Analysis of the fluctuations of the average monthly activity at a nuclear power plant with an RBMK-1000 reactor

The results of an analysis of the fluctuations of the relative activity of gaseous (inert) and the specific activity of volatile (iodine) fission products in the technological medium of the power-generating units of the Kursk and Smolensk nuclear power plants in 1996 and 1997 are presented. It is shown that these quantities behave in time as fluctuation bursts against a quasistationary background. Using a large set of statistical data, it is shown that this character of the activity is a consequence of two processes: the appearance of leaks in the fuel elements and the unloading of fuel assemblies containing unsealed fuel elements. A relation, which is the same for all power-generating units, between the number of bursts per year and the number of unloaded fuel assemblies is found. The amplitude distribution functions of the bursts, indicating the existence of groups of defects in RBMK-1000 fuel elements, are obtained. The results obtained are discussed and conclusions are presented. 3 figures, 1 table, 1 reference.