ML19221A955
| ML19221A955 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-75-087, NUREG-75-087-02.4.2, NUREG-75-87, NUREG-75-87-2.4.2, SRP-02.04.02, SRP-2.04.02, NUDOCS 7907120045 | |
| Download: ML19221A955 (6) | |
Text
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4 U.S. NUCLEAR REGULATORY COMMISSION
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STANDARD REVIEW PLAN OFFICE OF NUCLEAR REACTOR REGULATION SECTION 2.4.2 FLOODS REVIEW RESPONSIBILITIES l
Primary - Hydrology-Neteorology Branch (H"3)
Secondary - None I.
AREAS OF REV _IEW This section of the safety analysis report (SAR) identifies historical flooding (defined as occurrences of abnormally high water stago, or overflow from a stream, floodway, lake, or coastal area) at the proposed site or in the region of the site.
It summarizes and identifies the individual types of flood producing phenomena, and combinations of flood-producing phenomena, considered in establishing the flood design bases for safety-related plant features It also covers the potential effects of local intense precipitation.
Although topical information may appear in SAR sections 2.4.3 through 2.4.7, the types of l events cer3idered and the controlling event are reviewed in this section.
l The flood history and the potential for flooding are reviewed for the following sources and events. Factors affecting potential runoff (such as urbanization, forest fire, or i
change in agricultural use), erosion, and sediment deposition are considered in the i
review.
1.
Stream flooding; a.
Probable maximum flood (PMF) with coincident wind-induced waves, considering dam failure potential due to inadequate capacity. inadequate f: od-discharge capability or existing physical condition.
b.
Ice jams, both independently and coincident with a winter probable maximum storm.
c.
Tributary drainage area PMF potential, d.
Combinations of less severe river floods, coincident with surges and seiches.
2.
Surges; a.
Probable maximum hurricane (PMH) at coastal sites.
b.
PMH wind translated inland and resulting wave action coincident with runoff-induced flood levels.
c.
Probabl* maximum wind-induced (non-hurricane) storm surges and waves, d.
Combinations of less severe surges, coincident with runoff floods.
USNRC STANDARD REVIEW PLAN
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3.
Seiches; a.
Meteorologically-induced in inland lakes (e.g. Great Lakes and harbors) and at coast 11 harbors and embayments.
b.
Seismically-induced in inland lakes.
c.
Seismically-induced by tsunamis (seismic sea waves) on coastal emhayments.
d.
Corbinations of less severe surges and seiches, coincident with runoff floods.
4.
Tsunamis; a.
Near field, or local, excitation.
b.
Far field, or distant, excitation.
5.
Seismically-induced dam failures (or breaches), and maximum water level at site from:
a.
Failure of dam (or dams) during safe shutdown earthquake (SSE) coincident with 25 year flood.
b.
Failure during cperating basis earthquake (08E) coincident with standard project flood (SPF).
c.
Failure during other earthquakes, coincident with runoff, surge, or seiche floods where the coincidence is at least as likely as for 5.a. and 5.b. above.
6.
Flooding caused by landslides; a
Flood waves.
b.
Backwater effects due to stream blockage.
7.
Ice loadings from water bodies.
II.
ACCFPTANCE CRITERIA for SAR Section 2.4.2.1 (Flood History): The potential flood sources and flood response characteristics identified by the staff's review (descriced in Review Procedures) are compared to those of the applicant. If similar, the applicant's conclusions are accepted.
If, in the staff's opinion, sign'ficant discrepancies exist, the applicant will be requested to provide additional data, reestimate the effects on the plant, or revise the applicable flood design bases, as appropriate.
For SAR Section 2.4.2.2 (Flood Design Considerations): The applicant's estimate of control-ling flood levels is acceptable if it is no r.. ore than 5% less conservative than the staf f's {
independently determined (or verified) estimate. If the applicant's SAR estimate is more than 5 percen less conservative, the applicant should fully document and justify l
its estimate of the controlling level. Alternately, the applicant may accept the l
staff's estimate and redesign applicable flood protection.
For SAR Section 2.4.2.3 (Ef fect of Intense Precipitation): The applicant's estimates of local probable maximum precip.*tation (PMP) and the capacity of site drainage facilities (including drainage from the roof s of buildings and site ponding) are acceptable if the estimates are no more than 5% less conservative than the corresponding staff's assessment.
Similarly, conclusions relating to the potential for any adverse ef fects of blockage of 3 k c) 2746 Rev. 1 2.4.2-2 g
site drainage facilities by debris, ice, or snow should be based upon conservative assumptions of storm and veg6tation CCnditions likely to exist during storm periods.
If a potential hazard does exist (e.g., the elevation of ponding exceeds the elevation of plant access openings), the applicant should document and justify his local PMP basis and analysis and redesign any affected facilities.
Appropriate sections of the following documents are used by the staff to determine the acceptibility of the applicant's data and analyres. Regalatory Guide 1.59 provides i
guidance for estimating the design basis for flooding considering the worst single phenomena!
l and combinationi of less severe phenomena. Regulatory Guide 1.135 describes methods for determining normal water levels. (All estimated water levels should be referenced to mean !
I or normal water levels.) Regulatory Guide 1.29 identifies the safety-related structures, systems, and components, and Regulatory Guide 1.102 describes acceptable flood protection i
to prevent the safety-related facilities from being adversely affected. Publications of the U.S. Geological Survey (USGS), National Oceanic and Atmospheric Administration (NOAA),
Soil Conservation Service (SCS), Corps of Engineers, applicable state and river basin authorities, and other similar agencies are used to verify the applicant's data relating to hydrologic characteristics and extreme events in the region. SRP secticns 2.4.3 through 2.4.7 discuss methods of analysis to determine the individual flood producing phenomena.
III. REVIEW PROCEDURES Construction permit (CP) stage reviews are carried out under this SRP section to evaluate the sionificance of the controlling flood level with regard to the plant desic; basis for l
flood protection. At the operating license (OL) stage, a brief review is carried out to determine if new information has become available since the CP review and to evaluate the signi ficance of thc new information with regard to the plant design basis for flood protec-tion.
New information might arise, for instance, from the occurrence of a new maximum flood of record in the site region, from identification of a source of major flooding not prev ously considered, from c,nstruction of new dams, from flood plain encroachments, or i
from advances in predictive models and analytical techniques. If the CP-stage evaluation of flooding potential has been carefully done, all sources of major flooding should have been considered and any new floods of record should fall well within the design basis.
Improvements in calculational methods may occur, but generally will be concerned wit' increased accuracy in stream flow and water level predictions rather than with sub'tantive changes in the flows and levels predicted. Where the CL review reveals that the controlling flood level differs more than 5% less conservatively from the CP evaluation, any supplemental; provisions needed in the flood protection design basis should be directed toward early wirning measures and procedures for assuring safe shutdown of the plant or toward minor structural modification to accommodate the design flood level.
For SAR Section 2.4.2.1 (Flood History): The staff will review publications of the U.S.
Geological Su vey (USGS), National Oceanic arm Atmospheric Administration (NOAA), Soil Conservation tervice (SCS). Corps of Engineers, applicable state and river basin agencies, and others to i'nsure that historical maximJm events and the flood response characteristics ma 2.4.2-3 Rev. 1
of the region and site have been identified. Similar material, in addition to applicant-supplied information, will be reviewed to identify independently the potential sources of site flooding.
For SAR Sect :en 2.4.2.2 (Flood Design Considerati%): The potential flood levels from consideration of the worst single phenomenon and combinations of less seve e phenomena, are identified SRP Sections 2.4.3 through 2.4.7 and the controllir ; flood level is selected.
The contrnlling flood level is compared with the proposed rrotection levels to assure that the safety related facilities will not be adversely affected. If appropriate, additional provisions for flood protection will be imposed to assure adequate protection of the safety-related facilities.
For SAR Section 2.4.2.3 (Ef fect of Local Intense Precipitation): The staff's estimates of l flooding potential, excluding flooding potential frcm thunderstorms, are based on 24-hour FMP estimnes (f rom Hydrcmeteorological Report 33 and similar NOAA publicatior,s for western sites) with time distributions from the Corps of Engineers EM 1110-2-1411.
Staff estimates for local intense orecipitation caused by thunderstorms are based on PMP estimates from reports such as Reference 11.
The staff's estimates are compared with the applicant's estimstes to determine conformity to Acceptance Criteria in Subsection 17 Runoff models, such as the unit hydrograph if applicable, or other runoff discharge estimates presented in standard texts, are used to estimate discharge on the site drainage system
'Jhere generalized runoff models are used, coefficients used for the site and region are compared to information available at documented locations to evaluate hydrologic conditions used in determining the probaule maximum flood for the site-drainage system. Potential ponding on the site is also determined.
The above reviews are performed only when applicable to the site or site region. dome items of review may be done on a generic basis.
IV.
EVALUATION FINDINGS For constructinn permit reviews, the findings will consist of a statement indioting the completeness of the identification of site flood characteristics and floce design bases.
For OL reviews, the flood his cry will be updated if necessary, with special attention to any new flood of record. Sample statements for CP reviews follow:
"The maximum flood known to have occurred on the A River was in 1796. The peak discharge at B City, Montana, was estimated to be 360,000 cubic feet per second (cfs). The applicant estimated that a comparable flood would produce water surface elevation at the site of 116 feet MSL.
The maximum flood during the per;od since records were maintained (1883) at B City was 350,000 cfs and occurred on October 3, 1929. These floods cccurred prior to construction of several upstream dams. Flood ficws are now regulated by C and D Reservoirs as well as by upstream hydropower plants.
145 2747 2.4.24
"The applicant has estimated potential flooding frcm rainfall over the E River basin upstream from the site.
The probable maximum flood (PMF), the upper level of flooding the staff considers to be reasonably possible, was estimated to produce a flow of 5,000,000 cfs near the City of F.
This estimate was made by using 165% of the Corps of Engineers project design ficod (PDF) estimate of 3,030,000 cfs at the same location, as moa.fied by upstream flood control reservoirs.
Ine 3,030,000 cfs project design flood flow is estimated to be partially diverted to the levetd G and H Floodways upstream of the site, with I,500,000 cfs continuing downstream within the levee system past the plant site.
The applicant concluded that the PMF could result in overtopping of levees and flooding of the river valley well upstream from the site, thereby causing generally l w level flooding in the plant area.
The upstream levee overtopping and resulting valley flow during such an event would reduce the flow in the main levee channel adjacent to the site to levels equal to or less than those that would exist during a project design flood. We conclude that the combination of a runoff-type flood less severe than a PMF, but more severe than a PCF, and a coincident levee break in the vicinity of the site could occur before water approaches levee grade upstream. A failure or levee breach, when the levee is full to design capacity (3 feet below the top of the levee adjacent to the site plus the effects of any coincident wind generated wave activity), would result in a higher water suriace at the plant than a FMF spread over the valley as 3 result of levee failures upstream.
At our request the applicant evaluated various modes of levee failure in the vicinity of the plant. One of the conditions postulated is that of a flood, approaching the severity of a PMF, causing a massive failure of the upstream left bank levee along the G Floodway, resulting in flooding around the plant, coincident :ith a f ailure of the levee adjacent to the plant site.
The applicant estimated the resulting water level at the plant would reach elevation 22.5 feet MSL for this case. The case of an instantaneous levee failure adjacent to the plant, with no upstream levee failure, resulted in an estimated water level ' 24.6 feet MSL.
The staff concludes that the applicant should design for the condi ions associated with the 24.6 feet MSL water level."
V.
REFERENCESY 1.
" Surface Water Supply of the United States,"2/ U. S. 'ieological Survey.
2.
" Tide Tables," National Oceanic and Atmospheric Administration (similar situation as identified in footnote 2).
3.
Reports of Great Lakes levels by Lake Survo; Denver, National Oceanic and Atmospheric Administration.
4 Corps of Engineers records maintained in District and Division Of fices, Coastal Engineering Research Center, and Waterways Experiment Station.
5.
Regulatory Guide 1.29, " Seismic Design Classifi ation."
8 2.4.2-5 Rev. 1
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6.
Regulatory Guide 1.59, " Design Basis floods for Nuclear Power Plants."
7.
" Seasonal Variation of the Probable Maximum Precipitation East of the 105th Meridian for Areas from i0 to 1,000 Square Miles and Durations of 6, 12, 24 and 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />,"
Hydrometeorological Report No. 33, U.S. Weather Bureau (1956).
8.
" Standard Project Flood Determinations," Engineering Manual 1110-2-1411, Corps of Engineers, 26 March 1952 (rev. March 1965).
9.
Regulatory Guide 1.70, " Standard Format and Content of Safety Analysis Reports for Nuclear Power P13r.ts."
10.
ANSI N170, " Standards for Determining Design Basis Flooding at Power Reactor Sites" 11.
" Generalized Estimates of Probable Maximum Precipitation for the United States West l
of the 105th Meridian for Areas to 400 Square Miles and Durations to 24 Hours,"
i Technical Paper No. 38, U.S. Weather Service, NOAA (1960).
I t
12.
Regulatory Guide 1.102, " Flood Protection for Nuclear Power Plants."
t 13.
Regulatory Guide 1.135, " Normal Water Level and Discharge at Nuclear Power Plants."
i i
1/
- Referenc'; for PM? estimates, time distribution, etc., are in SRP section 2.4.3.
" Surface Water Supply" is a continuing series of water discharge measurements by the USGS and others.
It is not practical to list all the volumes (called " Water-Supply Papers") that are available. Numerous state and local authorities maintain river discnarge, lake level, and tide data.
i/5 270 Rev. 1 2.4.2-6 t