Keywords: VVER-440, loss-of-coolant accident, LOCA, thermohydraulics, thermomechanical simulation, TRANSURANUS, RELAP5, fuel rods, Zr1%Nb cladding, cladding failure, coolant loss, VVER reactors, nuclear power plants, nuclear energy, nuclear accidents, nuclear safety
Evaluation of fuel rod cladding failure during a loss-of-coolant accident
This paper describes a methodology for the quantification of fuel rod cladding failure as a result of a Loss-of-Coolant Accident (LOCA). The methodology is based on external coupling of the RELAP5 code and the TRANSURANUS code. The thermohydraulic response of the unit to the accident is simulated by the RELAP5 code, providing initial and boundary conditions for the thermomechanical simulation by the TRANSURANUS code. The cladding failure criterion of the TRANSURANUS code, derived and implemented into the code in the framework of the EXTRA EURATOM 5th Framework Programme, is used. The cladding failure probability is evaluated by the Monte Carlo algorithm varying the outer cladding temperature. In the second part of the paper, an example of an application of the methodology for a typical maximum design basis accident of the VVER-440 is given, presenting every step of the methodology and the typical failure rate for this type of accident.