[Tritium in the Water System of the Techa River].

The aim of the paper is to study modern tritium levels in various sources of the drinking water supply in the settlements situated in the riverside zone of the Techa. Almost everywhere the water entering water-conduit wells from deep slits (100-180 m) contains averagely 2-3 times higher tritium concentrations than the water from less deep personal wells, slits and springs. Tritium levels in the drinking water supply decrease with the distance from the dam; while in wells, springs and personal wells they are constant all along the river. The observed phenomenon can be explained by the fact that the river bed of the Techa is situated at a break zone of the earth crust, where the contaminated deep water penetrates from the reservoirs of the "Mayak" enterprise situated in the upper part of the regulated river bed. Less deep water sources (personal wells, slits and springs) receive predominantly flood, atmospheric and subsoil waters and are not connected with the reservoirs.

Plutonium Content in Soil Fractions of Various Sizes and Estimation of the Risks of the Chernobil Nuclear Power Plant Zone.

Based on the data from the literature the authors analyzed the methods used for the estimation of the risks of plutonium-contaminated areas. The analysis was based on the published data on the measured plutonium concentrations in the air and soil. To calculate plutonium concentrations in the near-surface air layer above the contaminated area a modification of the method of the load estimation from the mass was proposed: instead of the average plutonium specific activity in soil the authors suggested the use of the soil coefficient which consists of the sum of specific activities of every respirable fraction (size 0.05 to 10 µm) multiplied by the percentage of its activity in the total activity of the soil sample. Verification of the proposed method on independent data showed that the calculated values approached the measured ones.