Radioecological modeling of the 131I activity dynamics in the pasture vegetation of Mazovia in the year of the Chernobyl accident: Reconstruction, verification, reliability assessments

• Published in: Nuclear energy and technology 2023-12, Vol.9 (4), p.245-252
• Main Authors: Vlasov, Oleg K., Zvonova, Irina A., Shchukina, Nataliya V., Chekin, Sergey Yu
• Format: Article
• Language: English
• Subjects: Atmosphere; Atmospheric models; Cesium 137; Cesium isotopes; Cesium radioisotopes; Chernobyl accident; Clouds; Deposition; Differential equations; Food chains; Grasses; IAEA’s EMRAS p; Iodine; Mathematical models; Milk; Nuclear accidents; Nuclear energy; Nuclear power plants; Pasture; Radiation; Radioactive fallout; Radioisotopes; Rain; Rainfall; Reconstruction; Reliability analysis; Simulation; Vegetation
• ISSN: 2452-3038; 2452-3038
• DOI: 10.3897/nucet.9.116654

A radioecological model, which is a system of linear differential equations describing the dynamics of the transport of 137 Cs and 131 I radionuclides along the food chain after their release into the atmosphere after the Chernobyl accident, was used to reconstruct “instrumental” data of the 131 I activities in the grass pastures in the central part of Mazovia. Four atmospheric models were used for the reconstruction: direct calculation, homogeneous cloud – inhomogeneous rainfall, inhomogeneous cloud – homogeneous rainfall, and a model with recalculation of the 137 Cs and 131 I activities in the atmosphere. The “instrumental” data were reconstructed based on data from direct measurements of the 131 I activity in lawn grass. It has been shown that the direct calculation and homogeneous cloud models lead to a better agreement of the calculated and reconstructed “instrumental” data than the inhomogeneous cloud model. The arithmetic mean ratio of the calculated and reconstructed “instrumental” data lie in a range of 0.84 to 0.95 for the direct calculation and homogeneous cloud models, and in a range of 1.7 to 3.0 for the inhomogeneous cloud model. The mean geometric deviation for all models is constant and equal to 1.7. Instrumental and reconstructed “instrumental” data show a significant decrease in the specific activity of 131 I in grass due to its wash-off by continuous rainfall, both during rainfall and after most of the deposition takes place. Due to this effect, the coefficient of the 131 I retention on grass in the form of the maximum activity ratio to the 137 Cs deposition density decreases from 34 to 1.4 m 2 /kg while it increases from 1 to 29 kBq/m 2 as the result of the rainfall growth from 0 to 40 mm.