Ferraro, D.

Garcia, M.

Imke, U.

Kliem, S.

Leppänen, J.

Mercatali, L.

Sanchez-Espinoza, V.H.

Valtavirta, V.

Van Uffelen, P.

English

Sanchez-Espinoza, V. H.

KITopen

INSTITUTE for NEUTRON PHYSICS and REACTOR TECHNOLOGY (INR)www.mcsafe-h2020.euThis project is funded by the  Horizon 2020- Research and Innovation Framework Programme under the  GA Nr.755097High-fidelity multiphysics simulations for Light Water Reactors in the McSAFE H2020 projectL. Mercatali (KIT), V. H. Sanchez-Espinoza (KIT), M. Garcia (KIT), D. Ferraro (KIT), U. Imke (KIT), J. Leppänen (VTT), V. Valtavirta (VTT), S. Kliem (HZDR), P. Van Uffelen (JRC)• The McSAFE H2020 project• High-fidelity multiphysics• Coupling approaches• Depletion• ConclusionsContentsL. MercataliAAA Workshop – December 2, 2019 (GRS)2 18.11.2019Introduction Predictive simulations = backbone of nuclear reactor safety Most of the tools developed when computing resources and capabilities were limited Shift towards high-fidelity methods taking advantage of progress in computing (hardware/software) Reactor operating closer to their safety limits due to less conservative safety evaluations Core analysis relies mainly on deterministic neutronic codes (daily work) Alternative/supplementary option:• Use MC codes capable of simulating the neutron transport without approximations• Obtain reliable data for any core state at fuel pin level (experimental data at pin level is scarace and not easy to be measured)• Potential use taking advantage of HPC and parallelizationL. MercataliAAA Workshop – December 2, 2019 (GRS)3 18.11.2019The McSAFE H2020 project Three-year project (09.2017 - 08.2020) Participants:• 9 research institutions: KIT, VTT, HZDR, JRC, CEA, NRI, KTH, DNC, Wood• 3 industry partners: EKK, CEZ, EdF High-fidelity multiphysics for safety analysis of LWRs:• Monte Carlo neutron transport: Serpent2, Tripoli4, MCNP, MONK• Subchannel thermalhydraulics: SUBCHANFLOW (SCF)• Fuel-performance analysis: TRANSURANUS (TU) Main developments• Serpent2-SCF(-TU) coupling for steady-state, burnup and transient problems• Optimization of steady-state and transient capabilities for HPC• Optimization for massive (full-core pin-by-pin) depletion problems Validation with plant data• PWR-Konvoi• VVER-1000L. MercataliAAA Workshop – December 2, 2019 (GRS)4 18.11.2019McSAFE project structureL. MercataliAAA Workshop – December 2, 2019 (GRS)5 18.11.2019High-fidelity multiphysics Main objectives:• Avoid approximations (multi-scale approach) in neutronics• Calculate local safety parameters directly: Burnup cycle. Transient scenarios.• Provide reference solutions for lower order methods Neutronics:• Continuous-energy Monte Carlo neutron transport• Pin-by-pin power tallying and burnup calculation Thermal-hydraulics:• Pin-level subchannel thermal-hydraulics• Coolant and fuel safety parameters Fuel performance:• Pin-level thermomechanical analysis• Fuel safety parametersL. MercataliAAA Workshop – December 2, 2019 (GRS)6 18.11.2019Software design Master-slave internal coupling:• SCF and TU (slaves) modularized and embedded in Serpent2 (master).• Traditional approach, reference for performance. Object-oriented coupling:• Serpent2, SCF and TU modularized and coupling scheme implemented in a separate supervisor program.• More innovative approach, potential benefits from the object-oriented design.• Main features: Inheritance-based APIs. Object-oriented supervisor. Mesh-based feedback. Numerical method:• Operator splitting.• Picard iterations.• Pin-by-pin feedback.L. MercataliAAA Workshop – December 2, 2019 (GRS)7 18.11.2019Mesh-based field exchange Serpent2:• Multiphysics interfaces based on superimposing meshes on the tracking geometry to set densities and temperatures and get power• Internal meshes represented as unstructured meshes for feedback exchangePρ, TL. MercataliAAA Workshop – December 2, 2019 (GRS)8 18.11.2019Mesh-based field exchange SUBCHANFLOW:• Subchannel model defined by hydraulic parameters and connectivity• Channel and rod geometry given by coolant and fuel unstructured meshes for feedback exchange and interpolationρcool, TcoolTfuelPL. MercataliAAA Workshop – December 2, 2019 (GRS)9 18.11.2019Mesh-based field exchange TRANSURANUS:• Solution scheme independent for each rod• Rod mesh to manage input and output between the multiphysics interface and each solver instanceTfuelP, hclad-cool, Tcool, pL. MercataliAAA Workshop – December 2, 2019 (GRS)10 18.11.2019Depletion calculationsL. MercataliAAA Workshop – December 2, 2019 (GRS)11 18.11.2019Serpent2-SCF: steady-state calculation Standard steady-state neutronic-thermalhydraulic coupling:• Power calculated by Serpent2 and used in SCF as heat source• Cooling conditions calculated by SCF and ρcool, Tcool and Tfuel used in Serpent2• Iterative scheme with pin-by-pin feedback Verification with the VERA Core Physics Benchmark (PWR) [1]Result Keff ΔKeff (pcm)VERA-CS 1.16361 -RMC-CTF 1.16239±0.00010 -90MC21-CTF 1.16424±0.00003 47MCNP6-CTF 1.16500±0.00006 103Serpent2-SCF (OO) 1.16552±0.00003 141Serpent2-SCF (MS) 1.16560±0.00003 147[1] “Development of an object-oriented Serpent2-SUBCHANFLOW coupling and verification with Problem 6 of the VERA Core Physics Benchmark”, M. García, D. Ferraro, et al., M&C2019.L. MercataliAAA Workshop – December 2, 2019 (GRS)12 18.11.2019Serpent2-SCF: burnup scheme Monte Carlo depletion scheme with thermalhydraulic feedback:• Burnup calculation integrated in Serpent2• Predictor-corrector and Stochastic Implicit Euler (SIE) methods• Iterative quasi-stationary scheme with pin-by-pin feedback Verification with TVSA-type fuel assemblies (VVER-1000) [2]0 5 10 15 20 25 30 35 40010020030040050060070080090010000.850.900.951.001.051.101.151.201.251.301.350 100 200 300 400 500 600 700 800 900 1000MWd/kgUDifference [pcm]KeffFull power days MCU - 4.4U [Ref] S-SSCF - 4.4U MCU - 4.4 U-Er [Ref] S-SSCF - 4.4U-Er-ErDifference - 4.4U [pcm] Difference - 4.4 U-Er [pcm][2] “Serpent/SUBCHANFLOW coupled burnup calculations for VVER fuel assemblies”, D. Ferraro, M. García, et al., PHYSOR2020 (submitted).L. MercataliAAA Workshop – December 2, 2019 (GRS)13 18.11.2019Serpent2-SCF-TU: motivation Fuel behavior during burnup:• Extremely complex multi-physics problem• Important for safety assessment• Potential impact on the Doppler feedback SCF approach:• Thermal properties: cP(T), k(T), αT(T)• Gap width: thermal expansion, cracking and swelling dependent on burnup• Gap conductance: radiation and conduction TU approach:• Full thermomechanic analysis• Main relevant physics• Validated extensively• Reference solutionL. MercataliAAA Workshop – December 2, 2019 (GRS)14 18.11.2019Serpent2-SCF-TU: burnup scheme Main features [3]:• Semi-implicit burnup scheme• Fully coupled neutronics, depletion, thermalhydraulics and thermomechanics• Independent depletion in Serpent2 (detailed) and TU (simplified)• SCF simple fuel-rod solver replaced by TU thermomechanical analysis Verification [4]:• PWR depletion problem based on the VERA Benchmark• Comparison with Serpent2-SCF (w/o TU)[3] “A Serpent2-SUBCHANFLOW-TRANSURANUS coupling for pin-by-pin depletion calculations in Light Water Reactors”, M. García, D. Ferraro, et al., Annals of Nuclear Energy (in press).[4] “Serpent2-SUBCHANFLOW-TRANSURANUS pin-by-pin depletion calculations for a PWR fuel assembly”, M. García, D. Ferraro, et al., PHYSOR2020 (submitted).L. MercataliAAA Workshop – December 2, 2019 (GRS)15 18.11.2019Serpent2-SCF-TU: depletion analysis Gap temperatures:• Minor differences in cladding temperatures due to material properties• Significant differences in fuel outer temperatures relative to the temperature step in the gapL. MercataliAAA Workshop – December 2, 2019 (GRS)16 18.11.2019Serpent2-SCF-TU: depletion analysis Gap properties:• Heat transfer coefficient underpredicted by SCF (~50% on average)• Gap width over predicted by SCF (~0.005mm)• Larger gap temperature increase for SCFL. MercataliAAA Workshop – December 2, 2019 (GRS)17 18.11.2019Serpent2-SCF-TU: depletion analysis Fuel temperatures:• Significant underprediction by SCF• Differences mostly due to conductivity degradation with burnupL. MercataliAAA Workshop – December 2, 2019 (GRS)18 18.11.2019Serpent2-SCF-TU: depletion analysis Neutronic solution:• Very small impact on multiplication factor• No improvement using radial temperatures• Power dominated by statistical uncertaintyL. MercataliAAA Workshop – December 2, 2019 (GRS)19 18.11.2019Serpent2-SCF-TU: depletion analysis Fuel-performance results:Xe releaseGap conductance (EOC)L. MercataliAAA Workshop – December 2, 2019 (GRS)20 18.11.2019Takeaways from fully coupled burnup Gap behavior:• Significant improvement in the conductivity and width using TU.• Reference solution for SCF to improve correlations Fuel temperatures:• Underprediction in SCF up to ~350K (centerline) and ~175K (average)• Reference solution for SCF to improve material properties Neutronics:• Minor impact in local and global results Safety parameters:• No significant impact on neutronics• No impact on DNBR calculation• Large improvement in fuel temperatures• Pin-by-pin fission gas release• Pellet-cladding interaction modelledL. MercataliAAA Workshop – December 2, 2019 (GRS)21 18.11.2019Towards full-core pin-by-pin depletion Massive computational requirements [5]:• ~109 neutrons per transport cycle• ~1-5TB of memory, mainly for burnable materials[5] “Foreseen capabilities, bottlenecks identification and potential limitations of Serpent MC transport code in large-scale full 3-D burnup calculations”, D. Ferraro, M. García, et al., ICONE26.L. MercataliAAA Workshop – December 2, 2019 (GRS)22 18.11.2019Collision-based Domain Decomposition Traditional parallel scheme for Monte Carlo transport:• Particle-based parallelism with domain replication• Usually excellent speedup, but no memory scalability Collision-based domain decomposition:• Data decomposition for burnable materials• Memory scalability, acceptable speedupy = 3.90E+00x + 4.47E+009.7E+03 1.1E+05 2.1E+05 3.1E+05 4.1E+05 5.1E+05 6.1E+05 7.1E+05 8.1E+050501001502002503003504004505000501001502002503003504004505000 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90Number burnable materials (depletion zones)Required RAM [GB]Number of FA fully divided Total MEM [GB]MEM required by Materials [GB]01020304050607080901000.0E+001.0E‐012.0E‐013.0E‐014.0E‐015.0E‐016.0E‐017.0E‐018.0E‐019.0E‐011.0E+000 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100MPI scalability (1/ normalized time)Time relative to 1node with 20 processorsNumber of nodesTotal running time mins [normalized to 1 node with 20 cores]MPI node parallel efficiencyPerfect node scalabilityMultithread memory requirement Parallel scalabilityL. MercataliAAA Workshop – December 2, 2019 (GRS)23 18.11.2019Full-core steady-state calculations Verification with the X2 VVER-1000 benchmark [6]:• ~150 pcm agreement with measured data at EOC (critical state)• Good agreement in global results[6] “Serpent/SUBCHANFLOW coupled calculations for a VVER core at hot fullpower”, D. Ferraro, M. García, et al., PHYSOR2020 (submitted).L. MercataliAAA Workshop – December 2, 2019 (GRS)24 18.11.2019Subchannel coarsening Coarsening method [7]:• Build the subchannel model• Superimpose a mesh defining zones• Merge subchannels and condense hydraulic data for each coarse channel[7] “A subchannel coarsening method for Serpent2-SUBCHANFLOW applied toa full-core VVER problem”, M. García, D. Ferraro, et al., PHYSOR2020 (submitted).L. MercataliAAA Workshop – December 2, 2019 (GRS)25 18.11.2019Transient analysis (1/2) Goal: Monte Carlo simulations of transients with feedback→ “move towards high fidelity calculations” Development of dynamic MC-methods for transients analysis• Development of time-dependent dynSERPENT-SCF e.g. implementation of methods to account for the prompt neutron and gamma heat deposition in the coolant• Development of time-dependent dynTRIPOLI-SCF • Development of time-dependent dynMCNP-SCF• Variance reduction for MC-codes with dynamic capability to improve the efficiency of time-dependent MC solutions e.g. Uniform Fission Sites (UFS)• Methods for optimal parallel scalability of MC-TH codes for dynamic simulations to take profit of massively parallel environments in the frame of industry-like applications• Verification of developed tools on 3x3 pin cluster or PWR minicore (3x3 FA)L. MercataliAAA Workshop – December 2, 2019 (GRS)26 18.11.2019Transient analysis (2/2) Code-to-code verification with Tripoli4-SCF [8] Validation with SPERT-IIIE experiments [9][8] “Serpent/SUBCHANFLOW pin-by-pin coupled transient calculations for a PWR minicore”. D. Ferraro, M. García, et al. Annals of Nuclear Energy (in press).[9] “Serpent/SUBCHANFLOW pin-by-pin coupled transient calculations SPERT-IIIE hot full power tests”, D. Ferraro, M. García, et al., Annals of Nuclear Energy (submitted).L. MercataliAAA Workshop – December 2, 2019 (GRS)27 18.11.2019Dissemination Project web-page: www.mcsafe-h2020.eu User Group Synthesis reports Newsletters Training Course• March 25-27, 2020 (KIT)L. MercataliAAA Workshop – December 2, 2019 (GRS)28 18.11.2019Summary Development stage (first two years) almost over Serpent2-SCF(-TU) coupling implemented and optimized Validation stage (last year) beginning, preparation of experimental data and core specifications in progress Depletion calculations:• Serpent2-SCF-TU fully-coupled depletion scheme: Improvement in the modelling of the fuel during irradiation Minor impact on the neutronic solution Large impact on safety parameters such as gap behavior and fuel temperature• Optimization for full-core pin-by-pin problems: Subchannel coarsening methodology for SCF and CDD for Serpent2 The project will deliver improved and validated high-fidelity numerical simulations tools that can be used by different end-users to provide reference solutions to deterministic codes for safety demonstration

High-fidelity multiphysics simulations for Light Water Reactors in the McSAFE H2020 project

https://publikationen.bibliothek.kit.edu/1000105115/55091650

High-fidelity multiphysics simulations for Light Water Reactors in the McSAFE H2020 project

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