ML20064H395
| ML20064H395 | |
| Person / Time | |
|---|---|
| Issue date: | 12/11/1978 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20064H392 | List: |
| 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, NUDOCS 7812200110 | |
| Download: ML20064H395 (17) | |
Text
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NU REG-75/087
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g U.S. NUCLEAR RE0!LATORY COMMISSION f
i STANDARD REVIEW PLAN OFFICE OF NUCLEAR REACTOR REGULATION SECTION 6.2.4 CONTAIMMENT ISOLATION SYSTEM REVIEW RESPONSIEILITIES Primary - Containmort Systems Branch (CSB)
Secondary - Accident Analysis Branch (AAB)
Instrumentation and Control System Branch (ICSB) l Moct.anical Engineering Branch (MEB)
Structural Engineering Branch (SEB)
Reactor Systems Branch (R58)
Power Systees Branch (PSB) 1.
AREAS OF REVIEW The design objective of the containment isolation system is to allow the normal or emer-gency passage of fluids through the containment boundary while preserving the ability of the tmundary to prevent or limit the escape of fission prod'Jcts that may result from postulated accidents. This SRP section, therefore, is conce-ned with the isolation of fluid systems which penetrate the containment boundary, including the design and testing reoutrements for isolation barrters and actuators. Isolscion barriers include valves.
l closed piping systems, and blind flanges.
The C58 reviews the information presented ir. the applicant's safety analysis report (SAR) regarding containment isolation provisions to assure confomance with the requirements of General Design Criteria 54, 55, 56 and 57 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.e., the isolation valve arrange-ments and tPe physical location of isolation valves with respect to the containment.
b.
The actuation and control features for isolation valves.
a T14 positions of isolation valves for normal plant operating conditions (includ-c.
ing shutdown), post-accident conditions, and in the event of valve operator power failures.
d.
The valve actuation signals.
e.
The basis for selection of closure times of isolation valves.
USNRC STANDARD REVIEW PLAN
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a f.
The mechanical redundancy of isolation devices.
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g.
The acceptability of closed piping systems inside containment as isolation barriers.
2.
The protection provided for containment isolation provisions against loss of function from missiles, pipe wnip, and earthquakes.
i 3.
The emironmental conditions inside and outside the contairment that were considered in the design of isolation barriers.
4 The design criteria applied to isolation barriers and piping.
5.
The orovisions for detecting a possible need to isolate remote-manual-contmlied systems, such as engineered safety features systems.
6.
The design provisions for and technical specifications' pertaining to operability and leakage rate testing of the isolation barriers.
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7.
The calculation of containment atmosphere released prior to isolation valve closure for lines that provide a direct path to the environs.
PS8 nas primary responsibility for the qualification test program for electric valve operators, and the ICS8 has primary responsibility for the qualification test program for the sensing and e.ctuation instrumentation of the plant protection system located both inside and outside of containment. The ME8 has review responsibility for the qualifica-tion test program to demonstrate the perfomance and reliability of containment isolation valves. The ME8 and SE8 have review responsibility for mechanical and structural design l
of the containment isolation provisions to ensure adequate protection against missiles, pipe whip, and earthquakes. The AA8 reviews the rac(J1ogical dose consequence analysis for the release of containment atmosphere prior to closure of containment isolation valves in lines that provide a direct path to the environs. The R58 reviews the closure time for containment isolation valves in Ifnes that provide 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 the primary containment boundary. In general, two isolation barriers in series-are required to assure that the isolation function is satisfied assuming any single active failure in the containment isolation provisions.
The design of the containment isolation provisions will be acceptable to CS8 if the following criteria are satisfied:
1.
General Design Criteria 55 and 56 recuire that lines that penetrate the primary con-tainment boundary and either are part of t1e reactor coolant pressure boundary or Rev. 1 6.2.4-2
.. 2.
connec*. directly to the containment atmospnere should be provided with isolation valves as follows:
Onelockedclosedisolationvalve1# inside and one locked closed isolation a.
valve outsit.e 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 valveE#
c.
outside containment; or d.
One automatic isolation valve inside and one automatic isolation valveI#
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
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connected directly to the containment atmosphere should be provided with at least one locked closed, remote-manual, or automatic isolation valveI#outside containment.
l 3.
Tk general design criteria permit containment isolation provisions for lines pene-trating the primary containment boundary that differ from the expilcit requirements of General Design Criteria 55 and 56 f f the basis for acceptability is defined.
Following are guidelines for acceptable alternate containment isolation provisions for certain classes of lines:
a.
Regulatory Guide T.11 describes acceptable containment isolation provisions for j
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 4
containment.
c.
Containment isolation provisions for lines in systems needed for safe shutdown of the plant (e.g.,11ould 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.
ytoexeo closed isolacion valves are defined as sealed closed barriers (see item II.3.f).
j/A sim le check valve is not normally an acceptable automatic isolation valve for this application.
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d.
Containment isolation provisions for lines in the systems identified in itses b and c normally consist of one isolation valve inside and one isolation valve outside containment. If it is not practical to locate a valve inside contain-ment (for example, the valve may be under water as 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-tight or controlled leakage housing. If, in lieu of a housing, conservative design of the piping and valve is asstmed 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 nonsally consist of two isolation valves in series. A single isolation valve will be acceptable if it can be l
shown that the systes reliability is greater with only one isolation valve in the Ifne, the system is closed outside containment, and a single active failure can be accommodated with only one isolation valve in the line. The closed
'i 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 cor.tainment. The closed systee outside containment should be leak tasted, unless it can be showr= that the system integrity is being maintained 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 preclud= 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.
f.
Sealed closed barriers may be used in place of automatic isola 6 ion valves.
Sealed closed barriers include blind flanges and sealed closed isolation valves which may be closed annual valves, closed remote-manual valves, and closed autoestic valves which remain closed after a loss-of-coolant accident. Sealed closed isolation 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, g.
Relief valves may be used at isolation valves provided the relief set point is greater than 1.5 times the containment design pressure.
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4.
Isolation valves outside containment should be located as close to the containment l
as practical, 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 or 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 failure to the valve operator should be the " safe' position. Nomally 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
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be equipped with radiation monitors that are capable of isolating these lines upon a high radiation signal. A high radiation signal should not be considered one of the diverse containment isolation parameters.
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8.
Containment isolation valve closure times should be selected to assure rapid isola-tion of the containment following postulated accidents. The valve closure time is i
the time it takes for a power operated valve to be in the fully closed position i
after the actuator power has reached the operator assembly; it does not include the l
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-
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bilities should be considered in establishing valve closure times. For lines which i
provie's an open path from the containment to the environs; e.g., the containment prae and vent lines, isolation valve closure times on the order of 5 seconds or less may be necessary. The closure times of taese valves should be established on r
the basis of minimizing the release of containment atmosphere to the environs, to f
mitigate the offsite radiological consequences, and assure that emergency core cooling system (ECCS) effectiveness is not degraded 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
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provided to hstify the selected valve closure time. Additional guidance on the design and use of containment purge systems which may be used during the normal I
plant operating modes (f.e., startup, power operation, hot standby and hot shutdown) l' 1s provided in Branch Technical Position CS8 6-4 (Ref. 9). For plants under review for operating licenses or plants for which the Safety Evaluation Report for construc-tion permit apolication was issued prior to July 1,1975, the methods described in Section 8, Items 8.1., a, b, d, e, f, and g, 8.2 through 8.4, ano 8.5.b. c, and d of Branch Tecenical Position 6-4 should be isolemented. For these plants, BTP Items 8.1.c and 8.5.a. regarding the size of the purge system used during namel pit..t j
operation and the justificatrion by acceptable dose consecuence analysis, may be l
6.2.4-5 Rev. 1 L
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P waived if the appiteant commits 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 snould be incorporated into the Technical Specifications used in the operation of tne plant.
9.
The use of a closed system inside containment as one af the isolation barriers will be acceptante if the design of the closed system satisfies the following requirements:
t a.
The systes 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 is designated selseic Category 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 CSS is concerned with the structural design of containment internal structures and piping systees, the prntaction of isolation barriers against loss of function from missiles, pipe whip, and earthquakes will be acceptabit if isolation barriers are located behind missile barriars, pipe whip was considered in the design of pipe restraints and the location of piping penetrating the containment, and the
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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 salsaic Category I, in accorsance with Regulatory Guide 1.29.
Rev. I 6.2.4-6 m
- 11. The desiga 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, ar4 radiation level.
- 12. Provisions should be made in the oesign of the containment isolation system for l
operacility 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 safsty 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 otur branches, the acceptance criteria and their methods of application are contained in the SRP sections corresponding to those branches.
t III. REVIEW PROCEDURES The procedures oescribed 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 particular case. Portions of the review may be done on s 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 isolation pro isions.
Upon request from the primary reviewer, the seconcary review branches will provide input 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 acceptacility of the containment isolation systes by comparing the system design criteria to the design requirements for an engineered safety feature. The quality standaros and the seismic design classification of the containment isolation pro-visions, including the 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 isolation of the containment.
This is accomplished by reviewing the containment isolation provisions for eac'h line 6
penetrating the containment to determine that two isolation barriers in series are provided, and in conjunction with the PSB by reviewing the power sources to the valve operators.
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The CSB reviews the information in the SAR justifying containment isolation provisions which differ from the explicit requirements of Gsneral Design Criteria 55, 56 and 57.
The CSB judges the acceptacility of these containment isolation provisions based on a comparison with the acceptance criteria given in subsection II.
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The C58 reviews the position of isolation valves for normal ankshutdown plant operating conditions, post-accident conditions, and valve operator power failure conditions as Ifsted in the SAR. The position of an isolation valve for each of the above conditions 6
depends on the systes function. In general, power-operated 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 he the position of greater safety, which is normally the post-accident position. However, special cases may arise and these will be considered on an individual basis in detemining the acceptability of the prescribed valve positions. The C58 also ascertains from the SAR that all power-operated isolation valves have position indication capability in the main control roce.
The C58 reviews the' signals obtained from the plant protection systen to initiate contain-ment isolation. In general, there should be a diversity of parameters sensed; e.g.,
abnormal conditions in the reactor coolant systes, the secondary coolant system, and the containment, which generate containment isolation signals. Since plant designs differ in this regard and many different combinations of signals from the plant protection system are used to initiate containment isolation, the C58 considers the arrangement proposed on an individual basis in determining the overall acceptability of the containment isolation signals.
The C58 reviews isolation valve closure times. In general, valve closure times should be less than one minute, regardless of valve size. (See the acceptance criteria for valve closure times in subsection II.) Valves in Ifnes that provide a direct path to the l
environs, e.g., the containment purge and ventilation systes lines and main steam ifnes for direct cycle plants, may have to close in times much shorter than one minute. Closure times for these valves may be dictated by radiological dos; analyses or ECCS performance considerations. The C58 will request the AA8 or RS8 to review analyses justifying valve closure times for these valves as necessary.
The C58 determines the acceptability of the use of closed systems inside containment as isolation barriers by comparing the systes designs to 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 piping systems, including restraints, to assure that the contain-ment isolation provisons are adequately protected against missiles, pipe whip, and earth-quakes. The C58 determines that for all containment isolation provisions, missile pro-taction and protection against loss of function from pipe whip and earthquakes were design considerations. The C58 reviews the systes drawings (wnich should show the loca-tions of missile barriers relative to the containment isolation provis*2ns) to determine that the isolation provisions are protected from missiles. The C58 also reviews the design criteria applied to the containment isolation provisions to determine that protec-tion against dynamic effects, such as pipe whip and earthquakes, was cor.sidered in the design. The C58 will request the MEB to review the design adecuacy of piping and valves I
for which conservative design is assumed to preclude possible breach of system integrity in lieu of providing a leak tight housing.
Rev. 1 6.2.4-8 l
a 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 ostect leakage from these lines outsioe containment and to allow the operator in the main control room to isolate the system train should leakage occur. Leakage detection provisions may include instrumentation for measuring system flow rates, or the pressure, teamerature, radiation, or water level in areas outside the containment such as valve rooms or engi-neered safeguards areas. The CS8 bases its acceptance of the leakage detection provisions described in the SAR on the capacility to detect leakage and identify the lines that should be isolated.
The CS8 determines that the containment isolation provisions are designed to allow the isolation barriers to be individually leak testec. This information should be tabulated in the safety analysis report to facilitate the CS8 review.
The CSB determiSes from the descriptive information in the SAR that provisions have been made in the design of the containment isolation system to allow periodic operaDility testing of the power-operated isolation valves and the containment isolation system. At the operating license stage of review, the CS8 determines that the content and intent of proposed technical specifications pertaining to operability and leak testing of contain-ment isolation equipment is in agreement with requirements developed by the staff.
IV.
EVALUATION MNDINGS The informa. ton provided and the CS8 review should support concluding statements similar to the following, to be included in the stcff's safety evaluation report:
"Tha ses3e of review of the containment isolation system for the (plant name) has included schematic drawings and descriptive information for the isolation provisions l
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 furetional capability of the containment isolation system.
"The basis for the staff's acceptance has been the conformance of the containment isolation provisions to the Commission's regulations as set forth in the General l
Design Criteria, and to appitcable regulatory guides, staff technical positions, and l
industry codes and standards. (Special problems or exceptions that the staff takes to specific containment 1sesation 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 appicaele regulations, Guides, staff positions, and industry codes and standarcs, and is acceptable."
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REFERENCES 1.
10 CFR Part 50, Appendix A, General Design Criterion 54, " Piping Systems Penetrating Containment."
6.2.4-9 Rev. 1 1
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10 CFR Part 50, Appendix A, General Design Criterion 55, " Reactor Coolant Pressure Boundary Penetrating Containment."
3.
10 CFR Part 50, Appendix A, General Design Criterion 56, " Primary Containment Isolation."
4 10 CFR Part 50, Appendix A, General Design Criterion 57, " Closed Sys*m Isolation Valves."
5.
Regulatory Guide 1.141, " Containment Isolation Provisions For Fluid Systems."
6.
Regulatory Guide 1.11. " Instrument Lines Peoetrating Primary Reactor Containment."
7.
Regulatory Guide 1.26, " Quality Group Classifications and Standards for Water,
Stean, and Radioa dive-Weste-Containing Components of Nuclear Power Plants."
8.
Regulatory Guide 1.29, " Seismic Design Classification."
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9.
Branch Technical Position C58 6-4, " Containment Purging Ouring Normal Plant Opera-tions," attached to this SRP section.
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Branch Technical Position CSB 6-4 CONTAINMENT PURGING OURING NORMAL PLANT OPERATIONS A.
BACKGROUND This branch technical position pertains to system lines which can provide an open path from the containment to the environs during normal plant operation; e.g., the purge and vent lines of the containment purge system.. It fupplements the position taken in SRP section 6.2.4.
While the containment purge system provides plant operational flexibility, its design f
must consider the importance of minimizing the release of containment atmosphere to the environs following a postulated loss-of-coolant accident. Therefore, plant designs must not rely on its use on a routine basis.
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4 The need for purging has not always been anticipated in the design of plants, and there-l 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 purge system has been used in a variety of ways, for example, to alleviate certain operational problems, such as excess air leakage into the containment from pneumatic l
i controllers, for reducing the airborne activity within the contairment 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 or. 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 containment purging during normel plant operation. Under such conditions,
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calculated accident doses could be significant. Therefore, the use of these large contain-ment purge and went lines should be restricted to cold shutdown conditions and refueling operations, e
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6.2.4-11 Rev. 1 l
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2.
10 CFR Part 50, Appendix A, General Design Criterion 55, " Reactor Coolani. Pressure
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Boundary Penetrating Containment."
3.
10 CFR Part 50, Appendix A, General Design Criterion 56, " Primary Containment Isolation."
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 I.ines Penetrating Primary Reactor Containment."
7.
Regulatory Guide 1.26, " Quality Groep Classifications and Standards for Water,
Steas*, and Radioactive-Vaste-Containing Components of Nuclear Power Plar.ts."
8.
Regulatory Guide 1.29, " Seismic Design Classification."
9.
Branch Technical Positinn CSB 6-4, " Containment Purging Ouring Normal Plant Opera-tior.s," attached to this SRP section.
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The design and use of the purge and vent lines should be based on the premise of achieving arxoptable calculated offsf te radiological cor. sequences and assuring that emergency core cooling (ECCS) effectiveness is not aegraded by a reduction in the containment backpressure.
Purge system designs that are at.septacle for use on non-routine basis during normal plant operation can be =J..ieved by providing additional purge and vent lines. The size of these lines should be Ilmited such that in the event of a loss-of-coolant accident, assuming the purge and vent valves are open and subsequently close, the radiological consequences ".alculated in accordance with Regulatory Guides 1.3 and 1.4 would not exceed 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 following a LOCA.
The size of the purge and vent lines should De about eight inches in diameter for PWR
.I plants. This line size may be overly conservative from a radiological viewpoint for the f
Mark III 8WR plants and the HTGR plants because of containment and/or core design features.
Therefore, larger line sizes may be justified. However, for any proposed line size, the
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applicant must demonstrate that the radiological consequences following a loss-of-coolant accident would be within 10 CFR 100 guideline values. In sumstry, the acceptability of a specific line size is a function of the site meteorology, containment design, and radio-logical source term for the reactor type; e.g., BWR, PWR or HTGR.
B.
8 RANCH TECHNICAL POSITION The system used to purge the containment for the reactor operational modes of power operation, startup, hot standby and hot shutdown; 1.e., the on-line purge system, should be independent of the purge system used for the reactor operational modes of col ( shutdown and refueling.
I 1.
The on-line purge syste. should be designed in accordance with the following criteria:
a.
The performance and reliability of the purge system isolation valves should be l
ln consistent with the operability assurance program outlined in MES 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 containment pressure for the LOCA break spectrum, and i
the purge line and went line flows as a function of time to to anc 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 ifne.
The size of the purge and vent lines should not exceed About eight inches in c.
diameter unless detailed justification for larger line sizes is provided.
Rev. 1 6.2.4-12 m.
d.
The containment isolation provisions for the purge system Ifnes should meet the standards appropriate to ergineered safety features; i.e., quality, redundancy, testability and other appropriate criteria.
e.
Instrumentation and control systans provided to isolate the purge system lines should be independent and actuated Dy diverse parameters; e.g., cantainment pressure, safety injection actuation, and containment radiation level. If energy is required to close the valves, at least tise diverse sources of energy shall be provided, either of which can affect the isolation function.
f.
Purge system isolation valve closure 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 within 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 radiological 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 bn T
identified. The source term used in the radiological calculations should be
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based on a calculation under the terms of Appsndix K to determine the extent of fuel failure and the concomitant release of fission products, and the fission product activity in the primary coolant. A pre-exis*.ing fodine spike should be considered in determining primary coolant activity. The volume of containment I
in which fission products ce mixed should be justified, and the fission produc.s from the above sources should be assumed to be released through the open purge valves during the maximum interval required for valve closure. The radiological consequences should be within 10 CFR 100 guideline values.
1 b.
An analysis which denunstrates the acceptability of the provisions made to protect structures and safety-related equipment; e.g., fans, filters and duct-(
work, iocated beyond the purge system isolation valves against loss of function from the environment created by the esessing air and steam.
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d CONTAINMENT SYSTEMS r
BASES 3/4.6.1.8 CONTAINMENT VENTILATION SYSTEM i
The containment purge supply and exhaust isolation valves are required to be closed during prant operation since these valves have not bcon demonstrated capable of closing during a (LOCA or steam line break accident). Maintaining these valves closed during plant operations ensures that excessive quantities of radioactive materials will not be released via the containment purge system.
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c.
An analysis of the reduction in the containment pressure resulting from the partial loss of containment atmosphere during the accidert for ECCS backpressure determination.
d.
The allowable leak rates of the purge and went isolation valves should be specified for the spectrum of design basis pressures and flows against which the valves must close.
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CONTAINMENT SYSTEMS i
CONTAINMENT VE U ILATION SYSTEM (OPTIONAL *)
I LIMITING CONDITION FOR OPERATION 1
ir 3.6.1.8 The containment purge supply and exhaust isolation valves shall i
j be closed.
APPLICABILITY: MODES.1, 2, 3, and 4.
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ACTION:
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i With one containment purge supply and/or one exhaust isolation valve l
open, close the open valve (s) within one hour or be in at least NOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTCOWN within the follow-j ing 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
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SURVEILLANCE REQUIREMENTS 1
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i 4.6.1.8 The containment purge supply and exhaust isolation valves shall be detemined closed at least once per 31 days.
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