Patent Number: 
Section: claims

1. A method for selecting a loading map for a nuclear reactor core from a plurality of envisaged loading maps, the core comprising nuclear fuel assemblies, each assembly comprising nuclear fuel rods where nuclear fuel is enclosed in a cladding, the method comprising the following steps:a) providing production data relating to the nuclear fuel assemblies,b) providing neutron data which are representative of a past operation of the core of the nuclear reactor and a future operation, the future operation being at least during a next operating cycle,c) calculating a three-dimensional distribution of a local power in the core during the future operation for each of the plurality of envisaged loading maps by using a neutron calculation software, the production data and the neutron data,d) calculating an extreme value reached by at least one thermomechanical parameter within the nuclear fuel assemblies for each of the plurality of envisaged loading maps by using a thermomechanical calculation software and the calculated distribution of the local power, ande) selecting a loading map from the plurality of envisaged loading maps in accordance with the extreme values calculated. 2. The method as recited in claim 1 wherein step d) comprises the following sub-steps:d1) identifying at least one rod for which a value of the at least one thermomechanical parameter is the extreme value from the rods of the nuclear fuel assemblies,d2) calculating the extreme values reached by the at least one thermomechanical parameter for the rod(s) identified using the thermomechanical calculation software. 3. The method as recited in claim 2 wherein step d1) is carried out using sorting software. 4. The method as recited in claim 3 wherein the sorting software uses interpolations or correlations established from the thermomechanical calculation software. 5. The method as recited in claim 1 wherein the at least one thermomechanical parameter is representative of a stress state in the cladding. 6. The method as recited in claim 5 wherein the at least one thermomechanical parameter is a pressure inside the cladding and the extreme value calculated is a maximum value of the pressure. 7. The method as recited in claim 1 wherein the at least one thermomechanical parameter is representative of a corrosion state of the cladding. 8. The method as recited in claim 7 wherein the at least one thermomechanical parameter is a thickness of oxide on the cladding and the extreme value calculated is a maximum value of the thickness of oxide. 9. The method as recited in claim 1 wherein steps c) and d) are carried out in less than one week for each of the plurality of envisaged loading maps. 10. The method as recited in claim 9 wherein the steps c) andd) are carried out in less than one day for each of the plurality of envisaged loading maps. 11. The method as recited in claim 1 further comprising a stepf) for loading the core in accordance with the selected loading map. 12. A system for selecting a loading map of the nuclear reactor core, comprising a device programmed to implement the steps of the method as recited in claim 1. 13. The system as recited in claim 12 wherein the device includes at least one data-processing unit and a storage medium the storage medium storing at least one program for carrying out the steps of the selection method used by the system. 14. A non-transitory computer readable medium comprising a computer program comprising instructions for carrying out the steps of the method as recited in claim 1.