Tritium, in NPP, is mainly produced by neutron activation reactions with lithium and boron isotopes dissolved in the primary coolant as well as with naturally-occurring deuterium in the primary coolant. The use of enriched boric acid, the increase in lithium concentration to control the pH and the new fuel management increase the tritium production in the primary coolant and thus the tritium releases in the environment.In this context AREVA developed a computational tool for management of the tritium activity: AbsoluT-3. AbsoluT-3 allows estimating the tritium activity in the primary coolant taking into account the mode of operation (with or without load follow), water movements and many other parameters. This activity can be estimated for many cycles in power operation and during shutdown. If the tritium releases are regulatory imposed, AbsoluT-3 allows determining maximum tritium concentration to be reached in the primary coolant and the total tritium releases to respect the discharge authorization.AbsoluT-3 allows anticipating tritium management issues according to the design as well as operational constraints. These constraints are mainly twofold: radiation protection during shutdown and releases into the environment.
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