Pressure control device

A pressure control device of an FBR type reactor comprises a PI calculator for controlling and calculating a deviation between a pressure of a deodoring device and a set value to output an instruction for the opening degree of a drain recovery control valve of a flush tank, a function generator for outputting an instruction for the opening degree based on a function corresponding to a deviation between the pressure of the flush tank and the pressure of the deodoring device, and a low value selecting circuit for comparing the instruction for the opening degree sent from the PI calculator and the function generator, and selecting a lower value, to output instruction signals for the opening degree to the recovery control valve. The instruction for the degree of opening obtained by way of the function generator or the instruction for the degree of opening by the pressure of the deodoring device is selected by the lower value selecting circuit relative to a moderate increase of the pressure of the flush tank along with the operation of gradually opening a pressure control valve of a high pressure feedwater heater. The recovery of the flush tank drain to the deodoring device is stated automatically at most appropriate timing, to effectively suppress the amount of auxiliary steams from a boiler in the plant and avoid back flow phenomenon from the deodoring device to the flush tank. (N.H.)