Regulatory Guide 1.76
| ML003740273 | |
| Person / Time | |
|---|---|
| Issue date: | 04/30/1974 |
| From: | Office of Nuclear Regulatory Research |
| To: | |
| References | |
| RG-1.76 | |
| Download: ML003740273 (3) | |
April 1'74 U.S. ATOMIC ENERGY COMMISSION
REGULATORY
DIRECTORATE Of REGULATORY STANDARDS
G UIDE
REGULATORY GUIDE 1.76 DESIGN BASIS TORNADO FOR NUCLEAR POWER PLANTS
A. INTRODUCTION
functional, nor does this guide discuss the structund design requirements for tornado protection. Subsequent General Design Chiterion 2, "Design *Bases for guides are intended (1) to Identif the specific Protection Against Natural Phenomena," of Appendix structures, systems, and components which should be A, "General Design Criteria for Nuclear Power Plants," designed to withstand the effects of the design basis to 10 CFR Part SO, -"Ucensing of Production and tornado and (2) to describe design basis Utilization Facilities," requfres, in part, that structures, tomado-enerated missiles and other tornado-induced systems, and components important to safety be effects on nuclear power plant stmrctur, systems, and designed to withstand the effects of natural phenomena components important to safety. The Advisory such as tornadoes without loss of capability to perform Committee on Reactor Safeguards has been consulted their safety functions. Criterion 2 also requires that the concerning this guide and has concurred in the design bases for these structures, systems, and regulatory position.
components reflect (I) appropriate consideration of the most severe of the natural phenomena that have been
B. DISCUSSION
historically reported for the site and surrounding region, with sufficient margin for the limited accuracy and Nuclear power plants must be designed so that the quantity of the historical data and the period of time in plants remain in a safe condition in the event of the which the data have been accumulated, (2) appropriate most severe tornado that can reasonably be predicted to combinations of the effects of normal and accident occur at a site as a result of severe meteorologial conditions with the effects of the natural phenomena, conditions. For the last several years, many investigators and (3) the Importance of the safety functions to be have studied the meteorological circumstances preceding performed. and during tornado occurrences and the destruction following tornado strikes. Because of the Inherent Paragraph 100.10(c) of 10 CFR Part 100, "Reactor difficulty in directly observing a tornado and the great Site Criteria,' requires that physical characteristics of uncertainty in predicting the time and location of its the site, Including meteorological conditions at the site occurrence, the possibility of directly sensing tornado and in the surrounding area be considered In determining properties such as a maximum wind speed is remote.
the acceptability of a site for a nuclear power plant. Essentially all conclusions concerning tornado properties have been based on indirect observations of subsequent This guide describes a design basis tornado destruction, structural failure, generated missiles, or acceptable to the Regulatory staff for each of three tornado marlkings rather than direct measurement of the regions within the contiguous United States that a tornado. Determinations of maximum speeds in nuclear power plant should be designed to withstand tornadoes have been rough approximations. As a result without undue risk to the health and safety of the of these .studies, however, tornadoes have been public. This guide does not address the determination of characterized by a set of properties which are significant the design basis tornado for sites located in Alaska, for purposes of structural design and siting. These Hawaii, and Puerto Rico. Such determinations will be significant properties, or parameters, are (i)geographlcal evaluated on a case-by-case basis. This guide does not distribution of frequency of occurrence; (2) rotational identify the specific structures, systems, and wind speed, (3) translational wind speed, (4) pressure components which should be designed to withstand the drop across the tornado, (5) rate of this pressure drop, effects of the design basis tornado and remain and (6) radius of maximum rotational wind speed. Using USAEC REGULATORY GUIDES Copies of pubashed guide* my be obtained byirquest Indicti dis.hions dalred o the US. Atomic Energy Comnmision. Washington. Oz. 20M45, ilsulatory Guides are issued to deitibe and mak.eloshisoh to ubflc Attention: Director of Regulatory Standards. Corruais arid msgestions Sor athods ac*eptable to the AEC Ragulatory Buff of Implementwq sp-ifi a of arioneemnts in thoem ide e encouaged end should be mitteto the Saentary the Commission's regubtlons to delineate techniques used by the staff in of the Commission. US. Alomic Energy Commission, Washington. DC. 20545.
awsluetling pelfic problems or postulated accidents. or to provide guldance to Attention: Chief, Public Proaeings Staff.
spllmntgRegulaetory Guides are not sabstitutas for regulation end conlieance with them is rot sequifed. Mathod anid olutoions different from Nt mhoes out In The ldes armissued in the following sen broad dvisions:
t.hides=will be acemptable iNthey provide a basis for the findings requisite to theIsune or continuene ofa permit or lcense by the Commission. 1. Power Reactors
6. Products
2. Research and Test Reactors
7. Traruporteat
&. Fuels end Materials Peclitle . Occidntlonal Health Published ildes wil be leviaad periodically. a appropriate, to eccommodate 4. Envlronmental and Siting :. Antitrust Revtew?
coma nts mnd to reflect new Inforraitlon or experience. S. Materials and Plant Protection 1
0. General
these propeities, it. is possible to develop a definition for Figure I depicts the general boundaries or the three a de basib*tornado In terms of the six tornad6 regions to which the three sets of parameters apply. The paraniter and use analytlcal techniques for estimating western boundary of Region I lies generally in the values of these parameters for purposes of design with an eastern foothills of the Rocky Mountains.
adequate level of conservatism.
C. REGULATORY POSITION
I
The results of a study ' to obtain a regionalized design basis tornado are summarized in Table I and I. Nuclear power plants should be designed It.
Figure I of this guide. This study demonstrates the withstand the Design Basis Tornado (DBT). The values methods used to estimate probable values of tornado of the parameters specified in Table I for the appropriate parameters; The design basis tornado is defined in terms regions of Figure I are generally acceptable to the of values for the six descriptive parameters in Table I. Regulatory staff for defining the DBT for a nuclear power plant. Sites located near the general boundaries of These values are listed for each of the three tornado adjoining regions may involve ldditional consideration.
Intensity regions within the contiguous United States.
2. If a DBT proposed for a given site is characterized Thi study, entitled 'Technlcal Basis for'Interim Regional by less conservative values for the parameters than the Tornado Criteria:" b available as WASH-1300 from the regional values in Table I, a comprehensive analysis Superintendent of Documents, U.S. Government Printing Office. should be provided to justify the selection of the less Washington, D.C. 20402. conservative design basis tornado.
TABLE I
DESIGN BASIS TORNADO CHARACTERISTICS
Radius of Translational Maximum PMaximum Rotational Speed (mph) Rotational Pressure Rate of Wind Speed a Speed Speed Drop Pressure Region. (mph) Maximum Minimum b (feet) (psi) Drop (sitsed
360 290 70 5 150' 3.0 2.0
II 300 240 60 5 150 2.25 1.2 HIl 240 190 so 5 150 1.5 0.6 The maximum wind speed Is the sum of the rotational speed component and the maximum translational speed component.
b The minimum translational speed. which allows maximum transit time of the tornado across exposed plant features, bi to be used whenever low travel speeds (maximum transit time) are a limiting factor in design of the ultimate heat sink. The ultimate heat sink is that complex of water sources, including associated retaining structures, and any canals or conduits connecting the sources with, but not bcLtuding, the intake structures of nuclear reactor units. Regulatory Guide 1.27 (Safety Guide 27), "Ultimate Heat Sink," describes a bads that may be used to implement General DesignCriterion 44 of Appendix A to 10 CFR Part 50 with regard to the ultimate heat sink.
U.S. GOVERNMENT PRINTING OFFICE: 197d-S43.118:22n
1.76&2
U C
Figure 1. TORNADO INTENSITY REGIONS