Internal exposure optimisation at Cernavoda NPP. On-line tritium in air monitoring - A powerful tool for internal exposure reduction

Full text: CNE Cernavoda managers is committed to maintain under strict ALARA control both population and personnel doses and, consequently, to take appropriate measures in order to reasonably reduce doses. Tritium is the main contributor to internal exposure in CANDU plants. The design features in support of tritium control can be considered as conceptual barriers which prevent or minimize both occupational exposure and environmental emissions of tritium. Vapor Recovery System was designed to control tritium in air concentration and to recover heavy water loss from PHT and Moderator Systems. The system controls air circulation providing atmosphere separation between different areas of Reactor Building. Heavy water leakage rate is carefully steadily controlled. Operational limits for tritium in air concentration were established in order to early detection of tritiated heavy water leaks. On-line tritium detection system - TAM was implemented in Unit 2 and is in progress at Unit 1. TAM was integrated in the Radiation Monitoring System. Entailing the implementation of the radiation protection measures a significant reduction of internal exposure to tritium was registered last years in CNE Cernavoda NPP. (authors)