Große, M.

Sepold, L.

Steinbrück, M.

Stuckert, J.

English

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KIT – The cooperation of Forschungszentrum Karlsruhe GmbH and Universität Karlsruhe (TH)Institute for Materials Research I and IIILessons learned from the QUENCH Programme at FZKM. Steinbrück, M. Große, L, Sepold, J. Stuckert15th Int. QUENCH Workshop, Karlsruhe Institute of Technology, 3-5 Nov. 2009Martin Steinbrück, KIT-IMF I2 03.11.2009MotivationReflood is a prime accident management measure to terminate a nuclear accidentReflood may cause temperature excursion connected with increased hydrogen and FP release TMI2, LOFT, PBF, CORA ….. but only qualitative hydrogen measurementsCoolability of a degraded core is a matter of high priority (SARNET-SARP, OECD-GAMA)QUENCH experiments (bundle+SET) provide data for development of models and validation of SFD code systemsMartin Steinbrück, KIT-IMF I3 03.11.2009QUENCH ProgrammeApplicationModelling CODESValidationSeparate-effects testsBundle experimentsMartin Steinbrück, KIT-IMF I4 03.11.2009Basic informationCooling effect Chemical heat productionQc ∼ h (TZr - Tc) QR ∼ ΔRH (K/t)0.5Zr + 2 H2O → ZrO2 + 2 H2 + 580 kJInfluenced byΔTFlooding rateCooling mediumPressureHydraulic diameter…Oxidation kineticsTemperature (Arrhenius type)Degree of pre-oxidationSurface available for oxidationMaterial compositionSteam availabilityRefloodWater injection → steam productionMartin Steinbrück, KIT-IMF I5 03.11.2009Simulation of bundle test with and without excursionFast cool-down of the bundleLow to moderate hydrogen (FP) releaseIntact bundleTemperature escalationStrong hydrogen (FP) releaseFormation, relocation and oxidation of meltsStrongly degraded bundleMartin Steinbrück, KIT-IMF I6 03.11.2009QUENCH FacilityBundle with 21-31 fuel rod simulators of ~2,5 m lengthElectrically heated: ~1 m; max 70 kWFuel simulator: ZrO2 pelletsQuenching (from bottom) with water or saturated steamOff-gas analysis by mass spectrometer (H2, steam …)Extensive instrumentation for T, p, flow rates, level, etc.Removable corner rods during testCondensate collectorGAM 300Condenser+ -ÜberhitzerMartin Steinbrück, KIT-IMF I7 03.11.2009QUENCH Separate-effects tests: Main setupspyrometervideo systemAr + steam + H  + CO + CO  + CH  + ...22 4Specimen10-15 cmhigh frequency generatorinduction coil(water cooled)ZrO  tube2quartz tubeZrO  crucible(debris catcher)2TCZry-4melt specimenZrO  crucible2W crucible(susceptor)movable infrared-pyrometer forcrucible+susceptortwo colour pyrometeror TC for calibrationThermo balance1600 °C1250 °C (steam)Specimens: 0-2 cmMS couplingBOX Facility1700 °COxidising, reducing atmosphere (incl. steam)Specimens: 1-2 cmMS couplingQUENCH-SR Rig2000 °COxidising, reducing atmosphere (incl. steam)Specimens: 15 cmMS couplingLAVA Furnace2300 °CInert, reducing atmosphereSpecimens: 1-2 cmMS couplingMass spectrometerH2 Ar H O2 MixerArWater storageControlledevaporatormixerControl centerFurnaceLiquid flow controllerComputer systemGas supply systemTCH O2AirNor2Gas flow controllersCEM Air lockSpecimenINRO Facility1500°CSpecimens: 1-2 cmTransparent for neutronsGas inletAr/O , N , air2 2Vacuum system AnalyticalbalanceHigh-temperaturefurnaceSpecimenOff gas to MSmMartin Steinbrück, KIT-IMF I8 03.11.2009Phenomena of interest (for coolability)Crack oxidationTemperature at reflood initiationInfluence of absorber materials (B4C, AgInCd)Melt formation and oxidationSteam starvationAir ingressReflood rateMaterials, alloy compositionHydrogen absorptionMartin Steinbrück, KIT-IMF I9 03.11.2009Crack formation during reflood~ 200 µm ~ 250 µm ~ 350 µm~ 150 µm10.75 mm Zry-4 cladding pre-oxidised at 1200 °CDensity of through-wall cracks: 0.5 mm/mm2Oxidation of fresh-generated metallic surfacesEnhanced hydrogen absorption Martin Steinbrück, KIT-IMF I10 03.11.2009Crack formation in QUENCH-01 bundle test-200 mm0 mm200 mm400 mm600 mm800 mm1000 mm1200 mm913 mm573 mmShroudFuel rod simulatorCentral rodZry-4 rodTCTungstenheaterZrO  pellet2PartiallyoxidisedcladdingEpoxy-Zr(O) ZrO -Zr(O)2-x ZrO2Oxidation of crack surfacesduring floodingGrid spacer10 mm100 µmEstimation of hydrogen production by crack oxidation gives only ca. 1-2 g for the whole bundleBut:Solution enthalpy of 1 g H2 in 1 kg Zr increases temperature by 200 K Martin Steinbrück, KIT-IMF I11 03.11.2009Temperature at reflood initiationTest Date Quench  medium and injection rate Temp. at onset  of flooding1)H2 production before / during cooldown QUENCH-01 Febr 26, 1998 Water 52 g/s ≈ 1830 K 36 / 3 QUENCH-02 July 7, 1998 Water 47 g/s ≈ 2400 K 20 / 140 QUENCH-03 Jan 20, 1999 Water 40 g/s ≈ 2350 K 18 / 120 QUENCH-04 June 30, 1999 Steam 50 g/s ≈ 2160 K 10 / 2 QUENCH-05 March 29, 2000Steam 48 g/s ≈ 2020 K 25 / 2 QUENCH-06 Dec 13, 2000 Water 42 g/s ≈ 2060 K 32 / 4  Escalation of temperatures and significant hydrogen release during tests with maximum temperatures exceeding Zry melting temperature 1900 2000 2100 2200 2300 2400 2500 2600 270005001000150020002500 cladding -250 mm cladding 350 mm cladding 650 mm cladding 850 mm shroud 850 mm cladding 950 mm shroud 950 mm cladding 1050 mm cladding 1150 mm cladding 1250 mmTemperature, °CTime, sQuenchinitiationQU-02Martin Steinbrück, KIT-IMF I12 03.11.2009Bundle tests QUENCH-07/-08/-09 (B4C effect)Test Date Quench  medium and injection rate Temp. at onset  of flooding H2 production before / during cooldown Remarks QUENCH-07 July 25, 2001 Steam 15 g/s ≈ 2100 K 66 / 120 Impact of B4C absorber rod failure on bundle degradation and H2, CO, CO2, and CH4 generation. QUENCH-08 July 24, 2003 Steam 15 g/s ≈ 2090 K 46 / 38 As QUENCH-07, no absorber rod QUENCH-09 July 3, 2002 Steam 49 g/s ≈ 2100 K 60 / 400 As QUENCH-07, steam-starved conditions prior to cooldown.  Strong influence of boron carbide on hydrogen source term and bundle degradation due toEutectic interactions between B4C, SS, and Zry leading to rapid melt formation at about 1200 °CHigh oxidation potential of boron carbidee.g. B4C + 8 H2O → 2 B2O3 + 8 H2 + CO2 + 792 kJMartin Steinbrück, KIT-IMF I13 03.11.2009Influence of B4C absorber rodBundle cross sectionsQUENCH-07with B4CQUENCH-08w/o B4C550 mm 750 mm 950 mmMartin Steinbrück, KIT-IMF I14 03.11.2009T ≤ 1400 °C:Intact specimen due to “crucible effect” (melt kept by the external ZrO2 scale)T ≥ 1500 °C:Failure of the oxide shell and rapid oxidation of absorber melt and B4C pelletDegradation of boron carbide control rods1200 °C 1300 °C1400 °C 1500 °C 1600 °CZrO2 capZry-4 guide tubeSS claddingB4C pelletZrO2 cap1000 °C-2000 0 2000 4000 60000123max. H232 l/hisothermal phaseoff-gas systemblockedmax. H224 l/h 1000 °C 1200 °C 1300 °C 1400 °C 1500 °C 1600 °CH2 release, l/hTime, sH2-2000 0 2000 4000 60000.00.10.20.30.40.50.6isothermal phase 1000 °C 1200 °C 1300 °C 1400 °C 1500 °C 1600 °CCO2 release, l/hTime, sCONO Methane!Martin Steinbrück, KIT-IMF I15 03.11.2009Oxidation of B4C-SS-Zry eutectic melts0 500 1000 1500 2000 250002468108001000120014001600B4C SS Zry-4  0 100  0  0  0 100  100  0  0  5 95  0   9 81 10 TemperatureH2 release rate, l/hTime, s Temperature, °C  5 B4C + 95 SSEutectic meltAfter oxidationSignificant increase of oxidation rate above melting temperatureMartin Steinbrück, KIT-IMF I16 03.11.2009Steam starvation before refloodDissolution of oxide scaleThinning of oxide scale and precipitation of α-Zr(O) in oxideWeakening of protective effect of ZrO2 oxide layerOxidation Steam starvation at 1700 KMartin Steinbrück, KIT-IMF I17 03.11.2009Influence of air ingress on coolability (QUENCH-10)In comparison to steam:Higher exothermal energy releaseIncreased oxidation kineticsLess cooling effectEscalations from low temperaturesEarly loss of cladding barrier effect02004006008001000120014001600180020000 2000 4000 6000 8000 10000 12000 14000Time, sTemperature, °C010203040506070Power, kWTIT A/13    TCRC13TIT C/12    TCRC 12     TFS 5/17    TFS 5/16    TFS 3/16    TFS 5/15    TFS 2/15    TFS 5/14    TFS 3/14    TFS 4/13    TFS 3/13    TFS 2/11    TFS 5/11    TFS 4/9     TFS 5/9     TFS 2/9     TFS 5/8     TFS 3/8     TFS 5/7     TFS 2/7     TFS 5/6     TFS 2/5     TFS 5/4/180 TFS 2/3     P_elW/ReshieldiedNiCr/NElevation: -50 mmElevation: 950 mm1350 mmPre-oxidationCool-downAir ingressQuenchingTransient11500 12000 12500 13000 135000.00.10.20.30.40.50.60.70.80.91.0051015202530N2 and O2 rate, g/sTime, s O2 N2 H2Consumptionof nitrogenConsumptionof oxygenAir ingress Quench H2 Rate, mg/sTest phases, power input and temperatures in the QUENCH-10 bundleOxygen starvation and nitrogen consumption during QUENCH-10Martin Steinbrück, KIT-IMF I18 03.11.2009Separate-effects tests on air oxidation… under prototypical conditions, includingPre-oxidation in steam/O2Tests in mixed air(N2)-steam atmospheressteam air50/50 steam/air1 hour at 1200 °C in1 hour at 1000 °C insteam50/50 steam/N2Nitrogen is not an inert gas under the conditions of a nuclear accident!Martin Steinbrück, KIT-IMF I19 03.11.2009Influence of reflood flow rateThe three tests QUENCH-07/-08/-11 with reduced reflood flow rate <1 g/(s rod) resulted in temperature escalations and enhanced hydrogen production.5200 5400 5600 5800 6000 62005001000150020000,00,20,40,60,81,065095085075010501250450 H2 release rate, g/sTemperature, KTime, sTemp. at 250 mm 450 mm 650 mm 750 mm 850 mm 950 mm 1050 mm 1250 mm HydrogenInitiationof refloodZry melting 2033 K250 Example QUENCH-11• SARNET benchmark• Cooldown at bundle elevations < 800 mm• Escalation at bundle elevations >800 mm• Strongest hydrogen production when bundle temperatures exceeded Zry melting temperatureMartin Steinbrück, KIT-IMF I20 03.11.2009QUENCH-ACM: Influence of cladding alloy1QU-06 (Zry-4)QU-14 (M5) QU-12 (E110) QU-15 (ZIRLO)ACM = Advanced cladding materialsOptimised for operational conditionsTo be tested for DBA and BDBA conditionsBundle tests and separate-effects testsMartin Steinbrück, KIT-IMF I21 03.11.2009QUENCH-ACM: Influence of cladding alloy0 1000 2000 3000 4000 5000 6000 7000 8000 9000500100015002000Temperature, KTime, s QUENCH-06 (Zry-4) QUENCH-12 (E110) QUENCH-14 (M5) QUENCH-15 (ZIRLO)Q-06 Q-12 Q-14 Q-15010203040506070ZIRLOM5E110 before reflood during refloodHydrogen release, gQUENCH testZry-4Max. bundle temperatures Hydrogen releaseSimilar test conditions for all four experimentsOnly limited effect of cladding alloy on integral bundle behaviourStrongest oxidation during QUENCH-12 Martin Steinbrück, KIT-IMF I22 03.11.2009Post-test QUENCH-12 bundle with E110 claddingMetalOxideZrO2 debris formation and relocation to bundle footE110 corner rodTypical breakaway oxidation at E110 corner rodMartin Steinbrück, KIT-IMF I23 03.11.2009Hydrogen absorption during QUENCH-15600 800 1000 1200 14000510152025303540  corner rod A, Zry-4, withdrawn after the test corner rod rod B, Zry-4, withdrawn after pre-oxidation phase corner rod rod C, E110, withdrawn before quenching corner rod rod H, E110, withdrawn after the test cladding tube 24, ZIRLO, withdrawn after the testHydrogen concentration, at.%axial position z, mmStrong correlation between oxide morphology and hydrogen uptakeE110Zry-4 ZIRLOMartin Steinbrück, KIT-IMF I24 03.11.2009ACM Separate-effects testsOxidation in steam and oxygenAlloys: Zircaloy-4, Duplex, M5, ZIRLO, E110, Zr702, HfTemperature: 600-1600 °CIsothermal and transient testsTest rigs: TG (online mass gain), BOX furnaceOxidation correlationsBreakaway transition times and critical oxide thicknessHydrogen uptakeIn pure hydrogen (Sieverts’ constants)During oxidation in steamMethods: Hot extraction and neutron radiography (post-test and in-situ)Martin Steinbrück, KIT-IMF I25 03.11.2009ACM Separate-effects tests: Main resultsOxidation of Zr alloys with only slightly different composition is quite complex with strong differences up to 1000 °C, and less, but significant variation at higher temperatures.The oxidation kinetics are mainly determined by the oxide scale (breakaway, crystallographic phase, degree of sub-stoichiometry).Strong correlation between breakaway oxidation and hydrogen uptake was found.0 4000 8000 120000100200300400500Δm/S, g/m2Time, s Zry-4 Duplex Zirlo M5 E1101000 °C15 at% H5 at% H3 h at 1000 °CZry-4M5Martin Steinbrück, KIT-IMF I26 03.11.2009Summary170018001900200021002200230024001 2 3 4 5 6 7 8 9 10 11 12 13 14 150100200300400Hydrogen release, gQUENCH test H2 before reflood H2 during reflood Temp. at initiation of reflood Temperature, KHigh temperaturesabove 2200 KEutectic meltformationLow floodingrateQUENCH bundle tests can be split into those:With successful flooding leading to immediate cooldown and low hydrogen releaseWith temporary temperature escalation and strong hydrogen productionSteamstarvationMartin Steinbrück, KIT-IMF I27 03.11.2009ConclusionsMain factors affecting cooling and chemical heat production during reflood have been identified.The heat balance at initiation of reflood is crucial for further development of reflood process.Melt formation, relocation, and oxidation as well as steam starvation before reflood are most important processes for enhanced oxidation after reflood.Reflood rate must be > 1 g/(s rod) for successful cooldown.Experimental results must not directly applied to plant analyses, but they help to improve the SA code systems.

Lessons learned from the QUENCH programme at FZK

https://publikationen.bibliothek.kit.edu/170077264/3815564

Lessons learned from the QUENCH programme at FZK

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