ML19263E790
| ML19263E790 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 06/15/1979 |
| From: | Counsil W NORTHEAST UTILITIES |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7906250282 | |
| Download: ML19263E790 (2) | |
Text
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P O. Box 270 v.',v$s\\.m.b '.m HARTFORD. CONNECTICUT 06101 (203) 666-6911
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June 15, 1979 Docket No. 50-245 Director of Nuclear Reactor Regulation Attn: Mr. D. L. Ziemann, Chief Operating Reactors Branch #2 U. S. Nuclear Regulatory Commission Washington, D. C.
20555
References:
(1)
W. G. Counsil letter to B. H. Grier dated April 24, 1979.
(2)
W. G. Counsil letter to D. L. Ziemann dated June 6,1979.
Gentlemen:
Millstone Nuclear Power Station, Unit No.1 I&E Bulletin #79-07 Additional Information In Reference (1), Northeast Nuclear Energy Company (NNECO) provided the response to I&E Bulletin 79-07 regarding seismic stress analysis of safety-related piping. Reference (2) supplied additional information on that subject.
Following that submittal, the Staff verbally requested further information which is provided herein.
In the attachment to Reference (2), NNECO tabulated pertinent data regarding modifications to the CRD exhaust line and the 1-CU2 bypass line piping.
Specifically, numerical data was presented resulting from piping analyses performed using techniques and criteria specified in the Millstone Unit No.1 FSAR. As stated in the body of Reference (2), these systems were evaluated and found in compliance with the requirements for Seismic Class I piping specified in the FSAR. Furthermore, the modifications were reviewed before-hand, as part of the necessary safety evaluations, and the conclusion was that the changes did not introduce any unreviewed safet.y questions as defined in 10CFR50.59.
The additional information now requested by the Staff for these two uodifications, involves an assessment of the effects of incorporating an additional 1.5 factor over and above the static seismic loadings that are specified as the licensing basis for Millstone Unit No.1.
NNECO has performed the assessment requested by the Staff for its information with the following results:
A) Stresses for the 0.B.E. condition for both piping systems remain below 1.2 S -
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. B) Stresses for the 3" CRD Exhaust line would remain below 1.8 SH for the DBE condition. The maximum stress in the 1/2" l-CU2 bypass line exceeds 1.8 SH by only 2.8%
Note that SH is based on minimum specified Code allowables.
C) All support and nozzle loadings for the 1-CU2 bypass line remain within acceptable limits.
D) The vertical support at data point 24 on the CRD exhaust line is capable of carrying the increased loading without exceeding code allowable limits.
E) The nozzle loading at data point 1 on the CRD exhaust line is within code allowable limits.
F) The anchor ab data poin: 25 on the CRD exhaust line was evaluated and the requirements of I&E Bulletin 79-02 addressed. The factor of safety of the anchor bolts (Hilti-Kwik Bolts) considering shear-tension inter-action ef fects and, using minimum specified concrete strength, is 3.42 for the total loading condition (SSE + normal operating loads).
Potentially, consideration of in-situ concrete properties would int rease the factor of safety near or above the factor of 4.0 recommended in I&E Bulletin 79-02.
NNECO will evaluate this concern further in a timefrane consistent with resolution of I&E Bulletin 79-02.
In summary, as stated previously, the two modifications did not introduce any un-reviewed safety questions as defined in 10CFR50.59. The techniques and criteria specified in the FSAR were used.
It is anticipated that durin; the SEP review of Millstone Unit No. 1 seismic margins inherent in the plant design will be quant ified.
NNECO has reviewed these modifications and finds these systems acce table for continued use.
The results summarized above were previously dis:,ussed verbally with NRC Staf f members to their satisfaction. We trust you find this information responsive to your interest in this issue.
Very truly yours, NORTilEAST NUCLEAR ENERGY, COMPANY
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W. G. Counsil Vice President 2214 346