Patent Number: 
Section: claims

1. A method of correction for a component of intrinsic uncertainty, associated with a collectron-type detector placed inside a nuclear power plant core, comprising:establishing a mapping as a representation of a power distribution inside the nuclear reactor core, said mapping being established by means of a reference instrumentation system, said mapping comprising;equipping, at least temporarily, a first set of fuel assemblies of the nuclear reactor core with detectors from said reference instrumentation system;equipping, at least temporarily, a second set of fuel assemblies of the nuclear reactor core with detectors from a second instrumentation system;performing a first partial series of activity measurements by means of the detectors from said reference instrumentation system;performing a second partial series of activity measurements by means of the detectors from the second instrumentation system;converting the activity measurements of the second partial series of measurements into activity measurements associated with said reference instrumentation system in order to obtain a series of converted measurements;establishing, by way of the first partial series of activity measurements, of the series of converted measurements, of a complete theoretical distribution of the theoretical activities associated with the reference instrumentation system, and of a complete theoretical distribution of the theoretical activities associated with the second instrumentation system, for every instrumented point of the nuclear reactor core, a final series of experimental reactor core activities, said data series only comprising the values relating to the activities associated with the reference instrumentation system; andestablishing, based on the final series of experimental data and of theoretical data simulating a state of the reactor core at the time of the performance of the first partial series of measurements and of the second partial series of measurements, the mapping being representative of a power distribution inside a nuclear reactor coreperforming a calibration operation on a collectron, the calibration operation being performed when the collectron-type detector has reached a given level of wear, the calibration operation consisting of performing a three-dimensional calibration using the mapping. 2. The method according to claim 1, wherein the detectors used in the reference instrumentation system are detectors of a mobile internal instrumentation system. 3. The method according to claim 1, wherein the step of performing a calibration operation comprises performing a three-dimensional calibration using the mapping and provides, at the given wear level at which the calibration operation is performed, as value on the intrinsic uncertainty component of the considered collectron-type detector, the value of the determined intrinsic uncertainty component for a new detector, increased by a calibration uncertainty value. 4. The method according to claim 1, wherein the level of given wear, for which a calibration operation of the considered collectron is performed, exceeds 50% of wear of the said collectron. 5. The method according to claim 1, wherein the detectors used in the reference instrumentation system are of the RIC type. 6. The method according to claim 1, wherein the step for converting the activity measurements of the second series of measurements into activity measurements associated with the reference instrumentation system complies with the following relation:      A          1      ←      2        CONV    =      g    ·                  (                              A            1                                A            2                          )            CAL        ·                  (                  A          2          MES                )            relatif      wherein:(A2MES)relatif is the distribution of the activities measured by the detectors of the second instrumentation system, whose elements are linked by a normalization of series;A1CAL and A2CAL are the distributions of the equivalent activities calculated for the detectors of the first instrumentation system and of the second instrumentation system, respectively;A1←2CONV is the conversion of an activity is measured by a detector of the second instrumentation system into an activity that would be detected by a detector of the first instrumentation system; andg is a coefficient reporting the normalization differences between the two distributions. 7. The method according to claim 6, wherein the step for converting the activity measurements of the second series of measurements into activity measurements associated with the reference instrumentation system is followed by a normalization operation complying with the following relation:      A    1    mixte    =                              ∑          1                      N            ⁢                                                  ⁢            1                          ⁢                              (                          A              1              MES                        )                    relatif                    +                        ∑          1                      N            ⁢                                                  ⁢            2                          ⁢                  A                      1            ←            2                    CONV                                    N        ⁢                                  ⁢        1            +              N        ⁢                                  ⁢        2            wherein:N1 and N2 are the number of acquisitions for the detectors of the first instrumentation system and of the second instrumentation system, respectively;(A1MES)relatif is the distribution of the activities is measured by the detectors of the first instrumentation system, whose elements are linked by a normalization of series; andA1←2CONV is the conversion of an activity is measured by a detector of the second instrumentation system into an activity that would be detected by a detector of the first instrumentation system. 8. The method according to claim 6, wherein the reference instrumentation system is a mobile detector system. 9. The method according to claim 6, wherein the second reference instrumentation system is a fixed detector system. 10. The method according to claim 6, wherein the reference instrumentation system is a RIC-type system. 11. The method according to claim 6, wherein the second instrumentation system initiates collectron-type detectors. 12. A method for establishing a mapping representative of a power distribution inside a nuclear reactor core, said mapping being performed by means of detectors placed at least temporarily inside the core of the reactor, the method comprising:equipping, at least temporarily, a first set of fuel assemblies of the nuclear reactor core with detectors from a reference instrumentation system;equipping, at least temporarily, a second set of fuel assemblies of the nuclear reactor core with detectors from a second instrumentation system;performing a first partial series of activity measurements by means of the detectors from said reference instrumentation system;performing a second partial series of activity measurements by means of the detectors from the second instrumentation system;converting the activity measurements of the second partial series of measurements into activity measurements associated with said reference instrumentation system in order to obtain a series of converted measurements;establishing, by way of the first partial series of activity measurements, of the series of converted measurements, of a complete theoretical distribution of the theoretical activities associated with the reference instrumentation system, and of a complete theoretical distribution of the theoretical activities associated with the second instrumentation system, for every instrumented point of the nuclear reactor core, a final series of experimental reactor core activities, said data series only comprising the values relating to the activities associated with the reference instrumentation system; andestablishing, based on the final series of experimental data and of theoretical data simulating a state of the reactor core at the time of the performance of the first partial series of measurements and of the second partial series of measurements, the mapping being representative of a power distribution inside a nuclear reactor core. 13. The method according to claim 12, wherein the step for converting the activity measurements of the second series of measurements into activity measurements associated with the reference instrumentation system complies with the following relation:      A          1      ←      2        CONV    =      g    ·                  (                              A            1                                A            2                          )            CAL        ·                  (                  A          2          MES                )            relatif      wherein:(A2MES)relatif is the distribution of the activities measured by the detectors of the second instrumentation system, whose elements are linked by a normalization of series;A1CAL and A2CAL are the distributions of the equivalent activities calculated for the detectors of the first instrumentation system and of the second instrumentation system, respectively;A1←2CONV is the conversion of an activity is measured by a detector of the second instrumentation system into an activity that would be detected by a detector of the first instrumentation system; andg is a coefficient reporting the normalization differences between the two distributions. 14. The method according to claim 13, wherein the step for converting the activity measurements of the second series of measurements into activity measurements associated with the reference instrumentation system is followed by a normalization operation complying with the following relation:      A    1    mixte    =                              ∑          1                      N            ⁢                                                  ⁢            1                          ⁢                              (                          A              1              MES                        )                    relatif                    +                        ∑          1                      N            ⁢                                                  ⁢            2                          ⁢                  A                      1            ←            2                    CONV                                    N        ⁢                                  ⁢        1            +              N        ⁢                                  ⁢        2            wherein:N1 and N2 are the number of acquisitions for the detectors of the first instrumentation system and of the second instrumentation system, respectively;(A1MES)relatif is the distribution of the activities is measured by the detectors of the first instrumentation system, whose elements are linked by a normalization of series; andA1←2CONV is the conversion of an activity is measured by a detector of the second instrumentation system into an activity that would be detected by a detector of the first instrumentation system. 15. The method according to claim 13, wherein the reference instrumentation system is a mobile detector system. 16. The method according to claim 13, wherein the second reference instrumentation system is a fixed detector system. 17. The method according to claim 13, wherein the reference instrumentation system is a RIC-type system. 18. The method according to claim 13, wherein the second instrumentation system initiates collectron-type detectors.