Containment Filtered Venting - A new approach

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Presentation during IAEA Regional Workshop on Advanced Level 2 Probabilistic Safety Analysis Bulgaria, Sofia, 15-19 July, 2013

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Containment Filtered Venting - A new approach

  1. 1. WorleyParsonsWorleyParsons Global NuclearGlobal Nuclear Regional Workshop on Ad anced Le el 2 Probabilistic SafetRegional Workshop on Advanced Level 2 Probabilistic Safety Analysis (PSA Level 2) Bulgaria Sofia 15 19 July 2013Bulgaria, Sofia, 15-19 July, 2013 Alexander Wolski, Director Strategic Projects
  2. 2. Industry Leadery 2 19-Sep-13
  3. 3. Global ReachGlobal Reach A combination of extensive global resources, world recognized technicalA combination of extensive global resources, world recognized technical expertise and deep local knowledge 40,800 personnel |163 offices | 41 countries
  4. 4. Stress Test Reports W l P A l i d R lt Reviewed and analyzed all EU Progress and Final Stress Tests reports + id tifi d l t d th d l t i l di IAEA id WorleyParsons Analysis and Results identified related methodology reports, including IAEA guidance • Developed an activity & task-level work breakdown structure (WBS) for performing stress tests E t t d ll id tifi d b t i t ( h th l d f d d• Extracted all identified robustness improvements (whether already performed, under implementation, planned or proposed) and developed categorized Improvements Database
  5. 5. Improvements Database G i C t i ti d C R f iGrouping, Categorization and Cross-Referencing SEISMIC ►> 1500 d t i t General FLOODING General Flooding protection engineering features/structures, e.g. dykes EXTREME WEATHER CONDITIONS ELECTRICAL SYSTEMS ►> 1500 raw data improvements ►Condensed to 209 across 72 plants Almaraz ■■ Asco ■■ Emergency diesel generator (EDG) (Primary) Mobile diesel generator (MDG) … Batteries HEAT REMOVAL SYSTEMS General Belene ■■ Borssele ■ Safety injection systems … Spent fuel pool Mobile pumps ACCIDENT MANAGEMENT General … … PWR / VVER ■ BWR General Staffing Procedures (Development & updating) … Hydrogen analysis and mitigation Ex-vessel cooling OTHER / GENERAL Vandellos II ■ Zaporizhzhya ■■■■■■ PHWR ♦ UNGG / AGR / Magnox ○ RBMK ‡ OTHER / GENERAL … RBMK ‡
  6. 6. On-Going Efforts P d t / S l ti D l t Hardened Vent Design • Finalized for Excelon & PPL plants Product / Solution Development • Finalized for Excelon & PPL plants • Dry filter system developed Passive Spent Fuel Cooling • VVER Pools and internals modeled • Residual Heat calculations finished • Mitigation strategies defined, engineered solutions under development Hydrogen mitigationHydrogen mitigation • WP MELCOR containment model for VVER- 1000/1200 • Cooperation with Bulgarian Academy of Science Alternative Battery Systems • Identified high-capacity FePO4-battery systems • Commercial dedication on-going Alternative EPS using GTG 0.4 0.45 CVH-X.4.14 CVH-X.4.15 CVH-X.4.22 Alternative EPS using GTG • Relationship with Kawasaki and Siemens • Joint definition of design & testing requirements Steam-driven Aux F/W pumps0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 -2000 0 2000 4000 6000 8000 10000 12000 Steam driven Aux F/W pumps • Transfer US concept to VVER time, sec
  7. 7. IAEA policy on PSAIAEA policy on PSA PSA is recognized to provide important safety insights in addition to those provided by deterministic safety analysis. IAEA pays a lot of attention and provides broad spectrum of support in PSA development and assessments.S p • Level 1 PSAs have now been carried out for almost all NPP worldwide. • Level 2 PSAs have been, or are being, carried out for most NPP, g, worldwide. • Level 3 PSAs have been carried out for some NPP in some States.
  8. 8. PSA level 2PSA level 2 Level 2 PSA deals with assessment of the last physical barrier in DID concept – Containment.Containment. In Level 2 PSA, the chronological progression of core damage sequences identified in Level 1 PSA is evaluated, including a quantitative assessment of, g q phenomena arising from severe core damage to reactor fuel. Level 2 PSA identifies ways in which associated releases of radioactive material from fuel can result in releases to the environment. Containment event tree analysis models the accident progression and identifies the accident sequences that could challenge the containment and release radioactive material to the environment.
  9. 9. Codes for SA Analysis Several thermal hydraulic codes are used for assessment and evaluation of Severe Accidents. MAAP (EPRI) d MELCOR (S di NL f NRC) i USAMAAP (EPRI) and MELCOR (Sandia NL for NRC) in USA ASTEC (IRSN and GSR) in Germany and France Country specific codes for other countries Canada Japan RussiaCountry specific codes for other countries – Canada, Japan, Russia MELCOR is the most used for SA evaluation for VVER reactors outside Russia. MELCOR is extensively validated against experimental data. Adopted by a worldwide group of users in regulatory, research and utility organizations. Modularly structured in interchangeable code packages with well-defined interfaces.
  10. 10. Containment Filtered Venting R ti l S id t lt i d t t Rationale Severe accidents can result in pressure and temperature increase which may lead to containment failure and uncontrolled release of radioactive products to thep environment Stress Test Results - “Containment venting must be id d i th filt d i d f id tconsidered via the filters designed for severe accident conditions, such as to ensure a sufficiently long venting time”e • Prevents over-pressurization • Minimizes the radioactive releases into the environment and decrease the off site dosesdecrease the off-site doses • Decreases the land contamination • H2 and other non-condensable gases concentration reduction
  11. 11. Containment Filtered Venting D i C id ti Maintain Defense in Depth, the containment is the last Barrier Design Considerations p , (retention of aerosols inside containment) Aerosol retention better than 99.9% A l i b l th 0 5 iAerosol size may be lower than 0.5 microns Ability to handle decay heat No catastrophic failure scenarioNo catastrophic failure scenario Passive actuation and operation Proven components with operating experience Minimum impact on operation and maintenance of the plant “Install and Forget” No additional “concrete” for installationNo additional concrete for installation Flexible dimensioning for every possible location Minimum weight for seismic qualificationg q
  12. 12. Sizing of the Filtered Venting SystemSizing of the Filtered Venting System 5x10 5 Simulation of severe accidents 3x10 5 4x10 5 MPa on VVER-1000, V-320 Model P and T in one different cavity geometries 1x10 5 2x10 5 P, O C it geometries • Containment design pressure = 5 bar 0 20 40 60 80 1x10 Time, h One Cavity Two Cavities 600 • LB LOCA + Loss of all AC power supply sources • Core Damage 500 550 • Vessel Failure + melt ejection • MCCI • Generation of steam and non 350 400 450 T,K • Generation of steam and non- condensable gases • P and T increase Diff t ti i f t t f th 0 20 40 60 80 300 350 Time, h One Cavity Two Cavities • Different timing for startup of the filtered venting
  13. 13. Sizing of the Filtered Venting SystemSizing of the Filtered Venting System 2,5x10 5 1 4 10 5 1,6x10 5 1,5x10 5 2,0x10 5 kg 8 0 10 4 1,0x10 5 1,2x10 5 1,4x10 5 kg 5,0x10 4 1,0x10 5 Mass,k 2 0x10 4 4,0x10 4 6,0x10 4 8,0x10 4 Mass, 0 2 4 6 8 10 -5,0x10 4 0,0 Cav 1 Cav 2 0 1 2 3 4 -2,0x10 4 0,0 2,0x10 Melt ejected • About 150 tons of melt transited to the cavity Time, hTime, h y • Steel door between the cavity and other containment compartment (2nd cavity) Door failure and corium spreading• Door failure and corium spreading
  14. 14. Sizing of the Filtered Venting SystemSizing of the Filtered Venting System 5x10 5 520 4x10 5 5x10 a 440 460 480 500 K 2 10 5 3x10 5 P,MPa VVER M 360 380 400 420 Temp, VVER M 0 10 20 30 40 50 1x10 5 2x10 5 VVER M VVER L Limestone M Limestone L 0 10 20 30 40 50 320 340 360 VVER M VVER L Limestone M Limestone L Comparison of P and T in VVER and Limestone concrete cases Time, h Time, h • Two cavities • Different structure of the molten pool Mechanistic Mixture (available since MELCOR Version 1 8 3B)− Mechanistic Mixture (available since MELCOR Version 1.8.3B) − Stratified corium layers
  15. 15. Sizing of the Filtered Venting SystemSizing of the Filtered Venting System Mass of Aerosols captured on filter Total Decay Heat inside Containment Decay Heat from Aerosols capturedAerosols captured on filter
  16. 16. Sizing of the Filtered Venting Systemg g y P t WPNS Uk i B l iParameter WPNS (typical) Ukraine Bulgaria Start of venting, h 50.5 5.8 (37.2) 26.9 Temperature, ºC 223.3 138 (220) 139 Steam, % 53.3 70.1 66.2 H2, % 13.6 12.0 4.1 O2, % 4.8 3.7 4.9 Mass flow through the filter, kg/s 5.5 4.1 8.1 Mass median diameter, µm 1.44 / 0.95 1.48 / --- Mass of filtered aerosols of the aerosols, kg 3.4 (229*) 11.0 (324*) --- (331*) Residual heat on the filter, kW 8.1 (80*) 14.6 (---) --- (236*)Residual heat on the filter, kW 8.1 (80 ) 14.6 ( ) (236 ) * Total released radioactive substances (solid and gaseous)
  17. 17. Sizing of the Filtered Venting SystemSizing of the Filtered Venting System The simulations produce substantially different resultsThe simulations produce substantially different results due to credible modifications of the starting conditions Many of the phenomena are not yet well understood (limited experimental data) • Molten Core Concrete Interaction (including H2 generation) • Chemical reactions in and above the melt• Chemical reactions in and above the melt • Behavior of iodine (revolatilization in the sump, etc.) • Condensation and Settlement of aerosols on “heat surfaces” • Recombiners (air-mixing, iodine chemistry) Limitations of the current code • One dimensional models are applied• One-dimensional models are applied • Nodalisation with gross transfers between nodes Mitigation measures must be able toMitigation measures must be able to handle a wide range of condition
  18. 18. Design Considerations A l Filt R i f i ti S l ti Dry solution (German) relies on stainless steel filter mesh Aerosol Filter – Review of existing Solutions Dry solution (German) relies on stainless steel filter mesh Dry solution (France) relies on sintered steel filter cartridges downstream of the gravel bedsg g Wet solution (Germany) relies on stainless steel filter mesh downstream of scrubber vessel Wet solution (Switzerland) relies on “intelligent mixing” in scrubber vessel Ultimate reliance on stainless steel filters is the pre-dominant solution
  19. 19. Implementation of Dry Filters Aerosol FiltersAerosol Filters Concept proposal: 3 filter modules, each with 85 filter cartridges (1m length) Cartridge design is extremely flexible (length, diameter, arrangement) and will fit any footprint. Robustness of design provided by fully welded metallic cartridges HEPA filter material: Sinterflo® F Metal Fibre
  20. 20. Design Considerations St i l St l filt Old & NStainless Steel filters – Old & New Filter area each module: 1.32m x 2.00m = 2.64 m2 Filter area each cartridge: 0.54 m2 (length of 1 m, outer diameter 60mm) Standard module w/ 8 surfaces 8 x 2.64 m2 = 21.12 m2 Module: 6.21 x 1.42 x 2.7 = 23.8 m3 Proposed module w/ 85 cartridges 85 x 0.54 m2 = 45.9 m2 (0.53m)2 x 3.14 x 1.43m = 1.26 m3 0.89 m2 filter / 1 m3 module volume ( ) 36.4 m2 filter / 1 m3 module volume
  21. 21. Implementation of Dry Filters Aerosol FiltersAerosol Filters HEPA filter material: Sinterflo® F Metal Fibre Ult Hi h ffi i HEPA FiltUltra-High efficiency HEPA Filter High Permeability - Low Pressure Loss Pleated - Low Foot Print Durability SS316 temperature resistant up to 340ºC Efficiency of Sinterflo® 2F3 Metal Fibre Durability SS316, temperature resistant up to 340 C y
  22. 22. Design Considerations St i l St l filt B k dStainless Steel filters - Background
  23. 23. Design Considerations R f M t i l C OH @ 60% idReference Material – CsOH @ 60% void Densest packing of spheres 26% VOID LiOH SiO2 CsOH CsI UO2 Tolerance against void fraction uncertainty CsOH(30%) = 22 mbar / CsOH(90%) = 3 mbarCsOH(30%) = 22 mbar / CsOH(90%) = 3 mbar LiOH(30/90%) = 455/2 mbar – UO2(30/90%) = 8/1 mbar
  24. 24. Design Considerations St i l St l filt P ti l SiStainless Steel filters – Particle Size R f P ti lReference Particle: 1 μm 13 mbar Δp- 13 mbar Δp 20 m2 filter will NOTNOT work if20 m filter will NOTNOT work if average particle smaller than .54 μm
  25. 25. Design Considerations St i l St l filt L di (T l )Stainless Steel filters – Loading (Tolerance) 11 kg of CsOH11 kg of CsOH result in - 50 μm cakeμ - 13 mbar Δp (@ 6200 m3/hr) 150 m2 filtration area provide t t l i t bl kiextreme tolerance against blocking
  26. 26. Design Considerations St i l St l filt Filt ti S fStainless Steel filters – Filtration Surface 11 k f C OH11 kg of CsOH 150 m2 are in a flat almost linearflat almost linear range of the variations. Option: 2 systems to increaseincrease robustness even further Surface Heatload Cake Δp 20 m2 750 W/m2 374 μm 725 mbarμ 150 m2 100 W/m2 50 μm 13 mbar 300 m2 50 W/m2 25 μm 3 mbar
  27. 27. Implementation of New Dry Filters in V-320p y Possible configuration - replacement of TL02 Aerosol Filtersg p EXISTING AEROSOL  FILTERS New AEROSOL  FILTERS
  28. 28. Implementation of New Dry Filters in V 320Implementation of New Dry Filters in V-320 Possible installation with the use of the existing penetrations TL42/TL22 A l filt i id t i t ( h f TL02 filt )Aerosol filters inside containment (exchange of TL02 filters) Iodine filters outside containment in A1022

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