The invention discloses a computation method for obtaining a high-fidelity resonating group constant of a
nuclear reactor. According to the method, a background section of target resonating nuclides on a target energy group is obtained based on high-efficiency iterative computation of an ESSM method, equivalent lattice
cell dimensions are obtained according to the background section obtained after heterogeneous
resonance integral table fitting and a lattice
cell dimension relation formula, the geometry, materials and temperature of fuel, jackets, etc. are kept unchanged, and equivalent 2-D lattice cells are established; and a
neutron moderation equation for a relevant superfine group is solved to obtain the high-fidelity resonating group constant. Compared with a non-deterministic
theory method, computation efficiency can be remarkably improved, and economical efficiency is improved; meanwhile, compared with a method based on directly solving a problem-related moderation equation,
collision probability computing time can be remarkably shortened, computation efficiency is improved, and meanwhile the defect of huge storage capacity is avoided; compared with a
resonance computation method based on a
resonance integral table, resonant interference, spatial self-shielding and a temperature distribution effect can be precisely treated by solving the
neutron moderation equation of the 2-D lattice cells, and the high-fidelity resonating group constant of fine distribution in each part of fuel is obtained.