Study of Reactivity Effect on Dynamic Behavior of VVER-1000 Reactor Core

In the study of stability of VVER-1000 reactor core the state variables method and Routh criterion were used. By calculating temperature reactivity coefficients for fuel and moderator we have shown that the reactor core remains stable against 1$ reactivity or less than 1$. The coefficients were calculated for different concentration of boric acid as a function of temperature. The concentration above 1800ppm prevails itself as a positive effect. It should be noted that 1800ppm boric acid concentration had minimal effect on fuel temperature reactivity coefficient. The simulation calculation for 1$ reactivity insertion showed that the prompt neutron life time between 2 to 50µs causes sharp rise in flux for shorter lifetime, while decays remain more or less the same for 2 to 50µs prompt neutron lifetime.