The creation and verification of a mutually agreed database of input information of the simulation model of transport of radionuclides Cs-137 and I-131 along the food chain on instrumental radioecological data (based on the materials of the "Prague" and "Warsaw" scenarios of the IAEA EMRAS project)

«Radiation and Risk», 2019, vol. 28, No. 3, pp.5-23

DOI: 10.21870/0131-3878-2019-28-3-5-23

Authors

Vlasov O.K.¹ – Head of Lab., D.Sc., Tech. Contacts: 4 Korolyov str., Obninsk, Kaluga region, Russia, 249036.
Tel.: (484) 399-32-45; e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. .
Krajewski P.² – Director, Prof. CLOR.
Bartuskova M.³ – Head of Lab., Ph.D. Branch of SURO.
Malatova I.⁴ – Senior Researcher, C.Sc., Phys. SURO.
Shchukina N.V.¹ – Senior Researcher.
Chekin S.Yu.¹ – Head of Lab.
Tumanov K.А.¹ – Head of Lab., C. Sc., Biol. A. Tsyb MRRC.
Zvonova I.A.⁵ – Main Researcher, D.Sc., Tech. P. Ramzaev RIRH.

¹ A. Tsyb MRRC, Obninsk.
² Central Laboratory for Radiological Protection (CLOR), Warsaw, Poland.
³ Branch of National Radiation Protection Institute (SURO), Ostrava, Czech Republic.
⁴ National Radiation Protection Institute (SURO), Prague, Czech Republic.
⁵ P. Ramzaev Research Institute of Radiation Hygiene, Saint-Petersburg.

Abstract

The technology of creating a mutually consistent database of input data of the simulation radioecological model after a radiation accident with the emission of products into the atmosphere is presented. The data set for the objects of study (the settlements or their areas) includes the average for the period of major deposition or time dependences of specific volume activities of ¹³⁷Cs in the atmosphere, precipitation during the deposition period, the deposition density of ¹³⁷Cs. Data deposition densities of ¹³⁷Cs in the territories of the Central parts of the regions of Mazovia (Poland) and Bohemia (Czech Republic) after the Chernobyl accident, weather rainfall and instrumental data on the dynamics of activities of ¹³¹I and ¹³⁷Cs in the atmosphere indicated weak spatial variability, indicating a relatively homogeneous structure of the parameters of radioactive contamination of the atmosphere and weak local rainfall in the period of major radioactive fallout in these regions. The maximum values of specific volume activities of ¹³¹I and ¹³⁷Cs in the atmosphere during the first peak of deposition in Bohemia and Mazovia are almost the same. In Mazovia, in the period from 11 to 13 days after the accident, in contrast to Bohemia, there was a second peak of ¹³¹I and ¹³⁷Cs activities in the atmosphere with their maximum values about an order of magnitude smaller than in the first peak. The integrals of the specific volume activity of ¹³¹I and ¹³⁷Cs in kBq/m3day was in Mazovia 0.39 and 0,023 respectively. In Bohemia – 0.2 and 0.03 respectively. The average value of the ratio of specific volume activities ¹³¹I to ¹³⁷Cs in the atmosphere of Mazovia for the period of the main fallout was 17.2, which is 2.3 times more than in Bohemia, equal to 7.1. The inconsistency of the input data base is manifested in significant differences in the instrumental deposition densities of ¹³⁷Cs in settlements and reconstructed by the direct calculation model: activity of ¹³⁷Cs in the atmosphere – precipitation meteorological data. To match the input data, the models of homogeneous clouds heterogeneous precipitation and heterogeneous clouds – homogeneous precipitation. In General, for human settlements, the direct calculation of ¹³⁷Cs deposition densities from the inconsistent data model (homogeneous cloud – precipitation data) provides a significant difference from both the instrumental data and the harmonized data models (homogeneous cloud – heterogeneous effective precipita-tion) and (heterogeneous cloud – homogeneous precipitation data). Moreover, the greater the drop density of ¹³⁷Cs. With the existing dynamics of the parameters of radionuclide activity in the atmosphere, the effect of precipitation on the precipitation density of ¹³¹I and ¹³⁷Cs and specific activity of ¹³¹I and ¹³⁷Cs in vegetation begins to appear only at their values greater than 0.2 mm. For grass, it ends at precipitation greater than 1-2 mm. For ¹³¹I, this effect is less than for ¹³⁷Cs. Regional differences in the dynamics of activity of ¹³⁷Cs and ¹³¹I in the atmosphere led to the fact that the density of "dry" deposition of ¹³¹I and its precipitation of 10 mm on vegetation were 1.8 and 2.1 times higher than in Bohemia, and for ¹³⁷Cs – less, respectively, 1.8 and 1.4 times. In fact, this means that in the same ratio were the doses of internal exposure to the thyroid gland and doses to the entire body of the population of Mazovia and Bohemia. The use of mutually agreed data, primarily precipitation during deposition and pollution parameters of the atmosphere, leads to an adequate reproduction of the measured data on the deposition densities of ¹³⁷Cs in the area, to significant reduction of uncertainties of transport of ¹³⁷Cs and ¹³¹I in the food chain and as a consequence a more accurate reconstruction of internal radiation doses of the population of the contaminated areas.

Key words
Chernobyl accident, simulation model in radioecological studies, IAEA project EMRAS, activity of ¹³⁷Cs and ¹³¹I in atmosphere, forms of ¹³¹I in atmosphere, precipitation over the period of deposition, deposition density of ¹³⁷Cs on soil, verification of the radioecological model, transport of radionuclides in the food chain, reconstruction of internal radiation doses.

References

1. Environmental Modelling for Radiation Safety (EMRAS): a summary report of the results of the EMRAS programme (2003-2007). IAEA-TECDOC-1678. Vienna, IAEA, 2012. 60 p.

2. Bartusková M., Malátová I., Berkovskyy V., Krajewski P., Ammann M., Filistovic V., Homma T., Horyna ., Kanyár B., Nedveckaite T., Vlasov O., Zvonova I. Radioecological assessments of the iodine working group of IAEA's EMRAS programme: presentation of input data and analysis of results of the Prague scenario. Radioprotection, 2009, vol. 44, no. 5, pp. 295-300.

3. Vlasov O.K. Radioecological model for transport of radioiodine and radiocesium in the food chains after radiological accidents and discharge of radioactive substances to atmosphere for study of mechanism of formation of internal radiation doses to population. Part 1. Description, formulation and properties of agro-climatic model. Radiatsiya i risk – Radiation and Risk, 2013, vol. 22, no. 2, pp. 16-34. (In Russian).

Full-text article (in Russian)