A control system using a programmable logic controller (PLC) has been developed for a dual tower dryer (DTD) in a canadian deuterium natural uranium reactor (CADND) type nuclear power plant. This system will replace the existing DTD control system which was implemented with mechanical timers and relays. The new control system makes it possible for an operator to perform more precise time and dew point control for the DTD, thanks to the high efficiency and flexibility of the PLC. The operational cost for the control system is much reduced compared to the existing system.