Institute for Neutron Physics and Reactor Technology (INR)

High fidelity Multiphysics based on Monte Carlo /SubChannel Codes

Research goal

The goal of Monte Carlo based high fidelity methods is to perform simulations of pin/fuel assembly clusters or whole cores using Monte Carlo codes and taking into account local thermal hydraulic conditions predicted by subchannel codes.

Potential applications

  • Static high fidelity simulations of an kind of reactor cores
  • Depletion calculations including feedbacks between neutronic, thermal hydraulic and thermo-mechanics at pin / subchannel level of real VVER / PWR-cores
  • Analysis of transients in reactor cores at pin / subchannel level of real cores
  • Provide reference solutions for any low order deterministic codes


  • Depletion capability: Validation done using plant data measured in a VVER-1000 and in a pre-Konvoi PWR core
  • Transient capability: validation done using the unique test series of the SPERT III E REA (T84, T85)
  • Extension of validation basis needed.

High fidelity Multiphysics coupled Codes

Novel coupling schemes were developed based on Monte Carlo solvers during different EU Projects (HPMC and McSAFE) as listed hereafter:

  • MCNP5/SubChanFlow: Coupling based on internal coupling optimized to solve full cores at pin /subchannel level (FP7 HPMC Project)
  • Serpent2/SubChanFlow: Coupling based on an internal master-sleeve approach very much appropriate for the simulation of transients (H2020 McSAFE Project)
  • Serpent2/SubChanFlow/Transuranus: Coupling based on the modular and standardized ICoCo-approach for the static and depletion problems of full cores with square (PWR) and hexagonal (VVER) fuel assemblies optimized for pin /subchannel level simulations of real cores (H2020 McSAFE Project)


TRANSURANUS is a fuel performance code of JRC/ITU at Karlsruhe. The code predicts the physical status of the fuel at different fuel cycle stages. TRANSURANUS simulates the fuel behaviour using e.g. fuel manufacturing and operational data, reactor and fuel-cladding material properties data as well as operational history for both steady-state and transient simulations (RIA, LOCA, etc.).



 Internal coupling of Serpent2/SubChanFlow:   

ICoCO-based coupling of Serpent2/SubChanFlow and Serpent2/SubChanFlow/Transuranus   

Internal master/sleeve coupling of Serpent2/SubChanFlow for transient analysis: Dynamic SERPENT2/SCF coupling approach developed within H2020 McSAFE project for the analysis of transients in real LWR cores.  


  1. Diego Ferraro, Manuel Garcia, Ville Valtavirta, Uwe Imke, Riku Tuominen, Jaakko Leppännen, Victor Sanchez-Espinoza; Serpent/SUBCHANFLOW pin-by-pin coupled transient calculations for the SPERT-IIIE hot full power tests. ANE 42(2020)107387.
  2. Manuel Garcia, Jaakko Leppänen, Victor Sanchez-Espinoza; A Collision-based Domain Decomposition scheme for large-scale depletion with the Serpent 2 Monte Carlo code. ANE submitted June 2020.
  3. Diego Ferraro, Ville Valtavirta, Manuel Garcia, Uwe Imke, Riku Tuominen, Jaakko Leppännen, Victor Sanchez-Espinoza; OECD/NRC PWR MOX/UO2 core transient benchmark pin-by-pin solutions using Serpent/SUBCHANFLOW
  4. Manuel García, Riku Tuominen, Andre Gommlich, Diego Ferraro, Ville Valtavirta, Uwe Imke, PaulVan Uffelen, Luigi Mercatali, Victor Sanchez-Espinoza, Jaakko Leppänen, Sören Kliem; Serpent2-SUBCHANFLOW-TRANSURANUS coupling for pin-by-pin depletion calculations in Light Water Reactors. ANE 139 (2020 May) 107213.
  5. Manuel Garcia, Diego  Ferraroa,Ville Valtavirta, RikuTuominen, Uwe Imke, Jaakko Leppänen, Victor Sanchez-Espinoza; Serpent2-SUBCHANFLOW pin-by-pin modelling capabilities for VVER geometries. ANE 135 (2020 January)106995.
  6. Diego Ferraro, Manuel Garcia, Uwe Imke, Ville Valtavirta, Jaakko Leppänen, Victor Sanchez-Espinoza; Serpent/SCF pin-level multiphysics solutions for the VERA Fuel Assembly benchmark. ANE 128 (2019 June) p-102-114.
  7. Däubler M., Ivanov A., Sjenitzer B., Sanchez V., Stieglitz R., Macian-Juan R.; High-Fidelity coupled Monte  Carlo Neutron transport and thermal-hydraulic simulations using Serpent 2/SUBCHANFLOW - Part I: Implementation and Solution Verification.  Annals of Nuclear Energy 83 (2015) 352–375.
  8. Bart L. Sjenitzer, J. Eduard Hoogenboom , Javier Jiménez Escalante , Victor Sanchez Espinoza; Coupling of dynamic Monte Carlo with thermal-hydraulic feedback. ANE 76 (2015)27-39.