MELCOR model development for ARIES Safety Analysis

Transcription

1 MELCOR model development for ARIES Safety Analysis Paul Humrickhouse Brad Merrill INL ARIES Meeting UCSD San Diego, CA January 23 rd -24 th, 2012

2 Presentation Outline Status of MELCOR modeling for ARIES-ACT SiC DCLL Follow up on VV permeation result from last meeting Plans and action items for next meeting

3 Status of ARIES-ACT MELCOR Models An item from the last meeting was to start the update of existing MELCOR ARIES-AT models to perform accident analyses, primarily loss-of-coolant-accidents (LOCAs) Two models exist, one with the advanced SiC/SiC blanket and one with the DCLL blanket Both models lacked vacuum vessel, cryostat, and bioshield thermal models, need for decay heat removal and/or VV pressure relief accidents, and to answer the question of whether or not the VV can be cooled by helium Since the last meeting, we have modified and added the ARIES- CS VV to the ARIES-AT models, plus a cryostat based on ARIES-AT drawings. This required switching the VV cooling system to helium from water We are testing these models on a long-term-station-blackout (LTSBO) accident, with decay heat removal by gas injection into the cryostat volume

4 MELCOR Model Elevations Based on ARIES-AT Heat transfer vault Circ. HXs Pump Header PbLi drain tank"

5 Vacuum Vessel/Cryostat/Divertor Model CV15 Cryostat HS7102 HS6102 CV10 Bioshield HS10299 HS10128 CV310 HS340 HS HS7023 CV HS10126 CV20 HS10026 HS7101 HS6101 HS450 CV450 CV700 HS10028 CV300 HS HS HS10298 HS6103 HS7103

6 Schematic of Radial Blanket Thermal Segments HS431 HS441 CV440 HS332 CV340 CV430 HS440 HS430 HS322 HS330 CV410 CV320 HS401 HS411 HS320 CV420 CV330 CV400 HS410 HS400

7 Advanced SiC Blanket Model IBVV U-IBHTS HS7023 CV700 HS7021 CV310 HS10299 Convection, and radial/axial radiation and/or conduction accounted for in model ITER-like thermal cryo-shields on outer surface of vacuum vessel (VV) UD CV HS10128 HS IBHTS 245 IBB OBB I OBB II OBHTS To VV HTS OBVV HS7013 CV700 HS7011 CV310 HS340 HS330 CV330 HS320 CV320 HS322 CV340 HS332 HS400 CV400 HS410 CV420 HS411 CV410 HS401 HS430 CV430 HS440 CV440 HS441 CV430 HS431 HS450 CV450 CV460 HS7001 CV700 HS LD CV300 HS10028 HS10026 L-IBHTS HS10298 CV HS7031 CV700 HS7033 OTHDR ITHDR CV CV From PbLi HTS From VV HTS To PbLi HTS

8 Super-insulation or Thermal-Shield? Super-insulations relies on thermal radiation heat transfer across gaps between multi-layered metal foils of high emissivity. For a vacuum in the gaps, the heat flux, q (W/m2-K), across N foils of emissivity ε is: q= ε ( N + 1) σ (TH4 TL4 ) Super-insulation used for LHC VV and cryostat* ITER s Thermal-Shield is constructed is a shell around the VV coated with silver for low surface emissivity. The low temperature shell is cooled by helium at 80 K. Air injected into the cryostat during a long term station blackout (LTSBO) will add air heat convection in the gap between the shell and the VV. LHC employs both a super-insulation blankets and Thermal-shields. Which option will be used for ARIES-AT? *A. Poncet, Series-Produced Helium II Cryostats for the LHC Magnets: Technical Choices, Industrialization, Costs, Adv. Cryo. Engr., Vol. 53

9 MELCOR DCLL Model Schematic IB Shield IB blanket OB blanket OB Shield fl650 fl660 PbLi heat exchanger fl710 fl551 VV HS340 CV300 fl200 fl240 HS341 CV310 fl280 HS342 HS325 CV324 fl653 fl245 HS324 CV322 HS323 CV323 fl281 fl651 fl652 HS322 CV321 fl205 FW HS321 CV320 HS320 fl630 CV020 FW HS400 CV400 HS401 fl640 fl661 fl265 CV401 HS402 CV402 HS403 CV403 HS404 CV404 fl215 fl662 fl271 fl663 HS405 HS450 Zone 1 Zone 2 fl275 CV450 HS451 CV460 HS452 fl300 fl230 VV CV530 to CV535 fl416 HS21000 to HS21500 CV700 to CV705 CV710 HX- Secondary Side fl716 fl410 fl430 CV550 CV551 He toroidal header CV605 fl620 fl600 CV610 HS650 CV615 HS750 CV036 He heat exchanger fl615 fl816 CV630 to CV635 HS22000 to HS22500 CV800 to CV805 CV810 HX- Secondary Side fl810 fl610 CV502 fl290 CV500 CV503 fl220 CV510 fl420 CV520 HS520 CV540 HS540 CV036 PbLi concentric pipe CV600 He concentric pipe PbLi toroidal header fl425

10 SiC Results for a LTSBO with Air Injection in the Cryostat The inboard side of the VV is being cooled by the helium interior to VV, suggesting that internal natural convection from the inboard to the outboard of the VV may be important. However, because the VV model only has a single fluid volume, additional modeling will have to be performed to verify this possibility. Model overstates inboard cooling

11 DCLL Results for a LTSBO with Air Injection in the Cryostat Calculation has not progressed as far as SiC case. Steady state FW temperatures do not include enhancement for helium cooling. Need guidance on this.

12 Summary ARIES-AT MELCOR models have been modified and expanded to model ARIES-ACT, including both SiC and DCLL cases Preliminary LTSBO analysis verifies model is wired correctly Future work will focus on refinement of the model to reflect ARIES-ACT parameters Many model details are still for ARIES-AT Helium vs. Water cooled VV Thermal Shield vs. Super-insulation Divide VV into multiple control volumes Natural convection may occur within the VV from the inboard to the outboard side of the VV; present model doesn t capture this correctly

13 Follow up - Vacuum Vessel Permeation Simple equilibrium permeation model used for scoping Surface concentrations u upstream d - downstream u u CT = K s pt 2 d d CT = K s pt 2 Fick s law of diffusion u C T u pt 2 Coolant d p T 2 0 Γ T = -D T A s C x T DT Ks As Δt d u PAs u ( pt pt ) pt Δt d C T 0 Parameters used for the VV permeation analysis: Upstream T 2 pressure 5 Pa and downstream pressure of zero Question from last time on the validity of 5 Pa Detailed ITER divertor analysis* gives similar neutral pressures: (a) 15 *A. S. Kukushkin et. al, Effect of neutral transport on ITER divertor performance, Nuclear Fusion 45 (2005) P D2 [Pa] 10 5 no n-n n-n on x floor [cm]