ML17286B266

Requests Approval to Revise Tornado Design Criteria,Per Reg Guide 1.76,Section C.1.2 for Rotational & Translational Velocities. Justification for Revised Tornado Design Criteria Encl

ML17286B266
Person / Time
Site:	Satsop
Issue date:	06/07/1991
From:	Sorensen G WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML17286B267	List: ML17286B266 ML17286B268
References
RTR-REGGD-01.076, RTR-REGGD-1.076 GO2-91-116, NUDOCS 9106180001
Download: ML17286B266 (5)

Text

ACCELERATED DI UTION DEMON TION SYSTEM REGULATORY XNFORMATXON DISTRXBUTION SYSTEM (RIDS)

ACCESSION NBR:9106180001 DOC.DATE:'1/06/07 NOTARIZED: NO DOCKET FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH. NAME . AUTHOR AFFILXATION SORENSEN,G.C. Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Requests approval to revise tornado design criteria,per Reg Guide 1.76,Sects.on C.1.2 for rotational 6 translational velocities. "Justification for Revised Tornado Design Criteria" encl.

DISTRIBUTION CODE: AOOID COPIES RECEIVED:LTR I ENCL: I SIZE:

TITLE: OR Submittal: General Distribution NOTES:

REClPIENT COPIES RECXPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL D PD5 LA 1 1 PD5 PD 1 1 ENG, P. L. 2 2 D XNTERNAL: ACRS 6 6 NRR/DET/ECMB 7D 1 1 NRR/DET/ESGB 1 1 NRR/DOEA/OTSB11 1 1 NRR/DST 8E2 1 1 NRR/DST/SELB 7E 1 1 NRR/DST/SICB8H7 1 1 NRR/DST/SRXB 8E 1 1 NUDOCS-ABSTRACT 1 1 OC/LFMB 1 0 OGC/HDS1 1 0 E ILE 1 1 RES/DSIR/EIB 1 1 EXTERNAL: NRC PDR 1 1 NSIC 1 1 D

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NOTE TO ALL "RIDS" RECIPIENTS:

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WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968 ~ 3000 George Washington Way ~ Richland, Washington 99352 June 7, 1991 G02"91-116 910618 po~ A o01 910607

$ )7 mDR Docket No. 50-397 t/

U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gentlemen:

Subject:

NUCLEAR PLANT NO. 2, OPERATING LICENSE NPF-21 RE(VEST FOR APPROVAL TO REVISE TORNADO DESIGN CRITERIA In accordance with the guidance of Regulatory Guide 1.76, Section C. 1.2 the Supply System hereby requests approval to revise the WNP-2 tornado design criteria.

WNP-2 current tornado design criteria, as stated in FSAR 2.3. 1.2. 1.3 and 3.3.2. 1, are for wind speeds of 300 and 60 mph rotational and translational respectively with a pressure drop of 3 psi to occur in 3 seconds. These criteria were found acceptable by the Staff as documented in the WNP-2 SER for the Operating License (NUREG-0892); section 3.3.2 of the. original issue. The Supply System proposes to change the design criteria to 135 and 45 mph rotational and translational velocities with a pressure drop of 0.65 psi occurring at 0.29 psi/sec.

Relative to the requirements of Regulatory Guide 1.76 the current design requirements represent an over commitment in that WNP-2 is a Region III site for which the criteri a are 190 and 50 mph and a 1.5 psi pressure drop at 0.6 psi/sec.

FSAR 3.3.2.4 and Appendix C.3 discuss the WNP-2 design relative to Regulatory Guide 1.76. It is also apparent that the proposed criteria are less than those proposed by the Regulatory Guide for a Region III plant.

In addition, FSAR 3.5. 1.4 establishes the following design basis tornado generated missi-les:

Weight Hori zontal Impact Vel oci ty Missile ~ibs Dimensions ft sec Utility Pole 1600 14" dia x 35 ft 241 Steel Rod 8 1" diax3 ft 259 The NRC found these missiles acceptable in SER 3.5. 1.4.

'age Two .

RE(VEST FOR APPROVAL TO REVISE TORNADO DEISGN CRITERIA Based upon the guidance of the above mentioned Regulatory Guide section, NRC approval of the use of revised tornado design criteria is requested. The criteria are:

Wind Speeds 180 mph maximum 135 mph rotational 45 mph translational Pressure Drop 0.65 psi at 0.29 psi/sec Missiles Weight Horizontal Impact Vel ocity Missile ~lbs Dimensions ft sec Wood Plank 115 3.6"x 0.94'x 12'long 167 6" Sch 40 Pipe 287 6.6" dia x 15'ong 17 1" Steel Rod 8.8 1" dia x 3'ong 20 12" Sch 40 Pipe 750 12.75" dia x 15'ong 13 The utility pole and automobile are not included as they are not considered to be credible missiles for wind speeds of less that 200 mph.

The selection of these criteria is based on extensive studies which define site specific tornado hazards for the Hanford area. These include Department of Energy (DOE) sponsored studies of various DOE nuclear related sites including the Hanford Site and NRC sponsored studies of tornado climatology in the United States, These and other studies are discussed in detail in the attached report titled "Justification for Revised Tornado Design Criteria."

The Supply System believes the proposed tornado design criteria will continue to provide adequate protection to safety related structures, systems and components such that, for the most severe tornadoes that would be reasonable to postulate to occur near the site, the safety functions of these structure, systems and components will not be impacted.

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Page Three

'E(UEST fOR APPROVAL TO REVISE TORNADO DESIGN CRITERIA The initial application of the revised tornado design criteria may be to provide for hard bolting of the Reactor Building roof to improve its reliability for differential and straight wind loads. To support this potential change a response to this request by September 1, 1991 is requested.

Very truly yours, G. C. orensen, Hanager Regulatory Programs AGH/bk Attachments cc: JB Hartin - NRC RV NS Reynolds - Winston 8 Strawn PL Eng - NRC DL Williams - BPA/399 NRC Site Inspector - 901A