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Report CopyRight/DMCA Form For : Pwr Debris Transport In Ice Condenser Containments
LA UR 99 5111 Rev 1, PWR DEBRIS TRANSPORT IN ICE CONDENSER CONTAINMENTS. PHENOMENA IDENTIFICATION AND RANKING TABLES,B E Boyack PIRT Panel Chairman. T S Andreychek,P Griffith,F E Haskin,December 14 1999. LA UR 99 5111 Rev 1,LA UR 99 5111 Rev 1,Executive Summary. The United States Nuclear Regulatory Commission NRC has sponsored the. formation of a Phenomena Identification and Ranking Table PIRT panel to. identify and rank the phenomena and processes associated with the transport of. debris in a pressurized water reactor PWR containment following the initiation of. one or more accident sequences The PIRT documented herein will be used to. support decision making regarding analytical experimental and modeling efforts. related to debris transport within a PWR containment. The issue of degradation of long term cooling by debris transport and deposition was. considered during the early 1980s through efforts associated with unresolved safety. issue USI A 43 The accumulation of debris on sump screens or strainers will. increase the resistance to flow across the screen and thus reduce the net positive. suction head available to the emergency core cooling system ECCS pumps drawing. suction from the sump, In 1993 following several suction strainer debris blockage events at boiling water. reactor BWR stations the NRC initiated a reevaluation of the potential for loss of. coolant accident LOCA generated debris to block BWR suction strainers and. prevent the ECCS from performing its long term cooling function The BWR. focused evaluation concluded that debris generated during a LOCA might prevent. the ECCS from performing its long term cooling function It was determined that. the ECCS would not function as intended following events that generated and. transported debris to the BWR wetwell Based upon the results of the evaluation. effort the NRC issued bulletin 96 03 and Regulatory Guide 1 82 Revision 2. Given the insights developed from the BWR debris transport and blockage study. the NRC is now reassessing debris blockage of PWR sumps to determine if there is a. need for further actions to be taken for PWRs beyond the original resolution of USI. A 43 One element of the reassessment is the preparation of the PIRT documented. The PIRT development process facilitates the structured collection and. documentation of informed expert judgment with respect to phenomena. identification and ranking The quality and accuracy of a PIRT are directly related to. the expertise of the panel members and the technical database available to the panel. For this PIRT activity a modest database of experimental and technical results. existed to support the PIRT effort A vita for each member of the PIRT panel is. presented in Appendix A, There are a number of PWR containment types including large dry. subatmospheric and ice condenser An essential element of the PIRT process is that. the panel focuses on a specific containment design and accident scenario Once the. initial PIRT is completed other containment designs and plant types can be. considered building upon the base of the original PIRT PIRTs have previously been. prepared for large dry containments and the results have been reported in a. companion document See Section 2 Ref 2 2 For this PIRT the panel identified. the base configuration as a Westinghouse four loop PWR with ice condenser. LA UR 99 5111 Rev 1, containment The panel selected a double ended cold leg large break LOCA for the. baseline scenario, The event scenario was divided into three time phases blowdown between event. initiation and 40 s post blowdown between 40 s and 30 min and sump operation. between 30 min and 2 days Each phase was characterized with respect to physical. conditions key phenomena and processes and equipment operation. The containment was partitioned into five components 1 the containment upper. compartment open area 2 the containment lower compartment open area. excluding the potential pool in the bottom of the containment and the debris. generating zone of influence in the vicinity of the break 3 the containment lower. compartment structures and 4 the containment floor upon which a liquid pool. forms in the lower containment elevations and 5 the ice condenser. The panel identified a primary evaluation criterion for judging the relative. importance of the phenomena and processes important to PWR containment debris. transport The criterion was the fraction of debris mass generated by the LOCA that. is transported to the sump entrance Each phenomenon or process identified by the. panel was ranked relative to its importance with respect to the transportation of. debris to the sump entrance Highly ranked phenomena and processes were judged. to have a dominant impact with respect to the primary evaluation criterion. Medium ranked phenomena and processes were judged to have a moderate impact. with respect to the primary evaluation criterion Low ranked phenomena and. processes were judged to have a small impact with respect to the primary evaluation. The results of the panel s identification and ranking efforts are tabulated below All. processes and phenomena that were ranked as being either of Medium or High. importance relative to the primary evaluation criteria presented The High. ranked processes and phenomena are highlighted in bold type The complete. tabulation of processes and phenomena and the ranking for each are presented in. During the 40 s blowdown phase ten high ranked processes phenomena were. identified Pressure driven bulk flows in the containment lower compartment. open areas move debris advection to the ice condenser The dynamics of the pool. developing on the containment floor including agitation serves to keep debris. suspended and in movement They also promote the disintegration of any calcium. silicate insulation in the pool Debris enters the pool by transport within liquid. streams primarily the flows associated with the melting ice Steam and non. condensable flow pass into the ice condenser where essentially all the steam is. condensed so that only noncondensables pass into the upper compartment The. steam melts ice The resultant water flows backward into the containment lower. compartment carrying debris that had passed into the ice condenser. During the nearly 30 min post blowdown phase five high ranked. processes phenomena were identified The large scale flows associated with pool. LA UR 99 5111 Rev 1, dyamics and agitation of the pool on the containment floor keep the smaller debris. suspended in the pool Calcium silicate fragments erodes and disintegrates in the. agitated pool Both fiber and calcium silicate are subject to transport within the pool. prior to sump activation Heavier debris settles to the floor of the pool. During the period of sump operation beginning at 30 min and continuing to 48 h. seven high ranked processes phenomena were identified all of which occur in the. pool on the containment floor Pool thermal hydraulic processes of importance. were pool agitation by liquid streams still entering the pool from above and the. associated pool dynamics leading to re entrainment of debris that had settled to the. containment floor Transport of the debris to the sump following sump activation. and transport of debris over the sump curb to the trash rack were also of high. importance, A total of 22 processes phenomena were judged to be of medium importance. Although priority is naturally assigned to highly ranked processes and phenomena. the medium ranked processes and phenomena should also be considered when. planning experimental programs,Blowdown Phase 0 40 s. Component Phenomenon Phenomenon Rank, CONTAINMENT LOWER Thermal hydraulic related Pressure driven flows bulk flows H. COMPARTMENT OPEN Debris related Advection M,AREAS Entrapment space below ice condenser M. Gravitational settling M, CONTAINMENT Thermal hydraulic related Surface wetting condensation impact M. STRUCTURES IN Deluge streaming M, LOWER COMPARTMENT Debris related Deluge streaming transport M. Inertial impaction M L L L,Adhesion M L L L, CONTAINMENT FLOOR Thermal hydraulic related Pool agitation H. Pool dynamics H,Debris related Entry via liquid transport HIH H L. Reentrainment M M M L,Disintegration M H L L,Pool transport MJM M L. Entrapment M, ICE CONDENSER Thermal hydraulic related Steam and noncondensable flow H. Ice to liquid melting H,Liquid draindown M,Condensation H. Debris related Debris advection H H L L,Debris suspension MWMWLIL. Debris draining downward H H L L, D Multiple rankings appear e g L M L H fibrous calcium silicate reflective metallic insulation other where the. panel found it necessary to differentiate between debris types H M L are High Medium and Low importance. LA UR 99 5111 Rev 1,Post Blowdown Phase 40 s 30 min. Component Phenomenon Phenomenon Rank, CONTAINMENT LOWER Thermal hydraulic related None ranked H or M. COMPARTMENT OPEN Debris related None ranked H or M. CONTAINMENT Thermal hydraulic related Deluge streaming L M L L. STRUCTURES IN Debris related Deluge transport L M L L. LOWER COMPARTMENT Disintegration L M L L, CONTAINMENT FLOOR Thermal hydraulic related Pool formation M. Pool agitation H,Pool flow dynamics M H M L,Debris related Disintegration L H L L. Pool transport H H L L,Settling H H L L,Entrapment M. ICE CONDENSER Thermal hydraulic related Ice to liquid melting M. Condensation M,Debris related None ranked H or M,Post Blowdown Phase 40 s 30 min. Component Phenomenon Phenomenon Rank, CONTAINMENT LOWER Thermal hydraulic related None ranked H or M. COMPARTMENT OPEN Debris related None ranked H or M. CONTAINMENT Thermal hydraulic related None ranked H or M. STRUCTURES IN Debris related None ranked H or M,LOWER COMPARTMENT. CONTAINMENT FLOOR Thermal hydraulic related Pool agitation H. Pool flow dynamics H,Debris related Sump induced flow H. Reentrainment H,Disintegration L M LJL,Pool transport H H H H. Sump induced overflow H,Adhesion M, ICE CONDENSER Thermal hydraulic related None ranked H or M. Debris related None ranked H or M, T Multiple rankings appear e g L M L H fibrous calcium silicate reflective metallic insulation other where the. panel found it necessary to differentiate between debris types H M L are High Medium and Low importance. LA UR 99 5111 Rev 1,Acknowledgments, Several organizations and individuals were most supportive of the PIRT panel. efforts Although the PIRT panel maintained an independent and separate. perspective the panel acknowledges the help received from. Michael Marshall Jr of the NRC s Office of Nuclear Regulatory Research for his. help in facilitating the panel s understanding of needs as well as providing. invaluable assistance in each of the panel s meetings. D V Rao and Bruce Letellier and other staff of LANL Group TSA 11 for their. help in facilitating the panel s understanding of debris transport processes by. assisting in our review of plant designs experimental data and analytical results. Gary Wilson was the chairman of the counterpart boiling water reactor debris. transport PIRT panel Much of the structure and tables of the current document. is modeled after the final report of that effort Mr Wilson had the lead role in. preparing that document We also acknowledge the contributions of the other. members of the panel to the BWR debris transport PIRT document They are. Brent E Boyack Mark T Leonard Ken A Williams and Lothar T Wolf. Finally we thank Gloria E Mirabal of LANL Group TSA 10 for editing this report. 1119 66 Ufl VI,LA UR 99 5111 Rev 1,Nomenclature,B W Babcock and Wilcox. B WR Boiling Water Reactor,Cal Sil Calcium Silicate. CE Combustion Engineering,CFD Computational Fluid Dynamics. CL Cold Leg,DEGB Double Ended Guillotine Break,ECCS Emergency Core Cooling System. GSI Generic Safety Issue,HL Hot Leg,LB Large Break. L D Length to Diameter Ratio,LOCA Loss of Coolant Accident. LWR Light Water Reactor,MIT Massachusetts Institute of Technology. NA Not Applicable,NPP Nuclear Power Plant,NPSH Net Positive Suction Head. NRC United States Nuclear Regulatory Commission,NSSS Nuclear Steam Supply System. PIRT Phenomena Identification and Ranking Table,PWR Pressurized Water Reactor. RHR Residual Heat Removal,RMI Reflective Metallic Insulation. USI Unresolved Safety Issue,W Westinghouse,ZOI Zone of Influence. LA UR 99 5111 Rev 1,LA UR 99 5111 Rev 1,Executive Summary iii. Acknow ledgm ents vii,Nom enclature ix,Abstract 1 1. 1 IN TRO DU CTION 1 2,1 1 Background 1 2,1 2 PIRT Panel M embership 1 4. 1 3 PIRT Overview 1 4,1 4 PIRT O bjectives 1 6,1 5 References 1 6. 2 PIRT PRELIM IN AR IES 2 1,2 1 Selected Plant and Containm ent 2 1. 2 2 Ice Condenser Containm ent Description 2 2,2 3 Accident Scenario 2 4. 2 4 Scenario Phases 2 4,2 5 Containm ent Partitions Com ponents 2 8. 2 6 System Level Processes 2 9,2 7 Potential Debris Sources 2 9. 2 8 Primary Evaluation Criterion 2 11,2 9 Phenomena Ranking Scale 2 11. 2 10 References 2 12,3 DA TABA SES 3 1,3 1 Experim ental 3 1. 3 2 Analytical 3 10,3 3 Other 3 13,4 PWR DEBRIS TRANSPORT PIRTS 4 1. 4 1 Blowdow n 4 1,4 2 Post Blow down 4 2,4 3 Sump O peration 4 2. Appendix A Members of the PWR Debris Transport PIRT Panel A 1. Appendix B Phenomena Descriptions for PWR Debris Transport PIRTs B 1. Appendix C Ranking Rationales for PWR Debris Transport PIRTs C 1. LA UR 99 5111 Rev 1,Fig 1 1 Illustration of typical PIRT process 1 5. Fig 2 1 Component partitioning of PWR ice condenser containment 2 3. Fig 2 2 Break location in a W four loop plant with ice condenser containment 2 5. Fig B 1 Thermal hydraulic processes in PWR containment upper and. lower compartment open areas during the blowdown phase of. a CL LBLO CA B 8, Fig B 2 Transport deposition processes for debris in containment upper and. lower compartment open areas during the blowdown phase of a. C L LBLO CA B 9, Fig B 3 Thermal hydraulic processes on containment lower compartment. structures during the blowdown phase of a CL LBLOCA B 10. Fig B 4 Transport deposition processes for debris on containment lower. compartment structures during the blowdown phase of a CL LBLOCA B 11. Fig B 5 Thermal hydraulic processes on the basemat floor during the. blowdown phase of a CL LBLOCA B 12, Fig B 6 Transport deposition processes for debris on the basemat floor. during the blowdown phase of a CL LBLOCA B 13, Fig B 7 Ice condenser processes during the blowdown phase of a CL LBLOCA B 14. Fig B 8 Thermal hydraulic processes in PWR containment upper and. lower compartment open areas during the post blowdown phase. of a CL LBLOCA B 21, Fig B 9 Transport deposition processes for debris in containment upper and. lower compartment open areas during the post blowdown phase of a. CL LBLOCA B 22, Fig B 10 Thermal hydraulic processes on containment lower compartment. structures during the post blowdown phase of a CL LBLOCA B 23. Fig B 11 Transport deposition processes for debris on containment. lower compartment structures during the post blowdown phase. of a CL LBLO CA B 24, Fig B 12 Thermal hydraulic processes on the basemat floor during the. post blowdown phase of a CL LBLOCA B 25, Fig B 13 Transport deposition processes for debris on the basemat floor. during the post blowdown phase of a CL LBLOCA B 26. Fig B 14 Ice condenser processes during the post blowdown phase of. a CL LBLO CA B 27, Fig B 15 Thermal hydraulic processes in PWR containment upper and. lower compartment open areas during the sump operation phase. of a CL LBLOCA B 35,LA UR 99 5111 Rev 1,FIGURES cont. Fig B 16 Transport deposition processes for debris on containment upper. and lower compartment open areas during the sump operation. phase of a CL LBLOCA B 36, Fig B 17 Thermal hydraulic processes on containment lower compartment. structures during the sump operation phase of a CL LBLOCA B 37. Fig B 18 Transport deposition processes for debris on containment. lower compartment structures during the sump operation phase. of a CL LBLO CA B 38, Fig B 19 Thermal hydraulic processes on the basemat floor during the. sump operation phase of a CL LBLOCA B 39, Fig B 20 Transport deposition processes for debris on the basemat floor. during the sump operation phase of a CL LBLOCA B 40. Fig B 21 Ice condenser processes during the sump operation phase of. a CL LBLOCA B 41,Table 2 1 Description of Scenario Phases 2 6. Table 4 1 PWR Debris Transport Behavior 4 3, Table 4 2 PWR Debris Transport Blowdown Phase PIRT 0 40 s 4 4. Table 4 3 PWR Debris Transport Post Blowdown Phase PIRT 40s 30 min 4 7. Table 4 4 PWR Debris Transport Sump Operation Phase PIRT 30 min 48 h 4 10. Table B 1 Phenomena Descriptions for PWR Debris Transport during. Blowdown Phase PIRT B 2, Table B 2 Phenomena Descriptions for PWR Debris Transport during. Post Blowdown Phase PIRT B 15, Table B 3 Phenomena Descriptions for PWR Debris Transport during. Sump Operation Phase PIRT B 28, Table C 1 Ranking Rationales for PWR Debris Transport during Blowdown. Phase PIRT C 2, Table C 2 Ranking Rationales for PWR Debris Transport during Post Blowdown. Phase PIRT C 8, Table C 3 Ranking Rationales for PWR Debris Transport during. Sump Operation Phase PERT C 15,LA UR 99 5111 Rev I.
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