Control Rod Worth Calculations in Research Reactors

Abstract

Nuclear reactor physics requires broad knowledge of parameters affecting reactor operation. Power distribution, control rod worth, shutdown margins, etc., have to be determined throughout the reactor cycle. The efficiency of predicting these quantities depends on the models used to determine neutron density in space, direction and energy. In this work, control rod worth for different core configurations of the ET-RR-2 (Egypt Second Them1al Research Reactor) is evaluated. This requires the performance of neutronic calculations, which involves three steps. First, solving the neutron transport equation to obtain the effective cross sections for the different zones of the reactor in a five energy group structure. The cell calculation code WIMSD4 is used in this step. Intermediate module is developed to prepare and transfer cross section data and other cell parameters from the cell calculation code to the core calculation code, in a second step. The third step is the solution of the multigroup neutron diffusion equation to obtain values for the effective multiplication factor. In this step, the core calculation code DIXY2 is used, with the effective cross sections obtained from step (I) as input. The calculations were performed using nuclear data based on ENDF/BV library. The neutrortic calculation codes solve the transpmt and the multigroup diffusion equations. The methods used to solve these equations are discussed in this thesis. The variation of cross sections as a function of neutron energy is given for each isotope in the control rod material, which is a silver-indium-cadmium alloy.