The existing dosimetry systems will be improved : the film dosimetry system of Mayak by studying the energy dependence of the film sensitivity and by taking into account the spectral properties of the radiation fields at the working places, the dosimetry system of URCRM with the help of radionuclide transport in the Techa river and the radiation transport with the help of luminescence analysis of bricks, ceramics and sediments. Results of the different methods will be compared to achieve the objectives.
The Production Association Mayak in Osjorsk (former Cheljabinsk 65) started the operations of the first Soviet industrial nuclear reactor in June 1948. In the same year, a radiochemical reprocessing plant for irradiated fuel was opened. Due to the absence of the necessary professional experience and due to the haste because of the military competition with the US, workers in both facilities received high radiation doses during the first years of operation. Annual individual doses reached up to 4 Sv with maximal total individual doses of up to 10 Sv. These radiation exposures resulted in health effects. Beginning from the middle of the 1950's, the personnel was medically surveyed by Branch 1 of the Biophysical Institute of the Health Department.
Techa riverside residents were mainly exposed due to the radioactive liquid discharges of Mayak with a total activity of 2.7-106 Ci during the period 1949 to 1956. Internal exposures occurred due to ingestion of radionuclides with drinking water and due to the use of the Techa river water for irrigation. Inhabitants of the upper techa riverside settlements received high external exposures from the contaminated river sediments. Among the population cases of chronic radiation sickness and a significant increase of leukemia were observed. There is also some evidence that solid tumors are in excess. A central registry about the Techa riverside residents, including health status and radiometric measurements was established in URCRM.
From the beginning, the personnel of Mayak was under individual dosimetry control. However, the occupational doses determined during the first years have large uncertainties. Concerning the population exposure; environmental measurements were started in 1951, followed by in-vivo beta-ray measurements on teeth since 1960 and by stronium whole body measurements. Also this dosimetry system has large uncertainties for persons with early exposures, since the measured strontium contents have to be extrapoled backwards to the assumed time of intake and since the knowledge on the external exposures that occurred in the first years is limited.
The main objectives of the proposed research are :
(i) to test the capabilities of several methods of dose reconstruction by applying them to the same members of two cohorts (workers of Mayak and Techa riverside residents) for which independent dose assessments exist,
(ii) to further develop the methods of dose reconstruction according to the experiences gained during the exercise, and
(iii) to contribute to the improvement of the dose assessment for the individuals of these cohorts which are currently burdened by large uncertainties.
Funding SchemeCSC - Cost-sharing contracts