GO2-95-212, Requests Approval to Revise Tornado Design Criteria
| ML17291B079 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 10/10/1995 |
| From: | Parrish J WASHINGTON PUBLIC POWER SUPPLY SYSTEM |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GO2-95-212, NUDOCS 9510190006 | |
| Download: ML17291B079 (7) | |
Text
qp PRIORITY 1 (ACCELERATED RIDS PROCESSING) r REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCESSION NBR:9510190006 DOC.DATE: 95/10/10 NOTARIZED: NO DOCKET FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 p
AUTH.NAME AUTHOR AFFILIATION PARRISH,J.V.
Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION R
Document Control Branch (Document Control Desk)
SUBJECT:
" Requests approval to revise Tornado Design Criteria.
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WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968
~ 3000 George Washington Way
~ Richland, Washington 99352-0968
~ (509) 372-5000 October 10, 1995 G02-95-212 Docket No. 50-397 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C.
20555 Gentlemen:
Subject:
WNP-2, OPERATING LICENSE NPF-21 REQUEST FOR APPROVALTO REVISE TORNADODESIGN CRITERIA
References:
1)
Letter G02-91-116, dated June 7, 1991, GC Sorensen (SS) to NRC, same subject 2)
Letter G02-94-001, dated January 6, 1994, JV Parrish (SS) to NRC, same subject 3)
Final Safety Evaluation Report Related to the Certification of the Advanced Boiling Water Reactor Design, NUREG-1503, July 1994 4)
NUREG-0892, Safety Evaluation Report Related to the Operation of WPPSS Nuclear Project No.2, March 1982 5)
NUREG-0800, Standard Review Plan, June 1987 6)
Regulatory Guide 1.76, April-1974, Design Basis Tornado for Nuclear Power Plants.
By References 1 and 2, in accordance with the guidance of Reference 6, Section C.2, the Supply System requested approval to revise the WNP-2 tornado design criteria.
Reference 1 requested that the total design basis tornado wind speed for WNP-2 be revised to 180 mph.
Based on discussions with the staff, the Supply System revised its request via Reference 2 to set the tornado design basis wind speed to 192 mph.
Although the Supply System feels that each of these submittals is technically justified, the Supply System is hereby further revising its request to establish the total design basis wind speed to 200 mph.
The current request is based on further discussions with the staff and is consistent with the design basis tornado characteristics accepted by the NRC in Reference 3 for the tornado intensity region containing WNP-2.
The complete definition of the proposed design basis tornado characteristics including the proposed design basis missiles are provided in the attachment.
9510190006 951010 y0 PDR ADOCK 05000397
..P...,
Page 2 REQUEST FOR APPROVAL TO REVISE TORNADO DESIGN CRITERIA Should you have any questions or desire additional information regarding this matter, please call me or D. A. Swank at (509) 377-4563.
Sincerely,
. V. Parrish (Mail Drop 1023)
Vice President, Nuclear Operations WLL/REB/ml Attachment CC:
LJ Callan - NRC RIV KE Perkins, Jr. - NRC RIV, Walnut Creek Field Office NS Reynolds - Winston & Strawn JW Clifford - NRC DL Williams - BPA/399 NRC Sr. Resident Inspector - 927N
Attachment 4
WNP-2 current tornado design criteria, as stated in WNP-2 FSAR Sections 2.3.1.2.1.3 and 3.3.2.1, are for wind speeds of 300 mph rotational and 60 mph translational, with a pressure drop of 3 psi to occur in 3 seconds.
These criteria were found acceptable by the staff as documented in Reference 4, Section 3.3.2.
The Supply System proposes to change the design criteria to 160 and 40 mph rotational and translational velocities with a pressure drop of 0.90 psi occurring at 0.30 psi/sec.
Relative to the requirements of Reference 6, the current design requirements are conservative in that WNP-2 is a Region IIIsite for which the criteria are 190 mph rotational and 50 mph translational with a 1.5 psi pressure drop at 0.6 psi/sec.
WNP-2 FSAR Section 3.3.2.4 and Appendix C.3 discuss the WNP-2 design relative to Reference 6.
It is apparent that the currently proposed criteria are less than. those proposed by the Regulatory Guide for a Region IIIplant.
WNP-2 FSAR Section 3.5.1.4 establishes the foHowing design basis tornado generated missiles:
Missile UtilityPole Steel Rod Weight (lbs) 1600 Dimensions 14"dia x 35'"dia x
3'orizontal Impact Velocity (ft/sec) 241 259 The NRC found these missiles acceptable in Section 3.5.1.4 of Reference 4.
Based upon the guidance of Reference 6, NRC approval of the use of revised tornado design criteria is requested.
The criteria are:
Wind Speeds:
200 mph maximum 160 mph rotational 40 mph translational Pressure Drop:
0.90 psi at 0.30 psi/sec
Attachment Page 2 of 3 Missiles:
Missile Wood Plank 6" Sch 40 Pipe 1" Steel Rod UtilityPole 12" Sch 40 Pipe Automobile Weight (lbs) 115 287 8.8 1124 750 3990 Dimensions 3.6" x 0.94' 12'long 6.6 "dia x 15'long 1" dia x 3'ong 13.5 "dia x 35'ong 12.75" dia x 15'ong 16.4' 6.6' 4.3'orizontal Impact Velocity (ftlsec) 161.7 27.0 24,9
'0.7 21.8 105.2 Consistent with Reference 5, Section 3.5.1.4, these missiles are considered to strike surfaces in any direction.
Vertical velocities are taken to be 70 percent of the horizontal velocities except for the 1" steel rod which is assumed to have the same velocity in any direction.
The utility pole and the automobile are considered to strike surfaces at any elevation up to a maximum elevation of 30 feet above the highest finished grade within 0.5 miles of the plant.
The other missiles are considered to strike at any elevation.
Based on Reference 5, Section 3,3.2, total tornado loads resulting from wind loads, differential pressure loads, and tornado generated missiles willbe established from the followingequations:
where:
W'W W'=W P
W'=W W'
W+ 0.5 Wp W'=W+W W'
W+0.5Wp+ W W'
Wp W
= Total tornado load
. = Tornado wind load
= Tornado differential pressure load
= Tornado generated missile load
Attachment Page 3 of 3 The above wind speed and pressure drop parameters are consistent with those values approved by the NRC for the Advanced Boiling Water Reactor Design for Tornado Intensity in Region IIIas defined in Section 2.0 of Reference 3.
Based on the extensive studies which define site specific tornado hazards for the Hanford area, these wind speed and pressure drop parameters are conservative for the WNP-2 site.
These studies are discussed in detail in the report attached to Reference 2.
In addition, the Supply System is proposing that the missiles to be considered consist ofthe full spectrum ofmissiles contained in Reference 5, Section 3.5.1.4. For those missiles, the proposed velocities are based on the above wind speed and pressure drop parameters.
These missile velocities were developed by the Supply System using a methodology that we feel is consistent with that used to develop the SRP missile velocities.
The Supply System willformalize the calculations associated with the development ofthese missile velocities after NRC has concurred with the proposed revised tornado design criteria, but prior to use in design work.
By implementing the proposed revisions, the tornado design criteria willconservatively reflect the tornado hazards at WNP-2 while maintaining the objective ofproviding an annual probability of exceedance of design loads of less than or equal to 1 x 107.
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 the revised tornado design criteria will facilitate construction.
An example of this application is the Supply System's current effort to procure and install a dry cask spent fuel storage facility.