Calculation of control rod worth and temperature reactivity coefficient of fuel and coolant with burn-up changes for VVRS-2MWth nuclear reactor

One of the main issues of a nuclear reactor is safety and controlling system. This system is designed to control the power of reactor and to prevent accidents. Control rods worth calculation is used to specify safety margin of reactor. Temperature reactivity coefficients of fuel and coolant are one of the inherent factors that can control reactor power. This study has been done about control rod worth calculation and temperature reactivity coefficients of a VVRS-2 MWth reactor. The reactor core has been simulated by using WIMSDB5 and CITATION-LDI2 codes to perform neutronic calculations. The WIMSDB5 code solves neutron transport equation and obtains macroscopic cross-sections (Winfrith, 1982). The CITATION-LDI2 code solves diffusion equation for the reactor core (Winfrith, 1972). These two codes were linked by an interface that has been programmed with DELPHI (Winfrith, 1998). The rod worth and reactivity coefficients are calculated considering burn-up calculations. The burn-up calculation is performed with WIMSDB5 code. The new macroscopic cross-sections were used in a new condition. Control rods worth and temperature coefficients are calculated with these models. The obtained results of control rods worth are compared with some experimental results; and the reliability of the method was confirmed. Reactivity coefficients results are compared with the results that were obtained from the simulation model. The simulation model has used Point Kinetic equations and single heated channel model respectively for neutronic and thermo hydraulic calculations (Kazimi et al., 1990).