NRC Generic Letter 1989-22

NRC Generic Letter 1989-022: Potential for Increase Roof Loads and Plant Area Flood Runoff Depth at Licensed Nuclear Power Plants Due to Recent Change in Probable Max. Precipitation Criteria Developed by National Weather Service

ML031210438
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000000, Zimmer, Fort Saint Vrain, Washington Public Power Supply System, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Clinch River, Crane
Issue date:	10/19/1989
From:	Partlow J G Office of Nuclear Reactor Regulation
To:
References
NUREG-0800 GL-89-022, NUDOCS 8910180273
Download: ML031210438 (5)

UNITED STATES t BNUCLEAR REGULATORY

COMMISSION

WASHINGTON, D. C. 20555 October 19, 1989 TO: ALL LICENSEES

OF OPERATING

REACTORS AND HOLDERS OF CONSTRUCTION

PERMITS*SUBJECT: POTENTIAL

FOR INCREASED

ROOF LOADS AND PLANT AREA FLOOD RUNOFF DEPTH AT LICENSED NUCLEAR POWER PLANTS DUE TO RECENT CHANGE IN PROBABLE MAXIMUM PRECIPITATION

CRITERIA DEVELOPED

BY THE NATIONAL WEATHER SERVICE (GENERIC LETTER 89-22)This letter is to inform you that the NRC staff has adopted for future plants the latest probable maximum precipitation (PMP) criteria published by the National Oceanic and Atmospheric Administration (NOAA), National Weather Service (NWS) to establish acceptable design configurations for safety-related nuclear power plant facilities.

The staff has been using the PMP concept in plant flood design for well over 15 years. The criteria appear in Regulatory Guides, ANSI Standards, and Standard Review Plans (NUREG-0800)

and were based primarily on procedures established in the 1940s and 1950s by the U.S. Army Corps of Engineers and National Weather Service (NWS).Since 1977, more recent PMP criteria have been published by the National Oceanic and Atmospheric Administration (NOAA), National Weather Service.These criteria are to be used to evaluate the degree of licensee compliance with the General Design Criterion 12 App A to 10 CFR Part 50. The new criteria are contained in NOAA/NWS Hydrometerological Reports (HMR) No. 49 (1977), No. 51 (1978), No. 52 (1982), No. 53 (1980) and No. 55 (1984). One of the more significant changes in the new HMRs is that they now provide PMP estimates for drainage areas as small as 1 square mile and for durations as small as 5 minutes. The previous reports generally only provided PMP estimates for areas of 10 square miles or greater and durations of 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> or more.There were empirical methods to subdivide the 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> duration to smaller increments, but there was never any methodology to estimate PMP for areas less than 10 square miles. Thus, the 10 square mile PMP values were used for site and roof drainage design. Current 1 square mile short duration PMP estimates are larger than those previously used.Staff has revised (Revision

3) Sections 2.4.2, Floods,' and 2.4.2, 'Probable Maximum Floods (PMF) on Streams and Rivers," of the Standard Review Plan (NUREG-0800)

to formally incorporate the latest NWS reports into the licensing 1* Five plants, Byron, Braidwood, Vogtle, South Texas, and River Bend, fully meet the new PMP Criteria and the licensees for these five plants may dis-i letter.91 180273t C

Generic Letter 89- 22 -2 -October 19, 1989 review process. In general, the latest NWS criteria call for higher rainfall intensities over shorter time intervals and smaller areas than have been previously considered.

In some cases, such events could result in higher site flooding levels and greater roof ponding loads than have been used in previous design studies.This information is provided for your review and determination of appropriate action, if any. No submittal is required.Sincerely, Jades G. Partlow Associate Director for Projects Office of Nuclear Reactor Regulation Enclosure:

List of Most Recently Issued Generic Letters

Technical Contact:

_____ _ __ _S. Chan, ESGB/NRR 492-0830

LIST OF RECENTLY ISSUED GENERIC LETTERS<_>

Generic Date of T 1 ciiand-Issued To c.. I; , 4_.Letter NO. uu vLL ------ -89-22 89-21 POTENTIAL

FOR INCREASED

ROOF 10/19/89 LOADS AND PLANT AREA FLOOD RUNOFF DEPTH AT LICENSED NUCLEAR POWER PLANTS DUE TO RECENT CHANGE IN PROBABLE MAXIMUM PRECIPITATION

CRITERIA DEVELOPED

BY THE NATIONAL WEATHER SERVICE (GENERIC LETTER 89-22)REQUEST FOR INFORMATION

10/19/89 CONCERNING

STATUS OF IMPLEMENTATION

OF UNRESOLVED

SAFETY ISSUE (USI) REQUIREMENTS

PROTECTED

AREA LONG-TERM

09/26/89 HOUSEKEEPING

89-20 89-19 ALL LICENSEES

OF OPERATING

REACTORS AND HOLDERS OF CONSTRUCTION

PERMITS (EXCEPT BYRON BRAIDWOOD, VOGTLEO SOUTH TEXAS, AND RIVER BEND)ALL HOLDERS OF OPERATING

LICENSES AND CONSTRUCTION

PERMITS FOR NUCLEAR POWER REACTORS ALL FUEL CYCLE FACILITY LICENSEES WHO POSSESS, USE, OR PROCESS FORMULA QUANTITIES

OF STRATEGIC

SPECIAL NUCLEAR MATERIAL ALL LICENSEES

OF OPERATING

REACTORS, APPLICANTS

FOR OPERATING

LICENSES AND HOLDERS OF CONSTRUCTION

PERMITS FOR LIGHT WATER REACTOR NUCLEAR POWER PLANTS ALL HOLDERS OF OPERATING

LICENSES OR CONSTRUCTION

PERMITS FOR NUCLEAR POWER PLANTS REQUEST FOR ACTION RELATED TO 09/20/89 RESOLUTION

OF UNRESOLVED

SAFETY ISSUE A-47 "SAFETY IMPLICATION

OF CONTROL SYSTEMS IN LWR NUCLEAR POWER PLANTS" PURSUANT TO 10 CFR 50.54(f)89-18 RESOLUTION

OF UNRESOLVED

SAFETY ISSUE A-17, "SYSTEMS INTERACTIONS

IN NUCLEAR POWER PLANTS 09/06/89 ACCESSION

NUMBER IS 8909070029

89-17 PLANNED ADMINISTRATIVE

CHANGES TO THE NRC OPERATOR LICENSING

WRITTEN EXAMINA-TION PROCESS -GENERIC LETTER 89-17 09/06/89 ALL HOLDERS OF OPERATING

LICENSES OR CONSTRUCTION

PERMITS FOR PWRS AND BWRS AND ALL LICENSED OPERATORS 89-16 INSTALLATION

WETWELL VENT LETTER 89-16)OF A HARDENED (GENERIC 09/01/89 ALL GE PLANTS

Generic Letter 89- 22-2 -October 19, 1989 review process. In general, the latest NWS criteria call for higher rainfall intensities over shorter time intervals and smaller areas than have been previously considered.

In some cases, such events could result in higher site flooding levels and greater roof ponding loads than have been used in previous design studies.This information action, if any.is provided for No submittal is your review and determination of appropriate required.Sincerely, ORIGINAL SIGNED BY JAMES G. PARTLOW James G. Partlow Associate Director for Projects Office of Nuclear Reactor Regulation Enclosure:

List of Most Recently Generic Letters

Technical Contact:

S. Chan, ESGB/NRR 492-0830 DISTRIBUTION:

Central Files NRC PDR I PD4 Reading P. O'Connor F. Hebdon G. Holahan F. Miraglia C. Berlinger J. Partlow 1K It1 VIaWY/ 14;~~I FTPD4JDRSP/PM

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NAME *: P. O'Connor x23026 SECRETARY

NAME: Beverly/Celeste x21340 SUBJECT: GENERIC LETTER 89-XX RE: DESIGN FOR PROBATE NAME E MAXIMUM DATE_ -°\ lokh 1°c\I I\F/Z/7 j 1.2.3.4.5.7.7.P. O'Connor F. Hebdon G. HoIahan3tj-'CA2 G. Holahan F. Miraglia C. Berlinger J. Partlow Secretary

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