ML20085D897

Forwards Response to 830617 Request for Addl Info Re IE Bulletin 80-11, Masonry Wall Design. Effects of Higher Modes Can Be Neglected in Considering Total Seismic Shear Loadings as Masonry Walls Assumed to Be Relatively Stiff

ML20085D897
Person / Time
Site:	Robinson
Issue date:	07/25/1983
From:	Zimmerman S CAROLINA POWER & LIGHT CO.
To:	Varga S Office of Nuclear Reactor Regulation
References
REF-SSINS-6820, REF-SSINS-SSINS-6 IEB-80-11, LAP-83-324, NUDOCS 8307290169
Download: ML20085D897 (4)

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CD&L Carolina Powes & Light Company JUL 251983 SERIAL: LAP-83-324 Director of Nuclear Reactor Regulation Attention: Mr. Steven A. Varga, Chief Operating Reactors Branch No. I Division of Licensing United States Nuclear Regulatory Commission Washington, DC 20555 H. B. ROBINSON STEAM ELECTRIC PLANT, LNIT NO. 2 DOCKET NO. 50-261 LICENSE NO. DPR-23 IE BULLETIN 80-11, MASONRY WALL DESIGN

Dear Mr. Varga:

As requested by your letter dated Junes17, 1983, Carolina Power &

Light Company (CP&L) has completed the response to your request for additional information concerning IE Bulletin 80-11, Masonry Wall Design, for the H. B.

Robinson Steam Electric Plant Unit No. 2. The responses to your questions are attached.

Should you have any further questions on this subject, please contact a member of the Nuclear Licensing Staff.

Yours very truly, mn - ~_ -

S. . immerman Manager Licensing & Permits ONH/ccc Attachment cc: Mr. J. P. O'Reilly (NRC-RII)

Mr. G. Requa (NRC)

Mr. Steve Weise (NRC-HBR) 8307290169 830725 PDR ADOCK 05000261 h

G pop I y 411 Fayetteville Street

• P. O. Box 1551

• Raleigh, N. C. 27602 ms:xwem.:RnMW= c ems::==p: * . rcr'm m -

Response to Request for Additional Information Concerning Masonry Wall Design, IE Bulletin 80-11 With reference to the transmittal submitted by the licensee to the NRC on February 4,1983 (Ref.1), the following areas require additional information or clarification:

(1) In Response No. 4 of Ref.1 it appears that the multi-mode effects were considered only in the building dynamic analysis but not in the analysis of masonry walls. For an equivalent static analysis the Standard Review Plan (Section 3.7.2) recommends a factor of 1.5 be ,

applied to the peak response of the applicable floor response spectra to account for the multi-mode effects. Indicate if any increase factor was used. If not, provide justification.

CP&L Response Standard Review Plan, Section 3.7.2, allows a reduction in the 1.5 factor if adequate justification is provided. Additionally, a factor of 1.0 applied to the peak of the floor response spectra is allowed by the Standard Review Plan for equipment which can be modeled adequately as a one-degree-of-freedom system.

The block wall structural systems have all been considered as simple one-degree-of-freedom systems. No interaction or coupled effects from adjacent structure or interconnecting block walls were considered. Block walls were modeled and analyzed as cantilevers and/or simple beams between steel supports. Also, as masonry walls l

are normally assumed to be relatively stiff (above 33 hertz) with low first-mode natural periods, effects of higher modes can normally be l negiccted in considering total seismic shear loadings.

CP&L feels justified in not using an increased factor based on the above rationale and based on the standard review plan relaxation of l the 1.5 factor for equipment considered as one-degree-of-freedom l systems. Although block walls are not equipment, the intent of the l Standard Review Plan, Section 3.7.2, has been adhered to.

Reference l 1. Letter from S. R. Zimmerman of CP&L to S. A. Varga of NRC, dated February 4, 1983.

(2) In Response No. 6 of Ref. I the licensee stated that an increase l factor of 1.33 was used for the allowable stresses of masonry walls. For a load combination involving the safety shutdown earthquake (SSE) this factor is acceptable but the SGEB criteria (ceveloped by the Structural and Geotechnical Engineering Branch of the NRC, Ref. 2) does not allow any increase factor for a load combination involving the operating basis earthquake (OBE). Thus, the allowable stresses for an OBE event are smaller than a SSE .

event. Clarify whether a seismic analysis for the OBE was performed Indicate whether and whether this increase factor of 1.3 was used. If the walls can be qualified without use of any increase factor.

walls cannot be qualified, the licensee is requested to explain all conservative measures used in the OLE analysis to justify the proposed increase factor and also identify the number of af fected  !

walls along with the actual increase factor used for each wall.

CP6L Response In re-analysis per Bulletin 80-11, a seismic horizontal acceleration factor of 0.2g was used to evaluate each block wall and steel support system.

This was considered to be equivalent to an SSE ground acceleration loading. As can be seen from the analysis of wall 6 (included as a sample calculation in Appendix A of Reference the 1), no increase in allowable stresses was actually used to evaluate block wall systems. CP&L's consultant chose not to apply the 1/3 increase in allowable stresses allowed by design codes for the SSE event as a worst case condition. As such, the response to comment 10 of Reference 1 essentially shows that the block wall structural systems are qualified safe for either the OBE cy; the SSE event seismic loadings.

l Reference

2. dGEB Criteria for Safety-Related Masonry Walls Evaluation, Structural and Geotechnical Engineering Branch, July 1981 ( Also, SRP Section 3.8.4, Appendix A).

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(3) The licensee indicated that the results of the analysis of a missile shield wall will be submitted on or before March 1, 1983. Provide these results for staff's review.

4 CP&L Response -

The requested information was discussed in a CP&L letter dated April 5, 1983 from S. R. Zimmernan to Mr. S. A. Varga.

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