Neutronic and Thermal-hydraulic modelling of high performance light water reactor

In EU, the use of supercritical-pressure water as coolant in a light water reactor is studied under the name High Performance Light Water Reactor (HPLWR). During the “HPLWR2” project, the technological feasibility of the concept is examined using various analysis methods. In a HPLWR core the temperature of the coolant increases from 280 ºC to 500 ºC. Consequently, the large decrease of coolant density induces a strong coupling between neutronics and thermal-hydraulics. Because of this, coupled codes are required for conducting analysis of transients with large spatial variations in thermal- hydraulic or neutronic properties. In addition, the three pass core design can only be modelled using a three-dimensional code for core calculation. At the Technical Research Centre of Finland (VTT), an advanced three dimensional nodal code TRAB-3D was selected for calculating neutronics. It is internally coupled to a system code SMABRE for thermal-hydraulics. This paper outlines the modifications made on SMABRE to extend its functionality to supercritical pressures and presents the current state of the HPLWR model for TRAB-3D/SMABRE. Parametrized two-group cross-sections for a HPLWR fuel assembly generated with MULTICELL deterministic transport code and a subroutine for handling the cross-sections was received from KFKI Atomic Energy Research Institute [1]. Group constants for HPLWR were also generated using a new Monte Carlo code, PSG, developed at VTT. Comparison of the group constants is presented together with multiplication factors calculated with MCNP4C.