT-2) are required for detection of leakage. The staff finds these tests adequate in providing assurance of the continued structural integrity of the valve bodies and concludes that relief from the visual examination requirements for the internal surfaces may be granted as requested.

Dated: November 9, 1987 Principal Contributor: George Johnson, reviewer I

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