METHOD FOR LOADING IRRADIATED FUEL INTO SUBCRITICAL NEUTRON MULTIPLICATION SYSTEM AND METHOD FOR CALCULATING EFFECTIVE MULTIPLICATION FACTOR OF IRRADIATED FUEL

摘要

PPROBLEM TO BE SOLVED: To propose a method for predicting an effective neutron multiplication factor after the next loading step following the loading in a loading step and judging whether it is appropriate or not to load fuels on the basis of the result of the prediction. PSOLUTION: In a method for calculating the effective multiplication factor of a subcritical neutron multiple system where numerous irradiated fuels are loaded sequentially, the neutron counting rate in a prescribed position inside or on the outer periphery of the subcritical neutron multiple system is measured (S206), the neutron counting rate in the measurement position is found by conducting the neutron transport/diffusion calculation with a group constant distributing in an axial direction for each irradiated fuel, a neutron generation rate and the geometry of the system where irradiated fuels are loaded (S205), the group constant of the system where the irradiated fuels are loaded is modified as necessary so that the ratio between the measured value and the calculated value of the neutron counting rate can be almost constant in each loading step for the irradiated fuels (S208) and the effective multiplication factor in the next loading step is calculated by conducting the neutron transport/diffusion calculation with the modified group constant, the neutron generation rate in the next loading step and the geometry of the system where the irradiated fuels are loaded in the next loading step (S214). PCOPYRIGHT: (C)2008,JPO&INPIT