Solid Cancer Incidence Risk among the Population Exposed in the East Urals Radioactive Trace over 1957–2014

Purpose: Assessment of solid cancer incidence risk in the cohort of exposed population on the territory of the East Urals radioactive trace over the period of follow-up from 1957 to 2014 with the use of the individual doses provided by the latest TRDS dosimetry system. Material and methods: The explosion of the liquid radioactive waste storage tank at the «Mayak» Production Association on 29 September 1957 led to the pollution of the territories of the Chelyabinsk and Sverdlovsk Regions and the formation of the EURT, and the population residing on its territory was subjected to protracted chronic external and internal exposure. The analyzed cohort includes 21,384 people, 2,055 of whom received additional radiation before the 1957 accident due to residing in one of the Techa River settlements. The mean dose to the stomach for the members of the EURT cohort was 36 mGy, the maximum — 1.13 Gy. The analysis was performed using the DATAB and AMFIT programs (statistical software package EPICURE). A simple parametric model of excess relative risk (ERR) was used. Statistical significance and confidence intervals were obtained using the maximum likelihood method. Results: As a result of the analysis of the solid cancer incidence risk in the EURT cohort during the 57-year follow-up period using the linear model and the 5-year latent period, a statistically significant ERR was obtained which equals to 0.052 / 100 mGy (95 % CI 0.01–0.10, p = 0.02) in the entire EURT cohort. When the group of people additionally exposed on the Techa River before the 1957 accident was excluded from the cohort, the risk became insignificant. No significant modification of the dose dependence by non-radiation factors was revealed. The obtained results are compared well with the previous studies of the exposed population in the Southern Urals which were conducted in the Urals Research Center for Radiation Medicine, as well as in the world, devoted to the study of the effects of radiation exposure on population.

Radiation survey around “the 30th shipyard” company: 30 years after the accident

Introduction. The objective of this work was the radiation survey in the vicinity of “The 30th Shipyard” Company. The studies were carried out during the period between 2014 and 2016 within the supervision area and in the area of the radioactive trace formed after the accident of 1985 in the nuclear submarine.Material and methods. The following methods were used in the course of the survey: pedestrian gamma surveys, gamma spectrometry measurements of radionuclides using a gamma spectrometer, and radiochemical extraction of 90Sr, followed by measurement of its activity at radiometric installations.Results. Gamma ambient dose equivalent rate within the supervision area beyond the radioactive trace varies within the range between 0.09 and 0.18 µSv/h. The specific activities of 90Sr, 137Cs, and 235U in soil do not exceed 11, 34, and 5.8 Bq/kg, respectively. The specific activity of 60Co in the soil of the Dunay village is lower 0.42 Bq/kg and does not exceed 4.9 Bq/kg at the rest part of the supervision area. The area of the radioactive trace limited by 0.13 µSv/h iso-line does not exceed 0.5 km2, while that limited by 0.3 µSv/h iso-line - 0.0063 km2. Within the area of the trace, the highest value of the gamma dose rate accounts for 0.60 µSv/h. Soils contaminated with emergency radionuclides do not belong to solid radioactive waste. Emergency radionuclides migrated in soil up to 20 cm depth. Today, 137Cs is firmly fixed in the soil. 40-45% of 60Co activity is in acid-soluble form. Under specific conditions, it can migrate deep into the soil and be accessible to plants.Conclusions. Within the supervision area of “The 30th Shipyard” Company, except for the area of the radioactive contamination trace induced by the accident, the radiation situation is the same as that in the area of the Primorskiy Krai. The soil of the radioactive trace does not belong to solid radioactive waste. In the future, the improvement of the radiation situation on the trace will be mainly due to the physical decay of radionuclides.