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 90 Sr, 137 Cs, and 235 U in soil do not exceed 11, 34, and 5.8 Bq/kg, respectively. The specific activity of 60 Co 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 km 2 , while that limited by 0.3 µSv/h iso-line - 0.0063 km 2 . 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, 137 Cs is firmly fixed in the soil. 40-45% of 60 Co 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.