Adaptation of the Nagra Activation Analysis Methodology to Serpent

Transcription

1 Adaptation of the Nagra Activation Analysis Methodology to Serpent Valentyn Bykov May 31, 2018, Serpent UGM 2018

2 Nuclear Power in Switzerland Reactor Type Net First MWe power Beznau 1 PWR Beznau 2 PWR Gösgen PWR Mühleberg BWR Leibstadt BWR Closure scheduled for 2019 (Nagra supports decommissioning planning activities)

3 3D MCNP Models Made mostly manually Cart. & Hex. Lattice Nodal core definition (240x25) - Void (mat. card) - Power (sdef probability) Explicit, detailed reactor internals

4 ORIGEN-based Activation Calculations Hybrid VR ADVANTG ww MCNP run multi-group flux information (fmesh) Operating History User input Material definition Ray-trace geometry with LAVA Activation ORIGEN.csv.csv.csv.csv.silo Based on ORNL work for ITER

5 Flux Information (MCNP) Run Mesh tally for each component - Cartesian - Millions of cells (generally 5cm res.) - SCALE-56 energy group structure (can use any other) Very difficult transport problem: Accelerated with Hybrid variance reduction

6 Variance Reduction (ADVANTG) Hybrid VR with ADVANTG User defines (structured) grid - only non-rotated Cartesian :-( LAVA ray-traces MCNP model, assigns materials to each cell DENOVO solves adjoint flux (CADIS and FW-CADIS) WW file generated Separate optimization for each component run Makes calculations affordable for single CPU workstations (but sometimes there are issues)

7 Validation Phase 1: Transport - Foil Activation Phase 2: Activation - Direct spectroscopy of modeled components

8 Material Definition (LAVA) Use LAVA (from ADVANTG) to ray-trace the model, assign materials for each cell of mesh tally Can use modified MCNP input removing surroundings of the component (water, other components) Impurities defined here, taken from: - from elementary analysis of the actual component (best) - from elementary analysis of similar components, other plants (ok) - from literature (risky!)

9 Operation History Operation History provider by the user in the input file Describe full NPP life + decay until reference date Two vectors: time (in sec) and power (value by which to multiply the MCNP result particles / s) Merely scales MCNP result no changes in void profile, power distribution / leakage - Generally: pic one point in time as representative, accept effects - Can split calculation into two separate ones, e.g.: 50yr full power = (25yr full power + 25yr decay) core1 + (25yr full power) core

10 Activation Calculations Using ORIGEN (like SCALE 6.2 but modified to have a C++ API) - Based on CRAM = very fast (1-2 sec per cell with full NPP history) Information provided over API MPI Parallelization Results output as both text (CSV) and graphic (SILO) - User defines nuclides of interest - For each nuclide, mesh tally sized table with values in Bq or Bq/g - Can post-process CSV (bash scripts, spreadsheet operations) - Can post-process SILO (VisIt)

11

12 Application to Packaging Planning Detailed activation distribution used to plan segmentation, packaging ILW cask (with various shielding) LLW cask (cheaper, bigger) Iterative process with the NPP Number of subcomponents ILW casks LLW casks

13 Application to Packaging Planning 13 Datum/Autorenkürzel Filename

14 Application to Decommissioning Planning Dose Rate fields repeatedly requested Currently no automated way, but link planned ORNL accelerates calculations with MS-CADIS VR

15 Current Methodology Under development, but already used for production runs Done for Swiss NPPs (all by 2019), but also commercially - Gundremmingen B&C (Germany s two biggest BWRs) - Basel Research Reactor Nuclear Eng. MSc students involved - 7 MSc Theses But there is room for improvement for VR, post-processing Could the same (and more) be done with Serpent?

16 Transition Checklist N/A Models with large, complex geometry Powerful variance reduction Flux mesh tallies or Direct Component Activation (given known operation history) Possibly define resulting gamma source term (for dose rate calculations) Tools for results post-processing 16 Datum/Autorenkürzel Filename