Study on Semi-Analytical Nodal Method for Solving SP3 Equation

Solving the SP3 equation is the key technology of the Next Generation Reactor Physics Calculation, and has been widely concerned. The semi-analytical nodal method (SANM) based on transverse-integrated neutron diffusion equation has the advantages of high accuracy and convenience for multi-group calculation. The 0th-order flux and the 2nd-order flux being Expanded with the existing 4th-order SANM polynomials and being solved respectively, the 4th-order algebraic accuracy flux distribution is also obtained, however, this solving process is not the semi-analytical nodal method since the polynomial expansion process does not take the special modality of SP3 equation and it’s analytical solution into consideration. There are two modality SP3 equation, so there are two SANM expansion forms. A code is developed to solve the SP3 equation under the two different forms. After the calculation of the same benchmark, the difference between the two forms of SP3 equation is found. According to the results, and in view of the special modality of the SP3 equation, advices for a strict semi-analytical method for solving SP3 equation are discussed.