کوروش قیصری

In order to manage the fuel and design of the reactor core cycle, the burnup should be calculated according to the type and amount of fuel and the amount of energy produced during the reactor's cycle. A modern solution in the nuclear industry is to increase the cycle time of the reactor. In order to increase the performance of the VVER-1000 reactors for a period of 18 months, Russian TVEL has provided various designs for fuel assemblies. Increasing the cycle time will increase the operating time of the reactor and, on the other hand, reduce the time spent on fuel switching operations. The new generation of TVSA fuel assemblies in this study provides the ability to optimize the fuel's uranium capacity, high burnup, improve thermal reliability and enhance safety in its design. In this study, fuel assemblies of Bushehr reactor and TVSA model reactor have been studied in two work periods using MCNPX2.6 computational code. Also, the cross-sections of neutron reactions at working temperatures are calculated using the NJOY code. In the design of the TVSA assemblies, the standard burnable absorbers material of CrB2 has been change to gadolinium oxide burnable absorber rods (Gd2O3) and, in addition, they have decreased, and the length of the reactor fuel cycle has increased from 12 months to 18 months. As a result of these changes, the burnup increased significantly and in addition, the uniform distribution of power was achieved at the core of the reactor.