TRETA and TIZONA fast running thermal-hydraulic codes

TRETA and TIZONA codes have been developed to help analysts with the understanding of probabilistic safety analysis (PSA) event trees involving complex transients taking place in nuclear power plants. The two-phase thermal-hydraulic sections of the TIZONA code convey an original model that hinges on the assumption that one of the phases is in the saturation condition. The simulation extends to virtually all plant systems, including control, protection and balance of plant. However, the codes are not tightly bound to a particular technology and can be used to perform simulations of other physical systems. The design of the codes is modular, their inputs being built as a block diagram in which each block is an instance of a more general entity called module provided with particular data. Other particular-purpose codes can be connected to TRETA and TIZONA to perform a joint simulation in which several tasks may be run in parallel if the problem so allows.