Modeling and flux reconstruction of unstructured geometric reactor

•The CSG modeling is applied to generate arbitrary triangular meshes.•A flux reconstruction method based on the statistics of biharmonic spline interpolation of Green’s function is proposed. Innovative reactors are typically designed with complex geometric structures, which put forward higher requirements for deterministic reactor core calculation. In the complex geometric reactor core calculation, the LAVENDER code in the SARAX code system was used, which is based on the three-dimensional neutron transport nodal method. A modeling method based on constructive solid geometry was applied to generate arbitrary triangular-z meshes. To meet the requirements of coupling core physics calculation with thermal and other physics fields, a flux reconstruction method based on the statistics of biharmonic spline interpolation of Green’s function has been proposed, which was used to reconstruct the flux of specified region. Three reactors with different types were calculated to verify the accuracy of the flux reconstruction method. Numerical results show that the fluxes of specified region calculated by the proposed flux reconstruction method in the SARAX code were in good agreement with the direct full-core Monte-Carlo results.