Study of the Effect of Utilizing Thorium and Protactinium-231 in Vodo-Vodyanoi Enyergeticheskiy Reactor-1000 Fuel Assembly Using Monte Carlo N-particle (MCNP) Simulation

One type of nuclear reactor is the Vodo-Vodyanoi Enyergeticheskiy Reactor-1000 (VVER-1000). In this work, we will discuss the effect of giving thorium as a fuel and protactinium as a combustible poison in the VVER-1000 fuel assembly using a simulation program based on Monte Carlo N-Particle (MCNP). The purpose of this work was to determine the multiplication factor of the fuel assembly with variations in ThO 2 (without fissile material) and variations in the fractions of gadolinium and protactinium-231, as well as the burnup rate for 5 years. Thorium-232 is predicted to be a substitute for UO 2 fuel in reactors because of its abundant material and can produce uranium-233 which is a better fuel than uranium-235. While protactinium-231 has a function other than absorbing neutrons, generating it can further produce fissile material that aids in chain reactions. Based on the simulation, the multiplication factor with protactinium-231 has a higher value than gadolinium. In addition, the larger the burnable poison fraction, the smaller the multiplication factor value is. In addition, the multiplication factor and burnup rate for 5 years were also obtained. The optimal fuel composition to use is a mixture of ThO 2 of 5% - 15% (from non-burnable poison) and 5% (from burnable poison), as well as the optimal amount of burnable poison used in the case of fuel given 5% ThO 2 is 4% - 6% for Pa-231 and 0.5% - 2.5% for Gd 2 O 3 .