Barnsley, R.

Bertalot, L.

De Bock, M.

Fischer, U.

O\u27Connor, R.

Serikov, A.

Thenevin, R.

English

KITopen

Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM Page 1 Neutronics for Diagnostic Systems of ITER Port Plugs  A. Serikov *, R. Barnsley **, L. Bertalot **, M. De Bock **, R. O’Connor**, U. Fischer *, R. Thenevin **  *  Karlsruhe Institute of Technology (KIT), Germany  **  ITER Organization (IO), France   2015 ANS Winter Meeting and Nuclear Technology Expo, November 8-12, 2015    Page 2 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM Content • Fusion neutronics in ITER tokamak • Parallel Monte Carlo runs on supercomputers    • Shielding for Diagnostics Ports:  Upper Port #3  Equatorial Port #17    Applications General info Page 3 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM  Diagnostics Port Plugs  • House 80% of ITER Diagnostics  • Port plugs are large structures which play the dual and conflicting roles of providing diagnostic access while ensuring that the vacuum vessel ports are adequately “plugged” against the leakage of nuclear radiation and are vacuum leak tight.  • ITER has 18 ports at the Equatorial and Upper levels  • ITER's operational phase is expected to last for 20 years:  "shakedown" period H-H, D-D, D-T with 500 MW fusion power  First Plasma and subsequent D-T full power operation: originally scheduled for 2020 and 2027, Updates will be reported to the ITER Council in November 2015, check: www.iter.org  ITER tokamak: CAD model  Page 4 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM PF Coils Building ITER HQ Subcontractors Area Tokamak Complex Assembly Hall 400 kV switchyard Cryostat Workshop Progress on the ITER platform The 42-hectare ITER platform HQ Extension Storage Area 2 Storage Area  1 Page 5 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM Summer 2015: circle marks the location of the future ITER Tokamak. Components will enter on the far side of the Assembly Building (structural pillars already in place) for verification, pre-assembly, transfer to the Tokamak Pit for integration into the machine. ITER progressing: tokamak pit and assembly building  (toroidal'naya kamera s magnitnymi katushkami) — toroidal chamber with magnetic coils  Page 6 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM Autumn 2015: The roof segment of the ITER Assembly Building is successfully raised to its final position in September. Work is underway on the second basement level of the Tokamak Complex (B1).  Page 7 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM Deliveries have started 20 April 2015:          US-procured transformer (90 t.) 7 May 2015:            2 US-procured drain tanks(79 t.) 21 May 2015:          US-procured transformer (90 t.) 14 Jan. 2015:            US-procured transformer (90 t.) 20 March 2015:        Europe-procured detritiation tank (20 t.) 2 April 2015:             Europe-procured detritiation tank (20 t.) Page 8 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM Safe maintenance at ITER Ports – from behind the Port Plugs: Poject Requrements for Shut-Down Dose Rate (SDDR) 106 sec after shut-down,  SDDR < 100 microSv/h  24 hrs after shut-down,   SDDR < 10 microSv/h  Upper Port Interspace Equatorial Port Interspace Diagnostics Port Plugs: UPP & EPP  “Another flaw in the human character is that everybody wants to build and nobody wants to do maintenance…”  ― Kurt Vonnegut, Hocus Pocus  .... Except of personnel at ITER (Diagnostic physicists, engineers, experimentalists...)  Neutronics computational support must be provided for the Port Plugs design development  Page 9 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM Neutronics computational methodology: Codes, Tools, Nuclear Data  SpaceClaim  software reads CAD models, solves geometry problems, allows to work in 3D without having to be a CAD expert  CAD-to-MCNP conversion tools:  MCAM 5.2 (FDS Team, China)  McCad (KIT, Germany)   Radiation transport calculations (n/gamma fluxes, nuclear heat, gas production):  Monte Carlo code MCNP5 v1.60, MCNP6 (LANL)  FENDL-2.1 (IAEA) neutron cross-section library  B-lite MCNP model (IO) 40 tor-degree with all the components of ITER with modifications for the Upper Port area. C-lite model is not ready for Upper Port.  Activation and Shut-Down Dose Rate (SDDR) calculations:  FISPACT-2007 (CCFE) inventory code and EAF-2007 (EU)  D1S code (ENEA)  R2Smesh (KIT)  Vizualisation: Paraview (Kitware) in vtk-format   We have used the state-of-the-art codes and interfaces approved for ITER neutronics applications Page 10 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM Monte Carlo (MC) radiation transport runs on supercomputers  Simulation of independent random pathways on microscopic level, i. e. tracking of individual particle histories from "birth" to "death"   Simulation can be computed on parallel multiprocessor systems Particle #1 on  CPU Slave #1          …….. Particle #N on  CPU Slave #N Monte Carlo method is most suitable computational technique for nuclear fusion applications. Because of: • Geometry: complex fusion devices can be modelled in 3D geometry without major geometry approximations • Data: continuous energy representation as stored on evaluated data files in ENDF format • Calculation accuracy: only limited by statistics and data uncertainties (no numerical approximations) Page 11 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM 1. Plot the map of statistical relative errors 2. To reduce the statistical relative errors - use Monte Carlo Variance Reduction Techniques (VRTs), like the most advanced MCNP6 weight window generator in an iterative manner.  Arrange the target tally of VRTs close to the area of interest. 3. Confirm that area of interest cross the area of statistically reliable results. MCNP speed-up on HELIOS supercomputer Methodological 3 steps to get the reliable MCNP results:  HELIOS: OpenMP/MPI parallelization for non-biased MCNP5 run speed-up is about 2500 on 4096 cores !   0 1024 2048 3072 409601024204830724096Speed-up (times)Numbers of cores MPI MPI/OpenMP(4 threads/task) IdealHELIOS  Page 12 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM 12   3D decay - source   Neutron 3D flux map   Irradiation scenario   Mesh description   Material description     MCNP input file   1. MCNP   neutrons   2. MCNP   Decay photons    FISPACT    Activation calculation Shut-Down Dose  Rate (SDDR) map   Rigorous 2-Step mesh (R2Smesh-2.2) code (KIT) for SDDR calculations Page 13 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM Advanced-D1S approach developed by ENEA: block-scheme workflow  Time correction factors Fictitious material Representative neutron flux Decay data FISPACT  Activities Irradiation scenario MCNP- Advanced D1S Neutron & decay gamma transport  Shutdown dose rate map FISPACT  Atoms Geometry, materials,  source,tallies Total irradiation 1s scenario Special  data libraries Replacement of prompt photons by decay gammas in MCNP transport calculation    One single MCNP run for neutron and decay photon transport calculation   Special purpose MCNP activation data files: Replacement of prompt photon production data (yields & spectra) by decay gamma data  No activation calculation for decay gamma sources – use of time correction factors  Adjustment of time correction factors required for decay gamma source to assess correct decay gamma dose rate  Depending on radio-nuclide, irradiation history and cooling times. Method developed by ITER JCT and ENEA teams specifically for application to ITER shutdown dose rate estimations  Direct 1-Step (D1S) method of SDDR calculations Page 14 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM Fusion Neutronics Applications Charge eXchange Recombination Spectroscopy (CXRS) and Glow Discharge Cleaning (GDC) installed in UPP#3       Aims:  - Provide neutronics support for design development of Charge eXchange Recombination Spectroscopy (CXRS) in UPP #3 and all the diagnostic systems inside the EPP#17 - Check the current design to satisfy the ITER radiation requirements; - Recommend possible shielding improvements in accordance with ALARA principle – for the Shut-Down Dose Rate (SDDR) in Port Interspace (PI) UPP#3  EPP#17  EPP#17 Diagnostic tenants: • Visible/Infrared wide angle viewing diagnostics (WAV-VIR)  • Core Imaging X-Ray Spectrometer (CIXS) • Tritium Monitor • Divertor thermography Page 15 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM MCAM code for model geometry conversion F3 F4 UPP interspace control volumes F3 & F4 MCNP modeling of the Generic Upper Port Plug (GUPP) MCNP  CAD Page 16 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM GDC CXRS main path MCNP neutronic model CAD CAD-to-MCNP model geometry conversion (using MCAM and McCad codes) Nuclear heating (n+gamma) distribution  Page 17 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM Mirror M5 PI Strong impact of CXRS shutter Impact of CXRS shutter – on neutron flux streaming UPP gap UPP gap FW GDC Page 18 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM EPP#17: MCNP Local Modeling Approach Core Imaging X-Ray Spectrometer (CIXS) with straight 3 Line-of-Site (LOS) apertures  1) Radiation shielding optimization - Shut-Down Dose Rate (SDDR) as the target parameter 2) Reducing the fluence levels on the detectors to minimize the number of their changes  In-port shield Ex-port shield MCNP5 Local Model Page 19 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM The neutron absorption is high on B-10 and on the resonances of W-184. For moderation the best are hydrates (TiH2) materials with hydrogen. Average number of collisions required to reduce a neutron’s energy from 2 MeV to 0.025 eV by elastic scattering Neutron shielding: moderate and absorb ! n - Moderation  n – Absorption on reactions (n,g), (n,alpha),…  Map of total n-flux for the CIXS model with collimated LOS beams Map of total n-flux for the CIXS model having no-collimated LOS beams Tungsten (W) collimators inside the CIXS beams Effect: split of sweeping poloidal angle – neutrons are collided with W-collimators. Result: less length of direct-streaming neutrons. CAD-to-MCNP conversion MCNP model perpendicular cut MCNP model cut along the beams Plasma FW Investigating various shielding combinations during maintenance with significant cost impact:   Outcomes are used to determine whether the maintenance access: • manual  pseudo remote with long reach tools • completely remote handling  EPP#17 maintenance: distribution of decay gamma sources in the MCNP model Plasma FW CIXS with removed shield MCNP Plasma FW CIXS with removed shield Page 22 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM CAD model Screen plate 150 cm Vacuum Ext. flange CIXS maintenance Screen plate placed in Port Interspace (PI) for a worker protection during the Vacuum Extension Flange maintenance. Screen plate is not irradiated by neutrons, it is made of steel, 5 cm thick. Its purpose is to absorb decay gammas from the radioactive materials of CIXS and EPP#17  Screen plate as a temporal shield of personnel Plasma FW Page 23 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM Vertical cross-cut of MCNP local model with Vis/IR in DSM#1 and bulk shield in DSMs #2, #3 filled with B4C (yellow color) and steel (magenta). Local Modeling Approach: Vis/IR system in DSM#1 of EPP #17 Empty slots are filled with B4C  MCNP model CAD model Page 24 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM Map of total neutron flux (n/cm2/s) for the Reference DSM#1 EPP-local model  Max radiation behind CP at beam #3 – contribution 73% of SDDR FW-DSM space shielding (95% steel and 5% water) DSM shielding material: powdered B4C encapsulated in steel cases Closure Plate (CP ) Vertical labyrinth of the Divertor-view system Page 25 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM V1 V2 V3 V4 Vertical distributions of SDDR (microSv/h) behind CP in Reference DSM#1 EPP-local model    CP     30 cm                  100 cm          146 cm                           246 cm     73 169 238 71 31 53 56 29 23 28 20 11 10 beam #3 Strongest impact to SDDR: Void in all windows of CP Page 26 Neutronics for Diagnostic Systems of ITER Port Plugs, 2015 ANS WM SDDR detector SDDR (microSv/h) in Ref. EPP-local model with powdered B4C, density 1.89 g/cc, at 30cm/100cm from CP SDDR (microSv/h) at 30 cm from CP, DSM with BGlass + B4C 70, dens. 2.541 g/cc SDDR (microSv/h) at 30 cm from CP, DSM with BGlass + B4C 80, dens. 2.534 g/cc SDDR (microSv/h) at 30 cm from CP, DSM with sintered B4C, dens. 2.52 g/cc V4 73/31 -7% -15% -41% V3 238/53 -22% -21% -35% V2 169/56 -24% -37% -48% V1 71/29 -12% -36% -22% Effect on SDDR behind CP by varying shielding material compositions  (Sintered and two types of vitrified B4C were considered instead of powdered B4C used as Reference shielding materials) Conclusions for Vis/IR system neutronics • Shield improvement of the Divertor-view vertical labyrinth has been provided. • Father design work could be focused on horizontal labyrinth inside the beam #3, which contributes up to 73% in middle detector behind the Closure Plate (CP). • Reduction of SDDR behind the Closure Plate windows are expected by closing the holes with window materials. These SDDR calculated with void CP windows. • The best shielding performance is proven for the sintered B4C, resulting to SDDR reduction by 40%, while increasing the weight only by 424 kg (5% of the total weight of DSM). • The SDDR results are presented with 5% -11% MCNP statistics of the D1S method.   

Neutronics for diagnnostic systems of ITER port plugs

https://publikationen.bibliothek.kit.edu/240102855/3816952

Neutronics for diagnnostic systems of ITER port plugs

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