The Use of Radioactive Tracers for Hydrodynamics Studies of Danube-Black Sea Channel

Carmen Varlam1, Ioan Stefanescu1, Vasile Patrascu2, Mihai Varlam1, Cristina Bucur3, Mircea Raceanu1, Adrian Enache1,  Ionut Faurescu1

1National Institute R&D for Cryogenic and Isotopic Technologies, Rm. Valcea,  P.O. Box 10, 250040 
2National Institute for Marine Research “Grigore Antipa”, Constanta
3Environmental Laboratory of NPP- Cernavoda
contact mail: cvarlam@ns-icsi.icsi.ro; vasile@alpha.rmri.ro

The possibility of a contamination agent being accidentally or intentionally spilled upstream from a water supply is a constant concern to those diverting and using water from this channel. A method of rapidly estimating traveltime or dispersion is needed for pollution control or warning system on channel where data are limited. Traveltime and mixing of water within a stream are basic streamflow characteristics needed in order to predict the rate of movement and dilution of pollutants that may be introduce in the stream. 
In this study we propose to use tritiated liquid effluents from CANDU type nuclear power plant as a tracer, to study hydrodynamics on Danube-Black Sea Channel. This channel is ideal for this kind of study, because wastewater evacuations are occasionally due to technical operations of nuclear power plant. Tritiated water can be used to simulate the transport and dispersion of solutes in Danube-Black Sea Channel because they have the same physical characteristics as 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 (1) the rate of movement of a solute through channel reach (2) the rate of peak attenuation concentration of a conservative solute with time, and (3) the length of time required for the solute plume to pass a point in the channel.
This paper presents the mixing length calculation for particular conditions (lateral branch of the channel, and lateral injection of wastewater from nuclear power plant). A study of experimental published formulas was used to determine proper mixing length. Simultaneous measurements in different location of the Channel confirm the beginning of the experiment.  Another result used in the further experiment concerns the tritium level along the Danube-Black Sea Channel. We measured tritium activity concentration in water sampled along the Channel between July-October 2002. We established tritium level and tritium concentrations significant for the edge and the tail of tritiated wastewater 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.