GO2-94-001, Forwards Request for Approval to Revise WNP-2 Tornado Design Criteria Per RG 1.76 Section C.1.2
| ML17290A890 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 01/06/1994 |
| From: | Parrish J WASHINGTON PUBLIC POWER SUPPLY SYSTEM |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML17290A891 | List: |
| References | |
| RTR-REGGD-01.076, RTR-REGGD-1.076 GO2-94-001, GO2-94-1, NUDOCS 9401240247 | |
| Download: ML17290A890 (6) | |
Text
ACCELERATED DI BUTION DEMONST ATION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCESSION NBR:9401240247 DOC.DATE: 94/01/06 NOTARIZED: NO FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe AUTH.NAME AUTHOR AFFILIATION PARRISH,J.V.
Washington Public Power Supply System LAFRAMBOISE,W.
Washington Public Power Supply System NOBLE,L.D.
Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)
DOCKET 05000397 R
I
SUBJECT:
Forwards request for approval to revise WNP-2 tornado design criteria per RG 1.76 section C.1.2.
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WASHINGTONPUBLIC POWER SUPPLY SYSTEM P.O. Bm 96'8 ~ 3000 George Wasbtngton Way ~ Rtcbland, 1Pasbtngton 993524968
~ (509) 372-5000 January 6, 1994 G02-94-001 Docket No. 50-397 V.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C.
20555 Gentlemen:
Subject:
NUCLEAR PLANTNO. 2, OPERATING LICENSE NPF-21 REQUEST FOR APPROVALTO REVISE TORNADODESIGN CRITERIA
Reference:
Letter, GO2-91-116, dated June'7, 1991, GC Sorensen (SS) to NRC, same subject II By the reference, in accordance with the guidance ofRegulatory Guide 1.76, Section C.1.2 the Supply System requested approval to revise the WNP-2 tornado design criteria.
Based upon discussions with the Staff, the Supply System has decided to revise this request with regard to the assumed wind speeds, pressure drops and the missiles to be considered.
This revised request follows. This request is a complete replacement for the reference.
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 occurring at 1.0 psi/sec.
These criteria were found acceptable by the Staff as documented in the WNP-2 SER for the Operating License Safety Evaluation Report (NVREG-0892); Section 3.3.2.
The Supply System proposes to change the design criteria to 157 and 35 mph rotational and translational velocities with a pressure drop of 0.70 psi occurring at 0.24 psi/sec.
Relative to the requirements ofRegulatory Guide 1.76 the current design requirements represent an over-commitment in that WNP-2 is a Region IIIsite for which the criteria 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 IIIplant.
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,PDR ADOCK 05000397 P,
Page Two REQUEST FOR APPROVAL TO REVISE TORNADO DESIGN CRITERIA In addition, FSAR 3.5.1.4 establishes the following design basis tornado generated missiles:
~Mi iie UtilityPole Steel Rod Weight Qbbs 1600 8
limen i n 14" dia x 35'"
diax3'orizontal Impact
~VI i
f 241 259 The NRC found these missiles acceptable in SER 3,5.1.4.
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 192 mph total 157 mph rotational 35 mph translational Pressure Drop 0.70 psi at 0.24 psi/sec Missiles Missile Weight Qbbs Dimensions Horizontal Impact Velocity ft/ ec Wood Plank 6" Sch 40 Pipe 1" Steel Rod UtilityPole 12" Sch 40 Pipe Automobile 115 287 8.8 1124 750 3990 3.6 "x 0.94'x 12'long 6.6" dia x 15'ong 1" diax 3'ong 13.5" dia x 35'ong 12.75" dia x 15'ong 16.4' 6.6' 4.3'50.7 29.2 27 33.1 23.8 95.9 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."
Page Three REQUEST FOR APPROVAL TO REVISE TORNADO DESIGN CRITERIA As listed above, this request is based upon a total wind speed of 192 mph.
The request of the referenced letter was for 180 mph. As is discussed in the attached report, the proposed 192 mph design basis is consistent with the results contained in NUREG/CR-4461, which is the most conservative of the three recent tornado hazards studies applicable to the WNP-2 site.
In addition, the Supply System is proposing that the missiles to be considered consist of the full spectrum of missiles contained in Standard Review Plan (SRP) Section 3.5.1.4.
For these missiles, the proposed velocities will be based on a wind speed of 192 mph.
These missile velocities were developed by the Supply System using a methodology we believe is consistent with that used to develop the SRP missile velocities for each of the tornado intensity regions.
The previous request did not include an automobile and utilitypole as potential missiles.
There were concerns expressed by the Staff that there was insufficient evidence that the automobile and utilitypole missiles would not become airborne at the postulated wind speeds.
In addition, the methodology used to predict missile speeds was not previously reviewed and approved by the NRC (i.e., EPRI Report NP-748).
The current request addresses these concerns.
For comparison purposes, the following table summarizes the horizontal missiles speeds for the original design basis, NRC Tornado Intensity Region III,the referenced request, and the current request.
Missile Wood Plank 6" Pipe Automobile 1" Rod UtilityPole 12" Pipe Original WNP-2 Design Basis Qffs~
259 241 NRC Tornado Intensity Region III
~fs~ec 190 33 134 26 85 23 WNP-2 Proposed 6/7/91
~fs~ec 167 17 20 13 Current WNP-2 Proposed
~ft/.~ec 150.7 29.2 95.9 27.0 33.1 23.8 By implementing the proposed revisions, the tornado design criteria willrealistically reflect the tornado hazards at WNP-2 while maintaining the objective of providing an annual probability of exceedance of design loads of less than or equal to 1 x 10 These revisions willresult in more realistic wind velocities, differential pressure
- loads, missile velocities, and load combinations.
The proposed revisions will benefit the design of exterior structures and components that must consider postulated tornado effects. Significant benefit is expected during the implementation of future plant modifications where relief of tornado design criteria will facilitate construction.
Page Four REQUEST FOR APPROVAL TO REVISE 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 structures, systems and components willnot be impacted.
Sincerely,
. V. Parrish (Mail Drop 1023)
Assistant Managing Director, Operations WLF/AGH/bk Attachments CC:
KE Perkins - NRC RV NS Reynolds - Winston & Strawn JW Clifford-NRC DL Williams - BPA/399 NRC Site Inspector - 927N