ML19221A985
| ML19221A985 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-75-087, NUREG-75-087-06.2.4, NUREG-75-87, NUREG-75-87-6.2.4, SRP-06.02.04, SRP-6.02.04, TAC-08291, TAC-8291, NUDOCS 7907120132 | |
| Download: ML19221A985 (14) | |
Text
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STANDARD REVIEW PLAN OFFICE OF NUCLEAR REACTOR REGULATION SECTION 6.2.4 CCNTAINMENT ISCLATION SYSTEM REVIEW RESPON31BILITIE5 Primary - Containment Systems Branch (C58)
Secondary - Accident Analysis Branch (AAB)
Instrumentation and Control System Branch (ICSB) l Mechanical Engineering Branch (MEB)
Structural Engineering 3 ranch (SEB)
Reactor Systems Branch (RSB)
Pcwer Systems Brach (PSB) 1.
AREAS OF REVIEW The design objective of the contalnment isolation system is to allow the normal or emer-gency passage of fluids through the containmerit boundary while preserving the ability of the boundary to prevent or limit the escape of fission products that may result from postulated accidents. This SRP section, therefore, is concerned with the isolation of fluid systems which penetrate the containment boundary, including the design and testing requirements for isolation barriers and actuators. Iselation barriers include valves, closed piping systems, and blind flanges.
The CSB reviews the information presented in the applicant's safety analysis report (StR) regarding containment isolation provisions to assure conformance with the requirements of General Design Criteria 54, 55, 56 and $7.
The CSB review covers the following aspects of containment isolation:
1.
The design of containment isolation provisions, including:
a.
The number and location of isolation valves, i.
the isolation valve arrange-ments and the physical location of isolation valces with respect to the containment.
b The actuation and control features for isolation valves.
c.
The positions of isolation valves for normal plan' ope,? ting conditions (includ-ing shutdown), post accident conditions, and in t e event 01 valve operator h
power failures, d.
The valve actuation signals, e.
The basis for selection of closure times of isolation valves.
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f.
The mechanical redundancy of isolation devices.
g.
The acceptability of closed piping systems inside containment as isolation barriers.
2.
" e protection provided for containment isolation provisions against loss of function frem missiles, pipe whip, and earthquakes.
3.
The environmental conditions inside and outside the containment that were considered in the design of isolation barriers.
4.
The design criteria applied to isolation barriers and piping.
5.
The provisions for detecting a possible need to isolate remote-manual contro' leo systems, such as engineered safety features systems.
The design provisions for and technical specifications pertaining to operability and leakage rate testing of tre isolation barriers.
7.
The calculation of containment atmosphere released prior to isolation valve closure fer lines that provide a direct path to the environs.
PSB has primary responsibility for the qualification test program for electric valve operators, and the ICSB has primary responsibility for the qualification test program for the sensing and actuation instrumentation of the plant protection system located both inside and outside of containment. The MEB has review responsibility for the qualifica-tion test program to demonstrate the performance and reliability of containment isolation valves.
The MEB and SEB have review responsibility for mechanical and structural design l
of the containment isolation provisions to ensure adequate protection aoainst missiles, pipe whip, and earthquakes. The AAB reviews the radiological dose consequence analysis for the release of containment atmosphere prior to cloture of containment isolation valves in lines that pr.
ide a direct path to the environs. The RSB reviews the closure time for containment isolation valves in lines that prtvide a direct path to the environs, with respect to the prediction of onset of accident induced fuel failure.
II.
ACCEPTANCE CRITERIA The general design criteria establish requirements for isolation barriers in lines pene-trating cne primary containment boundary. In general, two isolation barriers in series are required to assure that the isobtion function is satisfied assumirg any single active failure in the containment isolation provisions.
The design of the containment isolation provisions will be acceptable to CSB if the following criteria are satisfied:
1.
General Design Criteria 55 and 56 require that lines that penetrate the primary con-tainment boundary and either are part
<>f the reactor coolant pressure boundary or Rev. 1 6.2.4-2 I A7 2H
connect directly to the containment atmosphere should be provided with isolation Vdives as follows:
One locked closed isolation valve 1/ inside and one locked closed isolation a.
valve outside containment; or b.
One automatic isolation valve inside and one locked closed isolation valve out-side containment; or One locked closed isolation valve inside and one automatic isolation vclve /
2 c.
outside containment; or d.
One automatic isolation valve inside and one automatic isolation valve outside containment.
2.
General Design Criterion 57 requires that lines that penetrate the primary contain-ment boundary and are neither part of the reactor coolant pressure boundary nor connected directly to the containment atmosphere should be provided with at least one locked closed, remote mar.ual, or automatic isolation valve outside containment.
3.
The general design criteria permit containment isolation provisions for lines pene-trating the primary containment boundary that differ from the explicit requirements of General Design Criter;a 55 and 56 if the basis for acceptability is defined.
Following are guidelines for acceptable alternate containment isolation provisions fnr certain classes of lines:
Regulatory Guide 1.11 describes acceptable containment isolation provisions for a.
instrument lines. In addition, instrument lines that are closed both inside and outside containment, are designed to withstand the pressure and temperature conditions following a loss of-coolant accident, and are designed to withstand dynamic effects, are acceptable without isolation valves.
b.
Containment isolation provisions for lines in engineered safety features or engineered safety feature-related systems may include remote-manual valves, but provisions should be made to detect possible leakage from these lines outside containment.
c.
Contair, ment isolation provisions for lines in systems needed for safe shutdown of the plant (e.g., liquid poison system, reactor core isolation cooling system, and isolation condenser system) may include remote-manual valves, but provision should be made to detect possible leakage from these lines outside containment.
1/ Locked closed isolation valves are defined as sealed closed barr 2 67 9
2/A simple check valve is not normally an acceptable automatic isolation valve for this application.
6.2.4-3 Rev. 1
d.
Containment isolation provisions for lines in the systems identified in items b and c normally cm,3ni of one isolation valve inside and one isolation valve outside contai. ment.
If it is not practical to locate a valve irsioe contain-ment (for example, the valve may be under water es a result of an accident),
l both valves may be located outside containment. For this type of isolation valve arrangement, the valve nearest the containment and the piping between the containment and the valve should be enclosed in a leak-tights or controlled leakage housing.
If, in lieu of a housing, conservative'r*> sign of the piping and valve is assumed to preclude a breach of piping integrity, the design should conform to the requirements of SRP section 3.6.2.
Design of the valve and/or the piping compartment should provide the capability to detect leakage from the valve shaft and/or bonnet seals and terminate the leakage.
e.
Containment isolation provisions for lines in engineered safety feature or engineered safety feature-related systems normally consist of two isolation valves in series. A single isolation valve will be acceptable if it can be j
shown that the system reliability is greater with only one isolation valve in the line, the system is closed outside containment, and a single active failure can be accommodated with only one isolation valve in the line. The closed system outside containment should be protected from missiles, designed to seismic Category I standards, classified Safety Class 2 (Ref. 5), and should have a design temperature and pressure rating at least equal to that for the containment. The closed system outside containment should be leak tested, unless it can be shown that the system integrity is being rnaintained during normal plant operations. For this type of isolation valve arrangement the valve is located outside containment, and the piping between the containment and the valve should be enclosed in a leak tight or controlled leakage housing.
If, in lieu of a housing, conservative design of the piping and valve is assumed to preclude a breach of piping integrity, the design should conform to the requirements of SRP section 3.6.2.
Design of the valve and/or the piping compartment should provide the capability to detect leakage from the valve shaft and/or connet seals and terminate the leakage.
f.
Sealed clased barriers may be used in place of automatic isolation valves.
Sealed closed barriers include blind flanges and sealed closed isolation valves which may be closed manual valves, closed remote-manual valves, and closed automatic vilves which remain closed after a loss-of-coolant accident. Sealed closed isolition valves should be under administrative control to assure that they cannot be inadvertently opened. Administrative control includes mechanical devices to seal or lock the valve closed, or to prevent power from being sup-plied to the valve operator.
point is g.
Relief valves may be used as isolation valves provided the 71ief
- c greater than 1.5 times the containment design pressure.
9 h
h Rev. l 6.2.4-4
4.
Isolation valves outside containment should be lecated as close to the containment as practica'., as required by General Design Criteria 55, 56, and 57.
5.
The position of an isolation valve for normal and shutdown plant operating conditions and post-accident conditions depends on the fluid system function. If a fluid system does not have a post-accident function, the isolation valves in the lines should be automatically closed. For engineered safety feature er engineered safety feature-related systems, isolation valves in the lines may remain open or be opened.
The position of an isolation valve in the event of power failute to the valve operator should be the " safe" position. Normally this position would be the post-accident valve position. All power-operated isolation valves should have position indication in the main control room.
6.
There should be diversity in the parameters sensed for the initiation of containment isolation.
7.
System lines which provide an open path from the containment to the environs should be equipped with radiation monitors that are capable of isolating these lines uoan a high radiation signal. A high radiation signal should not be considered one of the diverse containment isolation parameters.
8.
Containment isolation vaive closure times should be selected to assure rapid isola-tion of the containment following postulated accidents. The valve closure time is the time it takes for a power operated valve to be in the fully closed position after the actuator power has reached the operator assembly; it does not include the time to reach actuation signal setpoints or instrument delay times, which should be considered in determining the overall time to close a valve.
System design capa-bilities should be considered in establishing valve closure times. For lines which provide an open path from the containment to the environs; e.g., the containment purge and vent lines, isolation valve closure times on the order of 5 seconds or less may be necessary. The closure times of these valves should be established on the basis of minimizing the release of containment atmosphere to the environs, to mitigate the offsite radiological consequences, and assure that emergency core cooling system (ECCS) effectiveness is not deg aded by a reduction in the containment backpressure. Analyses of the radiological consequences and the effect on the containment backpressure due to the release of containment atmosphere should be provided to justify the selected valve closure time. Additional guidance on tne design and use of containment purge systems which may be used during the normal plant operating modes (i.e., startup, power operation, hot standby and hot shutdown) is provided in Branch Technical Position CSB 6-4 (Ref. 9).
For plants under review for operating licenses or plants for which the Safety Evaluation Report for construc-tion permit application was issued prior to July 1, 1975, the methods described in Section B, Items B.l., a, b, d, e, f, and g, B.2 through B.4, and B.S.b, c, and d of Branch Technical Position 6-4 should be implemented. For these plants, BTP Items B.l.c and B.S.a regarding the size of the purge system used during normal plant operation and the justification by acceptable dose consequence analysis, may be 147 269 6.2.4-5 Rev. I
waived if the applicant com. nits to limit the use of the purge system to less than 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year while the plant is in the startup, power, hot standby and hot shutdown modes of operations. This commitment should be incorporated into the Technical Specifications used in the operation of the plant.
9.
The use of a closed system inside containment as one of the isolation barriers will be acceptable if the design of the closed system satisfies the following requirements:
a.
The system does not communicate with either the reactor coolant system or the containment atmosphere.
b.
The system is protected against missiles and pipe whip, c.
The system s designated seismic Category I.
i d.
The system is classified Safety Class 2 (Ref. 5).
e.
The system is designed to withstand temperatures at least equal to the contain-ment design temperature.
f.
The system is designed to withstand the external pressure from the containment structural acceptance test.
g.
The system is designed to withstand the loss"of-coolant accident transient and environment.
Insofar as CSB is concerned with the structural design or containment internal structures and piping systems, the protection of isolation barriers against loss of function f rom missiles, pipe whip, and earthquakes will be acceptable if isolatinn barriers are located behind missile barriers, pipe whip was considered in the design of pipe restraints and the location of piping penetri. ting the containment, and the isolation barriers, including the piping between isolation valves, are designated seismic Category I, i.e.,
designed to withstand the effects of the safe shutdown earthquake, as recommended by Regulatory Guide 1.29.
10.
The design criteria applied to components performing a containment isolation function, l
including the isolation barriers and the piping between them, or the piping between the containment and the outermost isolation barrier, are acceptable if:
l a.
Group B quality standards, as defined in Regulatory Guide 1.26 are applied to the components, unless the service function dictates that Group A quality standards be applied.
b.
The components are designated s.sismic Category I, in accordance with Regulatory P,uide 1.29.
147 270 Rev. I 6.2.4-6
11.
The design of the containment isolation system is acceptable if provisions are made to allow the operator in the main control room to know when to isolate fluid systems that are equipped with remote manual isolation valves. Such provisions may include instruments to measure flow rate, sump water level, temperature, pressure, and radiation level.
12.
Provisions should be made in the design of the containment isolation system for l
operability testing of the containment isolation valves and leakage rate testing of the isolation barriers. The isolation valve testing program should be consistent with that proposed for other engineered safety features. The acceptance criteria for the leakage rate testing program for containment isolation barriers are presented in SRP section 6.2.6.
For those areas of review identified in subsection 1 of this SRP section as being the responsibility of other branches, the acceptance criteria and their methods of application are contained in the SRP sections corresponding to those branches.
III. REVIEW PROCEDURES The procedures described below provide guidance on review of the containment isolation system. The reviewer selects and emphasizes material from the review procedures as may be appropriate for a parti alar case. Portions of the review may be done on a generic basis for aspects of containment isolation common to a class of containments, or by adopting the results of previous reviews of plants with essentially the same containment icolation provisions.
Upon request from the primary reviewer, the secondary review branches will provide input l
for the areas of review stated in subsection 1.
The primary reviewer obtains and uses such input as required to assure that this review procedure is complete.
The CSB determines the acceptability of the containment isolatior system by comparing the system design criteria to the design requirements for an engineered safety feature. The quality standards and the seismic design classification of the containment isolation pro-visions, including tne piping penetrating the containment, are compared to Regulatory Guides 1.26 and 1.29, respectively.
The CSB also ascertains that no single fault can prevent isolatica of the containment.
This is accomplished by reviewing the containment isolation provisions for each line penetrating the containment to determine that two isolation barriers in series are provided, and in conjunction with the PSB by reviewing the power scurces to the valve operators.
l The CSB reviews the information in the SAR justifying containment isolation provisions which differ from the explicit requirements of General Design Criteria 55, 56 and 57.
The CSB judges the acceptability of these containment isolation provisions based on a 9
147 2/1 l
comparison with the acceptance criteria given in subsection II.
6.2.4-7 Rev. 1
The CSB reviews the position of isolation valves for normal and shutdown plant operating conditions, post-accident conditions, and valve operator power f ailure conditions as listed in the SAR.
The position of an isolation valve for each of the above conditions depends on the system function. In general, power-operatad valves in fluid systems which do not have a post-accident safety function should close automatically. In the event of power failure to a valve operator, the valve position should be the position of gre3ter safety, which is normally the post-accident position. However, special cases may arise and these will be considered on an individJal basis in determining tne acceptability of the prescribed valve positions. The CSB also ascertains from the SAR that all power-operated isolatior va'.ves have position indication capability in the main control room.
The CSB reviews the signals obtained from the plant protection system to initiate contain-ment isolation. In general, there should be a riiversity of parameters sensed; e.g.,
abnormal conditions in the reactor ccclant system, the secondary coolant system, and the containment, which generate containment isolation signals. Since plant designs differ in this regard and mary different combinations of signals from the plant protection system are used to initiate containment isolation, *he CSB considers the arrangement proposed on individual basis in determining the overall acceptabili'.y of the containment isolation an signals.
The CSB rev;'ws isolation valve closure times.
In general, valve closure times should be less than one m;'ute, regardless of valve size.
(See t.he acceptance criteria for valve closure times in subsection II.) Valves in lines that provide a direct path to the l
- environs, e.g., the containment purge and ventilation system lines and main steam lines for direct cycle plants, may m ve to close in times much shorter than one ninute. Closure times for these valves may be dictated by radiological dose analyses or ECCS performance considerations. The CSB will request the AAB or RSB to review analyses justifying valve closure times for those valves as necessary.
The CSB determines the acceptability of the use of closed systems inside containrvnt as isolation barriers by comparing the system desigt
- the acceptance criteria specified in subsection II.
l The MEB and SEB have review responsibility for the structural design of the containment internal structures and oiping systems, incluaing restraints, to assure that the contain-ment isolation provisons are adequately protected against missiles, pipe whip, and earth-quakes.
The CSB determines that for all containment isolation provisions, missile pro-tection and protection against loss of function from pipe whip and earthquaxes were design considerations. The CSB reviews the system drawings (which shnuld show the loca-tions of missile barriers relative to the containment isclation provisions) to determine that the isolation provisions are protected from missiles. The CSB also reviews the design criteria applied to the containment isolation provisions to determine that protec-tion against dynamic effects, such as pipe whip and earthouakes, was considered in the design. The CSB will request the MEB to review the design adequacy of piping and valves ter which conservative design is assumed to preclude pcssible breach of system integrity in lieu of providing a leak tight hcusing.
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Rev. I 6.2.4-8
Systems having a post-accident safety function may have remote-manual isolation valves in the lines penetrating the containment. The CSB reviews the provisions made to detect leakage from these lines outside containment and to allow the operator in the main control room to isolate the system train should leakage occur. Leakage detection provisions mav include instrumentation for measuring system fiow rates, or the pressure, temperature, radiation, or water leve: in areas outside the containment such as valve rooms or engi-neered safeguards areas.
The CSB bases its ace.eptance of the leakage detection provisions described in the SAR on the capability to detect leakage and identify the lines that should be i<
ted.
The CSB determines that the containment isolatiot. provisions are designed to allow the isolation barriers to be individually leak tested. This information should be tabulated in the safety analysis report to facilitate the CSB revirw.
The CSB determines from the descriptive information in the SAR that provisions nave been made in the design of the containment isolatien system to allow pericdic operability testing of the power-operated isolation valves and the containment isolation system. At the operating license stage of review, the CSB determines that the content and intent of proposed technical specifications pertaining to operability and leak testing of contait-ment isolation equipment is in agreement with requirements developed by the staff.
IV.
EVALUATION FINDINGS The information provided and the CSB review should support concluding statements similar to the following, to be included in the staf f's saf ety evaluation report:
"The scope of review of the containment isolation system for the (plant name) has included schematic drawings and descriptive information for the isolation provisions for fluid systems which penetrate the containment boundary. The review has also included the applicant's proposed design bases for the containment isolation provi-sions, and analyses of the functional capability of the containment isolation system.
"The basis for the staff's acceptance hat been the conformance of the containment isolation provisions to the Commission's regulations as set forth in the General Design Criteria, and to applicable regulatory guides, staff technical positions, and industry codes and standards. (Special problems or exceptions that the staff takes to specific containment isolation provisions or the functional capability of the containment isolation system should be discussed.)
"The staff concludes that the containment isolation system design conforms to all applicable regulations, guides, staff positions, and industry codes and standards, and is acceptable."
REFERENCES 9
V.
1.
10 CFR Part 50, Appendix A, General Design Criterion 54, "Pipinc Systems Penetrating Conta i nme nt. "
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2.
10 CFR Part 50, Appenoix A, General Design Criterion 55, " Reactor Coolant Pressure Boundary Penetrating Containment."
3.
10 CFR Part 50, Appendix A, General Design Criterion 56, " Primary Containment Iso ation."
4.
10 CFR Part 50, Appendix A, General Design Criterion 57, " Closed System Isolation Valves."
5.
Regulatory Guide 1.141, " Containment Isolation Provisions For Fluid Systems."
6.
Regulatory Guide 1.11, " Instrument Lines Penetrating Primary Reactor Containment."
7.
Regulatory Guide 1.2i., " Quality Group Classifications and Standards for Water,
Steam, and Radioactive-Waste-Containing Components of Nuclear Power Plants."
8.
Regulatory Guide 1.29, " Seismic Design Classification."
9.
Branch Technical Position CSB 6-4, " Containment Purging During Normal Plant Opera-tions," attached to this SRP section.
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'fk Rev. 1 6.2.4-10
Branch Technica) Pos tion CSB 6-4 CONTAINMENT PURGINC DURING NORMAL PLANT OPERATIONS A.
B3 KGROUND This branch ttchnical position pertains to system lines which can provide an open path from the containmen-t4 the environs during normal plant operation; e.g., the purge and went lir.es of the containment purge syst'm.
It supplements the position taken in SRP section 6.2.4.
1 While the containment purge system provides plant operational flexibility, its design must consider the importance of minimizing the release of containment atmosphere to the environs followir.g a postulated loss of-coolant accident. Therefore, plant designs must not rely on its use on a routine basis.
The need for purging has not always been anticipated in the design of plants, and there-fore, design criteria for the containment purge system have not been fully developed.
The purging experience at operating plants varies considerably from plant to plant. Some plants do not purge during reactor operation, some purge intermittently for short periods and some purge continuously.
The containment pJrge system has been used in a variety of ways, for exampie, to alleviate certain operational problems, such as excess air leakage into the containment from pneumatic j
contrallers, for reducing the airborne activity within the containment to facilitate personnel access during reactor power operation, and for controlling the containment pressure, temperature and relative humidity. However, the purge and vent lines provide an open path from the containment to the environs. Should a LOCA occur during containment purging when the reactor is at power, the calculated accident doses should be within 10 CFR 100 guideline values.
The sizing of the purge and vent lines in most plants has been based on the need to control the containment atmosphere during refueling operations. This need has resulted in very large lines penetrating the containment (about 42 inches in diameter). Since these lines are normally the only ones provided that will permit some degree of control over the containment atmosphere to facilitate personnel access, some plants have used them for centairiment purging during normal plant operation. Under such conditions, calculated accident doses could be significant. Therefore, the use of these large contain-ment purge and mat lines should be restricted to cold shutdown conditions and refueling operations.
147 275 Rev. I 6.2.4-11
The design and use of the purge and vent lines should be based on the premise of achieving acceptable Calculated offsite rddiological Consequences and assuring that emergency core cooling (ECCS) effectiveness is not degraded by a reduction in the cantainment backpressure.
Purge system desigus that are acceptable for use on non-routine basis d Wirg normal plant operation can be achieved by praviding additional nurge and vent lines. 15e size of these lines should be limited such that in the event of a loss-of-coolant accident, assuming the purge and vent valves are open and subrequently close, the radiological consequences calculated in accordance with Regulatory Guides 1.3 and 1.4 would not m ceed the 10 CFR 100 guideline values. Also, the maximum time for valve closure should not exceed five seconds to assure that the purge and vent valves would be closed before the onset of fuel failures folicwing a LOCA.
The size of the purge ana vent lines should be about eight inches in diameter for FWR plants.
This line size may be overly conservative from a radiological viewpoint for the Mark III BWR plants and the HTGR plants oecause of containment and/or core design features.
Therefora, larger line sizes aay be justified. However, for any proposed line size, the applicant Lust demonstrate that the radiological consequences fo. lowing a loss-of-coolant accident would be within 10 CFR 100 guideline values. In summary, the acceptability of a (pecific iine size is a f unction of the site rreteorology, containment design, and radio-logical scace term for tne reactor type; e.g., BWR, f'WR or HIGR.
B.
BRANCH TECHNICAL POSITION The system used to purge the containment for the 'eactcr operational modes of power operation, startup, hot standby and hot shutdown; i.e., the on-line purge system, should be independent of the purge system used for the reactor operational modes of cold shutdown and refueling.
1.
The on-lire purge system should be designed in accordance with the following criteria:
a.
The performance and reliability of the purge system isolation valves should be consistent with the operability assurance program outlined in MEB Branch Tech-nical Position MEB-2, Pump and Valve Operability Assurance Program. (Also see SRP Section 3.9.3.)
The design basis for the valves and actuators should l
include the buildup of ccntainment pressure for the LOCA break spectrum, and the purge line and vent line flows as a function of time up to and during valve closure.
b.
The number of purge and vent lines that may be used should be limited to one purge line and one vent line.
c.
The size of the purge and vent lines should not exceed about eight inches in diameter unless detailed justification for larger line sizes is provided.
147 276 Rev. I te. 2. 4 -12
d.
The containment isolation provisions for the purge system lines shaald meet the standards appropriate to engineered safety features; i.e., quality, redundancy, testability and other appropriate criteria.
Instrumentation and control systems provided to isolate the purge system lines e.
shuuld be independent and actuated uy diverse parameters; e.g., containment pressure, safety injection actuation, and containment radiation level. If energy is required to close the valves, at least two dive,se sources of energy shall be provided, either of which can affect the isolation function.
f.
Purge system isolation valve clo;ure times, including instrumentation delays, should not exceed five seconds.
g.
Provisions should be made to ensure that isolation valve closure will not be prevented by debris which could potentially become entrained in the escaping air and steam.
2.
The purge system should not be relied on for temperature and humidity control within the containment.
3.
Provisions should be made to minimize the need for purging of the containment by providing containment atmosphere cleanup systems w; thin the containment.
4.
Provisions should be made for testing the availability of the isolation function and the leakage rate of the isolation valves, individually, during reactor operation.
5.
The following analyses should be performed to justify the containment purge system design:
a.
An analysis of the rad:ological consequences of a loss of coolant accident.
The analysis should be done for a spectrum of break sizes, and the instrumenta-tion and setpoints that will actuate the vent and purge valves closed should be identified. The source term used in the radiological calculations should be based on a calculation under the terms of Appendix K to determine the extent of fuel failure and the.oncomitant release of fission product 3, and the fission product activity in the primary coolant. A pre existing iodine spike should be considered in determining primary coolant activity. The volume of containment in which fission products are mixed should be justified, and the fission products from the above sources should be assumed to be released through the open purge valves durir.g the muimum interval required for valve closure. The radiological consequences should be within 10 CFR 100 guideline values.
b.
An analysis which demonstrates the acceptability of the provisions made to protect structures and safety-related equipment; e.g.,
far,s, filters and duct-work, located beyond the purge system isolation valves against loss of fung from the environment created by the escaping air and steam.
\\k 6.2.4-13 Rev. 1
c.
An analysis of the reduction in the containment pressure resulting from the partial loss of containment atmosphere during the accident for ECCS backpressure determination.
d.
The allowable leak rates of the purge and vent isolation valves should be specified for the spectrum of design basis pressures and flows against which the valves must close.
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) 4 -l7 Liu Rev. I 6.2.4-14