ML19263C385

Applicants Will Use square-root-sum-of-the-square Load Combination Methodology in Component Design & Use of Absolute Summation Method for Structures Design.Requests This Be Reflected in FSAR Suppl.W/Encl Suppl Matl

ML19263C385
Person / Time
Site:	Black Fox
Issue date:	02/13/1979
From:	Fate M PUBLIC SERVICE CO. OF OKLAHOMA
To:	Varga S Office of Nuclear Reactor Regulation
Shared Package
ML19263C386	List: ML19263C385 ML19263C387
References
62121253500211, NUDOCS 7902220050
Download: ML19263C385 (3)

Text

.

61.Z DIN 8 - 014 - 560 PUBLIC SERVICE COMPANY OF OKLAHOMA A CENTRAL AND SOUTH WEST COMPAfJY

[7kw{N I

P P Q{;  ;

P O BOX 201/ TULSA. OKLAHOMA 74102 /(918)583-3611 %Md/

Februsry 13, 1979 r t v5 nien, File: 6212.125.3500.21L Public Service Company of Oklahoma Black Fox Station Methodology for Combining Dynamic Responses of Structures, Systems aid Components Importan* to Safety Docxet STN 50-556 and STN 50-557 Office of Nuclear Reactor Regulation Division of Pro ject Management Light Water Reactors Branch No. 4 U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attn: Steven A. Varga, Chief Gentlemen:

In correspondence with you dated December 20, 1978, we presented a proposal for using square-root-sum-of-the-square (SRSS) load combination methodology in the design of the Black Fox Station, Units 1 and 2. We are now prepared to commit to employing the methodology as outlined below. This commitment will be included as part of PSAR Amendment 15, dateo February 16, 1979 and is consistent with the testimony of Mr. Vaughn L. Conrad and others filed with the Atomic Safety and Licensing Board February 5,1979.

The purpose of Mr. Conrad's testimony is to state the Applicants' commitment with respect to the use of the square-root-sum-of-the-squares (SRSS) 'oad combination methodology for the design of the Black Fox Station Project.

A working group of the NRC Staff issued a report in September, 1978, (NUREG-0484),

that reviewed and discussed the present methods used by nuclear power station designers for combining various load combinations. As a result of the NUREG-0484 analysis, the NRC Staff approved the application of the SRSS methodology for com-bining SSE and LOCA dynamic loads within the e:cactor coolant pressure boundary and its supports. This application of the Sl<SS methodology was in addition to uses previously approved by the NRC Staff, i.e., the combining of certain modal combinations and direction combination responses caused by earthquakes, and the combining of LOCA and SSE loads in the analysis of PWR fuel bundles. Significantly, NUREG-0484 recognized that the NRC Staff is actively considering the application of SRSS methodology to the evaluation of Mark I and Mark II containment dynamic loads, and suggested the development of the justification to expand the application 7902220050; CENTRAL AND SOUTH WEST SYSTEM D

{er t 1 Pyrgnd L:ght c e ce Company of Oklahoma h ',

tern Egric Po6er gt T,eg UtAt es

U.S. Nuclear Regulatory Commission February 13, 1979 Docket STN 50-556 and STN 50-557 Page 2 of SRSS methodology on a generic basis, including Fbrk III applications.

Since the publication of NUREG-0484, a significant new development has occurred with the creation of criteria justifying the generic use of SBSS in combining loads for reactor design by Dr. Nathan Newmark and Dr. R. P. Keanedy (herein-after referred to as the "Newmark-Kenne('.y Criteria"). A copy of the criteria, as amended by Dr. Kennedy for the Black Fox Station, is attached to this letter.

We believe the criteria can and should serve as a basis for complying with Mr.

Varga's letter of October 31, 1978, requesting a PSAR commitment on load com-bination methodology for the design of the Black Fox Station.

As the testimony of Drs. Kennedy and Subramanian, Mr. Fuller, and Mr. Conrad indicate, the Applicants firmly believe the criteria justify the use of SRSS methodology for generic nuclear power station design. We understand that the NRC Staff has some reservations with respect to the application of the criteria to structures as distinguished from components and equipment. Ilowever, we be-lieve that the Staff will ultimately approve the use of SRSS for structures after completing their consideration of technical bases such as we have presented.

Therefore, as a matter of compromise, I am hereby committing on behalf of Applicants to:

A. The une of the absolute summation method to combine dynamic loads as defined in Appendix 3C of the PSAR, as amended through Amendment 14, in connection with the design of structures for the Black Fox Station.

If these loads are subsequently redefined in a significant manner, or if loads for structures other than those defined in Appendix 3C are defined, the loads may be combined as provided in B. below or by absolute summation.

B. The use of the SRSS load combination method to combine dynamic loads defined in connection with the design of piping and components for the entire Black Fox Station provided that each load can be shown to meet Criterion 1. or each load combination can be shown to meet Criterion 2. of the Newmark-Kennedy Criteria. Applicants agree to cooperate with the NRC Staff during the implementation of the Newmark-Kennedy Criteria, including the opportunity to review the actual appli-cation of the criteria by Applicants' NSSS supplier and Architect /

Engineer.

C. In the unlikely event the application of the SRSS load combination methodology for any particular load or load combination, as speci-fled in A or B above, results in neither Criterion 1. nor 2. cf the Newmark-Kennedy Criteria being met, Applicants agree to cooperate with the NRC Staf f to determine an acceptable load combination method.

U.S. Nuclear Regulatory Commission February 13, 1979 Docket STN 50-556 and STN 50-557 Page 2 We request that this commitment be reflected in your fr rthcoming supplement to the Black Fox Station Safety Evaluation Report.

Very t.ruly yours, /

{'

y

/f[ ,

Y-MEF:VLC:1h Attachments cc: BFS Service List