Software structure for tritium-in-air monitoring in classified locations

Full text: In the working areas of heavy water detritiation facilities, were hydrogen gas is generated, the risk of air-hydrogen explosive mixture production is present. This paper gives the description of a software architecture solution for a fixed area tritium-in-air monitoring system suitable to be used in such hazardous locations. Tritium-in-air monitoring system was designed as a distributed system containing a number of fixed tritium in air monitoring units, each of them being composed of an ionisation chamber flow-through type and a fix sampling unit with a number of sample lines and one additional blow line. For each unit, software and hardware architecture structure enable independent performance with a fail-safe concept, remote control operation and data storage in a DCS-DCU module. This software architecture secures the setting possibility of alarm levels for tritium concentration, graphical visualisation and acoustic alarm in the case of level overtaking. The afferent software architecture contains applications in connection with hardware architecture and with a hydrogen detection system: RU-1 software application for control sampling; RU-2 software application for measured values display; RU-3 software application for remote data display; RU-4 software application for SQL conversion server; RU-5 software application for OPC standard conversion. The interconnection of all hardware components, between each PLC and each display unit, between tritium-in-air monitoring units and PLC sampling units will be internally carried out using interfaces. The interconnection between PLCs and tritium-in-air monitoring DCU will be made using a communication network, for instance Ethernet Profibus or RS 485. (authors)