Estimation of the contribution of gamma-emission of incorporated cesium radioisotopes in interpretation of the results of the public survey to assess the thyroidal iodine content following a radiation accident at the nuclear power plant

Aim. A detail consideration has been done to assess an importance of the contribution of gamma-emission of incorporated cesium radioisotopes to the exposure rate measured near the thyroid by the public survey for following the Chernobyl accident. Empirical ratios have been derived to take into account that contribution under interpretation of the results of survey meter monitoring of the public. Materials and methods. Model calculations for typical radionuclide intake by the residents living in contaminated territories after the Chernobyl accident have been carried out in order to assess the contribution of gamma-emission of incorporated cesium radioisotopes to the exposure rate measured near the thyroid by the survey. Under such calculations two the most important modes of intake have been considered: 1) inhalation and 2) ingestion with cow milk. Results. According to the estimates received the contribution of gamma-emission of incorporated cesium radioisotopes to the exposure rate measured near the thyroid during the first 20 days does not exceed 20% for the residents of southern areas of Gomel region and 30% for the residents of Mogil'yov region. During 60 days following the accident that contribution is estimated to be within (50-80) % for the residents of southern areas of Gomel region and (80-95) % for the residents of Mogil'yov region. Conclusion. For the period of intensive thyroid measuring in the southern areas of Gomel region (the second part of May) account of the contribution of gamma-emission of incorporated cesium radioisotopes is relatively unimportant, but for Mogil'yov region (the end of May) — it is important to account for. For the thyroid measurements conducted in June of 1986 it is important for all residents living in Belarus to take into account the contribution of gamma-emission of incorporated cesium radioisotopes.