Fischer, U.

Leichtle, D.

Serikov, A.

English

KITopen

KIT – University of the State of Baden-Wuerttemberg and National Laboratory of the Helmholtz AssociationAssociation KIT-Euratom, Institute for Neutron Physics and Reactor Technologywww.kit.eduNeutronics Analysis of the IVVS/GDC Plug in ITERU. Fischer,  D. Leichtle, A. SerikovISFNT-10, Portland, USA, September, 12-16, 20112OutlineIntroductionComputational approachNuclear responses during operationActivation, shutdown nuclear heating and occupational dose ratesSummaryU. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITERISFNT-10, Portland, USA, September, 12-16, 20113IntroductionIVVS/GDC plug unit In-Vessel Viewing System (IVVS)Laser based optical system for inspections between plasma pulses or during ITER shut-downGlow Discharge Cleaning Unit (GDC)Cleaning and wall conditioning during intermediate ITER maintenance periodsCommon port for IVVS/GDC plug assumed in this workNeutronics analysis to provide input required for design strategyOperational nuclear loads on GDC electrode headActivation, afterheat and radioactive waste  Occuptational radation dose distributions around GDC/IVVS after shutdownU. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITERISFNT-10, Portland, USA, September, 12-16, 20114IVVS/GDC plug unitIVVS deployment system To move the IVVS along the tube from parking position to various working positions GDC deployment system To move the GDC in parked position, shielding and working position Housing structure Providing the support/guidance to the deployment systems (rails, racks, stops, ...)VV port tube  Equipped with end flange and feed-troughs for the various servicesIVVS probe Laser-based in-vessel viewing and metrology GDC electrode Producing glow discharge in the vacuum vesselU. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITERISFNT-10, Portland, USA, September, 12-16, 20115Computational ApproachNeutron transport, activation and decay photon transport calculationsTransport calculations: Monte Carlo code MCNP5 using FENDL-2.1 nuclear cross-section dataActivation calculations: Inventory code FISPACT using EAF-2007 activation cross-section dataShut-down dose rate calculations Rigorous-2-step (R2S) approach of KIT coupling transport and activation calculations through automated interfaces  Nuclear responsesPovided in IVVS/GDC geometry cells, and, on superimposed fine mesh grids U. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITERISFNT-10, Portland, USA, September, 12-16, 20116Modelling ApproachPreliminary MCNP model of isolated IVVS/GDC plug unit provided by F4E, BarcelonaIVVS/GDC model corrected, updated, and integrated into full Alite torus sector model (lower port).Geometry model based on Alite 4.1 MCNP model, provided by ITER IOU. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITERISFNT-10, Portland, USA, September, 12-16, 20117Geometry model Alite model with integrated IVVS/GDC plugBeVacuum VesselBioshieldCuCrZrSS316L(N)-IGH2OVertical cut Horizontal CutGDCIVVSPlasma Equatorial portU. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITERISFNT-10, Portland, USA, September, 12-16, 20118Calculational DetailsMCNP calculations on HPC-FF/JUROPA at FZ Jülich using parallel MPI communication tchnique Mesh-based weight window generator for variance reductionTypically 2 109 source neutron histories tracked consuming around 6200 CPUh on 560 CPUs of HPC-FFNormalisation to 500 MW fusion powerSA2 irradiation scenario for activation calculations (20 y ITER operation), cooling times: 0s, 1h, 1d, 12d, 100dDurationNeutron wall load MW/m2 Fusion powerNorm. to 500 MWNorm. to neutron source rate  at 500 MW Repetition2 yr 0.003 2.68 0.00536 1.057E+1710 yr 0.0231 20.6 0.0412 8.124E+170.667 yr 0 0 0 0.000E+001.325 yr 0.0465 41.5 0.083 1.637E+183920 s 0 0 0 0.000E+00400 s 0.56 500 1 1.972E+193920 s 0 0 0 0.000E+00 3 times3920 s 0 0 0 0.000E+00400 s 0.784 700 1.4 2.761E+1917 times3 timesonceU. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITERISFNT-10, Portland, USA, September, 12-16, 20119Operational Nuclear ResponsesNeutron flux distributionTotal neutron flux density from 1014 (at first wall) to 105 cm2s-1(at bioshield level) over length of about 11 m1013 cm2s-1 at GDC tipNuclear heatingPhoton contribution dominant for structural materials (steel, copper)Maximum  0.6 Wcm-3 in copper cap of GDC tip3.2 kW total nuclear heating power in GDC electrode (Be, CuCrZr, steel)  U. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITERISFNT-10, Portland, USA, September, 12-16, 201110Activation and waste classificationActivity inventoryCalculated for all IVVS/GDC components 12 days after shutdown assuming full SA2 irradiation scenario.Radioactive waste classificationAccording to French radwaste regulations, classification depends on specific nuclide activity, half-life and radio-toxicityLMA (maximal level of activity) discriminates low level active A-type from medium level B-type wasteAll IVVS/GDC components, except Be protective layer of GDC probe, were shown to be classifiable as low level A-type wasteOnly Be cover will be medium level B-type waste with specific activity of 3.85 108 Bq/g (LMA limit: 2 105Bq/g) due to tritium accumulationU. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITERISFNT-10, Portland, USA, September, 12-16, 201111Shutdown heating and absorbed decay photon radiation doseNuclear heating after shutdown calculated for IVV/GDC material cells and on superimposed mesh assuming SA2 operation of ITERAfterheat dominated by decay photon heatingMaximum is 4mW/cm3 in Cu heat sink of GDC probe, i. e. less than 1% of respective maximum operational heating.Decreases to values in the order of 10-8 W/cm3 at the entrance to the bioshieldU. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITERDecay photon heating distribution [W/cm3] at shutdownISFNT-10, Portland, USA, September, 12-16, 201112Shutdown heating and absorbed decay photon radiation doseDecay photon and operational nuclear heating rates (in Gy/s) at the GDC tip (SA2 20y irradiation scenario)U. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITERMaterial Operationaldose [Gy/s]Absorbed decay photon radiationdose [Gy/s]0 s 12d after shutdownCuCrZr heat sink 67.3 0.47 3.9 10-3Be layer 286 1.4 4.1 10-3SS316 core rod 24.1 0.08 1.2 10-3SS316 shaft 4.5 0.03 6.4 10-4• Total absorbed  dose during 20 y ITER operation: 1100 MGy in CuCrZr heat sink and 400 MGy in steel core rod.• At 12 d after shutdown, absorbed decay photon radiation sums up to 0.01 MGy (Cu heat sink) and 0.004 MGy (steel core rod).ISFNT-10, Portland, USA, September, 12-16, 201113Occupational shutdown dose ratesAssessment of  shutdown dose rate distribution in and around IVVS/GDC plug using R2S approachRequired to ensure safe handling of  activated plug during maintenance periods including extraction and transport  to Hot CellU. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITERShutdown dose rate distribution [Sv/h] 12d after shutdown following 20y SA2 ITER operationDose rate dominated by heavily activated GDC head with peaking values around 5 Sv/h1.5 m behind GDC head doserate falls below 50 mSv/h Further downstream, doserate is less than 5 mSv/hRecommendation to facilitate maintenance: separation of GDC head from other parts of the systemISFNT-10, Portland, USA, September, 12-16, 201114SummaryDetailed neutronics analysis performed to provide input to design process of IVVS/GDC system.Focus on operational loads, activation, and decay photon radiation doses.GDC head gets heavily activated and dominates decay gamma activity of the entire plug and the resulting shutdown dose rate around the plug.It is recommended to separate GDC head from the system prior to further operations in Hot Cell.All IVVS/GDC components, except Be protective layer, were shown to be classifiable as low level radwaste of A-type according to French regulations.U. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITERISFNT-10, Portland, USA, September, 12-16, 201115AcknowledgementThe work leading to this publication has been partially fundedby the European Joint Undertaking for ITER and theDevelopment of Fusion Energy (Fusion for Energy) undercontract No. F4E-OPE-144. The views and opinions expressedherein reflect only the author’s views. Fusion for Energy is notliable for any use that may be made of the informationcontained therein.The analyses made use of an adaptation of the Alite MCNPmodel which was developed as a collaborative effort betweenthe FDS team of ASIPP China, ENEA Frascati, JAEA Naka, andthe ITER Organization.U. Fischer et al., Nuclear analysis of IVVS/GDC plug in ITER

Neutronics analysis for the IVVS/GDC plug in ITER

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Neutronics analysis for the IVVS/GDC plug in ITER

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