The use of radioactive tracers for hydrodynamics studies of Danube-Black Sea Canal

Full text: The possibility of a contaminating agent being accidentally or intentionally spilled upstream in a water supply is a constant concern to those diverting and using water from the canal. A method of rapidly estimating travel time or dispersion is needed for pollution control or warning system on channel where data are limited. Travel time and mixing of water within a stream are basic stream flow characteristics needed in order to predict the rate of movement and dilution of pollutants that may be introduced in the stream. In this study we propose to use tritiated liquid effluents from CANDU type nuclear power plant as tracers, to study hydrodynamics on the Danube-Black Sea Canal. This canal is ideal for this kind of study, because waste water evacuations are occasionally due to technical operations of the nuclear power plant. Tritiated water can be used to simulate the transport and dispersion of solutes in Danube-Black Sea Canal because they have the same physical characteristics as the water. Measured tracer-response curves produced from injection of a known quantity of soluble tracer provide an efficient method of obtaining necessary data. This method can estimate the rate of movement of a solute through the canal reach, the rate of peak attenuation concentration of a conservative solute with time, and the length of time required for the solute plume to pass a point in the canal. This paper presents the mixing length calculation for particular conditions (lateral branch of the canal, and lateral injection of waste water from nuclear power plant). A study of published experimental formulas was used to determine proper mixing length. Simultaneous measurements in different location of the canal confirm the beginning of the experiment. Another result used in the further experiment concerns the tritium level along the Danube-Black Sea Canal. We measured tritium activity concentration in water sampled along the Canal between July-October 2002. We found tritium level and tritium concentrations significant for the edge and the tail of tritiated waste water evacuations. We obtained unit-peak-attenuation (UPA) curve as related to different mixing times using three locations in which we measured tracer-response curves. The UPA curve, along with the time-of-travel curves, provides a ready means of predicting maximum soluble contaminant levels that would be experienced at any location in the investigated area. (authors)