Regulatory Guide 3.40

Rev. 1, Design Basis Floods for Fuel Reprocessing Plants and for Plutonium Processing and Fuel Fabrication Plants

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Issue date:	12/31/1977
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U.S. NUCLEAR REGULATORY

COMMISSION

Revision 1 December 1977 REGULATORY

GUIDE OFFICE OF STANDARDS

DEVELOPMENT

REGULATORY

GUIDE 3.40 DESIGN BASIS FLOODS FOR FUEL REPROCESSING

PLANTS AND FOR PLUTONIUM

PROCESSING

AND FUEL FABRICATION

PLANTS

A. INTRODUCTION

Paragraph (a)(1) of §50.34, "Contents of Applica tions: Technical Information," of 10 CFR Part 50, "Licensing of Production and Utilization Facilities," requires, among other things, that each application for a construction permit for a production or utiliza tion facility, including fuel reprocessing plants,. in clude a description and safety assessment of the site on which the facility is to be located, with appro priate attention to features affecting facility desig

n. Paragraph

70.22 (f) of 10 CFR Part 70, "Special Nu clear Material," requires that each application for a license to possess and use special nuclear material in a plutonium processing and fuel fabrication plant. con tain, among other things, a description and safety as sessment of the design bases of the principal struc ture, systems, and components of the plant, including provisions for protection against natural phenomena.

Paragraph

70.23 (b) of 10 CFR Part 70 provides that the Commission will approve construction of the principal structures, systems, and components of a plutonium processing and fuel fabrication plant when it has determined, among other things, that the design bases of the principal structures, systems, and com ponents provide reasonable assurance of protection against natural phenomena and the consequences of potential accidents.

This guide describes methods of determining the design basis floods that fuel reprocessing plants and plutonium processing and fuel fabrication plants t should be designed to withstand without loss of safety-related functions.

It does not identify struc tures, systems, and components that should be de'The term "nuclear facility" will be used in this guide to refer to fuel reprocessing plants and to plutonium processing and fuel fabrication plants.signed to withstand the effects of floods or discuss the design requirements for flood protection.

ANSI N170-1976, "Standards for Determining Design Basis Flooding at Power Reactor Sites,"' presents standards to establish design basis flooding for safety-related features at power reactor sites. ANSI N170-1976 also contains, among other things, methodology for estimating probable maximum surges and seiches at estuaries and coastal areas on oceans and large lakes. Appendix B to Regulatory Guide 1.59, "Design Basis Floods for Nuclear Power Plants," gives timesaving alternative methods of es timating the probable maximum flood along streams.

Appendix C to Regulatory Guide 1.59 gives a simplified method of estimating probable maximum surges on the Atlantic and Gulf Coasts. It is the'con sensus of the NRC staff that ANSI N170-1976 and Appendices B and C to Regulatory Guide 1.59 are also applicable to nuclear facilities, and therefore they are referenced in this guide. The methods described in this guide result from re view of and action on specific cases, and as such, reflect the latest general approaches to the problem that are acceptable to the NRC staff. If an applicant desires to employ new information that may be de veloped or to use an alternative method, the NRC staff will review the proposal and approve its use, if found acceptable.

The flood analysis described in this guide need not be considered by applicants in their submittals in connection with applications for special nuclear ma terial licenses, operating licenses, or construction permits for nuclear facilities located at sites above the design basis flood level where it can be demonstrated

• Lines indicate substantive changes from the previous issue. 'Copies of ANSI N170-1976 may be purchased from the American Nuclear Society, 555 N. Kensington Avenue, La Grange Park, IL 60525.*USNRC REGULATORY

GUIDES Comments Should be sent to the Secretary of the Commission, US. Nuclear Regu latory Commission, Washington.

D.C. 20555. Attention Docketing and Service Regulatory Guides are issued to describe and make available to the public methods Branch. acceptable to the NRC staff of implementing specific parts of the Commission's regulations.

to delineate techniques used by the staff in evaluating specific problems The guides are issued in the following ten broad divisions or postulated accidents, or to provide guidance to applicants.

Regulatory Guides are not substitutes for regulations, and compliance with them is not required.

1. Power Reactors 6. Products Methods and solutions different from those set out in the guides will be accept. 2. Research and Test Reactors 7. Transportation able if they provide a basis for the findings requisite to the issuance or continuance

3. Fuels and Materials Facilities

8. Occupational Health of a permit or license by the Comminsion.

4. Environmental and Siting 9. Antitrust Review 5. Materials and Plant Protection

10. General Comments and suggestions for improvements in these guides are encouraged at all Requests for single copies of issued guides (which may be reoroduced)

or for plac. times, and guides will be revised, as appropriate, to accommodate comments and ment on an automatic distribution list for single copies of future guides in spicilif to reflect new information or experience.

This guide was revised as a result of divisions should be made in writing to the US Nuclear Regul~atory Commissioii substantive comments received from the public and additional staff review. Washington, D.C 20555, Attentioin Director, Division of Document Coitrol that safety-related structures, systems, and compo nents are not affected by flooding.

B. DISCUSSION

Nuclear facilities should be designed to prevent a release of radioactivity resulting from the effects of the most severe flood conditions that can reasonably be predicted to occur at a site as a result of severe hydrometeorological conditions, seismic activity, or both. The Corps of Engineers for many years has studied conditions and circumstances relating to floods and flood control. As a result of these studies, it has de veloped a definition for a Probable Maximum Flood (PMF)3 and attendant analytical techniques for es timating, with an acceptable degree of conservatism, flood levels on streams resulting from hy drometeorological conditions.

An acceptable degree of conservatism, for estimating seismically induced flood levels and for evaluating the effects of the in itiating event, is provided in Appendix A, "Seismic and Geologic Siting Criteria for Nuclear Power Plants," to 10 CFR Part 100, "Reactor Site Criteria.'" The conditions resulting from the worst site-related flood probable at the nuclear facility (e.g., PMF, seismically induced flood, seiche, surge, severe local precipitation)

with attendant wind-generated wave ac tivity constitute the design basis flood conditions that safety-related structures, systems, and components, whose failure during such conditions would constitute a threat to the public health and safety, should be de signed to withstand and remain functional.

For sites along streams, the PMF generally pro vides the design basis flood. For sites along lakes or seashores, a flood condition of comparable severity could be produced by the most severe combination of hydrometeorological parameters reasonably possi ble, such as may be produced by a Probable Maximum Hurricane (Refs. 1, 2) or by a Probable Maximum Seiche. On estuaries, a Probable Maximum River Flood, a Probable Maximum Surge, a Probable Maximum Seiche, or a reasonable combi nation of less severe phenomenologically caused flooding events should be considered in arriving at design basis flood conditions comparable in fre quency of occurrence with a PMF on streams.

In addition to floods produced by severe hy drometeorological conditions, the most severe seis 3 The Corps of Engineers'

Probable Maximum Flood definition appears inr many publications of that agency such as Engineering Circular EC 1110-2-27, Change 1, "Engineering and Design Policies and Procedures Pertaining to Determination of Spillway Capacities and Freeboard Allowances for Dams," February 19, 1968. The Probable Maximum Flood is also directly analogous to the Corps of Engineers' "Spillway Design Flood" as used for dams whose failures would result in a significant loss of life and property.

A similar definition for Probable Maximum Flood is given in ANSI N170-1976.

mically induced floods reasonably possible should be considered for each site. Along streams and estuaries, seismically induced floods may be produced by dam failures or landslides.

Along lakeshores, coastlines, and estuaries, seismically induced or tsunami-type flooding should be considered.

Consideration of seismically induced floods should include the same range of seismic events as is postulated for the design of the nuclear facility.

For instance, the analysis of floods caused by dam failures, landslides, or tsunami requires consideration of seismic events equivalent in severity to the Safe Shutdown Earthquake

4 occurring at the location that would produce the worst such flood at the nuclear facility site. In the case of seismically induced floods along riv ers, lakes, and estuaries that may be produced by events less severe than a Safe Shutdown Earthquake, consideration should be given to the coincident oc currence of floods due to severe hydrometeorological conditions.

This combination of events, however, should be considered only where the effects on the nuclear facility are worse than and the probability of such combined events may be greater than an indi vidual occurrence of the most severe event of either type. ANSI N170-1976 contains combinations of such events acceptable to the NRC staff. For the spe cific case of seismically induced floods due to dam failures, an evaluation should be made of flood waves that may be caused (1) by domino-type dam failures triggered by a seismically induced failure of a critically located dam and (2) by multiple dam fail ures in a region where dams may be located close enough together that a single seismic event can cause multiple failures.

Each of the severe flood types discussed above should represent the upper limit of all potential phenomenologically caused flood combinations con sidered reasonably possible.

Analytical techniques are available and should generally be used for predic tion at individual sites. Those techniques applicable to PMF and seismically induced flood estimates on streams are presented in ANSI N170-1976 and Ap pendix B to Regulatory Guide 1.59. For sites on coasts, estuaries, and large lakes, techniques are pre sented in ANSI N170-1976 and in Appendix C to Regulatory Guide 1.59. Analyses of only the most severe flood conditions may not indicate potential threats to safety-related systems that might result from combinations of flood conditions thought to be less severe. Therefore, rea sonable combinations of less-severe flood conditions should also be considered to the extent needed for a consistent level of conservatism.

Such combinations should be evaluated in cases where the probability of their existing at the same time and having significant consequences is at least comparable to that associated with the most severe hydrometeorological or seismi'Determined as outlined for nuclear power plants in Appendix A to 10 CFR Part 100.3.40-2 cally induced flood. For example, a failure of rela tively high levees adjacent to a nuclear facility could occur during floods less severe than the worst site related flood but would produce conditions more se vere than those that would result during a greater flood (where a levee failure elsewhere would produce less severe conditions at the nuclear facility site). Wind-generated wave activity may produce severe flood-induced static and dynamic conditions either independent of or coincident with severe hy drometeorological or seismic flood-producing mechanisms.

For example, along a lake, reservoir, river, or seashore, reasonably severe wave action should be considered coincident with the probable maximum water level conditions.

5 The coincidence of wave activity with probable maximum water level conditions should take into account the fact that suf ficient time can elapse between the occurrence of the assumed meteorological mechanism and the maximum water level to allow subsequent meteorological activity to produce substantial wind generated waves coincident with the high water level. In addition, the most severe wave activity at the'site that can be generated by distant hydrometeorological activity should be considered.

For instance, coastal locations may be subjected to severe wave action caused by a distant storm that, although not as severe as a local storm (e.g., a Probable Maximum Hur ricane), may produce more severe wave action be cause of a very long wave-generating fetch. The most severe wave activity at the site that may be generated by conditions at a distance from the site should be considered in such cases. In addition, assurance should be provided that safety systems are designed to withstand the static and dynamic effects resulting from frequent flood levels (i.e., the maximum operat ing level in reservoirs and the 10-year flood level in streams) coincident with the waves that would be produced by the Probable Maximum Gradient Wind" for the site (based on a study of historical regional meteorology).

C. REGULATORY

POSITION 1. The conditions resulting from the worst site related flood probable at a nuclear facility (e.g., PMF, seismically induced flood, hurricane, seiche, surge, heavy local precipitation)

with attendant

'Probable Maximum Water Level is defined by the Corps of Engineers as "the maximum still water level (i.e., exclusive of local coincident wave runup) which can be produced.by the most severe combination of hydrometeorological and/or seismic parameters reasonably possible for a particular location.

Such phenomena are hurricanes, moving squall lines, other cyclonic meteorological events, tsunami, etc., which, when combined with the physical response of a body of water and severe am bient hydrological conditions, would produce a still water level that has virtually no risk of being exceeded." 'Probable Maximum Gradient Wind is defined as a gradient wind of designated duration, which there is virtually no risk of exceeding.

wind-generated wave activity constitute the design basis flood conditions that structures, systems, and components important to safety must be designed to withstand without impairing their capability to per form safety functions.

a. The standards for determining design basis flooding at power reactor sites contained in ANSI N170-1976 are considered by the NRC staff to be generally acceptable for nuclear facilities, subject to the following:

(1) Footnote 1 and the list of safety-related structures, systems, and components in Section 3.1.3 of ANSI N170-1976 are not applicable to nuclear facilities.

A list of pertinent elevations of safety related structures should be provided for comparison with design basis flood levels. It should be referenced to maps and drawings of such facilities.

(2) Footnote 2 in Section 4.3.1 of ANSI N170 1976 is not applicable to nuclear facilities.

The words "safe shutdown" in Section 4.3.1 of ANSI N170 1976 should be interpreted to mean "safe curtailment of operations." (3) Sections 5.5.4.2.3 and 5.5.5 of ANSI N170-1976 contain references to methods for evaluat ing the erosion failure of earthfill or rockfill dams and determining the resulting outflow hydrographs.

The staff has found that some of these methods may not be conservative because they predict slower rates of erosion than those that have historically occurred.

Modifications to the models may be made to increase their conservatism.

Such modifications will be re viewed by the NRC staff on a case-by-case basis. (4) Instead of Section 7.4.5.1 of ANSI N170-1976, the following should be used: "7.4.5.1 Structure Being Considered.

In gen eral, the structures that need to be considered for the wave activities are protective dikes, waterfront banks and shores, auxiliary and control buildings, and other safety-related facilities, and non-safety related facilities whose failure could adversely af fect safety-related facilities." (5) The terms "safe shutdown earthquake (SSE)" and "operating basis earthquake (OBE)" are used in Section 9.2.1.2 of ANSI N170-1976.

For the purposes of this guide, the safe shutdown earthquake (SSE) and the operating basis earthquake (OBE) should be determined as outlined for nuclear power plants in Appendix A to 10 CFR Part 100. (6) Instead of Section 10.1 of ANSI N170 1976, the following should be used: "10.1 General. Guidance is available if canals, reservoirs, and related structures are used." (7) Instead of Section 10.3 of ANSI N170 1976, the following should be used: "10.3 Reservoirs.

Guidance is available if a re servoir is used." b. The PMF on streams, as defined in ANSI N170-1976 and based on the analytical techniques summarized in ANSI N170-1976 and Appendix B to 3.40-3 Regulatory Guide 1.59, provides an acceptable level of conservatism for estimating flood levels caused by severe hydrometeorological conditions.

c. Along lakeshores, coastlines, and estuaries, estimates of flood levels resulting from severe surges, seiches, and wave action caused by hy drometeorological activity should be based on criteria comparable in conservatism to those used for PMFs. Criteria and analytical techniques providing this level of conservatism for the analysis of these events are summarized in ANSI N170-1976.

Appendix C to Regulatory Guide 1.59 presents an acceptable method for estimating the stillwater level of the Probable Maximum Surge (PMS) from hurricanes at open coast sites on the Atlantic Ocean and Gulf of Mexico. d. Flood conditions that could be caused by dam failures from earthquakes should also be considered in establishing the design basis flood. Analytical techniques for evaluating the hydrologic effects of seismically induced dam failures discussed herein are presented in ANSI N170-1976.

Techniques for evaluating the effects of tsunami will be presented in a future appendix to Regulatory Guide 1.59. e. Where upsteam dams or other features that provide flood protection are present, in addition to the analyses of the most severe floods that may be induced by either hydrometeorological or seismic mechanisms, reasonable combinations of less-severe flood conditions and seismic events should also be considered to the extent needed for a consistent level of conservatism.

The effect of such combinations on the flood conditions at the nuclear facility site should be evaluated in cases where the probability of such combinations occurring at the same time and having significant consequences is at least comparable to the probability associated with the most severe hy drometeorological or seismically induced flood. For relatively large streams, examples of acceptable combinations of runoff floods and seismic events that could affect the flood conditions at the nuclear facil ity are contained in ANSI N170-1976.

Less-severe flood conditions, associated with the above seismic events, may be acceptable for small streams that exhibit relatively short periods of flooding.

f. The effects of coincident wind-generated wave activity to the water levels associated with the worst site-related flood possible (as determined from paragraphs a, b, c, d, or e above) should be added to generally define the upper limit of flood potential.

Acceptable procedures are contained in ANSI N 170 1976. 2. As an alternative to designing hardened protec tion for all safety-related structures, systems, and 'Hardened protection means structural provisions incorpo rated in the nuclear facility design that will protect safety related structures, systems, and components from the static and dynamic effects of floods. In addition, each component of the protection must be passive and in place, as it is to be used for flood protection, during normal facility operation.

components as specified in regulatory position 1 above, it is permissible to curtail operation of the facility and initiate suitable protective measures pro vided that: a. Sufficient warning time is shown to be avail able to curtail operations and implement adequate emergency procedures;

b. Those structures, systems, and components necessary for confinement of radioactivity during the emergency are designed with hardened protective fea tures to remain functional while withstanding the en tire range of flood conditions up to and including the worst site-related flood probable (e.g., PMF, seismi cally induced flood, hurricane, surge, seiche, heavy local precipitation), with coincident wind-generated wave action as discussed in regulatory position 1 above. 3. During the economic life of a nuclear facility, unanticipated changes to the site environs that may adversely affect the flood-producing characteristics of the environs are possible.

Examples include con struction of a dam upstream or downstream of the nu clear facility, or comparably, construction of a high way or railroad bridge and embankment that obstructs the floodflow of a river, and construction of a harbor or deepening of an existing harbor near a coastal or lake site nuclear facility.

Significantly adverse changes in the runoff or other flood-producing characteristics of the site environs, as they affect the design basis flood, should be iden tified and used as the basis to develop or modify emergency operating procedures, if necessary, to mitigate the effects of the increased flood. 4. Proper utilization of the data and procedures in Appendices B and C to Regulatory Guide 1.59 will result in PMF peak discharges and PMS peak stillwa ter levels that will in many cases be approved by the NRC staff with no further verification.

The staff will continue to accept for review detailed PMF and PMS analyses that result in less conservative estimates than those obtained by use of Appendices B and C to Regulatory Guide 1.59. In addition, previously re viewed and approved detailed PMF and PMS analyses will continue to be acceptable even though the data and procedures in Appendices B and C to Regulatory Guide 1.59 result in more conservative estimates.

D. IMPLEMENTATION

The purpose of this section is to provide informa tion to applicants regarding the NRC staff's plans for using this regulatory guide. This guide reflects current NRC staff practice.

Therefore, except in those cases in which the appli cant proposes an acceptable alternative method for complying with specified portions of the Commis sion's regulations, the methods described herein are being and will continue to be used in the evaluation

3.40-4 of submittals for operating license or construction permit applications for fuel reprocessing plants and for license applications submitted pursuant to 10 CFR Part 70 authorizing possession and use of special nu clear material at plutonium processing and fuel fabri cation plants until this guide is revised as a result of suggestions from the public or additional staff re vie

w. REFERENCES

1. U.S. Army Coastal Engineering Research Center, "Shore Protection Manual," Second Edition, 1975. 2. U.S. Weather Bureau (now U.S. Weather Service, NOAA), "Meteorological Characteristics of the Probable Maximum Hurricane, Atlantic and Gulf Coasts of the United States," Hurricane Research Interim Report, HUR 7-97 and HUR 7-97A, 1968.3.40-5 UNITED STATES NUCLEAR REGULATORY

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