Method for protecting a nuclear reactor and corresponding nuclear reactor

A method for protecting a nuclear reactor, the nuclear reactor comprising a core having a plurality of nuclear fuel assemblies, each assembly comprising a plurality of fuel rods, each fuel rod comprising a cladding and nuclear fuel enclosed in the cladding, the method comprising repeatedly carrying out the following steps:

• reconstructing a current maximum linear power released among the fuel rods of the nuclear fuel assemblies of the core, the reconstructing step being repeated with a time constant less than one minute;
• calculating a thermomechanical state and a burnup fraction for each of the fuel rods and storing the calculated thermomechanical state and calculated burnup fraction for a control section of one of the fuel rods;
• calculating a current mechanical stress or a current deformation energy density in the cladding of the one fuel rod using the reconstructed current maximum linear power, the stored thermomechanical state and the stored burnup fraction, by a meta-model of a thermomechanical code;
• comparing the calculated current mechanical stress or the calculated current deformation energy density with a respective threshold;
• and
• stopping the nuclear reactor if the calculated current mechanical stress or the calculated current deformation energy density exceeds the respective threshold.