Patent Number: 
Section: claims

1. A computer implemented method for modelizing a nuclear reactor core, comprising the steps of:partitioning, by a computer processor, the core in cubes to constitute nodes of a grid for computer implemented calculation,calculating, by the computer processor, neutron flux by using an iterative solving procedure of at least one eigensystem, components of an iterant of the eigensystem corresponding either to a neutron flux, to a neutron outcurrent or to a neutron incurrent, for a respective cube to be calculated,wherein a control parameter is varied to impact a neutron eigenvalue μ through a perturbed interface current equation and drive the neutron eigenvalue μ towards 1,the perturbed interface current equation being defined by            j      out        +          δ      ⁢                          ⁢              j        out              =                    (                  μ          +                      δ            ⁢                                                  ⁢            μ                          )            ⁢                        c          1                ⁡                  (                      ϕ            +                          δϑ              ⁢                                                ∂                  ϕ                                                  ∂                  ϑ                                                              )                      +                  Ω        ^            ⁢                        Y          ^                ⁡                  (                                    j              out                        +                          δ              ⁢                                                          ⁢                              j                out                                              )                    where jout designates the neutron outcurrent, Φ designates the neutron flux, θ designates the control parameter, Ŷ is a coupling operator, {circumflex over (Ω)} is a mono-directional current throughflow operator, and c1 is an operator depending on the cube properties, the control parameter being a parameter of the model representing a feature of the nuclear reactor core. 2. The method of claim 1 wherein the control parameter θ is given by a determinative output of the following equation:      ϑ          (      new      )        =            ϑ              (        prev        )              +                  〈                              ω            †                    |                      r            out                          (              prev              )                                      〉                    〈                              ω            †                    |                                    c              1                        ⁢                                          ∂                ϕ                                            ∂                ϑ                                                    〉            wherein ω† is a weighting function,rout is given by: jout−c1φ+{circumflex over (Ω)}Ŷjout. 3. The method of claim 2 wherein the control parameter represents a boron concentration of the nuclear reactor core. 4. The method of claim 2 wherein the control parameter represents a rod insertion depth for a group of selected control rods of the nuclear reactor core. 5. The method of claim 1 wherein the control parameter is a neutron eigenvalue λ, and wherein, during an iteration of the iterative solving procedure, the neutron eigenvalue λ is varied to drive the neutron eigenvalue μ towards 1, and wherein the variation of the neutron eigenvalue λ is an application of a variation a δλ to λ, such that λ is driven to λ+δλ, which impacts the neutron eigenvalue μ through the perturbed interface current equation. 6. The method of claim 5, wherein the neutron eigenvalue λ is preconditioned prior to the iteration of the eigensystem solving procedure according to:      λ          (      new      )        =            λ              (        prev        )              +                  〈                              ω            †                    |                      r            out                          (              prev              )                                      〉                    〈                              ω            †                    |                                    c              1                        ⁢                                          ∂                ϕ                                            ∂                λ                                                    〉            where ω† is a weighting function,rout is given by: jout−c1φ+{circumflex over (Ω)}Ŷjout. 7. The method of claim 6 wherein the partial operator derivative      ∂    ϕ        ∂    λ  is iteratively solved through application of:                    [                              ∂                          ϕ              ~                                            ∂            λ                          ]                    (        new        )              =          s      +              2        ⁢        λ        ⁢                                  ⁢                                            B              ^                        ⁡                          [                                                ∂                                      ϕ                    ~                                                                    ∂                  λ                                            ]                                            (            old            )                              -                        λ          2                ⁢                                                            B                ^                            2                        ⁡                          [                                                ∂                                      ϕ                    ~                                                                    ∂                  λ                                            ]                                            (            old            )                                          where      ⁢                          ⁢                        ∂          ϕ                          ∂          λ                      ≅                  ∂                  ϕ          ~                            ∂        λ            {circumflex over (B)}({circumflex over (R)}−ŜLD)−1{circumflex over (F)}s={circumflex over (B)}({circumflex over (R)}−ŜLD)−1ĜŶjout=({circumflex over (R)}−ŜLD)−1{circumflex over (F)}({circumflex over (R)}−ŜLD)−1ĜŶjout {circumflex over (R)} designates a removal operator, ŜLD is a lower-diagonal part of an inscatter operator Ŝ, {circumflex over (F)} is a production operator, and Ĝ is an incurrent operator. 8. The method of claim 1 further comprising a step of building the nuclear reactor core on the basis of the calculated neutron flux. 9. The method of claim 1 further comprising a step of operating the nuclear reactor core on the basis of the calculated neutron flux. 10. A nontransitory computer readable medium comprising a computer program for controlling a computer to:partition the core in cubes to constitute nodes of a grid for computer implemented calculation, andcalculate neutron flux by using an iterative solving procedure of at least one eigensystem, components of an iterant of the eigensystem corresponding either to a neutron flux, to a neutron outcurrent or to a neutron incurrent, for a respective cube to be calculated,wherein a control parameter is varied to impact a neutron eigenvalue μ through a perturbed interface current equation and drive the neutron eigenvalue μ towards 1,the perturbed interface current equation being defined by            j      out        +          δ      ⁢                          ⁢              j        out              =                    (                  μ          +                      δ            ⁢                                                  ⁢            μ                          )            ⁢                        c          1                ⁡                  (                      ϕ            +                          δϑ              ⁢                                                ∂                  ϕ                                                  ∂                  ϑ                                                              )                      +                  Ω        ^            ⁢                        Y          ^                ⁡                  (                                    j              out                        +                          δ              ⁢                                                          ⁢                              j                out                                              )                    where jout designates the neutron outcurrent, Φ designates the neutron flux, θ designates the control parameter, Ŷ is a coupling operator, {circumflex over (Ω)} is a mono-directional current throughflow operator, and c1 is an operator depending on the cube properties, the control parameter being a parameter of the model representing a feature of the nuclear reactor core. 11. The nontransitory computer readable medium of claim 10 further controlling the computer to operate the nuclear reactor core on the basis of the calculated neutron flux. 12. A method for at least one of operating and building a nuclear reactor core comprising:modelizing a nuclear reactor core by performing the computer implemented steps of:partitioning, by a computer processor, the core in cubes to constitute nodes of a grid for computer implemented calculation,calculating, by the computer processor, neutron flux by using an iterative solving procedure of at least one eigensystem, components of an iterant of the eigensystem corresponding either to a neutron flux, to a neutron outcurrent or to a neutron incurrent, for a respective cube to be calculated; andat least one of operating and building the nuclear reactor core on the basis of the calculated neutron flux,wherein a control parameter is varied to impact a neutron eigenvalue μ through a perturbed interface current equation and drive the neutron eigenvalue μ towards 1,the perturbed interface current equation being defined by            j      out        +          δ      ⁢                          ⁢              j        out              =                    (                  μ          +                      δ            ⁢                                                  ⁢            μ                          )            ⁢                        c          1                ⁡                  (                      ϕ            +                          δϑ              ⁢                                                ∂                  ϕ                                                  ∂                  ϑ                                                              )                      +                  Ω        ^            ⁢                        Y          ^                ⁡                  (                                    j              out                        +                          δ              ⁢                                                          ⁢                              j                out                                              )                    where jout designates the neutron outcurrent, Φ designates the neutron flux, θ designates the control parameter, Ŷ is a coupling operator, {circumflex over (Ω)} is a mono-directional current throughflow operator, and c1 is an operator depending on the cube properties, the control parameter being a parameter of the model representing a feature of the nuclear reactor core. 13. The method of claim 12 wherein the control parameter θ is given by a determinative output of the following equation:      ϑ          (      new      )        =            ϑ              (        prev        )              +                  〈                              ω            †                    |                      r            out                          (              prev              )                                      〉                    〈                              ω            †                    |                                    c              1                        ⁢                                          ∂                ϕ                                            ∂                ϑ                                                    〉            wherein ω† is a weighting function,rout is given by: jout−c1φ+{circumflex over (Ω)}Ŷjout. 14. The method of claim 13 wherein the control parameter represents a boron concentration of the nuclear reactor core. 15. The method of claim 13 wherein the control parameter represents a rod insertion depth for a group of selected control rods of the nuclear reactor core. 16. The method of claim 12 wherein the control parameter is a neutron eigenvalue λ, and wherein, during an iteration of the iterative solving procedure, the neutron eigenvalue λ is varied to drive the neutron eigenvalue μ towards 1, and wherein the variation of the neutron eigenvalue λ is an application of a variation δλ to λ, such that λ is driven to λ+δλ, which impacts the neutron eigenvalue μ through the perturbed interface current equation. 17. The method of claim 16, wherein the neutron eigenvalue λ is preconditioned prior to the iteration of the eigensystem solving procedure according to:      λ          (      new      )        =            λ              (        prev        )              +                  〈                              ω            †                    |                      r            out                          (              prev              )                                      〉                    〈                              ω            †                    |                                    c              1                        ⁢                                          ∂                ϕ                                            ∂                λ                                                    〉            where ω† is a weighting function,rout is given by: jout−c1φ+{circumflex over (Ω)}Ŷjout. 18. The method of claim 17 wherein the partial operator derivative      ∂    ϕ        ∂    λ  is iteratively solved through application of:                    [                              ∂                          ϕ              ~                                            ∂            λ                          ]                    (        new        )              =          s      +              2        ⁢                                  ⁢        λ        ⁢                                  ⁢                                            B              ^                        ⁡                          [                                                ∂                                      ϕ                    ~                                                                    ∂                  λ                                            ]                                            (            old            )                              -                        λ          2                ⁢                                                            B                ^                            2                        ⁡                          [                                                ∂                                      ϕ                    ~                                                                    ∂                  λ                                            ]                                            (            old            )                                          where      ⁢                          ⁢                        ∂          ϕ                          ∂          λ                      ≅                  ∂                  ϕ          ~                            ∂        λ            {circumflex over (B)}=({circumflex over (R)}−ŜLD)−1{circumflex over (F)}s={circumflex over (B)}({circumflex over (R)}−ŜLD)−1ĜŶjout=({circumflex over (R)}−ŜLD)−1{circumflex over (F)}({circumflex over (R)}−ŜLD)−1ĜŶjout {circumflex over (R)} designates a removal operator, ŜLD is a lower-diagonal part of an inscatter operator Ŝ, {circumflex over (F)} is a production operator, and Ĝ is an incurrent operator.