Using a user–defined function in Ansys Fluent to implement the energy release profile in model fuel elements taking into account radiation heating

Abstract

The paper presents a model of an experimental device tested on the complex of impulse graphite reactor of the Branch IAE RSE NNC RK, designed to study the possibility of changing the neutron spectrum of the reactor from thermal to fast. At the stage of preparation for testing, a series of neutron-physical studies were carried out using the MCNP. The purpose of these studies is to determine the specific energy release both in the model fuel elements and in non-fuel structural elements of the experimental device during their radiation heating, taking into account the thermal state of the reactor core. After that, the obtained data are used as initial conditions for development of user-defined functions and conducting thermophysical calculations to determine the distribution of the temperature field in the tested device, the ANSYS Fluent software package. The method for calculating the specific energy release in non-fuel structural elements during their radiation heating in the impulse graphite reactor, considering its thermal state, has been used relatively recently. It requires a special approach to the implementation of the required energy release profile when carrying out thermophysical calculations in the Ansys software. The paper also illustrates the advantages of using a custom function in Ansys Fluent to define the profile of the energy release in model fuel elements and structural elements of an experimental device depending on time and height. In addition, the results of a thermophysical calculation of the experimental device for determining the distribution and maximum values of temperature in fuel and non-fuel structural elements are presented.