Deterministic Neutronics Calculation Method for Fast/Thermal-Combined System

For a system consisting of both high energy external neutron source and thermal neutron zone, a neutronics calculation method is developed based on the combination of the Sn and cell parameter calculation codes. The method is used in the calculation of k_eff for a sub-critical system prior to the later use for a fast/thermal combined system, and the calculated k_eff is given.