Patent Number: 
Section: claims

1. A method of determining a value of an operability parameter representative of the operability of a nuclear reactor, the nuclear reactor having a reactor core comprising nuclear fuel assemblies, each fuel assembly comprising nuclear fuel rods in which nuclear fuel is enclosed in a cladding, the method comprising:periodically implementing, with a data processing system adapted to command and/or control an operation of the nuclear reactor, during a same operating cycle of the reactor, the following steps:a) calculating a three-dimensional distribution of local power in the reactor core from measurements provided by sensors present in the reactor,b) simulating at least one accidental transient occurrence of power applied to the calculated three-dimensional distribution of local power,c) identifying at least one rod most likely to be subject to a fracture of the cladding during the simulated accidental transient occurrence of power using thermomechanical calculations,d) determining the value of the operability parameter representative of the operability of the nuclear reactor using further thermomechanical calculations on the identified at least one rod, ande) at least one of commanding and controlling the reactor based on the determined value of the operability parameter,wherein the steps a) to d) are carried out periodically with a time step being less than one month. 2. The method according to claim 1, wherein the steps a) to d) are carried out with a time step being less than one week. 3. The method according to claim 2, wherein the steps a) to d) are carried out with a time step being less than one day.