A study on analytical method for a large shielding system with neutron streaming by the Monte Carlo

Monte Carlo coupling technique of which the Monte Carlo calculation was divided two steps, lying the pseudo - detector of the coupling surface between the first step and the second, was proposed to analyze neutron streaming in a large shielding system. The coupling technique was applied to large shielding systems with neutron streaming: the first was the neuton slit - streaming problem, the second the two - legged cylindrical - annular - duct neutron streaming, and the third the 14 MeV neutron streaming through a narrow hole - duct of a fusion reactor. Those shielding systems had large total flux attenuation of more than ten orders of magnitude between neutron sources and detectors. Statistical error propagation in the Monte Carlo coupling calculation was estimated by the newly intronduced equation of error propagation. As result of the practical application to those problems, the Monte Carlo coupling technique was demonstrated that the technique could produce the results of good FSD's (fractional standard deviation) in a practical computation time, of neutron flux distributions in the large shielding system. (author)