Evaluation of Source Term for the Supply of Activation Radionuclides into the Techa River

In the 1950s, V-2 reservoir (Lake Kyzyl-Tash) was used for cooling industrial uranium–graphite reactors (IUGRs). When water passed through the IUGR core, activation radionuclides (ARs) were produced by nuclear reactions of reactor neutrons with nuclei of chemical elements present in water and were accumulated in water. The AR activity concentration in water from V-2 reservoir depends on the concentration of chemical elements in the reservoir. Data on the content of 16 elements in V-2 water in the period 1948–1956 were collected. These data were analyzed taking into account the characteristic natural abundance of elements in water of the Irtyash–Kasli lake system and the additional technogenic pollution of the reservoir in the course of its operation. The main source of AR transfer from V-2 reservoir to the Techa River was controlled water discharge through open shutters of the P-2 dam (or uncontrolled water seepage through closed shutters). A mathematical model was suggested, and the activity concentrations in V-2 water were calculated for 16 elements and 31 nuclear reactions yielding 20 ARs. The model was verified using the archive data on the activity concentrations of ³²Р in V-2 water in 1953–1956. All the calculation results well agree with the available experimental data. The source term for AR transfer from V-2 reservoir to the Techa River in relation to the water flow rate through P-2 dam was determined. The experimental data on the scale of the distribution of the ³²Р activity concentration along the Techa River were analyzed. The results obtained allow taking into account the AR contribution to the total radioactive pollution of the river and evaluating the possible radiation impact on the population and biota.