containment filtered venting - a new approach
DESCRIPTION
Presentation during IAEA Regional Workshop on Advanced Level 2 Probabilistic Safety Analysis Bulgaria, Sofia, 15-19 July, 2013TRANSCRIPT
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
Industry Leadery
2 19-Sep-13
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
Stress Test ReportsW l P A l i d R ltReviewed 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 testsE 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
Improvements DatabaseG i C t i ti d C R f iGrouping, Categorization and Cross-Referencing
SEISMIC
►> 1500 d t i t GeneralFLOODINGGeneralFlooding protection engineering features/structures, e.g. dykesEXTREME WEATHER CONDITIONSELECTRICAL SYSTEMS
►> 1500 raw data improvements►Condensed to 209 across 72 plants
Almaraz ■■
Asco ■■
Emergency diesel generator (EDG) (Primary)Mobile diesel generator (MDG)…BatteriesHEAT REMOVAL SYSTEMSGeneral
Belene ■■
Borssele ■
Safety injection systems…Spent fuel poolMobile pumpsACCIDENT MANAGEMENTGeneral
…
…
PWR / VVER ■BWR �
GeneralStaffingProcedures (Development & updating)…Hydrogen analysis and mitigationEx-vessel coolingOTHER / GENERAL
Vandellos II ■
Zaporizhzhya ■■■■■■
PHWR ♦UNGG / AGR / Magnox ○
RBMK ‡
OTHER / GENERAL…
RBMK ‡
On-Going EffortsP 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 developmentHydrogen 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 GTG0.4
0.45CVH-X.4.14CVH-X.4.15CVH-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
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.
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 qphenomena 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 identifiesthe accident sequences that could challenge the containment and release radioactive material to the environment.
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 USAASTEC (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 aworldwide group of users in regulatory, research and utility organizations.
Modularly structured in interchangeable code packages with well-definedinterfaces.
Containment Filtered VentingR 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 the penvironmentStress 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
Containment Filtered VentingD i C id ti
Maintain Defense in Depth, the containment is the last Barrier
Design Considerationsp ,
(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 micronsAbility to handle decay heatNo catastrophic failure scenarioNo catastrophic failure scenarioPassive actuation and operation Proven components with operating experienceMinimum impact on operation and maintenance of the plant “Install and Forget”No additional “concrete” for installationNo additional concrete for installationFlexible dimensioning for every possible locationMinimum weight for seismic qualificationg q
Sizing of the Filtered Venting SystemSizing of the Filtered Venting System5x105
Simulation of severe accidents
3x105
4x105
MP
a
on VVER-1000, V-320 ModelP and T in one different cavity geometries
1x105
2x105
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 80300
350
Time, h
One Cavity Two Cavities
• Different timing for startup of the filtered venting
Sizing of the Filtered Venting SystemSizing of the Filtered Venting System2,5x105
1 4 105
1,6x105
1,5x105
2,0x105
kg8 0 104
1,0x105
1,2x105
1,4x105
kg
5,0x104
1,0x105
Mas
s, k
2 0x104
4,0x104
6,0x104
8,0x104
Mas
s,
0 2 4 6 8 10-5,0x104
0,0 Cav 1 Cav 2
0 1 2 3 4-2,0x104
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
Sizing of the Filtered Venting SystemSizing of the Filtered Venting System
5x105
520
4x105
5x10
a 440
460
480
500
K
2 105
3x105
P, M
Pa
VVER M 360
380
400
420
Tem
p,
VVER M
0 10 20 30 40 501x105
2x105 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
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
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 theaerosols, 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)
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 conditionsMany 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
Design ConsiderationsA 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 meshDry solution (France) relies on sintered steel filter cartridges downstream of the gravel bedsg gWet solution (Germany) relies on stainless steel filter mesh downstream of scrubber vesselWet solution (Switzerland) relies on “intelligent mixing” in scrubber vessel
Ultimate reliance on stainless steel filters is the pre-dominant solution
Implementation of Dry FiltersAerosol 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 cartridgesHEPA filter material: Sinterflo® F Metal Fibre
Design ConsiderationsSt 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 surfaces8 x 2.64 m2 = 21.12 m2
Module: 6.21 x 1.42 x 2.7 = 23.8 m3
Proposed module w/ 85 cartridges85 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
Implementation of Dry FiltersAerosol FiltersAerosol Filters
HEPA filter material: Sinterflo® F Metal FibreUlt Hi h ffi i HEPA FiltUltra-High efficiency HEPA FilterHigh Permeability - Low Pressure LossPleated - Low Foot PrintDurability SS316 temperature resistant up to 340ºC
Efficiency of Sinterflo® 2F3 Metal Fibre
Durability SS316, temperature resistant up to 340 C
y
Design ConsiderationsSt i l St l filt B k dStainless Steel filters - Background
Design ConsiderationsR f M t i l C OH @ 60% idReference Material – CsOH @ 60% void
Densest packingofspheres 26% VOID
LiOH
SiO2
CsOH
CsI
UO2
Tolerance against void fraction uncertaintyCsOH(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
Design ConsiderationsSt 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
Design ConsiderationsSt i l St l filt L di (T l )Stainless Steel filters – Loading (Tolerance)
11 kg of CsOH11 kg of CsOHresult in
- 50 μm cakeμ- 13 mbar Δp
(@ 6200 m3/hr)
150 m2 filtration area providet t l i t bl kiextreme tolerance against blocking
Design ConsiderationsSt 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 Δp20 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
Implementation of New Dry Filters in V-320p y
Possible configuration - replacement of TL02 Aerosol Filtersg pEXISTINGAEROSOL FILTERS
NewAEROSOL FILTERS
Implementation of New Dry Filters in V 320Implementation of New Dry Filters in V-320Possible 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