Programmable Logic Controller based mitigation of obsolescence control unit of GHARR-1 Pneumatic Transfer System

Ghana Research Reactor-1 (GHARR-1) is a Miniature Neutron Source Reactor (MNSR) used mainly for Neutron Activation Analysis (NAA), Education and Training. GHARR-1 uses an auxiliary Pneumatic Transfer System (PTS) for the transfer of sample capsules in and out of the irradiation sites. The 90.2 % highly enriched uranium (HEU) core of GHARR-1 was recently converted to a 13 % low enriched uranium (LEU) core. The conversion resulted in the thermal power of GHARR-1 increased from 30 kW to 34 kW whiles maintaining the neutron flux at 1 x 10¹² n/cm²s. Most of the components used to design the existing one-short conventional NAA controller unit are outmoded and out of stock in the local Ghanaian market, posing threat to future maintenance. To address this situation, a Programmable Logic Controller (PLC) has been used to design a control unit to facilitate the NAA application. This paper outlines the design of a stable +12 /+24 VDC voltage regulated power supply to operate the PLC and control an 8-way solid state relay bank. The relay bank was designed to operate the solenoid valves that open and close a compressed-air to transfer samples into the reactor for irradiation. Function block diagram programming language was used for the design of the PTS controller unit. The paper highlights the simulation results in which electric bulbs were used to represent the solenoid valves to achieve the opening and closing mechanism for the transfer of samples.  Implementation of the results obtained from the study would eliminate the difficulty of getting up-to-date components to replace the outmoded ones in the PTS controller.