Detection and characterisation method of fuel element sheathing failures in nuclear reactors.

摘要

1. Process for determining the rupture characteristics of the jackets of fuel elements of nuclear reactors characterized in that, after having detected such a rupture, the following operations are conducted : - determination by calculation from the given characteristics of the reactor core and the rate of reaction of the fuel elements : (a) one series of first graphs giving, for a certain number of nucleides, their total activity in the primary coolant as a function of the median temperature of a ruptured element for a rupture-state of the jackets arbitrarily defined by a single rupture, each graph of the series being established for a particular value of the coefficient vg which characterises the proportion per second of the total activity leaving the ruptured jacket ; (b) a second graph giving, for different values of the coefficient vg and as a function of the median temperature of a ruptured element, the ratios of activity of pairs of different nucleides whereby to produce two groups of ratios, a first group of ratios which are substantially independent of temperature, and a second group of ratios which increase with temperature ; (c) a third graph, derived from the activity ratios of the above-mentioned first group, giving for the same ratios of the first group, the variation of the coefficient vg as a function of the ratio of the activities themselves ; - determination of a median value of the coefficient vg from the values of the activity ratios of the nucleides of the first group measured in the primary coolant of the reactor and set out in the above-mentioned third graph ; - determination of a median value of the temperature of the ruptured element, from the values of the activity ratios of the nucleides of the second group measured in the primary coolant of the reactor and set out in the above-mentioned second graph at the same time as the previously-determined value of coefficient vg ; - determination of the real number of ruptures corresponding to the determined value of the coefficient vg, from the measured activity of a certain number of nucleides present in the primary coolant of the reactor and set out at the same time as the above-mentioned temperature on the first graph.