[en] A relationship between temperature pulsations of cooling water and surfaces of actuator parts in the control and protection systems (CPS) of WWER type reactors is investigated on the base of solution of a non-stationary problem of thermal conductivity. A technique for determination of statistical characteristics of the temperature-and stress pulsations on the surfaces of the parts investigated is considered as well as the pulsations effect on the durability of various elements in the CPS drives. It is concluded that the rated characteristics satisfactorily agree with the analogous values obtained in measurements conducted at the Novovoronezh NPP units 1 and 2