ML003740249

Regulatory Guide 1.82 (Draft Was Issued as DG-1038), Revision 2, Water Sources for Long-Term Recirculation Cooling Following Loss-Of-Coolant Accident

ML003740249
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Issue date:	05/31/1996
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RG-1.082, Rev 2
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2 RevIsion U.S. NUCLEAR REGULATORY COMMISSION Revision 2 May 1996

) REGULATORY GU IDE OFFICE OF NUCLEAR REGULATORY RESEARCH REGULATORY GUIDE 1.82 (Draft was Issued as DG-1038)

WATER SOURCES FOR LONG-TERM RECIRCULATION COOLING FOLLOWING A LOSS-OF-COOLANT ACCIDENT A. INTRODUCTION respect to the sumps and suppression pools performing the functions of water sources for emergency core General Design Criteria 35, "Emergency Core cooling, containment heat removal, or containment Cooling"; 36, "Inspection of Emergency Core Cooling atmosphere cleanup. The guide also provides guide System"; 37, "Testing of Emergency Core Cooling lines for evaluating the adequacy of the sump and System"; 38, "Containment Heat Removal"; 39, suppression pool for long-term recirculation cooling *

"Inspection of Containment Heat Removal System"; following a loss-of-coolant accident (LOCA). This and 40, "Testing of Containment Heat Removal guide applies to light-water-cooled reactors. Addi System," of Appendix A, "General Design Criteria for tional information is provided in NRC Bulletin 96-03, Nuclear Power Plants," to 10 CFR Part 50, "Domestic "Potential Plugging of Emergency Core Cooling Licensing of Production and Utilization Facilities," Suction Strainers by Debris in Boiling Water Reactors" require that systems be provided to perform specific (Ref. 1); NRC Bulletin 95-02, "Unexpected Clogging functions, e.g., emergency core cooling, containment of a Residual Heat Removal Pump Strainer While heat removal, and containment atmosphere clean up Operating in Suppression Pool Cooling Mode" (Rdf.

following a postulated design basis accident. These 2); NRC Bulletin 93-02, "Debris Plugging of Emer systems must be designed to permit appropriate gency Core Cooling Suction Strainers" (Ref. 3);

periodic inspection and testing to ensure their integrity Supplement 1 to NRC Bulletin 93-02, "Debris Plug and operability. General Design Criterion 1, "Quality ging of Emergency Core Cooling Suction Strainers" Standards and Records," of Appendix A to 10 CFR (Ref. 4); and Generic Letter 85-22, "Potential for Loss Part 50 requires that structures, systems, and com of Post-LOCA Recirculation Capability due to Insula ponents important to safety be designed, fabricated, tion Debris Blockage" (Ref. 5).

erected, and tested to quality standards commensurate with the importance of the safety functions to be This regulatory guide has been revised to alter the performed. debris blockage evaluation guidance for boiling water reactors (BWRs) because operational events, analyses, This guide describes methods acceptable to the

• Lines indicate substantive changes from Revision 1.

NRC staff for implementing these requirements with USNRC REGULATORY GUIDES Written eonTvTents may be submitted to the Rules Review and Directives Sranch. DFPS. ADM. U.S. Nuclear Regulatory Commission. Washing Regulatory Guides are Issued todescrbe and make available to the public to DoC 20555-0001.

such Information as methods acceptable to the NRC staff for knplement The guides are Issued in the following ten broad divisions:

ing specific parts of the Commisslon's regulations. technlques used by the staff In evaluating specific problems or postulated accldents, and 1. Power Reactors 6. Products data needed by the NRC staff In ts review of applications for permits and 2. Research and Test Reactors 7. Transportation licenses. Regulatoryguides are not substitutes for regulations. and com 3. Fuels and Materials FaclItles '. Occupational Health pliance with them Is not required. Methods and solution different from 4. Environmental and Siting 6. Antitrust and Financial Review those set out In the guides will be acceptable If they provide a basis for the S. Materials and Plant Protection 10. General findings requisite to the Issuance or continuance of a permit or license by Single copies of regulatory guldes maybe obtained free of charge by wrlt the Commission. ing the Office of Admnitstratlon. Attention: D*stribution a Servies Section, U.S. Nuclear Regulatory Commisslon. Washington, DC 20655-.0001; or by fax at (301)415-2260.

This guide was issued after consideration of comments receliv from the public. Comments and suggestions for improvemets in these guides are Issued guides may also be purchased from the National Technical Infor encouraged at all times. and guldes will be revised, as appropriate, to mation Service on a standing order basis. Details on this service may be accommodate comments and to reflect new Information or experieme. obtalned by writing NTIS. 628S Port Royal Road, Springfield, VA 22161.

and research work after the issuance of Revision I provide long-term post-LOCA core cooling is not indicated that the previous guidance was not compre jeopardized. All potential debris sources should be hensive enough to adequately evaluate a BWR plant's evaluated, including but not limited to insulation susceptibility to the detrimental effects caused by materials (e.g., fibrous, ceramic, and metallic), filters, debris blockage of the suction strainers. Only the corrosion material, foreign materials, and paints or sections concerning BWRs have been changed from coatings. Relevant information for such evaluations is Revision I. provided in the Regulatory Position and in Appendix A to this guide. References 6 through 18 provide The information collections mentioned in this additional information relevant to the above concerns.

regulatory guide are covered by the requirements in 10 CFR Part 50, which were approved by the Office of PRESSURIZED WATER REACTrORS Management and Budget, approval number 3150.

0011. In pressurized water reactors (PWRs), the contain ment emergency sumps provide for the collection of B. DISCUSSION reactor coolant and chemically reactive spray solutions following a LOCA; thus, the sumps serve as water GENERAL sources to effect long-term recirculation for the fimc tions of residual heat removal, emergency core cool The primary safety concerns regarding long-term ing, and containment atmosphere cleanup. These recirculation cooling following a LOCA are (1) water sources, the related pump inlets, and the piping LOCA-generated and pre-LOCA debris materials between the sources and inlets are important safety transported to the debris interceptors, resulting in components. The sumps servicing the ECCS and the adverse blockage effects, (2) post-LOCA hydraulic containment spray systems (CSS) are referred to in this effects, particularly air ingestion, and (3) the combined guide as ECC sumps. Features and relationships of effects of items. (1) and (2) on long-term recirculation the ECC sumps pertinent to this guide are shown in pumping operability (i.e., effect on net positive suction Figure 1.

head (NPSH) available at the pump inlet).

The design of PWR sumps and their outlets in Debris resulting from a LOCA with debris that cludes consideration of the avoidance of air ingestion exists before a LOCA could block the emergency core and other undesirable hydraulic effects (e.g., circula.

cooling (ECC) debris interceptors (i.e., trash racks, tory flow patterns, outlets leading to high head losses).

debris screens, suction strainers) and result in degrada The location and size of the sump outlets within ECC tion or loss of NPSH margin. Such debris can be sumps is important in order to minimize air ingestion divided into the following categories: (1) debris since ingestion is a function of submergence level and generated by the LOCA and transported by blowdown velocity in the outlet piping. It has been experimen.

forces (e.g., insulation, paint), (2) debris generated or tally determined for PWRs that air ingestion can be I transported by washdown, and (3) other debris that minimized or eliminated if the sump hydraulic design existed before a LOCA (e.g., corrosion material, considerations provided in Appendix A to this guide foreign material, sludge in a BWR suppression pool). are followed. References 6, 8, 11, and 13 provide Debris can be further subdivided into (1) debris that additional technical information relevant to sump ECC has a high density and could sink but is still subject to hydraulic performance and design guidelines.

fluid transport if local recirculation flow velocities are high enough, (2) debris that has an effective specific Placement of the ECC sumps at the lowest level gravity of 1.0 and tends to be suspended or sink slowly practical ensures maximum use of available recircula but will nonetheless be transported by very low tion coolant Since there may be places within the velocities or local fluid turbulence phenomena, and (3) containment where coolant could accumulate during debris that will float indefinitely by virtue of low the containment spray period, these areas can be density and will be transported to and possibly through provided with drains or flow paths to the sumps to the debris interceptors. prevent coolant holdup. This guide does not address the design of such drains or paths. Because debris can Debris generation, early debris transport, long-term migrate to the sump via these drains or paths, they are post-LOCA transport, and attendant blockage of debris best terminated in a manner that will prevent debris interceptors must be evaluated to ensure that the ability of the emergency core cooling systems (ECCS) to from being transported to and accumulating on or within the ECC sumps.

K-1.82-2

Figure 1. PWR WATER FROM 4:

SPRAY LOCA 4

}

SCREEN DEBRIS INTERCEPTORS RACK RECIRCULATION PUMP (o) - SUMP OUTLET (I) = PUMP INLET "4AS DETERMINED DURING SAFETY ANALYSIS "CUBICOR HORIZONTAL SUPPRESSOR MAY BE USED WITH EITHER SUMP OUTLET Containment drainage sumps are used to collect and withstand the differential pressure loads imposed by monitor normal leakage flow for leakage detection the accumulation of debris. Considerations for select systems within containments. They are separated from ing materials for the debris interceptors include long the ECC sumps and are located at an elevation lower periods of inactivity, i.e., no submergence, and periods than the ECC sumps to minimize inadvertent spillover of operation involving partial or full submergence in a into the ECC sumps from minor leaks or spills within fluid that may contain chemically reactive materials.

containment. The floor adjacent to the ECC sumps Isolation of the ECC sumps from high-energy pipe would normally slope downward, away from the ECC lines is an important consideration in protection sumps, toward the drainage collection sumps. This against missiles, and it is necessary to shield the downward slope away from the ECC sumps will screens and racks adequately from impacts of ruptured minimize the transport and collection of debris against high-energy piping and associated jet loads from the the debris interceptors. High-density debris may be .break. When the screen and rack structures are ori swept along the floor by the flow toward the trash ented vertically, the adverse effects from debris col rack. A debris curb upstream of and in close proximity lecting on them will be reduced. Redundant ECC to the rack will decrease the amount of such debris sumps and sump outlets are separated to the extent reaching the rack. practical to reduce the possibility that an event causing the interceptors or outlets of one sump to either be It is necessary to protect sump outlets with debris damaged by missiles or partially clogged could ad interceptors of sufficient strength to withstand the versely affect other pump circuits.

vibratory motion of seismic events, to resist jet loads and impact loads that could be imposed by missiles It is expected that the water surface will be above that may be generated by the initial LOCA, and to the top of the debris interceptor structure after comple-1.82-3

tion of the safety injection. However, the uncertainties pendix A to this guide provides information for esti about the extent of water coverage on the structure, the mating NPSH margins in PWR sump designs where amount of floating debris that may accumulate, and the estimated levels of air ingestion are low (2% or less).

potential for early clogging do not favor the use of a References 6 and 13 provide additional technical horizontal top interceptor. Therefore, in the computa findings relevant to NPSH effects on pumps perform tion of available interceptor surface area, no credit may ing the functions of residual heat removal, emergency be taken for any horizontal interceptor surface; prefera core cooling, and containment atmosphere cleanup.

bly, the top of the interceptor structure is a solid cover When air ingestion is 2% or less, compensation for its plate that will provide additional protection from effects may be achieved without redesign if the "avail LOCA-generated loads and is designed to provide for able" NPSH is greater than the "required" NPSH plus the venting of any trapped air. a margin based on the percentage of air ingestion. If air ingestion is not small, redesign of one or more of Debris that is small enough to pass through the the recirculation loop components may be required to trash rack and that could clog or block the debris achieve satisfactory design.

screens or outlets needs to be analyzed for head loss effects. Screen and sump outlet blockage will be a To ensure the operability and structural integrity of function of the types and quantities of insulation debris the racks and screens, access openings are necessary to that can be transported to these components. A verti permit inspection of the ECC sump structures and cal inner debris screen would impede the deposition or outlets. Inservice inspection of racks, screens, vortex settling of debris on screen surfaces and thus help to suppressors, and sump outlets, including visual ensure the greatest possible free flow through the fine examination for evidence of structural degradation or inner debris screen. Slowly settling debris that is small corrosion, should be performed on a regular basis at enough to pass through the trash rack openings could every refueling period downtime. Inspection of the block the debris screens if the coolant flow velocity is ECC sump components late in the refueling period will too great to permit the bulk of the debris to sink to the ensure the absence of construction trash in the ECC floor level during transport. If the coolant flow veloc sump area.

ity ahead of the screen is at or below approximately 5 cm/sec (0.2 ft/sec), debris with a specific gravity of BOILING WATER REACTORS 1.05 or more is likely to settle before reaching the screen surface and thus will help to prevent blockage In boiling water reactors (BWRs), the suppression of the screen. pool, in conjunction with the primary containment, downcomers, and vents, serves as the water source for The size of openings in the screens is dependent on effecting long-term recirculation cooling. This source, the physical restrictions that may exist in the systems the related pump suction inlets, and the piping between that are supplied with coolant from the ECC sump. them are important safety components. Features and The size of the mesh of the fine debris screen is relationships of the suppression pool pertinent to this determined by considering a number of factors, includ guide are shown in Figure 2. Concerns with the ing the size of the openings in the containment spray performance of the suppression pool hydraulics and nozzles, coolant channel openings in the core fuel ECC pump suction strainers include consideration of assemblies, and such pump design characteristics as air ingestion effects, blockage of suction strainers (by seals, bearings, and impeller running clearances. debris), and the combined effects of these items on the operability of the ECC pumps (e.g, the impact on As noted above, degraded pumping can be caused NPSH available at the pump inlets). References 6 and by a number of factors, including plant design and 12 provide data on the performance and air ingestion layout. In particular, debris blockage effects on debris characteristics of BWR suction strainer configurations.

interceptor and sump outlet configurations and post LOCA hydraulic conditions (e.g, air ingestion) must It is desirable to consider the use of debris intercep be considered in a combined manner. Small amounts tors (i.e., suction strainers) in BWR designs to protect of air ingestion, i.e., 2% or less, will not lead to severe the pump inlets and NPSH margins. The debris pumping degradation if the "required" NPSH from the interceptor can be a passive suction strainer or an pump manufacturer's curves is increased based on the active suction strainer or active strainer system. A calculated air ingestion. Thus it is important to use the passive suction strainer is a device that prevents debris, combined results of all post-LOCA effects to estimate which may block restrictions in the systems served by NPSH margin as calculated for the pump inlet. Ap- the ECC pumps or damage components, from entering 1.82-4

Figure 2. BWR with a Mark II Containment the ECC pump suction line by accumulating debris on LOCAs of different sizes will affect the duration of a porous surface. An example of a passive suction LOCA-related hydrodynamic phenomena (e.g., con strainer is a trmcated cone-shaped, perforated plate densation oscillation, chugging). The LOCA-related strainer. An active suction strainer or an active strainer hydrodynamic phenomena and long-term recirculation system is a device or system that will take some action hydrodynamic conditions will affect the transport of to prevent debris, that may block restrictions in the debris in the suppression pool. Debris that is trans systems served by the ECC pumps or damage compo ported to the suppression pool during a LOCA, or that nents from entering the ECC pump suction lines, is present in the suppression pool prior to a LOCA remove debris from the flow stream upstream of the (Refs. 19, 20, and 21), could block or damage the ECC pumps, or mitigate any detrimental effects of suction strainers and needs to be analyzed for head loss debris accumulation. Examples of active mitigation effects. This head loss analysis should include filter systems are listed in Appendix B. ing of particulate debris by the accumulated debris bed. The head loss characteristics of a debris bed will be a function of the types and quantities of the debris, Suppression pool debris transport analysis should suction strainer approach velocities, and LOCA-related include the effects of LOCA progression because hydrodynamic phenomena in the suppression pool.

1.82-5

C. REGULATORY POSITION distributed over the available debris screen area.

Blockage should be calculated based on estimated

1. PRESSURIZED WATER REACTORS levels of destruction (References 6 and 17).

Reactor building sumps that are designed to be a 1.8. Evaluation or confirmation of(1) sump hydrau source of water for the functions of emergency core lic performance (e.g., geometric effects and air inges cooling, containment heat removal, or containment tion), (2) debris effects (e.g., debris transport, intercep atmosphere cleanup following a LOCA should meet tor blockage, and head loss),, and (3) the combined the following guidelines. impact on NPSH available at the pump inlet should be performed to ensure that long-term. recirculation 1.1. A minimum of two sumps should be provided, cooling can be accomplished. Such an evaluation each with sufficient capacity to service one of the should arrive at a determination of NPSH margin redundant halves of the ECCS and CSS. calculated at the pump inlet. An assessment of the susceptibility of the recirculation pump seal and 1.2. To the extent practical, the redundant sumps bearing assembly design to failure from particulate should be physically separated by structural barriers ingestion and abrasive effects should be made to from each other and from high-energy piping systems protect against degradation of long-term recirculation to preclude damage to the sump components (e.g., pumping capacity.

racks, screens, and sump outlets) by whipping pipes or high-velocity jets of water or stean. 1.9. The top of the debris interceptor structures should be a solid cover plate that is designed to be 1.3. The sumps should be located on tei lowest floor fully submerged after a LOCA and completion of the elevation in the containment exclusive of the reactor ECC injection. It should be designed to ensure the vessel cavity. The sump outlets should be protected by venting of air trapped underneath the cover.

at least two vertical debris interceptors: (1) a fine inner debris screen and (2) a coarse outer trash rack to 1.10. The debris interceptors should be designed to prevent large debris from reaching the debris screen. withstand the vibratory motion of seismic events with A curb should be provided upstream of the trash racks out loss of structural integrity.

to prevent high-density debris from being swept along the floor into the sump. 1.11. The size of openings in the debris screens should be based on the minimum restriction found in 1.4. The floor in the vicinity of the ECC sump systems served by the pumps performing the recircula should slope gradually downward away from the tion function. The minimum restriction should take sump. into account the requirements of the systems served.

1.5. All drains from the upper regions of the reactor 1.12. Sump outlets should be designed to prevent building should terminate in such a manner that direct degradation of pump performance by air ingestion and streams of water, which may contain entrained debris, other adverse hydraulic effects (e.g., circulatory flow will not impinge on the debris interceptors. patterns, high intake-head losses).

1.6. The strength of the trash racks should be ade 1.13. Materials for debris interceptors should be quate to protect the debris screens from missiles and selected to avoid degradation during periods of inactiv other large debris. Debris interceptors should be ity and operation and should have a low sensitivity to capable of withstanding the loads imposed by missiles, such adverse effects as stress-assisted corrosion that by the accumulation of debris, and by pressure differ may be induced by the chemically reactive spray entials caused by post-LOCA blockage. during LOCA conditions.

1.7. The available interceptor surface area used in 1.14. The debris interceptor structures should include determining the design coolant velocity should be access openings to facilitate inspection of these struc calculated to conservatively account for blockage that tures, any vortex suppressors, and the sump outlets.

may result. Only the vertical interceptor area that is below the design basis water level should be consid 1.15. Inservice inspection requirements for ECC sump ered in determining available surface area. Fibrous components (i.e., debris interceptors, any vortex sup.

insulation debris should be considered as uniformly pressors, and sump outlets) should include (1) inspec-1.82-6

tion during every refueling period downtime and (2) a openings in the core fuel assemblies, and such pump design characteristics as seals, bearings, and impeller visual examination for evidence of structural distress running clearances will need to be considered in the or corrosion.

design to ensure long-term pump operability. An assessment should be performed to determine the

2. BOILING WATER REACTORS ECCS pumps' susceptibility to degradation from debris ingestion and abrasive effects, and actions 2.1 Features Needed To Minimize the Potential should be taken to minimize the potential for degrada for Loss of NPSH tion of long-term recirculation pumping capacity.

The suppression pool, which is the source of water 2.1.1.3. ECC pump suction inlets should be for such functions as emergency core cooling and designed to prevent degradation of pump performance containment heat removal following a LOCA, in through air ingestion and other adverse hydraulic conjunction with the vents and downcomers between effects (e.g., circulatory flow patterns, high intake head the drywell and the wetwell, should contain an appro losses).

priate combination of the following features and actions to ensure the availability of the suppression 2.1.1A. All drains from the upper regions of the pool for long-term cooling. Implementation of all the reactor building should terminate in such a manner that features and actions listed below is not required to direct streams of water, which may contain entrained ensure BWRs are not susceptible to the detrimental debris, will not impinge on the suppression pool effects of debris blockage. A plant may discover suction strainers.

through evaluation that only one of the features and actions listed below is required to ensure availability of 2.1.1.5. The strength of the suction strainers the suppression pool for long-term cooling. Also, a should be adequate to protect the debris screen from licensee is not limited to the features and actions listed missiles and other large debris. Each suction strainer below. The adequacy of the combinations of the should be capable of withstanding the loads imposed features and actions taken should be evaluated using by missiles, debris accumulation, and LOCA-induced the criteria and assumptions in Regulatory Position hydrodynamic loads.

2.2.

2.1.1.6. The suction strainers should be designed 2.1.1 Passive Strainers to withstand the vibratory motion of seismic events without loss of structural integrity.

The inlet of pumps performing the above functions should be protected by a suction strainer placed 2.1.1.7. Material for suction strainers should be upstream of the pumps; this is to prevent the ingestion selected to avoid degradation during periods of inactiv of debris that may block restrictions in the systems ity and normal operations.

served by the ECC pumps or damage components.

The following items should be considered in the design 2.1.2 Minimizing Debris and implementation of a passive strainer.

The amount of potential debris (see Regulatory 2.1.1.1. A suction strainer design (i.e., size and Position 2.3.1) that could block the ECC suction shape) should be chosen that will avoid the loss of strainers should be minimized. This may be accom NPSH from debris blockage during the period that the plished by:

ECCS is required to operate in order to maintain long term cooling or maximize the time before loss of 2.1.2.1. Containment cleanliness programs should NPSH caused by debris blockage when used with an active mitigation system (see Regulatory Position be designed to clean the suppression pool on a regular 2.1.4). basis and plant procedures should be designed for control and removal of foreign materials from contain ment, or 2.1.1.2. The size of openings in the suppression pool suction strainers should be based on the minimum 2.1.2.2. Debris interceptors in the drywell in the restrictions found in systems served by the suppression vicinity of the downcomers or vents may serve effec pool. The minimum restriction should take into account the operability of the systems served. For tively in reducing debris transport to the suppression example, spray nozzle clearances, coolant channel pool. In addition to meeting Regulatory Position 2.1.1, 1.82-7

debris interceptors between the drywell and wetwell that the operator has adequate indications, time, and should not reduce the suppression capability of the system capabilities to perform the actions required.

containment.

In addition to a combination of the features and 2.1.3 Instrumentation actions described above, procedures may be estab lished to use existing systems and sources of water If relying on operator actions to prevent the other than the suppression pool to provide injection accumulation of debris on suction strainers or to and long-term cooling to the core. Establishing mitigate the consequences of the accumulation of procedures to use alternate water sources will provide debris on the suction strainers, safety-related instru a diverse means of providing injection and long-term mentation that provides operators with an indication cooling to the core. Procedures to align alternate and audible warning of impending loss of NPSH for water sources may already be contained in emergency ECCS pumps should be available in the control room. operating procedures. Because of the importance of the ECCS cooling function, consideration should be 2.1.4 Active Strainers given to including the valves and piping needed to align alternate water sources in a plants' maintenance An active component or system (see Appendix B) program.

should be provided to prevent the accumulation of debris on a suction strainer or mitigate the conse 2.3 Evaluation of Long-Term Recirculation quences of accumulation of debris on a suction strain Capability er. An active system should be able to prevent debris that may block restrictions found in the systems served by the ECC pumps from entering the system. The During any evaluation of the susceptibility of a operation of the active component or system should BWR to debris blockage, the considerations and events not adversely affect the operation of other ECC com shown in Figures 3 and 4 should be addressed. The ponents or systems. following techniques, assumptions, and criteria should be used in a deterministic, plant-specific evaluation to 2.1.5 Inservice Inspections ensure that any implementation of a combination of the features and actions listed in Regulatory Position 2.1 Inservice inspections should be established that are adequate to ensure a reliable water source for long include (1) inspection during every refueling outage to term recirculation after a LOCA. Unless otherwise I ensure the cleanliness of the suppression pool (Ref. 2),

(2) a visual examination for evidence of structural noted, the techniques, assumptions, and criteria listed below are applicable to an evaluation of passive and degradation or corrosion of the suction strainers and active strainers. The assumptions and criteria listed strainer system, and (3) an inspection of the wetwell below can also be used to develop test conditions for and the drywell, including the vents, downcomers, and suction strainers or strainer systems.

deflectors, for the identification and removal of debris or trash that could contribute to the blockage of 2.3.1 Debris Generation and Sources suppression pool suction strainers.

2.3.1.1. Consistent with the requirements of 10 2.2 Evaluation and Alternate Water Sources CFR 50.46, debris generation should be calculated for a number of postulated LOCAs of different sizes, locations, and other properties sufficient to provide In order to demonstrate that a combination of the assurance that the most severe postulated LOCAs are features and actions listed above are adequate to ensure calculated.

long-term cooling and that the five criteria of 10 CFR 50.46(b) will be met following a LOCA, an evaluation 2.3.1.2. An acceptable method for detennining the using the criteria and assumptions in Regulatory shape of the zone of influence of a break is described Position 2.3 should be conducted. If a licensee is in NUREG/CR-6224 (Ref. 18). The volume contained relying on operator actions to prevent the accumulation within the zone of influence should be used to estimate of debris on suction strainers or to mitigate the conse the amount of debris generated by a postulated break.

quences of the accumulation of debris on the suction The distance of the zone of influence from the break strainers, an evaluation should be performed to ensure should be supported by analysis or experiments for the 1.82-8

( C Figure 3. Debris Blockage Considerations 00 tJ Bmak Jet Deftxft Break Jet Blast Debits

'0 model Liftsj' (TAuiueced Me Jtbto i ofD~ ed rmotdt H~~~mftnspolI

Figure 4. Events that May Effect Debris Blockage TIME > LOCA LOCA EVENT DEBRIS DRYWELL SUPPRESSION POOL SUPPRESSION ECCS (seconds) PROGRESSION GENERATION TRANSPORT PHENOMENA POOL TRANSPORT RESPONSE ro 00 C j C

If debris interceptors (see Regulatory Position 2.1.2.2) break and potential debris. The shock wave generated have been installed in the drywell, the amount of during postulated pipe break and the subsequent jet debris transported to the suppression pool can be less should be the basis for estimating the amount of debris than 100%. The amount of the reduction of the trans generated and the size or size distribution of the debris port of debris to the suppression pool should be generated within the zone of influence. quantified experimentally or analytically.

2.3.1.3. Identify all sources of fibrous materials in 2.3.2.2. It should be assumed that LOCA-induced the containment such as fire protection materials, phenomena (i.e., pool swell, chugging, condensation thermal insulation, or filters that are present during oscillations) will suspend all the debris assumed to be operation. in the suppression pool at the onset of the LOCA.

2.3.1.4. All insulation, painted surfaces, and 2.3.2.3. The amount or concentration of debris in fibrous, cloth, plastic, or particulate materials within the suppression pool should be calculated based on the the zone of influence should be considered debris amount of debris estimated to reach the suppression sources. Analytical models or experiments should be pool from the drywell and the amount of debris and used to predict the size of the postulated debris. foreign materials estimated to be in the suppression pool prior to a postulated break.

2.3.1.5. As a minimum, the following postulated break locations should be considered. 2.3.2.4. Credit should not be taken for debris settling until LOCA-induced turbulence in the suppres

" Breaks on the main steam, feedwater, and recircula sion pool has ceased. The debris settling rate for the tion lines with the largest amount of potential postulated debris should be validated analytically or debris within the expected zone of influence, experimentally.

"* Large breaks with two or more different types of 2.3.2.5. Bulk suppression pool velocity from debris within the expected zone of influence, recirculation operations, LOCA-related hydrodynamic phenomena, and other hydrodynamic forces (e.g., local

"* Breaks in areas with the most direct path between turbulence effects or pool mixing) should be consid the &ywell and wetwell, and ered for both debris transport, including settling, and suction strainer velocity computations.

"* Medium and large breaks with the largest potential particulate debris to insulation ratio by weight.

2.3.3 Strainer Blockage and Head Loss 2.3.1.6. The cleanliness of the suppression pool 2.3.3.1. Strainer blockage should be based on the and containment during plant operation should be amount of debris estimated using the assumptions and considered when estimating the amount and type of criteria described in Regulatory Position 2.3.1 and on debris available to block the suction strainers. The the debris transported to the wetwell (Regulatory potential for such material (e.g., corrosion products)

Position 2.3.2). This volume of debris, as well as other and foreign materials (e.g., tape, wire ties, wire, paper, materials that could be present in the suppression pool plastic) to impact head loss across the suction strainer prior to a LOCA, should be used to estimate the rate of should also be considered.

accumulation of debris on the strainer surface.

2.3.1.7. The amount of particulates estimated to 23.3.2. The flow rate through the strainer and the be in the pool prior to a LOCA should be considered concentration of debris in the suppression pool should the maximum amount of corrosion products (i.e., be used to estimate the rate of accumulation of debris sludge) expected to be generated sinc' the last time the on the strainer surface.

pool was cleaned. The size distribution and amount of particulates should be based on plant samples. 2.3.3.2. The suppression pool suction strainer area 2.3.2 Debris Transport should be used in determining the approach velocity and should conservatively account for blockage that may result. Unless otherwise shown analytically or 23.2.1. It should be assumed that all the postu experimentally, debris should be assumed to be uni-lated debris will be transported to the suppression pool.

1.82-11

formly distributed over the available suction strainer tion to licensees and applicants regarding the NRC surface (See Refs. 6, 17, and 18). staffs plans for using this regulatory guide.

2.33.4. The NPSH available to the ECC pumps Except in those cases in which an applicant pro should be determined using the conditions specified in poses an acceptable alternative method for complying the plant's licensing basis (e.g., Regulatory Guide 1.1 with specified portions of the Commission's regula (Ref. 22)). tions, the methods described in this guide, which reflects public comments, will be used in the evalua 2.3.3.5. Estimates of head loss caused by debris tion of all:

blockage should be developed from empirical data based on the strainer design (e.g., surface area and geometry), postulated debris (i.e., amount, size distri 1. Applications for final design approval of stan bution, type), and approach velocity. Any head loss dardized designs thatare intended for referenc correlation should conservatively account for filtration ing in future construction permit or combined of particulates by the debris bed. license applications and have not received approval by April 1996.

2.3.3.6. The performance characteristics of a passive or an active strainer for the debris types and 2. Plant modifications *that may affect the avail amounts postulated should be supported by appropriate ability of water sources for long-term recircula test data. tion (e.g., altering potential sources of debris or strainer/sump designs).

D. IMPLEMENTATION

3. Licensees' implementation of the requested The purpose of this section is to provide informa- actions in NRC Bulletin 96-03 (see Ref. 1).

1.82-12

REFERENCES

1. NRC Bulletin 96-03, "Potential Plugging of Emer 8. G.G. Weigand et al., "A Parametric Study of Containment Emergency Sump Performance,"

gency Core Cooling Suction Strainers by Debris in Boiling Water Reactors," USNRC, May 6, 1996.' NUREG/CR-2758 (SAND82-0624), USNRC, July 1982.2

2. NRC Bulletin No. 95-02, "Unexpected Clogging of a Residual Heat Removal Pump Strainer While 9. M.S. Krein ct al., "A Parametric Study of Con tainment Emergency Sump Performance: Re Operating in Suppression Pool Cooling Mode,"

USNRC, October 17, 1995.' sults of Vertical Outlet Sump Tests," NUREG/

• CR-2759 (SAND82-7062), USNRC, October 1982.2

3. NRC Bulletin No. 93-02, "Debris Plugging of Emergency, Core Cooling Suction Strainers,"

USNRC, May 11, 1993.' 10. M. Padmanabhan and G.E. Hecker, "Assess ment of Scale Effects on Vortexing, Swirl, and Inlet Losses in Large Scale Sump Models,"

4. NRC Bulletin No. 93-02, Supplement 1, "Debris Plugging of Emergency Core Cooling Suction NUREG/CR-2760 (ARL-48-82), USNRC, June 1982.2 Strainers," USNRC, February 18, 1994.'

11. M. Padmanabhan, "Results of Vortex Suppres

5. Generic Letter 85-22, "Potential for Loss of Post LOCA Recirculation Capability due to Insulation sor Tests, Single Outlet Sump Tests, and Mis celaneous Sensitivity Tests," NUREG/CR-2761 Debris Blockage," USNRC, December 3, 1985.'

(SAND82-7065), USNRC, September 1982.2

6. A.W. Serkiz, "Containment Emergency Sump Performance (Technical Findings Related to Unre 12. M. Padmanabhan, "Hydraulic Performance of Pump Suction Inlets for Emergency Core Cool solved Safety Issue A-43)," NUREG-0897, Revi ing Systems in Boiling Water Reactors,"

sion 1, USNRC, October 1985.2 NUREG/ CR-2772 (ARL-398A), USNRC, June 1982.2

7. J. Wysocki and R. Kolbe, "Methodology for Evalu ation of Insulation Debris Effects," NUREG/

CR-2791 (SAND82-7067), USNRC, September 13. P.S. Kammath, T.J. Tantillo, W.L. Swift, "An 1982.2 Assessment of Residual Heat Removal and Containment Spray Pump Performance Under Air and Debris Ingesting Conditions," NUREG/

1Copies of these documents are available for CR-2792 (CREARE TM-825), USNRC, Sep inspection or copying for a fee from the NRC Public tember 1982.2 Document Room at 2120 L Street NW., Washington DC; the PDR's mailing address is Mail Stop LL-6, 14. D.N. Brocard, "Buoyancy, Transport, and Head Washington, DC 20555; telephone (202) 634-3273; Loss of Fibrous Reactor Insulation," NUREG/

fax (202) 634-3343. CR-2982 (SAND82-7205), Revision 1, USNRC, July 1983.2 2Copies of these documents are available for inspection or copying for a fee from the NRC Public 15. W.W. Durgin and J. Noreika, "The Suscep Document Room at 2120 L Street NW., Washington, tibility of Fibrous Insulation Pillows to Debris DC; the PDR's mailing address is Mail Stop LL-6, Formation Under Exposure to Energetic Jet Washington, DC 20555; telephone (202) 634-3273; Flows," NUREG/CR-3170 (SAND83-7008),

fax (202) 634-3343. Copies of NUREG-series USNRC, March 1983.2 documents may be purchased at current rates from the U.S. Government Printing Office, P.O. Box 37082, 16. J.J. Wysocki, "Probabilistic Assessment of 0402-9328 (telephone (202) 512-1800); or from the Recirculation Sump Blockage Due to Loss National Technical Information Service by writing of-Coolant Accidents," NUREG/CR-3394, Vol NTIS at 5282 Port Royal Road, Springfield, VA umes 1 and 2 (SAND83-7116), USNRC, July 22161. 1983.2 1.82-13

17. D.N. Brocard, "Transport and Screen Blockage 21. NRC Information Notice 94-57, "Debris in Characteristics of Reflective Metallic Insulation Containment and the Residual Heat Removal Materials," NUREG/CR-3616 (SAND83-7471), System," USNRC, August 12, 1994.1 USNRC, January 1984.2

18. G. Zigler et al., "Parametric Study of the Poten 22. Regulatory Guide 1.1, "Net Positive Suction tial for BWR ECCS Strainer Blockage Due to Head for Emergency Core Cooling and Contain LOCA Generated Debris," NUREG/CR-6224 ment Heat Removal System Pumps," USNRC, (SEA No. 93-554-06-A:1), USNRC, October November 2, 1970.3 1995.2

19. NRC Information Notice, 95-47, "Unexpected 3Requests for single copies should be made in Opening of a Safety/Relief Valve and Compli writing to the U.S. Nuclear Regulatory Commission, cations Involving Suppression Pool Cooling Washington, DC 20555, Attention: Distribution and Strainer Blockage," USNRC, October 4, 1995.1 Mail Services Section; requests may also be faxed to (301) 415-2260. Copies of NRC documents are also

20. NRC Information Notice 95-06, "Potential available for inspection or copying for a fee from the Blockage of Safety-Related Strainers by Mate NRC Public Document Room at 2120 L Street NW.,

rial Brought Inside Containment," USNRC, Washington, DC 20555; telephone (202) 634-3273; January 25, 1995.' fax (202) 634-3343.

1.82-14

APPENDIX A GUIDELINES FOR REVIEW OF WATER SOURCES FOR EMERGENCY CORE COOLING Water sources for long-term recirculation should be 3. Use of vortex suppressors to reduce air ingestion evaluated under possible post-LOCA conditions to effects to zero.

determine the adequacy of their design for providing long-term recirculation. Technical evaluations can be For PWRs, zero air ingestion can be ensured by use subdivided into (1) sump hydraulic performance, (2) of the design guidance set forth in Table A-I. Determi LOCA-induced debris effects, and (3) pump perfor nation of those designs having ingestion levels of 2%

mance under adverse conditions. Specific consider or less can be obtained using correlations given in ations within these categories, and the combination Table A-2 and the attendant sump geometric envelope.

thereof, is shown in Figure A-I. Determination that Geometric and screen guidelines for PWRs are con adequate NPSH margin exists at the pump inlet under tained in Tables A-3.1, A-3.2, A-4, and A-5. Table all postulated post-IOCA conditions is the final A-6 presents design guidelines for vortex suppressors criterion. that have shown the capability to reduce air ingestion to zero. These guidelines (Tables A-1 through A-6) were developed from extensive hydraulic tests on SUMP HYDRAULIC PERFORMANCE full-scale sumps and provide a rapid means of assess ing sump hydraulic performance. If the PWR sump Sump hydraulic performance (with respect to air design deviates significantly from the design bound ingestion potential) can be evaluated on the basis of aries noted, similar performance data should be ob submergence level (or water depth above the PWR tained for verification of adequate sump hydraulic sump or BWR suction strainer outlets) and required performance.

pumping capacity (or pump inlet velocity). The water depth above the pipe centerline (s) and the inlet pipe For BWRs, full-scale tests of suppression pool velocity (U) can be expressed nondimensionally as the suction strainer screen outlet designs for recirculation Froude number: pumps have shown that air ingestion is zero for Froude numbers less than 0.8 with a minimum submergence of U 6 feet, and operation up to a Froude number 1.0 with Froudenumber = the same minimum submergence may be possible before air ingestion levels of 2% may occur (Refs. A- I and A-2).

where g is the acceleration due to gravity. Extensive experimental results have shown that the hydraulic performance of ECC sumps (particularly the potential LOCA-INDUCED DEBRIS EFFECTS for air ingestion) is a strong function of the Froude number. Other nondimensional parameters (e.g., Assessment of LOCA debris generation and the Reynolds number and Weber number) are of secondary determination of possible debris interceptor blockage importance. is complex. The evaluation of this safety question is dependent on the types and quantities of insulation Sump hydraulic performance can be divided into employed, the location of such insulation materials three performance categories: within containment and with respect to the sump or suppression pool strainer location, the estimation of

1. Zero air ingestion, which requires no vortex sup quantities of debris generated by a pipe break, and the pressors or increase of the "required" NPSH above migration of such debris to the interceptors. Thus that from the pump manufacturer's curves. blockage estimates (i.e., generation, transport, and head loss) are specific to the insulation material, piping

2. Air ingestion of 2% or less, a conservative level at layout, and the plant design.

which degradation of pumping capability is not expected based on an increase of the "required" Since break jet forces are the dominant debris NPSH (see Figure A-2). generator, the predicted jet envelope will determine the 1.82-15

quantities and types of insulation debris. Figure A-2 in the range of 1% to 3%. A 2% limit on allowed air provides a three-region model that has been developed ingestion is recommended since higher levels have from analytical and experimental considerations as been shown to initiate degradation of pumping capac identified in References A-I and A-3. The destructive ity.

results (e.g., volume of insulation and other debris generated, size of debris) of the break jet forces will be The 2% by volume limit on sump air ingestion and considerably different for different types of insulation, the NPSH requirements act independently. However, different types of installation methods, and distance air ingestion levels less than 2% can also affect NPSH from the break. Region I represents a total destruction requirements. If air ingestion is indicated, correct the zone; Region H represents a region where high levels NPSH requirement from the pump curves by the rela of damage are possible depending on insulation. type, tionship:

whether encapsulation is employed, methods of attachment, etc.; and Region III represents a region NPSH,.ý.p.,%) = NPSH...M x.

where dislodgement of insulation in whole, or as fabricated, segments is likely occur. References A-i where 13= 1 + 0.50cr and cx is the air ingestion rate (in and A-3 provide a more detailed discussion of these percent by volume) at the pump inlet flange.

considerations. References A-I and A-3 through A-7 provide more detailed information relevant to assess ing debris generation and transport. COMBINED EFFECTS PUMP PERFORMANCE UNDER ADVERSE As shown in Figure A-1, three interdependent CONDITIONS effects (i.e., sump or suction strainer performance, debris generation and transport, and pump operation The pump industry historically has determined under adverse conditions) require evaluation for NPSH requirements for pumps on the basis of a detmnining long-term recirculation capability (i.e, percentage degradation in pumping capacity. The loss of NPSH margin).

percentage has at times been arbitrary, but generally is 1.82-16

FIGURE A-i. Technical Considerations Relevant to PWR ECC Sump Performance DEBRIS SUMPS PUMPS

"*Types. Chantitles. and Location "Loncado in Plant;

• Purp Design end Openning af insulation Redundancy Ck~anerlstica

"*Containment Layout WndUrek "* *eomelric Parameters a PISH flaquiremena NoAk' Locations

"*Estimated Quantity o@Dabris "aIntereptoes (eacks. Screens). aLump and Suction Piping . Losses Genereted . Cover. met.

1.82-17

FIGURE A-2. Multiple Region Insulation Debris Model for PWRs

/I I

I Circular Cylinder

~I LA Originating at the IPostulated oundary ofPipe a Right Break REGION I ' REGION II I REGION iII Total High Levels of I Clamage Possible.

• Dislodging in Destruction "As-Fabricated" I Materials and I Pieces or Attachment Segments Dependent I a . I I rd Eta S. . . . aI I Pressure Isobars Shown Are Calculated I Target Pressures for Break Conditions of 150 Bars and 35'K I Subcooling RID R Radius of Circular Flat Plate Target Bar L Distance D From Break to Target I. D - Diameter of Broken Pipe Pstag 0.5 pal of Major Wall Boundary 1.82-18

TABLE A-I PWR HYDRAULIC DESIGN GUIDELINES FOR ZERO AIR INGESTION item Horizontal Outlets Vertical Outlets Minimum Submergence, a (ft) 9 9 (in) 2.7 2.7 Maximum Froude Number, Fr 0.25 0.25 Maximum Pipe Velocity, U (ft/s) 4 4 (m/s) 1.2 1.2 NOE: These guidelines were established using experimental results from References A-8, A-9, and A-10 and are basea on mmps having a right rectangular shape.

Trash Rack 0 and Debris Screen Fr = U 1.82-19

TABLE A-2 PWR HYDRAULIC DESIGN GUIDELINES FOR AIR INGESTION <2%.

Air ingestion (c) is empirically calculated as a-a. + (a, x Fr) where c. and a, are coefficients derived from test results as given in the table below Horizontal Outlets Vertical Outlets' Item Dual Single Dual Single Coefficient at -2.47 -4.75 -4.75 -9.14 Coefficient &1 9.33 18.04 18.69 35.95 Minimum Submergence, a (ft) 7.5 8.0 7.5 10.0 (in) 2.3 2.4 2.3 3.1 Maximum Froude Number, Fr 0.5 0.4 0.4 0.3 Maximum Pipe Velocity, U (ft/s) 7.0 6.5 6.0 5.5 (na/s) 2.1 2.0 1.8 1.7 Maximum Screen Face Velocity (blocked and minimum submergence) (ftas) 3.0 3.0 3.0 3.0 (m/3) 0.9 0.9 0.9 0.9 Maximum Approach Flow Velocity (ft/a) 0.36 0.36 0.36 0.36 (M/S) 0.11 0.11 0.11 0.11 Maximum Sump Outlet Coefficient, C, 1.2 1.2 1.2 1.2 Cover Plate Trash Rack i" , ,creeand

.. / Debris Screen.

P1=

1.82-20

TABLE A-3.1 PWR GEOMETRIC DESIGN ENVELOPE GUIDELINES FOR HORIZONTAL SUCTION OUTLETS Size Su___ Outlet Position" Screen sump Out Min. Area let Aspect Min. Perimeter (ft) (in) *(t e/d (B-Mcyd c/d b/d td ejd Ratio (m-)

Dual I tos 36 11 >4 75 7

>1 >3 >1.5 >1 >1.5 Single Ito5 16 4.9 35 3.3 NOTE: Dimensions arc always measured to pipe centerline.

• Preferred location.

Trash Rack and Debris Sc renlI II II Is II Aspect 8 3i1o0

- ./B Mi nImum Perimeter - 21L - B) 1.82-21

TABLE A-3.2 PWR GEOMETRIC DESIGN ENVELOPE GUIDELINES FOR VERTICAL SUCTION OUTLETS Size Sump Outlet Position' Screen Sump Out let Aspect Min. Perimeter Min. Area Ratio (ft) (m) ey/d (B-cy)/d c/d b/d fd e/d

.I ~ (ft) (M')

Dual I to5 36 11 >0 >4 75 7

>1 >1 >1 >1.5 Single I to5 16 4.9 <_1S-.5 35 3.3 NOTE: Dimensions are always measured to pipe centerline.

• Preferred location.

1.82-22

TABLE A-4

IADDITIONAL GUIDELINES RELATED TO SUMP SIZE AND PLACEMENT

1. The clearance between the trash rack and any wall or obstruction of length I equal to or greater than the length of the adjacent screen/grate (B, or LQ) should be at least 4 feet (1.2 meters).

2. A solid wall or large obstruction may form the boundary of the sump on one side only, i.e., the sump must have three sides open to the approach flow.

3. These additional guidelines should be followed to ensure the validity of the data in Tables A-1, A-2, A-3.1, and A-3.2.

e> I.s 4ft LS (min) L

• 8Sump Pit I II* Trash Rack

_and is: Debris Screen Trash Rack and Debris Screen 1.82-23

TABLE A-S PWR DESIGN GUIDELINES FOR INTERCEPTORS AND COVER PLATE

1. Screen area should be obtained from Tables A-3.1 and A-3.2.

2. Minimum height of interceptors should be 2 feet (0.61 meter).

3. Distance from sump side to screens, g. may be any reasonable value.

4. Screen mesh should be V1/4 inch (6.4 mm) or finer.

5. Trash racks should be vertically oriented 1-to 11/2-inch(25- to 38-rm) standard floor grate or equivalent

6. The distance between the debris screens and trash racks should be 6'inches (15.2 cm) or less.

7. A solid cover plate should be mounted above the sump and should fully cover the trash rack. The cover plate should be designed to ensure the release of air trapped below the plate (a plate located below the minimum water level is preferable).

NOTE: See Reference A-I.

Solid Cover Plate

..- . Trash Rack SDebris Screen

'A" Mesh (max) 1.82-24

TABLE A-6 PWR GUIDELINES FOR SELECTED VORTEX SUPPRESSORS

1. Cubic arrangement of standard 11/2-inch (30-mm) deep or deeper floor grating (or its equivalent) with a characteristic length, ,, that is at least 3 pipe diameters and with the top of the cube submerged at least 6 inches (15.2 cm) below the minimum water level. Noncubic designs with t, > 3 pipe diameters for the horizontal upper grate and satisfying the depth and distances to the minimum water level given for cubic designs arc acceptable.

2. Standard 1'a-inch (38-mm) or deeper floor grating (or its equivalent) located horizontally over the entire sump and containment floor inside the screens and located below the lip of the sump pit.

NOTE: Tests on these types of vortex suppressors at Alden Research Laboratory have demonstrated their capability to reduce air ingestion to zero even under the most adverse conditions simulated.

Design 11: Trash Rack and

. Top

• olid S Co ver Debris Screen

. '. Floor atoing IIj Floor Grating Trash dck and Debris Screen Trash Rack and Design 1P2: D Solid 17.- Top Cover ,.,. Oubria Screen 1.82-25

APPENDIX A REFERENCES A-I A.W. Serkiz, "Containment Emergency Sump A-5 W.W. Durgin and J.Noreika, "The Susceptibil Performance (Technical Findings Related to ity of Fibrous Insulation Pillows to Debris Unresolved Safety Issue A-43)," NUREG-0897, Formation Under Exposure to Energetic Jet Revision 1, USNRC, October 1985.4 Flows," NUREG/CR-3170 (SAND83-7008),

USNRC, March 1983.'

A-2 M. Padmanabhan, "Hydraulic Performance of Pump Suction Inlets for Emergency Core Cool A-6 J.J. Wysocki, "Probabilistic Assessment of ing Systems in Boiling Water Reactors," Recirculation Sump Blockage Due to Loss NUREG/CR-2772 (SAND82-7064), USNRC, of-Coolant Accidents," NUREG/CR-3394, Vol June 1982.' umes 1 and 2 (SAND83-71 16), USNRC, July 1983.'

A-3 G. Zigler et al., "Parametric Study of the Poten tial for BWR ECCS Strainer Blockage Due to A-7 D.N. Brocard, "Transport and Screen Blockage LOCA Generated Debris," NUREG/CR-6224 Characteristics of Reflective Metallic Insulation (SEA No. 93-554-06-A:1), USNRC, October Materials," NUREG/CR-3616 (SAND83-7471),

1995.' USNRC, January 1984.'

A-4 D.N. Brocard, "Buoyancy, Transport, and Head A-8 G.G. Weigand et al., "A Parametric Study of Loss of Fibrous Reactor Insulation," NUREG/ Containment Emergency Sump Performance,"

CR-2982 (SAND82-7205), Revision 1, NUREG/CR-2758 (SAND82-0624), USNRC, USNRC, July 1983.1 July 1982.1 A-9 M.S. Krein et al., "A Parametric Study of Con

'Copies of these documents are available for tainment Emergency Sump Performance: Re inspection or copying for a fee from the NRC Public sults of Vertical Outlet Sump Tests," NUREG/

Document Room at 2120 L Street NW., Washington CR-2759 (SAND82-7062), USNRC, October DC 20555; telephone (202) 634-3273; fax (202) 634 1982.1 3343. Copies of NUREG-series documents may be purchased at current rates from the U.S. Government A-10 M. Padmanabhan and G.E. Hecker, "Assess Printing Office, P.O. Box 37082, 0402-9328 (tele ment of Scale Effects on Vortexing, Swirl, and phone (202) 512-1800); or from the National Techni Inlet Losses in Large Scale Sump Models,"

cal Information Service by writing NTIS at 5282 Port NUREG/CR-2760 (SAND82-7063), USNRC, Royal Road, Springfield, VA 22161. June 1982.1 1.82-26

APPENDIX B EXAMPLES OF ACTIVE MITIGATION SYSTEMS In-Line (or Pipline' Strainer A strainer installed in the piping system, upstream of equipment, that will remove harmful objects and particulates from the fluid stream by a badckwashing action.

Self-Cleaning Strainer A strainer that is used upstream of equipment to filter out harmful objects and particulates and is designed to clean itself without external help.

Strainer Backwashing System A system designed to dislodge objects and particulates from the surface of a strainer by directing a fluid stream in the opposite direction of the flow through the strainer.

1.82427

REGULATORY ANALYSIS A separate regulatory analysis was not prepared for this Revision 2 to Regulatory Guide 1.82 since the guidance for pressurized water reactors has not been changed; the guide is being revised to clarify the type of analysis applicable to boiling water reactors. Therefore a new regulatory analysis is not needed. The regulatory analysis (NUREG-0869, Revision 1, "USI A-43 Regulatory Analysis," October 1985) that was prepared for the resolution of USI A-43, "Containment Emergency Sump Performance," is available for inspection or copying for a fee in the Commission's Public Document Room at 2120 L Street NW., Washington, DC 20555 (telephone (202)634-3273, fax (202)634-3343).

1.82-28