ML19305D321
| ML19305D321 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 04/09/1980 |
| From: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8004140375 | |
| Download: ML19305D321 (2) | |
Text
D NORTHEAST trFILFFIES 3
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April 9, 1980 Docket No. 50-245 Director of Nuclear Reactor Regulation Attn:
Mr. D. L. Ziemann, Chief Operating deactors Branch #2 U. S.' Nuclear Regulatory Commission Washington, D. C.
20555
Reference:
(1) 10CFR50 55a(g).
Gentlemen:
Millst ine Nuclear Power Station, Unit No.1 Inservice Inspection and Testing Program Paragraph 5(iii) of Reference (1) requires that licensees notify the NRC if certain Code requirements are found to be impractical and submit informa-tion to support these determinations.
We have determined that the scheduling requirements of the ASME Code Section XI, for examination Category B-L-2, are impractical for the reactor recirculation pump casings at Millstone Unit No.1.
The Code requires that internal pressure boundary surfaces of one pump in each group of pumps performing similar functions be examined visually during each inspection interval. There are no pressure retaining welds in the Millstone pumps so examination Category B-L-1 is not applicable. We are requesting relief from the requirements of Table IWB-2500 for the reasons listed below. The requested relief would specifically allow a postponement of the B-L-2 examination until major maintenance needs to be performed on the pump.
(1) The Millstone pumps have operated satisfactorily for ten years.
Visual examinations of the casing exterior during operational leak tests at refueling outages have shown no signs of degradation.
(2) The structural integrity of BWR reactor coolant pressure boundary material used in pump and valve bodies (cast stainless steel) has been acceptable in BWR service to-date with no degradation noted in pump or valve casings. Based on successful experience with cast stainless steel in a vide variety of pump applications, it is very unlikely that erosion or cavitation damage to the pump casing would be expected to occur.
8004140 W
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(3) Assurance of the integrity of the reactor coolant pressure boundary has been provided by the normal inservice inspection program and by augmented examinations required by NUREG-0313 of the recirculation piping welds.
(4) As an alternate examination, NNECO vill continue to perform visual inspections of both pump casing exteriors during periodic leak tests or hydrostatic pressure testing during each refueling outage.
(5) Additional assurance vill be provided by perfonsing monthly vibration signature analysis on the recirculation pumps.
It is our belief that this analysis is sufficiently sensitive to detect any major internal pump changes, should they occur by crosion, wear, or cavita-tion.
(6) Disassembly and inspection of a recirculation pump will result in exposures on the order of 100 man-rem and require approximately
$200,000 in spare parts. Although the man-rem exposures would be kept to a minimum, the incremental increase in the assurance of pump casing integrity via disassembly does not warrant the 100 man-rem exposure.
(7) If any through-vall crack developed, the drywell leak detection system would provide the warning of pump degradation at an early stage when leakage first occurs. The Millstone Unit No.1 Technical Specifications limit unidentified leakage inside the containment to 2.5 gpm.
The last refueling outage in the first inspection interval is presently scheduled for September,1980. A response to this letter is, therefore, requested before August 30, 1980, in order'that we may proceed with our final outage planning at that time, for the recirculation pumps.
Should you have any questions, please contact us.
Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY g~ j/ :lG Vj )2 0- ]
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W. G. Counsil Vice President i
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