ML20004B197
| ML20004B197 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 05/13/1981 |
| From: | Lempges T NIAGARA MOHAWK POWER CORP. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| IEB-80-13, NUDOCS 8105270377 | |
| Download: ML20004B197 (4) | |
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AI Y NIAGARA RuMOHAWK NIAGAMA MOHAWK POWG CCRPORAT10N/300 ERIE BouLEVARo WEST. SYRACUSE. N.Y.13202/ TELEPHONE (315) 474-1511 5 %,
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May 13,1981
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Y Mr. Boyce H. Grier, Director a,
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U. S. thclear Regulatory Commi,.on Region I 631 Park Avenue King of Prussia, PA 19406 Re: Docket No. 50-220 I.E.Bulletin 80-13
Dear Mr. Grier:
In accordance with I. E.Bulletin 80-13, Niagara Mohawk has visually examined the Nine Mile Point Unit 1 core spray spargers and associated internal piping during the 1981 refueling outage.
The attached report includes an evaluation of the inspecticn results. Two cracks were found at one location on the spargers; no other indications were fou nd. The evaluation concludes no corrective action is required at this time.
Very truly yours, NIAGARA M0 HAWK POWER CORPORATION
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Thomas E. Lempges Vice President - Nuclear Generation DKG:ja l
Attachment cc: NRC Office of Inspection and Enforcement Division of Reactor Operations Inspection Washington, D. C. 20555 Director of ?bclear Reactor Regulation Attention: Mr. Thomas A. Ippolito Chief, Operating Reactors Branch #2 Washington, D. C. 20555
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Inspection Technique During the 1981 refueling outage, a remote underwater TV examination of the accessible portions of the Nine Mile Point Unit 1 core spray spargers and associated internal piping was performed. This examination i
was perforined in accordance with NRC I.E.Bulletin 80-13, f.e., resolution of 0.001 inch diameter wires was demonstrated and oblique lighting techniques were used. Scanning of the spargers was done using a TV camera held at a fixed distance from the spargers. Various lighting angles and intensities were used to enhance viewing of the sparger surface.
II. Inspection Results Approximately 45 hours5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br /> of videotape of the core spray spargers and internal piping were obtained. The only cracking found was on the upper core spray sparger at approximately 3300 azinuth. As shown on the attached sketch, the indication consists of two cracks; one segment approximately 1/2 inch 1cag by 0.020 inches wide and one segment l
approximately 1/4 inch long by 0.001 to 0.003 inches wide. The dimensions were established by placing hairlines and a linear scale beside the indications. No other cracks were found.
III.
Evaluation The cracking found on tha NMP-1 core. spray spargers is not extensive. Niagara Mohawk's evaluation of the sparger cracks was prasented at a meeting with NRC representatives on April 15, 1981. The evaluation results are summarized below.
l 1.
Intergranular stress corrosion cracking is considered the most probable cause of crack initiation.
2.
Crack propagation initially due to residual bending mcment loads left in the spargers after installation is limited because these loads are sol f relieving.
3.
There are no signi ficant operating loads in service (thermal, vibration, dead weight, seismic) 4.
The only loads which are significant are those associated with an injection, i.e., hydraulic di fferential pressure and thermal mismatch.
Injection loads are low and do not impair sparger integrity even in the presence of cracks. Crack opening due to the injection transient is bounded.
5.
The effect of the observed cracking on core spray system hydraulic performance is insignificant.
IV.
Conclusions and Corrective Action The following is concluded from the above evaluation, j
1.
The observed Nine Mile Point Unit 1 cracks are minor.
2.
The observed cracks have no appreciable effects on stnJctural integrity or hydraulic performance.
In view of these conclusions, no corrective action will be taken during the 1981 refueling outage. As required by I.E.Bulletin 80-13, the core spray spargers and internal piping will be inspected again during the 1983 refueling ou tage. Future inspections will afford the opportunity to monitor the existing cracks.
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