REACTOR FUEL NONDESTRUCTIVE BURNUP EVALUATION METHOD AND APPARATUS THEREFOR

摘要

PROBLEM TO BE SOLVED: To non-destructively evaluate burnup after the irradiation in a reactor of an atomic fuel containing plutonium before loading into the reactor.SOLUTION: Burnup BUis determined from a gamma-ray intensity C7 of cesium 137 (S12), an initial pultonium enrichment degree εis determined from a ratio (C4/C7) of gamma-ray intensities C4 and C7 of cesium 134 and Bu(S13), and a composition ratio fof fissile pultonium and a composition ratio Pof Pu 242 are determined from a ratio (Φ/C4) of neutron flux Φ and C4, BUand ε(S14). Then, a neutron effective multiplication factor (k) is determined (S16), and a neutron emission rate S is determined from an expression Φ=S×P/(1-k) (S17). By using a coefficient α and a coefficient β as functions of the initial pultonium enrichment degree ε, the composition ratio fof the initial fissile pultonium and the composition ratio Pof the initial Pu 242, burnup BUis determined from an expression S=α×BU(S18).