ML20072G149
| ML20072G149 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 06/24/1983 |
| From: | Musolf D NORTHERN STATES POWER CO. |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20072G151 | List: |
| References | |
| TAC-59523, NUDOCS 8306280340 | |
| Download: ML20072G149 (3) | |
Text
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Northem States Power Company 414 Nicollet Malt Minneapoks. Minnesota 55401 Telephone (612) 330 5500 June 24, 1983 Director Office of Nuclear Reactor Regulation U S Nuclear Regulatory Commission Washington, DC 20555 PRAIRIE ISLAND NUCLEAR CENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Request for Relief from 10 Year Inservice Inspection of Reactor Coolant Pump Casing Welds Reference (1) Letter from Florida Power & Light Company by R Uhrig to D G Eisenhut (NRC) dated November 18, 1982 (2) Letter from Connecticut Yankee Atomic Power Company by W G Counsil to D M Crutchfield (NRC) dated September 3, 1982 (3) Letter from Wisconsin Public Service Corporation by C W Giesler to D G Eisenhut (NRC) dated March 8, 1983 (4) Letter and Safety Evaluation Report from D M Crutchfield (NRC) to W G Counsil of Connecticut Yankee Atomic Power Company granting Inservice Inspection Relief - RCP inspection program dated December 21, 1982 The purpose of this letter is to request relief, in accordance with 10 CFR Part 50, Section 50.55a(g)(6)(1), from a requirement of the ASME Boiler and Pressure Vessel Code,Section XI, Inservice Inspection. This request is being submitted as Revision 9 to the Prairie Island Inservice Inspection and Testing Program. Also attached is a Licensing Fee Determination and a check for $4,400.00 f or the required NRC Staf f review.
NSP requests relief from performing the examinations of the Reactor Coolant Pump (RCP) internal casing welds as required by Section XI, Table IWB-2500 of the ASME Code. The code requirements are:
Category B-L-1 requires a volumetric examination of the reactor coolant pump casing weld. The exam shall include 100% of the pressure retaining welds in at least one pump in each group of pumps performing similar functions in the system. The examinations may be performed at or near the D
end of the inspection interval.
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-NORTHERN STATES POWER COMPANY Dir of NRR June 24, 1983 Page 2 Category B-L-2 requires a visual examination of' the internal pressure boundary surfaces of the pump. One pump in each
, group of pumps performing similar functions in the system shall be examined during each inspection interval.
The examinations may be performed at or near the end of the inspection interval.
Northern States Power Co. (NSP) considers the requests of relief for these two code requirements justified for the following reasons.
- 1. The radiation exposure for inservice inspection would more than double due to the pump inspection alone. The ISI radiation exposure for 1980, 1981 and 1982 were 42.2, 43.9 and 40.8 man-Rem.
Radiation exposure at other plants for the pump inspection range from 35 to 100 man-Rem. A plant recently completed an inspection on the same model pump as Prairie Island's during which the exposure was 46 man-Rem, 10 of _which was received to obtain a second radiograph.
The first radiograph was not acceptable.
- 2. Additional exposure is received by personnel from the movement of the upper internals. The upper internals need to be placed in the reactor to minimize exposure and airborne contamination when the cavity and reactor coolant system is drained for the pump casing ins pection. The upper internals need to be removed again for core reload.
- 3. The visual and/or volumetric examination will require complete disassembly of the pump. The pump manufacturer (Westinghouse) does not require or recommend pump disassembly to perform normal mainte-nance and inspections. There has been limited experience for personnel doing this task. Therefore, significant damage or degradation of the pump may result.
- 4. The estimated cost for the disassembly, inspection and assembly is approximately $500,000. This cost does not include additional loss in revenue if the outage is extended due to the inspection.
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- 5. A visual inspection was performed on 21 RCP in 1981 when disassembled for repairs.
The internal surface was visually inspected using an underwater TV camera. The pump casing was not drained. The inspection did not reveal any problems.
The visual inspection was completed to the requirements of ASME Code Section XI.
l
- 6. The reactor coolant pumps at Prairie Island have additional monitoring equipment not originally supplied with the pump. The instruments monitor the shaf t vibration, frame vibration, thrust position, phase
[
monitoring and locked rotor.- It was this instrumentation which.
alerted the plant personnel to the 21 RCP problem in 1981.
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- 7. The reactor coolant pump casing consists of two cast rings made from type 316 stainless steel. This type of naterial is widely used in the nuclear industry and has performed well.
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NORTHERN STATES POWER COMPANY Dir of NRR June 24, 1983 Page 3
- 8. EPRI is conductihg a study of inspection frequencies for the inservice' inspection program. A portion of that study is directed at the reactor coolant pumps. The preliminary findings indicate the interval for reactor coolant pumps casing weld inspection could be increased without significant risk.
EPRI will be issuing shortly a report on Research Project 2057. The report will discuss the reactor cool. ant pump _ casing weld inspection program. This report is titled "EPRI Report on Long Term Inspection Requirements for Nuclear Power Plants Components".
As an alternate to the B-L-1 and B-L-2 examinations, NSP will do the following:
- 1. Visually inspect the exterior of the pump casing during the hydrostatic pressura tests required by IWB-5000.
- 2. Perform a surface examination on the external surface of the welds to the extent practicable.
- 3. If maintenance or operational problems are encountered which require the disassembly of the pump, the pump's interior surface will be visually inspected. The need for performance of a volumetric examination will also be evaluated at that time.
Since we are now preparing the ten-year inservice inspection plans for both Prairie Island units, we ask that NRC Staff review of this request be given appropriate priority. We ask that this review be completed prior to January 1, 1984.
Please contact us if you have any questions related to our request.
w.
David Musolf Manager - Nuclear Sup Se rvices DMM/SAF/bd cc: Regional Administrator-III, URC NRR Project Manager, NRC Resident Inspector, NRC G Charnoff
Attachment:
Revision 9 pages to ASME Section XI Inservice Inspection and Testing Program Manual.
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