Dynamic properties of the primary circuit of a WWER-440 type nuclear power plant under various operating regimes

A dynamic model of the primary coolant circuit was developed for the control system of the WWER 440 type reactor, including the transient characteristics of the primary coolant circuit variables in dependence on possible operating states of the power plant. The graphs show some results of the computations of the transients of the primary coolant circuit variables in dependence on the reactor output and on the temperature reactivity coefficient which changes in operation depending on the concentration of boric acid. The results show that within the region of changes in reactor output of 100% to 10% and changes in the temperature reactivity coefficient of the coolant of 0 to -4x10-4, significant changes occur in the transients of the output and of the reactor core temperature. In order to secure the automatic operation of the reactor control system within the above ranges the said dynamic characteristics have to be observed. (O.K.)