Regulatory Guide 1.117: Difference between revisions

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{{Adams
{{Adams
| number = ML003739346
| number = ML13350A280
| issue date = 04/30/1978
| issue date = 06/30/1976
| title = Rev 1,Tornado Design Classification
| title = Tornado Design Classification.
| author name =  
| author name =  
| author affiliation = NRC/RES
| author affiliation = NRC/OSD
| addressee name =  
| addressee name =  
| addressee affiliation =  
| addressee affiliation =  
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| license number =  
| license number =  
| contact person =  
| contact person =  
| document report number = Reg Guide 1.117,Rev 1
| case reference number = FOIA/PA-2015-0456, FOIA/PA-2015-0458
| document report number = RG-1.117
| document type = Regulatory Guide
| document type = Regulatory Guide
| page count = 3
| page count = 3
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{{#Wiki_filter:U.S. NUCLEAR REGULATORY  
{{#Wiki_filter:U.S. NUCLEAR REGULATORY  
COMMISSION
COMMISSION
REGULATORY  
June 1976 REGULATORY  
GUIDE OFFICE OF STANDARDS  
GUIDE OFFICE OF STANDARDS  
DEVELOPMENT  
DEVELOPMENT
REGULATORY  
REGULATORY  
GUIDE 1.117 TORNADO DESIGN CLASSIFICATION
GUIDE 1.117 TORNADO DESIGN CLASSIFICATION
Line 24: Line 25:
==A. INTRODUCTION==
==A. INTRODUCTION==
General Design Criterion  
General Design Criterion  
2, "Design Bases for Protection Against Natural Phenomena," of Appen dix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, "Licensing of Produc tion and Utilization Facilities," requires, in part, that structures, systems, and components important to safety be designed to withstand the effects of natural phenomena such as tornadoes without loss of capabil ity to perform their safety functions.
2, "Design Bases for Protec-tion Against Natural Phenomena," of Appendix A,"General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, "Licensing of Production and Utiliza.tion Facilities," requires, in part, that structures, sys-tems, and components important to safety be designed to withstand the effects of natural phenomena such as tornadoes.
 
without loss of capability to perform their safety functions.


Criterion  
Criterion  
2 also requires that the design bases for these structures, systems, and components reflect (1) appropriate combinations of the effects of normal and accident conditions with the effects of natural phenomena and (2) the importance of the. safety functions to be per formed.  This guide describes a method acceptable to the NRC staff for identifying those structures, systems, and components of light-water-cooled reactors that should be protected from the effects of the Design Basis Tornado (see Regulatory Guide 1.76, "Design Basis Tornado for Nuclear Power Plants"), including tornado missiles, and remain functional.
2 also requires that thie design bases for these structures, systems, and components reflect (1) appropriate combinations of the effects of normal and accident conditions with the effects of natural phenomena and (2) the importance of the safety functions to be performed.


The Advis ory Committee on Reactor Safeguards has been con sulted concerning this guide and has concurred in the regulatory position.
structures and components themselves should be de-signed to withstand the effects of the tornado, including tornado missile strikes.It is not necessary to maintain the functional cap-ability of all Seismic Category I stnpltufres because the probability of the joint occurrten f low-probability events (loss-of-coolant accid i.'t Basis Tornado or smaller tornadQ or thquaki with Design Basis Tornado or smaller o sufficiently small.However, a source of', wt s"ii1 be available to provide long-term c0ecoolin Similarly, .1Noot'& -, ssary to protect the radio-active liquid w"i e'dup tanks since, even in the event of grosW c,X'i\hespills would be limited to small This guide describes a method acceptable to the NRC in It'luid4 foundations, which are designed for that staff for identifying those structures, systems, and r components of light-water-cooled reactors that should 4 be designed to withstand the effects of the Design Basis "Ný,.Strutures, systems, and components important to Tornado (see Regulatory Guide 1.76, "Design, .1;, saty that should be designed to withstand the effects Tornado for Nuclear Power Plants"), including toiado V41 mseadeif l .of a Design Basis Tornado are those necessary to ensure: missiles, and remain functional. , ,, ;-" ' 1. The integrity of the reactor coolant pressure


==B. DISCUSSION==
==B. DISCUSSION==
Nuclear power plants should be protected from the effects of tornado strikes. The likelihood of a credi ble tornado strike varies from about 10'- per year to values several orders of magnitude higher. Physical design parameters of tornado protection provisions are such that designated structures, systems, and components will be able to maintain their necessary capabilities in the event of a Design Basis Tornado (DBT), as defined in Regulatory Guide 1.76. This ensures that protection of the designated items against all credible tornadoes has been adequately -Lines indicate substantive changes from previous issue.considered.
boundary.,, .. \ A V: Nuclear power plants should.be designed o'iat the 2. The capability to shut down the reactor and plants can be placed and maintained in a safe shutdown maintain it in a safe shutdown condition.
 
A basic provision of tornado protection criteria is that those structures, systems, and components whose failure could result in conservatively calculated expo sures comparable to the guideline exposures of 10 CFR Part 100, "Reactor Site Criteria," should be protected against DBT effects to prevent such failure.
 
This provision by itself, however, would not provide protection for certain other structures, systems, and components which could be damaged by a less se vere, but more likely, tornado. In order to ensure pro tection for more probable events having less severe consequences, the selection of structures, systems, and components to be protected against the effects of a DBT is based on not allowing offsite exposures to exceed an appropriate fraction of 10 CFR Part 100 guidelines.
 
Protection of designated structures, systems, and components may generally be accomplished by de signing protective barriers to preclude tornado dam age. For example, the primary containment, reactor building, auxiliary building, and control structures should be designed against collapse and should pro vide an adequate barrier against missiles.


However, the primary containment need not necessarily main tain its leaktight integrity.
condition in the, event of ign Basis Tornado, as defined in Regulatory G Protection of struc- 3. The capability to prevent accidents that could tures, systems, and comp n sary to place and result in potential offsite exposures that are a significant maintain the plant , e tdown condition may fraction of the guideline exposures of 10 CFR Part 100, generally be acco.'lishe y esigning protective bar- "Reactor Site Criteria." Designs that differ substantially tiers to prfc-a.de sile trikes. For example, the from those now in use may require reevaluation with primary co or building, auxiliary build- respect to this objective.


If protective barriers are not installed, the structures and components them selves should be designed to withstand the effects of the tornado, including tornado missile strikes. The physical separation of redundant or alternative struc tures or components required for the safe shutdown of the plant is generally not considered acceptable by itself for protecting against tornado effects, including tornado-generated missiles.
ing, and co structures should be designed against collapse and s d provide an adequate barrier against The physical separation of redundant or alternative missiles.


This is because of the large number and random direction of potential mis siles that could result from a tornado as well as the need to consider the single failure criterion.
Howeve , the primary containment need not structures or components required for the safe shutdown necessarily maintain its leaktight integrity under pressure of the plant is generally not considered an acceptable loadings due to the pressure differentials developed by method for protecting against tornado effects, including the tornado. If protective barriers are not installed, the tornado-generated missile


It is not necessary to maintain the functional capa bility of all Seismic Category I structures, systems, and components because the probability of the joint occurrence of low-probability events (loss-of-coolant USNRC REGULATORY  
====s. USNRC REGULATORY ====
GUIDES Comments should be sent to the Secretary of the Commission, US. Nuclear Regu latory Commission.
GUIDES Regulatory Guides ere issued to describe and make available to the public methods acceptable to the NRC staff of implementing specific paeis of the Commistion's regulations, to delineate techniques used by the staff in evelu.ating specific problems ot postulated accidents.


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.
or to provide guidance to appli.c.nts. Rogulatoryv Guides are not substitutes fto regulatIons, and compliance with them is not required.


to delineate techniques used by the staff in evaluating specific problems The guides are issued in the following ten broad divisions or poslulated accidents, or to provide guidance to applicants.
Methods and solutions different from those set Out In the guides will be acceptable if they provide a basis for the findings requislte to the issuance or continuance at a permit or license by the Commission.


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. Traosporlation able if they provide a basis for the findings requisite to the issuance or continuance
Comments and suggestions for Improvements In these guides are encouraged at all times, and guides will be revised. as appropriate.
3 Fuels and Materials Facilities
8. Occupational Health of a permit or license by the Commitsion.


4 Environmental and Siting 9. Antitrust Review 5. Materials and Plant Protection
to accommodate com-ments end to reflect new information or experience, However. comments on this guide, if received within about two months after its Issuance.
10. General Comments and suggestions for improvements in these guides are encouraged at all Requests for single copies of issued guides (which may be reproduced)
or for place 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 specific to reflect new information or experience.
will be par.trculatly useful in evaluating the need for an early revision Comments should be sent to the Secretary of the Commission.


This guide was revised as a result of divisions should be made in writing to the US. Nuclear Regulatory Commission.
U.S. Nuclear Regulatory Commission.


substantive comments received 'from the public and additional staff review. Washington.
Washinglon.


D.C. 20555, Attention Director.
D.C. 20M5. Attention.


Division of Document Control.Revision 1 April 1978 accident with DBT or smaller tornado, or earthquake with DBT or smaller tornado) is sufficiently small.  However, equipment used to provide long-term core cooling following a LOCA should be protected, Similarly, it is not generally necessary to protect the radioactive waste systems since, even in the event of gross failure, offsite exposures would remain well below the guideline exposures of I0 CFR Part 100 because of the limited inventory allowed in these systems.
Docketing and Service Section.The guides ere Issued In the following ten broad divisions.


C. REGULATORY
1. Power Reactor, 2. Reseach and Teat Reactors 3. Fuels and Materials Facilities
POSITION Structures, systems, and components important to safety that should be protected from the effects of a Design Basis Tornado are: 1. Those necessary to ensure the integrity of the reactor coolant pressure boundary;
4. Environmental and Siting 5, Materials end Plant Protection
2. Those necessary to ensure the capability to shut down the reactor and maintain it in a safe shutdown condition (this includes both hot standby and cold shutdown capability);
6. Products 7. Transportetion a. occupational Health 9. Antitrust Review 10. General Copies of published guides may be obtained by written request Indicating the divisions desired to the U.S. Nuclear Regulatory Commission.
and 3. Those whose failure could lead to radioactive release.3 resulting in calculated offsite exposures greater than 25% of the guideline exposures of 10 CFR Part 100 using appropriately conservative ana lytical methods and assumptions.


The appendix to this guide lists structures, sys tems, and components, which together with their foundations and supports, should be protected from the effects of a DBT (see Regulatory Guide 1.76), including tornado missiles, without loss of capability to perform their safety functions.
Washington, D.C.20566. Attention:
Director.


Those structures, systems, and components that should be protected may require reevaluation for designs that differ sub stantially from those now in use.
Office of Standards Development, C. REGULATORY
POSITION


==D. IMPLEMENTATION==
==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. Except in those cases in which the applicant pro poses an acceptable alternative method for complying with specified portions of the Commission's regula tions, the method described herein will be used in the evaluation of construction permit applications doc keted after May 30, 1978. If an applicant wishes to use this regulatory guide in developing submittals for applications docketed on or before May 30, 1978, the pertinent portions of the application will be evaluated on the basis of this guide.1.1I17-2__
.The appendix to this guide lists those structures, systems, and components, including their foundations and supports, that should be designed to withstand the effects of a Design Basis Tornado (see Regulatory Guide 1.76), including tornado missiles, without loss of capa-bility to perform their safety function.Those portions of structures, systems, or _.omponents whose continued function is not required but whose failure could reduce to an unacceptable safety level the functional capability of any plant feature included in the items listed in the appendix should be designed and constructed so that the effects of the Design Basis Tornado would not cause failure (for example, of the containment walls).The purpose of this section is to provide information to applicants regarding the NRC staff's plans for using this regulatory guide.Except in those cases in which the applicant proposes an acceptable alternative method for complying with specified portions of the Commission's regulations, the method described herein will be used in the evaluation of construction permit applications docketed after Feb-ruary 15, 1977.If an applicant wishes to use this regulatory guide in daveloping submittals for applications docketed on or before February 15, 1977, the pertinent portions of the application wil' be evaluated on the basis of this guide.1.117-2 if ____________________________
APPENDIX STRUCTURES, SYSTEMS, AND COMPONENTS  
APPENDIX MINIMUM STRUCTURES, SYSTEMS, AND COMPONENTS
OF LIGHT-WATER-COOLED
TO BE PROTECTED  
REACTORS TO BE PROTECTED  
AGAINST TORNADOES 1. The reactor coolant pressure boundary.*
AGAINST TORNADOES I. The reactor coolant pressure boundary.1 2. Those portions of the main steam and main feedwater systems 2 in PWRs up to and including the outermost isolation valves. 3. The reactor core and individual fuel assemblies, at all times, including during refueling.
2. Those portions of the main steam and main feedwater systems in PWRs up to and including the outermost isolation valves.3. The reactor core and reactor vessel internals.
 
4. Systems or portions of systems that are required for (1) attaining safe shutdown, (2) residual heat re moval, (3) cooling the spent fuel storage pool, (4) mitigating the consequences of a tornado-caused PWR steam line break, 3 (5) makeup water for the primary system, and (6) supporting the above sys tems, e.g., cooling water, ultimate heat sink, air sup ply, auxiliary feedwater, and ventilation.
 
5. The spent fuel storage pool, to the extent neces sary to preclude significant loss of watertight integ rity of the storage pool and to prevent missiles from contacting fuel within the pool.  6. The reactivity control systems, e.g., control rod drives and boron injection system.  7. The control room, including all equipment needed to maintain the control room within safe habitability limits for personnel and safe environmen tal limits for tornado-protected equipment.
 
8. Those portions of the gaseous radwaste treat ment system whose failure due to tornado effects SAs defined in §50.2 of 10 CFR Part 50.  2 The system boundary includes those portions of the system re quired to accomplish the specified safety function and connecting piping up to and including the first valve (including a safety or relief valve) this is either normally closed or capable of automatic closure when the safe function is required.
 
Alternatively, the main steam system, up io and including a sec ond isolation valve such as a redundant series MSIV, qr a turbine stop valve, may be protected.
 
could result in potential offsite exposures in excess of the criterion given in subitem (3) of the regulatory position.


9. Systems or portions of systems that are required for monitoring, actuating, and operating tornado protected portions of systems listed in items 4, 6,.7, and 13.  10. All electric and mechanical devices and cir cuitry between the process sensors and the input ter minals of the actuator systems involved in generating signals that initiate protective actions by tornado protected portions of systems listed in items 4, 6, 7, and 13.  11. Those portions of the long-term emergency core cooling system that would be required to main tain the plant in a safe condition for an extended time after a loss-of-coolant accident.
4. Systems" or portions of systems that are re-quired for (1) reactor shutdown, (2) residual heat removal, (3) cooling the spent fuel storage pool, or (4)makeup water for the primary system and all systems that are necessary to support these systems, e.g., service water, cooling water source, component cooling, and auxiliary feedwater.


12. Primary reactor containment and other safety related structures, such as the control room building and auxiliary building, to the extent that they not col lapse, allow perforation by missiles, or generation of secondary missiles, any of which could cause unac ceptable damage to tornado-protected items. How ever, the primary containment need not necessarily maintain its leaktight integrity.
5. The spent fuel storage facility to the extent necessary to preclude significant loss of watertight integrity of the storage pool and to prevent missiles from contacting fuel within the pool.6. The reactivity control systems, e.g., control rod drives and boron injection system.7. The control room, including its associated vital equipment, cooling systems for the vital equipment and life support systems, and any structures or equipment inside or outside the control room whose failure could result in an incapacitating injury to individuals occupy-ing the control room.8. Those portions of the gaseous radwaste treatment system that by design are intended to store or delay*Asdeflned in §50.2 of IOCFR Part 50.*"The system boundary Includes those portions of the system required to accomplish the specified safety function and connecting piping up to and including the first valve (includ-ing a safety or relief valve) that is either normally closed or capable of automatic closure when the safety function is required.gaseous radioactive waste and portions of structures housing these systems, including isolation valves, equip-ment, interconnecting piping, and components located between the upstream and downstream valves used to isolate these components from the rest of the system, e.g., charcoal delay tanks in BWRs and waste gas storage tanks in PWRs.9. Systems or portions of systems that are required for (1) monitoring systems important to safety and (2)actuating and operating systems important to safety.10. All electric and mechanical devices and circuitry between the process sensors and the input terminals of the actuator systems involved in generating signals that initiate protective action.11. Those portions of the long-term emergency core cooling system that would be required to maintain the plant in a safe condition for an extended time after a loss-of-coolant accident.12. Primary reactor containment and other safety-related structures such as the control room building and auxiliary building to the extent that they not collapse.The primary containment need not necessarily maintain its leaktight integrity under pressure loadings due to the pressure differentials developed by the tornado, but the structure should be designed to withstand penetration by tornado-borne missiles that could jeopardize safety-related structures, systems, and components within the containment.


13. The Class 1E electric systems, including the auxiliary systems for the onsite electric power supplies, that provide the emergency electric power needed for the functioning of plant features included in items 1 through 11 above. 14. Those portions of structures, systems, and components whose continued function is not required but whose failure could reduce to an unacceptable safety level the functional capability of any plant fea tures included in items I through 13 above or could result in incapacitating injury to occupants of the con trol room.1.117-3}}
13. The Class IE electric systems, including the auxiliary systems for the onsite electric power supplies, that provide the emergency electric power needed for the functioning of plant features included in items 1.through 11. above.1.117-3}}


{{RG-Nav}}
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Revision as of 13:57, 17 September 2018

Tornado Design Classification.
ML13350A280
Person / Time
Issue date: 06/30/1976
From:
NRC/OSD
To:
References
FOIA/PA-2015-0456, FOIA/PA-2015-0458 RG-1.117
Download: ML13350A280 (3)
v • d • e


U.S. NUCLEAR REGULATORY

COMMISSION

June 1976 REGULATORY

GUIDE OFFICE OF STANDARDS

DEVELOPMENT

REGULATORY

GUIDE 1.117 TORNADO DESIGN CLASSIFICATION

A. INTRODUCTION

General Design Criterion 2, "Design Bases for Protec-tion Against Natural Phenomena," of Appendix A,"General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, "Licensing of Production and Utiliza.tion Facilities," requires, in part, that structures, sys-tems, and components important to safety be designed to withstand the effects of natural phenomena such as tornadoes.

without loss of capability to perform their safety functions.

Criterion

2 also requires that thie design bases for these structures, systems, and components reflect (1) appropriate combinations of the effects of normal and accident conditions with the effects of natural phenomena and (2) the importance of the safety functions to be performed.

structures and components themselves should be de-signed to withstand the effects of the tornado, including tornado missile strikes.It is not necessary to maintain the functional cap-ability of all Seismic Category I stnpltufres because the probability of the joint occurrten f low-probability events (loss-of-coolant accid i.'t Basis Tornado or smaller tornadQ or thquaki with Design Basis Tornado or smaller o sufficiently small.However, a source of', wt s"ii1 be available to provide long-term c0ecoolin Similarly, .1Noot'& -, ssary to protect the radio-active liquid w"i e'dup tanks since, even in the event of grosW c,X'i\hespills would be limited to small This guide describes a method acceptable to the NRC in It'luid4 foundations, which are designed for that staff for identifying those structures, systems, and r components of light-water-cooled reactors that should 4 be designed to withstand the effects of the Design Basis "Ný,.Strutures, systems, and components important to Tornado (see Regulatory Guide 1.76, "Design, .1;, saty that should be designed to withstand the effects Tornado for Nuclear Power Plants"), including toiado V41 mseadeif l .of a Design Basis Tornado are those necessary to ensure: missiles, and remain functional. , ,, ;-" ' 1. The integrity of the reactor coolant pressure

B. DISCUSSION

boundary.,, .. \ A V: Nuclear power plants should.be designed o'iat the 2. The capability to shut down the reactor and plants can be placed and maintained in a safe shutdown maintain it in a safe shutdown condition.

condition in the, event of ign Basis Tornado, as defined in Regulatory G Protection of struc- 3. The capability to prevent accidents that could tures, systems, and comp n sary to place and result in potential offsite exposures that are a significant maintain the plant , e tdown condition may fraction of the guideline exposures of 10 CFR Part 100, generally be acco.'lishe y esigning protective bar- "Reactor Site Criteria." Designs that differ substantially tiers to prfc-a.de sile trikes. For example, the from those now in use may require reevaluation with primary co or building, auxiliary build- respect to this objective.

ing, and co structures should be designed against collapse and s d provide an adequate barrier against The physical separation of redundant or alternative missiles.

Howeve , the primary containment need not structures or components required for the safe shutdown necessarily maintain its leaktight integrity under pressure of the plant is generally not considered an acceptable loadings due to the pressure differentials developed by method for protecting against tornado effects, including the tornado. If protective barriers are not installed, the tornado-generated missile

s. USNRC REGULATORY

GUIDES Regulatory Guides ere issued to describe and make available to the public methods acceptable to the NRC staff of implementing specific paeis of the Commistion's regulations, to delineate techniques used by the staff in evelu.ating specific problems ot postulated accidents.

or to provide guidance to appli.c.nts. Rogulatoryv Guides are not substitutes fto regulatIons, and compliance with them is not required.

Methods and solutions different from those set Out In the guides will be acceptable if they provide a basis for the findings requislte to the issuance or continuance at a permit or license by the Commission.

Comments and suggestions for Improvements In these guides are encouraged at all times, and guides will be revised. as appropriate.

to accommodate com-ments end to reflect new information or experience, However. comments on this guide, if received within about two months after its Issuance.

will be par.trculatly useful in evaluating the need for an early revision Comments should be sent to the Secretary of the Commission.

U.S. Nuclear Regulatory Commission.

Washinglon.

D.C. 20M5. Attention.

Docketing and Service Section.The guides ere Issued In the following ten broad divisions.

1. Power Reactor, 2. Reseach and Teat Reactors 3. Fuels and Materials Facilities

4. Environmental and Siting 5, Materials end Plant Protection

6. Products 7. Transportetion a. occupational Health 9. Antitrust Review 10. General Copies of published guides may be obtained by written request Indicating the divisions desired to the U.S. Nuclear Regulatory Commission.

Washington, D.C.20566. Attention:

Director.

Office of Standards Development, C. REGULATORY

POSITION

D. IMPLEMENTATION

.The appendix to this guide lists those structures, systems, and components, including their foundations and supports, that should be designed to withstand the effects of a Design Basis Tornado (see Regulatory Guide 1.76), including tornado missiles, without loss of capa-bility to perform their safety function.Those portions of structures, systems, or _.omponents whose continued function is not required but whose failure could reduce to an unacceptable safety level the functional capability of any plant feature included in the items listed in the appendix should be designed and constructed so that the effects of the Design Basis Tornado would not cause failure (for example, of the containment walls).The purpose of this section is to provide information to applicants regarding the NRC staff's plans for using this regulatory guide.Except in those cases in which the applicant proposes an acceptable alternative method for complying with specified portions of the Commission's regulations, the method described herein will be used in the evaluation of construction permit applications docketed after Feb-ruary 15, 1977.If an applicant wishes to use this regulatory guide in daveloping submittals for applications docketed on or before February 15, 1977, the pertinent portions of the application wil' be evaluated on the basis of this guide.1.117-2 if ____________________________

APPENDIX MINIMUM STRUCTURES, SYSTEMS, AND COMPONENTS

TO BE PROTECTED

AGAINST TORNADOES 1. The reactor coolant pressure boundary.*

2. Those portions of the main steam and main feedwater systems in PWRs up to and including the outermost isolation valves.3. The reactor core and reactor vessel internals.

4. Systems" or portions of systems that are re-quired for (1) reactor shutdown, (2) residual heat removal, (3) cooling the spent fuel storage pool, or (4)makeup water for the primary system and all systems that are necessary to support these systems, e.g., service water, cooling water source, component cooling, and auxiliary feedwater.

5. The spent fuel storage facility to the extent necessary to preclude significant loss of watertight integrity of the storage pool and to prevent missiles from contacting fuel within the pool.6. The reactivity control systems, e.g., control rod drives and boron injection system.7. The control room, including its associated vital equipment, cooling systems for the vital equipment and life support systems, and any structures or equipment inside or outside the control room whose failure could result in an incapacitating injury to individuals occupy-ing the control room.8. Those portions of the gaseous radwaste treatment system that by design are intended to store or delay*Asdeflned in §50.2 of IOCFR Part 50.*"The system boundary Includes those portions of the system required to accomplish the specified safety function and connecting piping up to and including the first valve (includ-ing a safety or relief valve) that is either normally closed or capable of automatic closure when the safety function is required.gaseous radioactive waste and portions of structures housing these systems, including isolation valves, equip-ment, interconnecting piping, and components located between the upstream and downstream valves used to isolate these components from the rest of the system, e.g., charcoal delay tanks in BWRs and waste gas storage tanks in PWRs.9. Systems or portions of systems that are required for (1) monitoring systems important to safety and (2)actuating and operating systems important to safety.10. All electric and mechanical devices and circuitry between the process sensors and the input terminals of the actuator systems involved in generating signals that initiate protective action.11. Those portions of the long-term emergency core cooling system that would be required to maintain the plant in a safe condition for an extended time after a loss-of-coolant accident.12. Primary reactor containment and other safety-related structures such as the control room building and auxiliary building to the extent that they not collapse.The primary containment need not necessarily maintain its leaktight integrity under pressure loadings due to the pressure differentials developed by the tornado, but the structure should be designed to withstand penetration by tornado-borne missiles that could jeopardize safety-related structures, systems, and components within the containment.

13. The Class IE electric systems, including the auxiliary systems for the onsite electric power supplies, that provide the emergency electric power needed for the functioning of plant features included in items 1.through 11. above.1.117-3


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