Transient events: Experiments in JUDITH (I and II) and modelling

Transcription

1 Transient events: Experiments in JUDITH (I and II) and modelling O.V. Ogorodnikova, J. Compan, T. Hirai, J. Linke

2 The electron beam test facility JUDITH I e-beam electron beam power: acceleration voltage: electron beam diameter: power density: pulse duration: JUDITH I 60 kw kv ~1 mm < 15 GW/m² > 1 ms aluminium ring stainless foil specimen 12*12*5 mm 3 TEM grid Thermal shock tests: Volumetric heating (Rp=120 µm for C)

3 The new electron beam test facility JUDITH II Forschungszentrum Jülich electron beam power: acceleration voltage: electron beam diameter: power density: pulse duration: scanning frequency: max. scanning area: combination of different loads: n-activated or toxic components: installed components per test: JUDITH II 200 kw kv ~ 5 mm < 10 GW/m² > 1 ms 10 khz 500 x 500 mm² yes yes 2x2 JUDITH II: more realistic simulation of ITER relevant static and transient thermal load conditions JUDITH I 60 kw kv ~1 mm < 15 GW/m² > 1 ms 100 khz 100 x 100 mm² no yes 1 1. electron beam (EB) gun; 2. vacuum chamber; 3. cooling circuit; 4. test component; 5. diagnostics; 6. carrier system; 7. alternative flange for the EB-gun.

4 The new electron beam test facility JUDITH II Forschungszentrum Jülich JUDITH II Less penetration depth Improve ELM s simulation Homogeneous power distribution Combination of different loads JUDITH II: more realistic simulation of ITER relevant static and transient thermal load conditions 1. electron beam (EB) gun; 2. vacuum chamber; 3. cooling circuit; 4. test component; 5. diagnostics; 6. carrier system; 7. alternative flange for the EB-gun.

5 JUDITH II

6 Forschungszentrum Jülich Modelling of thermal erosion: fine grain graphite 1 mm Pabs = 2.4 GWm-2, 4.4 ms, Iinc = 150 ma, 500 C 200 µm

7 Modelling of thermal erosion of CFC S. Pestchanyi

8 R&D - Continue thermal shock experiments and modelling for different graphites and CFC - Simulation of ELM s and disruption for W and Be in JUDITH II and modelling

9 Low energy D/T ions and neutrals Plasma-surface interaction He ions Fast neutrons Thermal load Impurity ions (C,O) erosion erosion erosion erosion PFM Damage, inventory Damage Damage Damage, inventory Modelling Sputtering and implantation: TRYDIN Inventory and permeation: DITR Thermal erosion: 3D-PEGASUS (CBM) and MEMOS- 1.5D Surface modification by impurities deposition: molecular dynamics Erosion: - Sputtering - Thermal erosion Synergistic effect!

10 Modelling of fine grain graphite - Preheating reduces the time to start of BD, t BD RT experiments Power, GW/m C t BD, ms

11 Modelling of fine grain graphite - Preheating reduces the time to start of BD, t BD - Calculations show the same onset of BD as experiments Power, GW/m 2 1 RT, calculations, experiments 500 C t BD, ms

12 Modelling of thermal erosion of CBM σ bulk Erosion, µm MGS=15 P= 2.4 GW/m 2 T 0 = 500 C σ bulk =2σ grain σ bulk =5σ grain σ bulk =10σ grain 6 σ grain σ grain is the mean failure stress of grain bonds σ bulk is the mean failure stress of bulk bonds σ bulk is higher than σ grain - The reduction of the binding energy between crystallites in grains reduces the size of eroded particles and enhances the erosion rate Number of clusters time, ms MGS=15 σ bulk = 10σ grain σ bulk =2σ grain grain size, µm

13 Modelling of thermal erosion of CBM e-beam MGS=10 c Number of clusters MGS=15 eroded particles The erosion increases with grain size e-beam Erosion, µm grain size, µm P=2.4 GW/m 2 T 0 =500 C MGS=15 MGS=10 experiment R6650 The model needs experimental verification time, ms

14 Modelling: Preheated at 500 C graphite R6650 Erosion increases with power Erosion, µm experiment 2,4 GW/m 2, 500 C 1,3 GW/m 2, 500 C time, ms

15 Modelling of fine grain graphite Erosion increases with pre-heating of graphite 2,5 Erosion, µm 2,0 1,5 1,0 0,5 0,0 1,3 GW/m 2, 500 C 1,3 GW/m 2, RT 1 2 time, ms

16 Thermal shock simulation in JUDITH II Fine grain graphite - Erosion is higher for the surface heating for short pulse duration P=2.4 GW/m 2 T=500 C surface heating Erosion, µm volumetric heating in JUDITH I time, ms New JUDITH II: JUDITH I - Less penetration depth - Volumetric heating (Rp=60 µm for C) Close to the surface heating

17 Modelling of thermal erosion of CFC S. Pestchanyi

18 Modelling of thermal erosion of CFC S. Pestchanyi

19 Modelling of thermal erosion of CFC S. Pestchanyi

20 Modelling of thermal erosion of CFC S. Pestchanyi

21 R&D - Calculations show a similar surface morphology and erosion for CBM as experiments for various power load, pulse duration and initial temperature - Continue thermal shock experiments and modelling for different graphite and CFC using PEGASUS code for code verification and prediction for ITER - Simulation ELM s and disruption for W and Be in JUDITH II and verification of MEMOS-1.5D code (heat transfer + fluid dynamics simulation of the melt motion erosion) by comparison with thermal shock experiments

22 Modelling of thermal erosion Erosion due to thermal shock Evaporation Particle emission Brittle destruction (BD) in carbon Or melt layer loss in metals 1) PEGASUS-3D (S. Pestchanyi) code adapted for JUDITH experiments for macroscopic erosion from fine grain graphite and CFC 2) FEM (ANSYS code) for thermal shock experiments for metals (Heat transfer + evaporation + radiation + moving boundary conditions) 3) MEMOS-1.5D for transient events for metals (in the future + DITR for H diffusion and trapping)

23 Modelling of thermal erosion Erosion due to thermal shock Evaporation Particle emission Brittle destruction (BD) in carbon Or melt layer loss in metals 1) PEGASUS-3D code adapted for JUDITH experiments for macroscopic erosion from fine grain graphite and CFC 2) FEM (ANSYS code) for thermal shock experiments for metals (Heat transfer + evaporation + radiation + moving boundary conditions) 3) MEMOS-1.5D for transient events for metals (in the future + DITR for H diffusion and trapping)