Core Neutronics Methods and Codes

Research goals

Improve the 3D core analysis by using neutronic solvers based on different approaches i.e. diffusion, transport and Monte Carlo as stand-alone or coupled with different thermal hydraulic codes (1D, 3D TH).  This neutronic codes allows the prediction of key-safety parameters that determine the inherent safety features of reactor cores and determine the core behaviour under accidental conditions. Coupled with thermal hydraulic codes, core transients e.g. REA, ATWS, etc. can be predicted with different degree of accuracy. All deterministic neutronic solvers applied a two-step approach, where the first one is devoted to the generation of nodal or pin level homogenized/heterogeneous cross sections in dependence of thermal hydraulic parameters covering a parameter variation range that is expected to occur under accidental conditions.  These so-called “branch calculations” must consider the design peculiarities e.g. heterogeneities of core loadings during the cross section generation process (condensation, homogenisation, shelf shielding) and the material compositions when performing lattice physics calculation either with deterministic or stochastic codes. They will determine the quality and accuracy of the core solvers.

Tools for lattice physics and branch calculations

At KIT, both deterministic (NEWT, POLARIS) or Monte Carlo (SERPENT2) codes are used for the generation of few group condensed cross sections for 3D core solvers e.g. PARCS, DYNSUB5.0, PARAFISH. 

  • Lattice physics: Deterministic SCALE6 code system: The Standardized Computer Analysis for Licensing Evaluation (SCALE) code system is being developed by ORNL.
  • Lattice physics: MC code SERPENT2: SERPENT is a three-dimensional continuous-energy Monte Carlo reactor physics burnup calculation code, developed at VTT Technical Research Centre.
  • Nodal 3D diffusion solver:  In the frame of the KIT international cooperation agreement CAMP with the US NRC, the 3D core simulator PARCS is being used, validated, improved and applied. The Purdue Advanced Reactor Core Simulator (PARCS) is based on multi-group nodal diffusion and SP3 steady state and transient solution for hexagonal and square fuel assembly geometries and The DYN3D (Diffusion and SP3) core simulator, developed at HZDR, is being validated and coupled with subchannel codes at KIT in the frame of the HGF NUSAFE Program.


The applications of neutronic codes is embedded in international activities of the NEA/OECD, in European H2020 projects, where core analysis of different details (nodal, high fidelity transport and stochastic) is envisaged, and in the frame of different doctoral thesis at the Mechanical Engineering Faculty of KIT. The core simulators (static and dynamic capability) are important tools for the safety evaluation of reactors and hence they are used in the frame of doctoral thesis and master studies.

Computational tools