Patent Number: 
Section: claims

1. A method, implemented by at least one electronic processor, for generating a pointwise fast neutron spectrum of a nuclear reactor, the method comprising:receiving composition data in the at least one electronic processor;receiving or calculating, by the at least one electronic processor, a fission source distribution, the fission source distribution including an energy distribution of fission neutrons of the nuclear reactor, the fission neutrons having a kinetic energy that is greater than or equal to 1 eV;receiving nuclear data in the at least one electronic processor; andcalculating, in the at least one electronic processor, the pointwise fast neutron spectrum based on numerical integration using the composition data, the fission source distribution, and the nuclear data, the calculating including,generating an energy mesh that includes a finite number of energy points for the fast neutron spectrum,adding additional energy points to the energy mesh in order to bound an error associated with the numerical integration, andthinning the generated energy mesh to remove some of the finite number of energy points,wherein the thinning of the energy mesh improves functioning of the at least one electronic processor by allowing faster processing of the numerical integration. 2. The method of claim 1, wherein the composition data includes information related to geometry of a nuclear reactor. 3. The method of claim 1, wherein the composition data includes information related to isotopes in a nuclear reactor. 4. The method of claim 1, wherein the composition data allows calculation of number densities of isotopes in a nuclear reactor. 5. The method of claim 1, wherein the composition data is input by one or more users. 6. The method of claim 1, wherein the received fission source distribution is input by one or more users. 7. The method of claim 1, wherein the received fission source distribution includes at least one value determined by a function. 8. The method of claim 1, wherein the received fission source distribution includes at least one unknown value that is calculated via the at least one electronic processor. 9. The method of claim 1, wherein the nuclear data includes data from at least one data library. 10. The method of claim 9, wherein the at least one data library includes one or more of the Evaluated Nuclear Data Files of Brookhaven National Laboratory, the Japanese Evaluated Nuclear Data Library, the Joint Evaluated Fission and Fusion File, the Russian Evaluated Neutron Data Library, the Russian File of Evaluated Neutron Data, the Chinese Evaluated Nuclear Data Library, and the International Neutron Cross Section Standards. 11. The method of claim 1, wherein calculating the pointwise fast neutron spectrum includes interpolating the nuclear data. 12. The method of claim 1, wherein the calculation of the pointwise fast neutron spectrum starts at a highest energy of the received fission source distribution or wherein the calculation of the pointwise fast neutron spectrum starts at a highest energy of the calculated fission source distribution. 13. The method of claim 12, wherein the calculation of the pointwise fast neutron spectrum continues from the highest energy of the received fission source distribution to successively lower energies or wherein the calculation of the pointwise fast neutron spectrum continues from the highest energy of the calculated fission source distribution to the successively lower energies. 14. The method of claim 1, wherein the numerical integration uses an adaptive algorithm. 15. The method of claim 14, wherein the adaptive algorithm uses an interval subdividing technique. 16. The method of claim 1, wherein the numerical integration is based on a quadrature rule. 17. The method of claim 16, wherein the quadrature rule is a nested quadrature rule. 18. The method of claim 17, wherein the nested quadrature rule is a Gauss-Kronrod Quadrature rule. 19. The method of claim 1, further comprising:modeling the nuclear reactor based on the calculated pointwise fast neutron spectrum. 20. The method of claim 1, further comprising:applying the calculated pointwise fast neutron spectrum in a reactor simulation. 21. The method of claim 1, wherein the nuclear reactor is a sodium fast reactor (SFR). 22. A method, implemented by at least one electronic processor, for generating a pointwise fast neutron spectrum of a nuclear reactor, the method comprising:receiving composition data in the at least one electronic processor;receiving or calculating, by the at least one electronic processor, a fission source distribution, the fission source distribution including an energy distribution of fission neutrons of the nuclear reactor, the fission neutrons having a kinetic energy that is greater than or equal to 1 eV;receiving nuclear data in the at least one electronic processor; andcalculating, in the at least one electronic processor, the pointwise fast neutron spectrum based on numerical integration using the composition data, the fission source distribution, and the nuclear data, the calculating including,generating an energy mesh that includes a finite number of energy points for the fast neutron spectrum,adding additional energy points to the energy mesh in order to bound an error associated with the numerical integration, andthinning the generated energy mesh to remove some of the finite number of energy pointswherein the thinning of the energy mesh improves functioning of the at least one electronic processor by reducing computing time for the calculating of the numerical integration,the calculating of the pointwise fast neutron spectrum starting at a highest energy of the received fission source distribution or starting at a highest energy of the calculated fission source distribution. 23. A method, implemented by at least one electronic processor, for generating a pointwise fast neutron spectrum of a nuclear reactor, the method comprising:receiving composition data in the at least one electronic processor;receiving or calculating, by the at least one electronic processor, a fission source distribution, the fission source distribution including an energy distribution of fission neutrons of the nuclear reactor, the fission neutrons having a kinetic energy that is greater than or equal to 1 eV;receiving nuclear data in the at least one electronic processor; andcalculating, in the at least one electronic processor, the pointwise fast neutron spectrum based on numerical integration using the composition data, the fission source distribution, and the nuclear data, the calculating including,generating an energy mesh that includes a finite number of energy points for the fast neutron spectrum,adding additional energy points to the energy mesh in order to bound an error associated with the numerical integration, andthinning the generated energy mesh to remove some of the finite number of energy points,wherein the thinning of the energy mesh improves functioning of the at least one electronic processor by reducing computing time for the calculating of the pointwise fast neutron spectrum. 24. The method of claim 23, wherein the numerical integration uses an adaptive algorithm. 25. The method of claim 23, wherein the calculating of the pointwise fast neutron spectrum starts at a highest energy of the received fission source distribution or starts at a highest energy of the calculated fission source distribution.