ML13310B526
| ML13310B526 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/14/1984 |
| From: | Medford M Southern California Edison Co |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8406180323 | |
| Download: ML13310B526 (3) | |
Text
Southern California Edison Company P. 0. BOX 800 2244WALNUTGROVEAVENUE ROSEMEAD. CALIFORNIA 91770 M.O. MEDFORD TELEPHONE MANAGER, NUCLEAR LICENSING J
n (213) 572-1749 Director, Office of Nuclear Reactor Regulation Attention:
D. M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C.
20555 Gentlemen:
Subject:
Docket No. 50-206 Criteria for Seismic Reevaluation of Pipe Supports and Mechanical Equipment San Onofre Nuclear Generating Station Unit 1 SCE's criteria for the seismic reevaluation of pipe supports and mechanical equipment for return to service were provided in my letters to you dated December 23, 1983 and January 16, 1984. The results of the NRC's review of these criteria were provided by letter from H. R. Denton to K. P. Baskin dated February 8, 1984. The purpose of this letter is to provide clarification and request approval for alternative criteria in three areas.
These items have previously been discussed with the NRC staff.
Pipe Support Yield Strength Section 2.1 of Enclosure 1 to my January 16 letter, indicated that we would apply a 30% increase to the material strength of structural steel in pipe supports due to actual versus minimum specified yield strength and strain rate effect considerations. This increased material strength would then be used in the ASME Code equations to define the appropriate allowable stress.
In the NRC's February 8 letter, it was indicated that an increase in the support allowable would be acceptable on a case by case basis; however, the a
maximum allowable stress was limited to 1.3 times the yield stress.
In tz subsequent discussions with the NRC staff, this allowable was discussed in light of the previous considerations. It was agreed that only the actual 00 'material strength factor would be applied. Therefore, on a case by case ain basis, SCE will apply a 20% increase to the pipe support material strength and V)e use this in the appropriate load equations to define the allowable stress.
oO Mechanical Equipment Anchor Bolts In Section 5.2.4.c of the enclosure to my December 23 letter, we indicated our intention to use the Balance of Plant Mechanical Equipment and o Piping Criteria for the evaluation of mechanical equipment. In accordance with these criteria, a safety factor of 4 would be used for concrete anchor bolts.
For pipe supports, a safety factor of 2 is being used as indicated in Section 2.1 of Enclosure 1 to my January 16 letter. This was based on Supplement 1 to IE Bulletin 79-02, which recognized the acceptability of this
Mr. D.
June 14, 1984 higher allowable for an interim period of time. Since the return to service criteria were developed only to apply on an interim basis, use of-the higher allowable is consistent with the IE Bulletin. It would also be appropriate to use this value for anchor bolts in equipment supports. Accordingly, a factor of safety of 2 will be used on a case by case basis for the evaluation of mechanical equipment anchor bolts for return to service-.
Welded Attachments to Elbows Item 20 in Enclosure 1 to my letter to you dated November 21, 1983 stated:
"All lugs (rectangular attachments) have been removed from the elbows of piping in the scope of the seismic reevaluation program."
This statement requires clarification since there are lug attachments on elbows which connect to spring hangers that will not be removed.
Specifically, there are eight such lug.attachments in the piping being evaluated for return to service. A typical example of this type of attachment is shown in the enclosed figure.
Since these.lug attachments connect to spring hangers, they do not transmit any seismic loading into the elbow. In addition, the local membrane stresses due to deadweight loading at the fillet weld interface were evaluated and found to be negligible. Therefore, our earlier statement should be clarified as follows:
"All seismic load carrying welded attachments on elbows (lugs and trunions) have been removed from piping in the scope of the seismic reevaluation program."
If you have any questions regarding any of the above items, please call me.
Your prompt review of these issues would be appreciated.
Very truly yours,
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SAN ONOF[E NUCLEAR GENERATING STATION NORWALK. CALIFORNIA FILE PIPE SUPPORT ASSEMBLY JOB NO DATE APPROVED SOUTHERN CALIFORNIA EDISON COMPANY 1 SCALE: NTS LOS ANGELES. CALIF.
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