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.

60CO and 137CS Activity of Nearshore Lake Ontario Sediments in the Vicinity of the Pickering Nuclear Generating Complex

Detectable 137Cs activity (<1 - 27 Bq/kg dry wt.) was widely distributed in sediments from a series of nearshore transects along Lake Ontario near Pickering Nuclear Generating Station (NGS) ‘A’. In contrast, detectable 60Co activity (<1 - 14 Bq/Kg dry wt.) was largely restricted to transects located near the discharge of Pickering ‘A’ NGS. The widespread distribution of 137Cs is consistent with diffuse input of the radionuclide through fallout, while the restricted distribution of 60Co indicates a localized input of this radionuclide. Adsorption distribution coefficients (Kd’s) of 60Co and 137Cs varied by more than an order of magnitude among representative sediments. Although Kd’s of both radionuclides were correlated with cation exchange capacity and particle size, neither the observed gamma activity nor the corresponding Kd were important in describing 60Co or 137Cs Kd’s. Thus factors other than adsorption affinity alone may be required to account for the distribution of these radionuclides in nearshore Lake Ontario sediments.