Method for Using Measurements of the Contamination of Bottom Deposits to Estimate the Source of Radioactive Substances Flowing into a River

Abstract

A method of estimating the strength of a stationary source of radioactive substances entering a river is proposed. The method is based on statistically reliable measurements of the concentration of radionuclides in bottom deposits. The stationary model of the transport of a radioactive impurity in a two-dimensionally uniform flow is used to determine a relation between the concentration of radionuclides in bottom deposits and the strength of the source. The model is based on the two-dimensional equation for turbulent diffusion and takes account of the interaction of radioactive substances between the water mass (solution, suspension) and bottom deposits. The source of 60 Co entering the Don River with contaminated underground waters as a result of an incident, which occurred in 1985, in a storage site for liquid wastes from the Novovoronezh nuclear power plant is examined as an example. The average yearly inflow of the radionuclide is estimated to be ~1·10 10 Bq/yr, which is several times less than the estimates made by experts.In problems of monitoring and in radioecological monitoring, it is often necessary to estimate the active sources of the radioactive substances flowing into river systems. Conventionally, this is done using models of contaminant transport in water together with measurements of the radionuclide concentration in water. Such models have been investigated quite completely, and they can be easily used to identify the sources of contamination of rivers and reservoirs by chemical substances [1]. For this, statistically reliable measurements of the concentration of a contaminant in water at certain points of the river channel, which are located at various distances from the source, are conducted. After the measurements have been completed, the model chosen can be used to estimate quite accurately the intensity of the source of the contaminant provided that the source can be assumed to be stationary or instantaneous.This method of estimating sources of radionuclide discharges is often difficult to use in the practice of radioecological investigations. This is due to the extremely low concentration of radionuclides in water, which is difficult to measure in a statistically reliable manner. Indeed, most of the most dangerous long-lived radionuclides entering a river or reservoir, mainly as a result of sorption and sedimentation, rapidly leave the water and enter the bottom deposits. Examples of such radionuclides are 137 Cs, 239 Pu, 152,154 Eu, 60 Co, 103,106 Ru, and others, which are most important from the sanitary standpoint. Consequently, in practice, such radionuclides are present in water in trace quantities, but they are detected in bottom deposits with good statistical reliability [2].In the present paper, a method is proposed for estimating the strength of a stationary source of certain long-lived radionuclides which enter river systems. The method is based on statistically reliable measurements of the concentration of

Improvement of Instantaneous Point Source Model for Simulating Radionuclide Diffusion in Oceans under Nuclear Power Plant Accidents

“…Many studies have focused on various simulation models to assess radionuclide migration following nuclear accident, such as the instantaneous point source model, the Cox ocean model, Hibler ice model, and coupled ice-ocean model (Monte et al, 2014;Kitamura et al, 2015;Lee et al, 2015). A diffusion equation for radionuclides in oceans has been developed that includes an instantaneous point source model and continuous point source model, and the former was widely applied (Nosov et al, 2005). Based on the tide model, a radionuclide simulation model was developed that is suitable for coastal ocean areas (Periá ñez et al, 1996).…”