General approach to dose reconstruction in the population exposed as a result of the release of radioactive wastes into the Techa River.

Massive releases of fission products from the plutonium production facility 'Mayak' resulted in the years 1949-1956 in the contamination of the river Techa and its flood lands. This led to the exposure of the population in many riverside villages due to external gamma-rays and due to the incorporation of radionuclides, primarily Sr-90. The exposure situation is described and the reconstruction of doses due to external and due to internal radioactivity is explained. The internal dosimetry is based on large scale measurements of Sr-90 beta-rays on the surface of teeth that were begun in 1960, and on whole-body measurements of Sr-90 that were begun in 1974. The details of the analyses are presented in Part 2 of the present report. Average doses due to the external and the internal exposure are given for the residents of the different villages along the river Techa. In the total population of about 28,000 persons that were assessed, the medium dose to the red bone marrow was about 0.25 Gy and the mean dose about 0.4 Gy. In about 5% of the individuals the dose to the red bone marrow was estimated to be in excess of 1 Gy.