Overview about cryogenic distillation control and safety approach for Isotopes Separation Facility (ISF)

•ISF with four distillation columns cascade to separate the deuterium-tritium mixture.•Control systems: Plant Control System (SCADA) and Safety Instrumented System (SIS).•SCADA – keep the process within the accepted limits - 1st layer of defence in depth.•SIS – performs the assigned security functions - 2nd defence layer in depth. Isotopes separation technologies are used in both Tritium Removal Facilities associated with CANDU reactors (to remove tritium from heavy water) and fusion applications (eq. ITER Isotope Separation System) to recover and enrich tritium for further operation. The expertise gained during design, manufacturing, building, commissioning and operation of the Cryogenic Distillation System (CDS) with proprietary four column design built at ICSI Rm. Valcea, could be applied for various tritium recovery applications, regardless of the type of front-end process used, Liquid Phase Catalytic Exchange or Combined Electrolysis and Catalytic Exchange. Cryogenic Distillation feed is a mixture of hydrogen isotopes which presents hazards in operation (explosion and tritium contamination), therefore the CDS of PESTD was designed to meet industrial and nuclear applicable standards. In this paper we present an overview of the CDS focusing on the process control and safety approach which meet specific conditions of Romanian codes and standards required for operation. However, specific information may be used later as reference for design consideration for other CDS. The cryogenic distillation process from ICSI Rm. Valcea is designed as four columns cascade inside a cold-box which acts as second barrier against hydrogen release and thermal insulation. The CDS process control is based on a Programmable Automation Controller (PACs), a Supervisory Control and Data Acquisition (SCADA) and specific low temperature field equipment and devices. The control room operator supervises the process using a specific designed Human Machine Interface (HMI) which permits to monitor process parameters, alarms acknowledgment and acts to adjust the process or override normal PACs control.