ML19221B135
| ML19221B135 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-75-087, NUREG-75-087-06.2.2, NUREG-75-87, NUREG-75-87-6.2.2, SRP-06.02.02, SRP-6.02.02, NUDOCS 7907120482 | |
| Download: ML19221B135 (8) | |
Text
NUREG 75/087
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U.S. NUCLEAR REGUi.ATORY COMMISSION i
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! "g 3 "w i STANDARD REVIEW PLAN OFFICE OF NUCLEAR REACTOR REGULATION
'5 SECTION 6.2.2 CONTAIhMENT HEAT REMOVAL SYSTEMS REVIEW RESPONSIBILITIES Primary - Containment Systems Branch (CSB)
Secondary Auxiliary Sv% ems Bi anch ( ASB)
'nstrumentation and Control Systems Branch (ICSB)
- cident Arial s's Branch ( AAS)
/
I.
AREAS OF REVIEW The CSB reviews the information in the applicant's safety analysis report (SAR) concern-ing containment heat removal under post-arcident conditions to assure conformance with the requirements of General Design Criteria 38, 39, 40 and 50.
The types of systems provided to reN.e heat from the containment include fan cooler systems, spray systems, and residual heat removal systems. These systems remove heat from the containment atmosphere and the containment sump water, or the water in the containment wetwell.
The CSB review includes the following analyses and aspects of containment heat removal system designs:
1.
Analyses of the ccnsequences of single component malfunction >
2.
Analyses of the available net positive suction head (NPSH) to the containment heat removal system pumps.
3.
Analyses of the heat removal capability of the spray water system.
4.
Analyses of the heat removal capability of fan cooler heat exchangers.
5.
The potential for surface fouling of fan cooler, recirculation, and residual heat removal heat exchangers, and the effect on heat exchanger performance.
6.
The quality group classification of each system.
7.
The seismic design classification of each system.
8.
The design provisions and proposed program for periodic inservice inspection and operability testing of each system or component.
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9.
The proposed technical specifications for each system.
10.
The instrumentation provideu to monitor system or component performance.
11.
The design of sumps for tmergency core cooling and containment spray systems.
12.
The effects of debris such as thermal insulation on rec rculating fluid systems.
i The ASB has the review responsibility for the secondary cooling systems which provide for heat removal from che containment systems to the ultimate heat sink.
The ASB is responsible for determining that the systems supplying cooling water to the heat ex-changers in the containment heat removal systems meet the design requirements for engineered safety features.
The ICSB has review responsibility for the sensing and actuatiun instrumentation for the containment heat removal systems (SRP Section 7.3) and for the qualification test pro-grams for their instrumentation.
The AAB reviews fission product control features of containment spray systems (SRP Section 6.5.2).
II.
ACCEPTANCE CRITERIA General Design Criteria 38, 39, 40 and 50 of 10 CFR Part 50, Appendix A, establish requirements for the design, periodic inspection and operability testing, ad f unctional capability of the containment heat removal systems (Refs.
1, 2, 3 and 4).
The items listed below amplify these general requirements and form the basis for the staff's detailed review of containment heat removal systems.
1.
The containment heat removal sy,tems should meet the redundancy and power source requirements for an engineered safety feature; i.e., the systems should be designed to accommodate a single active failure. The results of failure modes and etfects analyses of each system should assure that the system is capable of withstanding a single failure without loss of function. (Se Appendix A to 10 CFR Part 50, " General a
Design Criteria for Nuclear Power Plants," for the definition of Single Failure.)
2.
The recirculation spray system is reqJired to Circulate water in the containment in the long term (after about one hour) following a loss-of-coolant accident, and should be designed to accomplish this without pump cavitation occurring. Therefore, the net positive suction head available to tha recirculation pumps should be greater than the required NPSH. A supporting analysis should be presented in sufficient detail to permit the staff to determine the adequacy of the analysis and should show that the available NPSH is greater than the re'1uired NPSH.
The analysis will be acceptable if it is done in accordance with the guidelines of Regulatory Guide 1.1, i.e., is based on maximum expected temperature of the pumped fluid and with atmospheric pressure in the containment. For clarification, the analysis should be l
Rev. 2 6.2.2-2
based on the assumption that the containment pressure equals the vapor pressure of the sump water. This ensures that credit is not taken for containment pressuriza-tion during the transient.
The recirculation spray system for a subatmospheric containment is designed to start about five minutes after a loss-of-coolant accident, i.e.,
during the injec-tion phase of spray system operation. For subatmospheric containments, the guide-lines of Regulatory Guide 1.1 as defined above will apply after the injection phase has terminated, which occurs about one hour after the accident. Prior to termina-tion of the injection phase the N'SH analyses should include conservative predic-tions of the containment atmosphere pressure and sump water temperature transients.
3.
Analyses of the heat removal capability of the spray system should be based on the following considerations:
The locations of the spray headers relative to the internal structures.
a.
The arrangement of the spray nozzles on the spray headers and the expected b.
spray pattern.
c.
The type of spray nozzles used and tha nozzle atomizing capability, i.e.,
the spray drop size spectrum and mean drop size emitted from each type of nozzle as a function of differential pressure across the nozzle.
d.
The effect of dr;p residence time and drop size on the heat removal effective-ness of the spray droplets.
fhe spray systems should be dtsiy ad to assure that the spray header and nozzle arrangements produce soray patterns which maximize the containment volume covered and minimize the overlapping of the sprays.
4.
The design heat removal capability (i.e., heat removal rate vs. containment temper-ature) of fan coolers should be established on the basis of qualification tests on production units or acceptable analyses that take into account the expected post-accident environmental conditions and variations in major operating parameters such as the containment atmosphere steam-air ratio, condensation on finned surfaces, and c oling water temperature and flow rate.
The equipment housing and ducting as-sociated with the fan cooler system should be analyzed tu determine that the design is adequate to withstand the effects of containment pressure fol!owing a loss-of-coolant accident (see SRP Section 6.2.5).
Fan cooler system designs that contain components which do not have a post-accident safety function should be designed such that a failure of nom afety-related equipment will not prevent the fan cooler system from accomplishing its safety function.
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2 6.2.2-3
5.
The potential for surface fouling of the secondary sides of fan cooler, recircula-tion, and residual heat removal heat exchangers by the cooling water over the life of the plant and the effect of surface fouling on the heat removal capacity of the heat exchangers should be analyzed and the results discussed in the SAR.
The dnalysis Wi11 be acceptable if it is shown that provisions such as closed cooiine water systems are provided to prevent surface fauling or surface fouling has been accounted for in establi ning the beat removal capability of the heat exchangers.
6.
The containment heat re.noval systems should be designed, fabricated, erecteo, and tested to Group B quality standards, as recommended by Regulatory Guide 1.26.
7.
The containment heat removal systems should be designated Category I (seismic), as recommended by Regulatory Guide 1.29.
8.
Provisions should be made in the design of ccntainment heat removal systems for periodic inspection and operability testing of the systems and systam components such as pumps, valves, duct pressure reiieving devices, and spray nozzles. The inspection and test program will be acceptable if it is judged by the CSB to be consistent with that proposed for other engineered safety featurcs.
9.
Instrumentation should t,e provided to monitor containment heat removal system and system component performance under normal and accident conditicns. The instrumenta-tion should be capable of determining whether a system is performing its intended function, or a system train or component is malfunctioning and should be isolated.
The instrumentation should have adequatu range, accuracy and response to assure that the parameters can be tracked ar_ recorded. Regulatory Guide 1.97, "Instrumen-tation For Light Water Cooled Nuclear F]wer Plants To Assess Plant Conditions During and Following an Accident," should be followed.
10.
Provisions should be made to allow drainage of spray and emergency core cooling water to the sumps (recirculatior piping suction points). The design of protective screen assemblies around reciiculation piping suction points will be acceptable if it is capable of preventing debris from ente'ing the recirculation piping which could impair the performance of system pumps, valves, heat exchangers, or spray nozzles. Regulatory Guide 1.82 (Ref. 8) provides guidance on the design of sumps for emergency core cooling and containment spray systems.
For those areas of review identified in subsection I of this SRP sect, n as being the responsibility of other branches, the acceptanta 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 for the review of containment heat removal systems. 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 a Rev. 2 6.2.2-4 147 249
generic basis for aspects of heat removal systems common to a class of containments, or by adopting the results of previous reviews of plants with essentially the same system.
Upon request from the primary reviewer, the secondary review branches will provide input for the areas of review stated in subsection I.
The primary reviewer obtains and uses such input as required to assure that this re Jew procedure is complete.
CSB assures that the design and functional capability of the containment heat removal system conform to the requirements of General Design Criteria 38, 39, 40 and 50.
CSB determines the acceptability of a containment heat removal system design by review-ing failure modes and effects analyses of the system to be sure that all potential single f ailures have been identified and no sngle failure could incapacitate the entire system; comparing the quality standards applied to the system to Regulatory Guide 1.26; comparing the seismic design classification of the system to Regulatory Guide 1.29; reviewing qualification tests performed on system components such as fan coolers; review-ing the system design provisions for periodic inservice inspection and operability testing to ensure that the system and components are accessible for inspection and all active components can be tested; and reviewing the capability to monitor system perform-ance and control active components frcm the control room so that the operator can exer-cise control over system functions or isolate a malfunctioning system component.
For plants at the operating license stage of review, the CSB reviews the proposed tech-nical specifications for containment heat removal systems to assure that limiting condi-tions for operation and surveillance requirements satisfy the intent of General Design Criteria 39 and 40.
CSB reviews analyses of the net positive suction head available to the recirculation pumps since recirculation system operability is contingent upon adequate WPSH being available to preclude pump cavitation. CSB assures that calculations of the available NPSH are based on transient values of the suction head and the friction head.
The CSB determines that the assumption of containmer,t pressure being equal to the vapor pressure of the sump water, has been used in the available NPSH calculations. The CSB rev ews i
information provided by the applicant to identify and justify the conservatisims applied in determining the water level in the containment and the friction losses in the recircu-lation system suction piping. For example, the uncertainty in determining the free l
volume in the lower part of the containment that may be occupied by water, and the quantity of water that may be trapped by the reactor cavity and the refueling canal, shoLld be factored into the calculation of the suction head.
lhe CSB reviews analyses of the available NPSH for subatmospheric containments for the period prior to termination of the injection phase of containment spray to determine that containment pressure and sump water temperature transients have been conservatively used in the NPSH calculations. The CSB reviews information provided by the applicant to identify and justify the conservatisms in the analysis of the containment atmosphere pressure and sump water temperature transients. The CSB also reviews the conservatisms b*
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6.2.2-5 Pev. 2
used in determining the water lesel in the containment and the friction losses in the recirculation system piping.
The CSB compares the NPSH requirements for the containm:ent heat removal system pumps to the minimum calculated NPSH available to the pumps to assure that a positive margin is maintained. The CSB also reviews the preoperational test programs, and periodic in-service inspectio' and test programs, to verify that ade uate NP$H is available to the s
pumps and the continuing operability of the pumps during the lifetime of the plant.
If in the judgment of the CSB, the NPSH analyses were not done in a sufficiently conserva-tive manner, confirmatory analyses are performed using the CONTEMPT-LT computer code.
See Neferences 10, 11, and 12 for a description of this code.
The CSS also reviews the evaluation of the volume of the containment covered by the sprays and and the extent of overlapping of the sprays with respect to heat removal capabilities. A judgment will be made regarding the acceptability of the spray coverage and extent of overlapping; the volume of the containment covered by the sprays should be maximized and the extent of overlapping kept to a minimum. Elevation and plan drawings of the containment s'owing the spray patterns are used to determine coverage and overlapping.
In general, the design requirements for the spray systems with respect to spray drop size spectrum and mean drop size, spray drop residence time in the containment atmo-sphere, containment coverage by the sprays, and extent of overlapping of the sprays are more stringent when the acceptability of the system is being considered from an iodine removal capability standpoint rather than from a heat removal capability standpoint.
Consequently, when the iodine removal capability of the system is satisfied, the heat removal capability will be found acceptable. The Accident Analysis Branch is responsible for determining the acceptability of the iodine removal effectiveness of the sprays (See Standard Review Plan 6. S.2).
Since all plants do not use the containment sprays as a fic ion product removal system, the CSB reviews the system for cases where the system is use only as a heat
'moval system.
CSB reviews analyses of the heat removal capability of the spray system.
This capability is a function of the degree of thermal equilibrium attained by the spray water and the volume of the containment covered by the spray water.
The spray drop size and residence time in the containment atmosphere determine the degree of thermal equilibrium attained by the spray water. The CSB confirms the validity of the degree of thermal equilibrium attained using the following information: an elevation drawing of the containment showing the locations of the spray headers relative to the internal structures, including fall heights, and the results of the spray nozzle test program to determine the spectrum of drop sizes and mtan drop size emitted from the nozzles as a function of pressure drop across the nozzles.
O 147 251 Rev. 2 6.2.2-6
Reference 9 crsnbins information regarding the heating of spray drops in air-steam atmospheres which (yn be used to determine the validity of the degree of thermal equilibrium of tne spray water used in tne analyses.
CSB reviews the adequacy of provisions made to prevent overpressurization of fan cooler ducting following a loss-of-coolant accident (Standard Review Plan 6.2.5L CSB reviews the heat removal capability of the fan coolers. The test programs and calculation models used to determine the performance capability of fan coolers are reviewed for acceptability. If the secondary side of a f an coo!er heat exchanger is not a closed syst81, the CSB reviews the potential for surface fouling. The CSB determines whether or not surf ace fouling impairs the heat removal capability of a f an cooler.
CSB review. the system provided to allow drainage of containment spray water and emergency core cooling water to the recirculation suction points (sumps). CSB reviews the design of the protective screen assemblies around the suction points. CSB reviews plan and elevation drawings of the protective screen assemblies, showing the relative posi tions and orientations of the trash bars or gratiag and the stages of screening, to determine that the potential for debris cloaging the screening is minimized. CSB also reviews the drawings to dete-mine that suction points do not share the same screened enclosure. The effectiveness of the protective screen assembly will be determined by comparing the smallest mesh size of screening provided to the clogging potential of pumps, heat ex-changers, valves, and spray nozzles. The methods of attachment of the trash bars or grating and the screening to the protective screen assembly st ~ cture should be discussed in the SAR and shown on drawings. A discussion of the adequacy of the surface area of screening v n respect to assuring a low velocity of approach of the water to minimize the potentias for debris in the water being sucked against the screening should be presented. Regulatory Guide 1.82 (Ref. 8) presents guidelines for the acceptability of the design of containment sumps.
IV EVALUATION FINDINGS The reviewer verifies that sufficient information has been provided and that his evalua-tion supports conclusions of the following type, to be included in the staff's safety evaluation report:
"6.2.2 Containment Heat Removal Systems The containment heat removal systerr.s include (identify the systems).
"The scope of review of the containmen+. heat removal systems for the (plant name, has included system drawings and descriptive information. The review has included the applicant's proposed design bases for the containment heat removal systems, and the analyses of the functional capability of the systems.
"The basis for the staff's acceptance has been the conformance of system designs and design bases to the Commission's Regulations as set forth in the general design criteria, and to applicable regulatory guides, staff technical positions, and Hl qG o
6.2.2-7 Rev. 2
industry codes and standards. (Special problems or exceptions that the staff takes to the design or functional capability of the containment heat removal systems should be discussed.)
"The staff concludes that the design of the contair. ment heat removal systems conforms to all applicable regulations, guides, staff positions, and industry codes and standards, and is acceptable."
V.
REFERENCES 1.
10 CFR Part 50, Appendix A, General Cesign Criterion 38, " Containment Heat Removal."
2.
10 CFR Part 50, Appendix A. General Design Criterion 39, " Inspection of Containment Heat Remov31 System."
3.
10 CFR Part 50, Appendix A, General Design Crit (rion 40, " Testing of Containment Heat Removal System."
4.
10 CFR Part 50, Appendix A, General Design Criterion 50, "Containtent Design Basis."
5.
Regulatory Guide 1.1, "Nat Positive Suction Head for Emergency Core Cooling ana Containment Heat Removal System Pumps."
6.
Regulatory Guide 1.26, " Quality Group Classifi ations and Standards for Water,
Steam, and Radioactive-kaste-Containing Components of Nuclear Power Plants,"
Revision 1.
7.
Regulatory Guide 1.29, " Seismic Design Classification," Revision 1.
8.
Regulatory Guide 1.82, " Sumps for Emergency Core Cooling and Containment Spray Systems."
9.
L. F. Parsly, " Design Considerations of Reactor Containment Spray Systems - Part VI, The Heating of Spray Drops In Air-Steam Atmospheres," ORNL-1M-2412, Oak Ridge National Laboratory, January 1970.
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