ML17299B192

Forwards Evaluation of Adequacy of Nonstructural,Nonload Bearing Masonry Walls Used in Auxiliary & Control Bldgs & Subj to Lateral Seismic Inertial Loads,Per Concerns Raised During Recent Audit & 860320-21 & 0411 Meetings

ML17299B192
Person / Time
Site:	Palo Verde
Issue date:	04/16/1986
From:	Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	Knighton G Office of Nuclear Reactor Regulation
Shared Package
ML17299B193	List: ML17299B192
References
ANPP-36153-EEVB, TAC-60773, NUDOCS 8604180215
Download: ML17299B192 (9)

Text

REGULA wY INFORNATIQN DISTRIBUTIQ SYSTEH <R IDS)

ACCESSION NBR: 8604180215 DOC. DATE: 86/04/16 NOTARIZED: NO FACIL: STN-50-528 Palo Vev'de Nuclear Station> Uni t 1> Av'i zona Pub l i STN-50-529 Palo Vev'de Nuclear Station> Uni t 2> Arizona Pub 1 i STN-50-530 Palo Verde Nuclear Station> Uni t 3> Av i zona Pub l.i AUTH. NANE AUTHOR AFFILIATION VAN BRUNT. E. E. Arizona Nucleav'otuer Pro Ject (formerly Av i zona Public, Sev v RECIP. NANE RECIPIENT AFFILIATION KNIQHTON> Q. W. PWR Pv object Div ectov ate 7

SUBJECT:

Forwards evaluation of- adequacy of nonstv uctuv al> nonload bearing masonvg walls used in auxiliavg 0 control bldgs sub) to lateral seismic inertial loads> pev concevns raised duv'ing v ecent audit h 860320-21 Z~ 0411 meetings.

DISTRIBUTION CODE: 8021D COPIES RECEIVED: LTR ENCL "

SIZE:

TITLE: QR/Licensing Submittal: Combined General Distribution NOTES: Standardized plant. 05000528 Standardized plant. 0500052'P Standardized plant. 05000530 RECIPIENT COPIES RECIPIENT COP IES ID CODE/NANE LTTR ENCL ID CODE/NA~>1E LTTR ENCL PWR-8 ADTS 1 1 PWR-8 EB 1 PWR-8 PEICSB 2 2 PWR-8 FOB 1 PWR-8 PD7 LA 1 0 PWR-8 PD7 PD 05 1 LICITRA. E 01 1 PWR-8 PEICSB 1 PWR-8 RSB 1 INTERNAL: ACRS 29 8 8 ADN/LFMB 0 ELD/HDS3 1 0 NRR BWR ADTS 1.

NRR PWR-A ADTS NRR PWR-8 ADTS 0 DIR NRR/ORAS 1 EG FIL 04 1 RQN5 Al'9 I /NI8 1 0 EXTERNAL: 24X 1 1 LPDR 03 1 NRC PDR 1 NSIC Oh 1 1 PNL CRUEL> R 1 1 TOTAL NUj'1BER OF COPIES REQUIRED: LTTR 33 ENCL 29

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Arizona Nucfear Power Project P.O. BOX 52034 ~ PHOENIX, ARIZONA85072-2034 April 16, 1986 ANPP-36153-EEVB/RMB/98.00 Director of Nuclear Reactor Regulation Attention: Mr. George W. Knighton, Project Director PWR Project Directorate 87 Division of Pressurized Water Reactor Licensing B U.S. Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Units 1, 2 and 3 Docket Nos. STN 50-528 (License NPF-41)

STN 50-529 (License NPF-46)

STN 50-530 Evaluation of Masonry Walls File: 86-056-026

Dear Mr. Knighton:

A limited number of non-structural, non-load bearing masonry walls have been Used in the PVNGS Auxiliary and Control buildings. these walls are subject to lateral seismic inertial loads due to their own weight and the weight of light attachments.

Several questions were raised regarding the adequacy of these walls as a result of a recent NRC audit. Meetings have been held with the NRC to discuss these issues on March 20-21 and April ll, 1986. There have been telephone calls to provide additional data on the evaluation performed and to obtain the perspective of the Chairman of the ACX 531 Code Committee.

Specific issues related to the design of the masonry walls have been discussed during the meetings and subsequent telephone conversations. The enclosure to this letter is provided to summarize the significant attributes of the issues involved, describe the extensive documentation review and field investigations of the as-built condition of the masonry walls, and present the results of the evaluations performed.

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Mr. George W. Knighton Palo Verde Nuclear Generating Station Evaluation of Masonry Walls ANPP- 36153 Page 2 As background, the masonry walls were designed in October, 1975. In April, 1980, a letter was issued by the NRC to all Construction Permit and Operating license Applicants requesting information on Category I masonry walls employed by plants under CP and .,OL review. In August, 1980, ANPP responded to the NRC request that only non-structural concrete masonry walls were used and noted that at a few locations, conduits, instrumentation tubing and small electrical panels were attached to the masonry walls. A composite record of all these attachments have been kept to assure that wall integrity has not been

)eopardized. This information was incorporated into the FSAR in May, 1981.

Subsequently, Appendix A to SRP Section 3.8.4 "Interim Criteria For Safety-Related Masonry Wall Evaluation" was issued in July, 1981. No further action was taken until the recent evaluation performed as a result of the NRC audit findings.

Three questions were raised by the NRC regarding the adequacy of this evaluation: Use of full allowable stresses, adequacy of splicing in adjacent cells, and adequacy of available lap lengths. With regards to the first question, there are sufficient data based on recent investigations and review of available construction documentation to )ustify the use of special inspection values since the signficant structural attributes of the wall are known.

Staggered splices are adequate to transfer the rebar forces as evidenced by the available test data and as inferred from the applicable ACI code.

Finally, less than minimum splice lengths are acceptable provided the average bond stress does not exceed appropriate allowable levels.

Attachment C of the enclosure presents the critical'tresses in the walls, under the SSE conditions. The calculated flexural stresses are compared with the allowable values based on the ACI 531-79 Code, as modified by the SRP 3.8.4. The calculated bond stresses, are compared with the allowable values based on the ACI 318-63. Review of these results indicate the following:

A. Walls at Elevation 100'll the masonry, reinforcement and bond stresses are within their allowable values. The maximum flexural compression fiber stresses in the masonry exceeds the reduced allowable by only about 5X.

This is considered acceptable since the significant structural attributes of the wall are known, fulfilling the purpose of the special inspection.

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Mr. George W. Knighton Palo Verde Nuclear Generating Station Evaluation of Masonry Walls ANPP-36153 Page 3 B. Walls at Elevation to walls at elevation 100', all masonry, reinforcement and 74'imilar bond stresses are within their allowable values. The maximum flexural compression fibre stress in the masonry exceeds the reduced allowable value by 16X. This is considered acceptable because the significant structural attributes of the wall are known, fulfilling the purpose of special inspection.

Attachment C of the enclosure also includes the critical stresses in the walls, under the OBE conditions.

A. Walls at Elevation 100't elevation 100', all the stresses are less than the full allowable values. The calculated maximum flexural compression stresses exceed the reduced allowable by 5X. This is considered acceptable as noted for the SSE case.

B. Walls at Elevation 74'he bond stresses are within the values allowed by the ACI 318-63 Code for working stress design. The rebar stress exceeds the allowable stress by approximately 8X, but is well below the minimum yield stress. The masonry stress exceeds the reduced and the full allowable values, however, it is only 53% of the ultimate strength of the masonry and therefore will remain well within the elastic range. Conservatisms in the analysis are discussed in Attachment C.

The outmf-plane wall deflection for the OBE is small while vertical deflections are negligible. Calculated differential displacements of small magnitudes are acceptable with no adverse impact on the conduits, instrumentation tubing, or small electrical panels, and their supports.

Therefore, the wall is structurally capable of resisting the loads from the OBE and the light Category I attachments will perform all their intended functions.

Mr. George W. Knighton Palo Verde Nuclear Generating Station Evaluation of Masonry Walls ANPP-36153 Page 4 Our meetings with the NRC have been constructive in identifying certain results of testing and Code changes in the period since the PVNGS masonry walls were designed and constructed. This discussion and supporting information provide the basis to conclude that the walls are of sufficient strength so as not to cause a failure of any safety equipment. We believe that this information provides confidence so that licensing of PVNGS Unit 2 may proceed. At the same time, we recognize that in order to fully resolve this issue, some confirmatory items exist which require further resolution.

These include the following:

The intent of the Code definition for "special inspection" of the installation of masonry walls with respect to allowable stresses.

2. The applicability of industry tests to determine bond strength of reinforcing steel.

3. The capability of reinforcing steel splices in adjacent masonry block cells to resist the design loads.

4. Use of ACI 318-63 for bond stress allowables.

As a result ANPP will continue to work with the NRC Staff to accomplish a timely resolution of the items described. In the event total agreement on these issues is not reached, ANPP will perform appropriate additional calculations, testing and modifications to the masonry walls in question.

Additionally, while these issues are being resolved, ANPP will agree to inspect the units to assure there has been no sustained damage to the the masonry walls and safety related attachments following an OBE.

Very truly yours, E. E. Van Brunt, Jr.

Executive Vice President Project Director EEVB/RMB/dk Enclosure cc: E. A. Licitra R. P. Zimmerman A. C. Gehr

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