ERMSAR 2012, Cologne March 21 – 23, 2012 Pretest Calculations of QUENCH-DEBRIS-0 Test Using SOCRAT/V3 Code V ASILIEV A.D. N UCLEAR S AFETY I NSTITUTE OF R USSIAN A CADEMY OF S CIENCES (IBRAE), B.T ULSKAYA 52, M OSCOW, R USSIA

ERMSAR 2012, Cologne March 21 – 23, 2012 Content of Presentation 1. Purpose 2. QDEBRIS-0 Experiment Features 3. SOCRAT – Computer Modelling Code 4. SOCRAT Results of Modelling 5. Conclusions

ERMSAR 2012, Cologne March 21 – 23, 2012 Purpose The QUENCH-DEBRIS-0 test is planned at QUENCH facility, KIT, Karlsruhe, Germany. The objective of this bundle test is the investigation of thermo- hydraulic, thermo-mechanical and physico-chemical phenomena under severe accident conditions with debris and melt pool formation. The lessons learned from severe nuclear accidents at Three Mile Island, Chernobyl and Fukushima showed the very high importance of accident control measures to prevent the development of design basis accident to beyond design basis accident and to mitigate the consequences of beyond design basis accident. The deep understanding of hydraulic, mechanical and chemical processes taking place under accident conditions is necessary, in particular, during late phase with debris formation.

ERMSAR 2012, Cologne March 21 – 23, 2012 Hafnia QUENCH-DEBRIS-0 Features Hafnium will be used in QDEBRIS tests

ERMSAR 2012, Cologne March 21 – 23, 2012 Hafnium-containing rocket nozzle of the Apollo Lunar Module

ERMSAR 2012, Cologne March 21 – 23, 2012 QUENCH-DEBRIS-0 Features Hafnium-containing periphery rods, corner rods and shroud of QUENCH-DEBRIS facility

ERMSAR 2012, Cologne March 21 – 23, 2012 SOCRAT Computer Modelling Code SOCRAT/V3 SOCRAT/V2 SOCRAT/V1

ERMSAR 2012, Cologne March 21 – 23, 2012 SOCRAT Nodalization Scheme for QUENCH-DEBRIS

ERMSAR 2012, Cologne March 21 – 23, 2012 SOCRAT: Debris Behaviour Module Thermal Problem of SOCRAT Code DEBRIS THERMAL HYDRAULIC MODULE Debris solid and fluid oxidation Calculation of thermo-physical properties of debris solid/liquid phases System solution ( ,s,,,,p) for new timestep Calculation of debris materials relocation inside debris and between debris and non-debris meshes Geometry (topology) of debris from formation criteria or input data Matrix coefficients for conservation equations

ERMSAR 2012, Cologne March 21 – 23, 2012 SOCRAT: Debris Behaviour Module Equations timeconvectionpressuregravityBrinkmannDarcyForchheimer d diameter of particles permeability hydraulic diameter Ergun constant

ERMSAR 2012, Cologne March 21 – 23, 2012 Energy Equations Specific enthalpies internal heat generation rate due to fission products decay internal heat generation rate due to chemical reactions effective thermal conductivity due to hydrodynamic dispersion effective solid thermal conductivity taking into account radiative heat transfer

ERMSAR 2012, Cologne March 21 – 23, 2012 Radiative Heat Transfer Modeling effective conductivity of gas effective radiative conductivity emissivity constant of the order of unity Stefan-Bolzman constant volume-averaging conductivity of solid and liquid

ERMSAR 2012, Cologne March 21 – 23, 2012 Time, s Temperature, K Preliminary heat-up Preoxidation Final heat-up Cool- down fast cool- down, water flood slow cool- down, no water flood

ERMSAR 2012, Cologne March 21 – 23, 2012 Estimation of Melt Velocity Relocating Downward Kozeny constant Account of relative permeability

ERMSAR 2012, Cologne March 21 – 23, 2012 Basic Thermo-Physical Corium Parameters Pa·s, dynamic viscosity K -1, volumetric expansion W/(mK), thermal conductivity N/m, surface tension Zr oxidation extent

ERMSAR 2012, Cologne March 21 – 23, 2012 QUENCH-DEBRIS-0: Calculated Temperature Behaviour Maximum temperature is about 2500K The first heat-up phase and preoxidation phase are similar to classical QUENCH-06 test!

ERMSAR 2012, Cologne March 21 – 23, 2012 QUENCH-DEBRIS-0: Proposed Total Electric Power

ERMSAR 2012, Cologne March 21 – 23, 2012 QUENCH-DEBRIS-0: Chemical Reactions Zr + 2H 2 O = ZrO 2 + 2H 2 + Q 1 Zr + O 2 = ZrO 2 + Q 2 yes no yesHf + 2H 2 O = HfO 2 + 2H 2 + Q 3 Q 1 = J/kg Zr Q 2 = J/kg Zr Q 3 = J/kg Hf

ERMSAR 2012, Cologne March 21 – 23, 2012 E-110 (Zr1%Nb) Oxidation Rate weight gain, mg/cm 2 ; K - rate constant, mg 2 /(cm 4 s) Q - activation energy, J/mole; R – gas constant, J/(mole  K); T – temperature, K K= 550  C<T<1200  C 1300  C<T<1500  C 1500  C<T<1600  C Bibilashvili Yu.K., Sokolov N.B., Andreyeva-Andrievskaya L.N., Salatov A.V. High-Temperature Interaction of Fuel Rod Cladding Material (Zr1%Nb Alloy) with Oxygen-Containing Mediums. IAEA-TECDOC-921, Dimitrovgrad, 1995, p

ERMSAR 2012, Cologne March 21 – 23, 2012 QUENCH-DEBRIS-0: Hafnium Oxidation Rate K = 0.76 kg/(m 2 s 1/2 ) E a = J/mole Steinbrueck et. al. High-Temperature oxidation and quench behaviour of Zircaloy-4 and E110 cladding alloys. Progress in Nuclear Energy, 52(2010), pp Hafnium oxidation rate is several times lower!

ERMSAR 2012, Cologne March 21 – 23, 2012 QUENCH-DEBRIS-0: Calculated Heat Balances in Core 1 – total electric power 2 – heat transferred by gas 3 – heat to shroud 4 – chemical power All rods and shroud made of Zry!

ERMSAR 2012, Cologne March 21 – 23, 2012 QUENCH-DEBRIS-0: Calculated Electric Current and H 2 Rate Hydrogen generation rate

ERMSAR 2012, Cologne March 21 – 23, 2012 QUENCH-DEBRIS-0: Calculated Hydrogen Production 1 - total H 2 release 2 - H 2 release in debris All rods and shroud made of Zry!

ERMSAR 2012, Cologne March 21 – 23, 2012 QUENCH-DEBRIS-0: Diminishing Steam Mass Flow Rate Leads to More Wide Axial Temperature Profile Calculated Axial Distribution of Zirconia Layer Thickness

Discover new fundamental nature laws with QUENCH-DEBRIS! This ambitious program will help in more realistic desription of debris- related phenomena under NPP accident conditions!

LABORATORY A fast heat-up rate scenario after pre-oxidation is proposed to get massive high temperature porous debris and pool zone during QDEBRIS-0 test. Application of Hafnium instead of Zircaloy leads to more manoeuvrable and flexible experiment control. Conclusions SOCRAT code was used to estimate basic parameters of the test. Such important issues as debris oxidation and relocation phenomena, debris hydraulics as well as the coolability of massive debris bed can be investigated. -5 s-4 s-3 s-2 s-1 s 0 s