Lead cooled reactor BREST-OD-300 design is under development as a part of Russian federal project "PRORYV". Two circuits are used for heat removal from the reactor. The special feature of two-circuit heat removal system is the potential risk of steam ingress into the core in case of large leak in the steam generator as a result, for example, of steam generator tube rupture (SGTR). The main concern is caused by the possibility of positive reactivity insertion in case of steam ingress into the central section of the core because this can have an impact on nuclear safety.
The analysis of physical phenomena that are important for correct prediction of SGTR accident consequences was performed and it was concluded that for correct modeling of the transient in the core in the case of steam injection the following procedures are required:
a) Accurate modeling of neutronics and thermal-hydraulics taking into account their coupling;
b) 3D modeling of the accident considering strong non-symmetry of spatial distribution of concentration of steam entering the reactor core during the accident.
3D multi-physics (neutronics + thermal-hydraulics) UNICO-2F code was developed for studying SGTR accident. The code is capable of calculating transient 3D spatial distributions of coolant velocity, pressure and temperature, as well as steam concentration and power density in the core.
The analysis of BREST-OD-300 reactor parameters under SGTR accident conditions was performed and it was shown that even for the most conservative scenario of the accident maximum (during the transient) fuel pin cladding temperature was kept within permissible limits. Therefore, the self-protection of BREST-OD-300 reactor in case of SGTR accident was confirmed.
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|Country/Int. organization||Russian Federation|