Resonance calculation program and analyzing apparatus

A non-transitory computer readable media, comprising a resonance calculation program executable on hardware for performing a resonance calculation based on equivalence principle of calculating an effective cross section serving as an input value for neutron transport calculation at a time of calculating a neutron flux in a fuel assembly storing a cylindrical fuel rod by the neutron transport calculation, wherein

• a cross section of the fuel assembly taken along an orthogonal plane orthogonal to an axial direction of the fuel rod is defined as an analysis target region for the resonance calculation,
• the analysis target region is divided into a plurality of detailed regions, a part of the detailed regions serving as a resonance region where a resonance phenomenon occurs,
• a neutron escape probability in the resonance region is obtained by a polynomial rational expression including a first rational coefficient, a second rational coefficient, and a geographical coefficient, the first and second rational coefficients serving as factors representing a gray range from a black body the resonance region of which absorbs all neutrons to a white body the resonance region of which absorbs no neutrons, the geographical coefficient serving as a factor representing geographical shapes of a plurality of annular regions that are circumferentially annular and that are obtained by radially dividing a circular region that is an axial cross section of the fuel rod at predetermined intervals, and
• the resonance calculation program includes:
• a coefficient calculation step of calculating the first rational coefficient and the second rational coefficient to satisfy a physical quantity calculated over the gray range by a method of characteristics;
• a background cross-section calculation step of calculating a background cross section based on the calculated first rational coefficient and an average chord length corresponding to four regions expressing the annular regions;
• an effective cross-section interpolation step of interpolating the effective cross section from the background cross section;
• an effective cross-section calculation step of calculating the effective cross section depending on the annular regions by synthesizing the interpolated effective cross section based on the second rational coefficient and the geographical coefficient;
• and
• a radial-distribution calculation step of calculating distribution of the physical quantity in a radial direction of the circular region using the effective cross section dependent on the annular regions.