METHOD FOR MEASURING SUBCRITICAL MULTIPLICATION FACTOR OF IRRADIATED FUEL ASSEMBLY, MEASUREMENT DEVICE AND PROGRAM FOR MEASUREMENT, AND METHOD FOR CONFIRMING PREDICTION ACCURACY OF NUCLIDE COMPOSITION OF IRRADIATED FUEL ASSEMBLY

摘要

PROBLEM TO BE SOLVED: To calculate a subcritical multiplication factor ksub without calculating distribution of neutron fluxes ϕ inside an irradiated fuel assembly to be measured using information (such as combustion history, predicted nuclide composition for every fuel assembly evaluated by a nuclear reactor management system, etc.) regarding its subcriticality.

SOLUTION: This method for measuring the subcritical multiplication factor includes: storage means 3 which stores a neutron leak rate L of the fuel assembly 2 of which the composition and the shape at the point of new fuel are the same as those of preliminarily calculated irradiated fuel assembly 1 to be measured and the nuclide composition is known; absorption rate measurement means 5 for measuring neutron absorption rate A on the outside using a neutron source 4 with neutron emission intensity S0 for the submerged fuel assembly 1 to be measured; input means 6 for reading the neutron absorption rate A and the neutron emission intensity S0; and calculation means 7 for calculating neutron generation rate S of the fuel assembly 1 to be measured based on the neutron leak rate L and the neutron absorption rate A, and calculating the subcritical multiplication factor ksub of the fuel assembly 1 to be measured based on the neutron emission intensity S0 and the neutron generation rate S.

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