Changes of Radiohydroecological Conditions under Influence of the “Arch” Installation over the Shelter Object of the Chornobyl NPP

M. I. Panasiuk, N. V. Sosonna, I. A. Kovalenko, P. A. Lyushnya, G. V. Levin,
L. A. Palamar, L. B. Chikur, A. A. Onishchenko*

Institute for Safety Problems of Nuclear Power Plants, NAS of Ukraine,
36a, Kirova st., Chornobyl, 07270, Ukraine
*Scientific-Engineering Center for Radiohydroecological Field Research, NAS of Ukraine, 55b, O. Gonchara st., Kyiv, 01054, Ukraine

DOI: doi.org/10.31717/2311-8253.19.3.10

Abstract

To protect the environment from the impact of the 4th Chornobyl emergency block, a new safe confinement (NSC, hereinafter referred to as “Arch”) was constructed and installed in the design position in November 2016. A characteristic feature of the water regime of ground-water and block water at the site of the design position of the “Arch” is the termination of their water supply due to the absence of precipitation. The cessation of atmospheric precipitation infiltration led to a reduction of 2 to 4 times the concentrations of the main ions and the amount of mineralization in the upper part of the aquifer. In the block waters of the “Shelter” object (SO), the concentration of the main ions and mineralization increased by 1.7-8 times. Some water clusters in the premises of the SO have dried up, which has led to a significant increase of a gamma radiation Equivalent Dose. One of the mechanisms for enhancing the migration capacity of radionuclides in groundwater is associated with the formation of a highly alkaline environment with a pH greater than 9.5. High pH values are formed directly upon contact of ground-water with concrete of the foundations of structures or the entry into the aquifer of water masses in contact with concrete. However, despite the cessation of intensive inflow into the aquifer of infiltration and block waters, a significant decrease in the pH and volumetric activities of radionuclides other than tritium in groundwater under “Arch” is not happening yet. Concentrations of tritium in groundwater decreased from 900-1,100 to 30-50 Bq/lit-er. A change in the direction of movement of groundwater from north to north-east led to the formation of new pathways for the distribution of radionuclides with groundwater. So, in the S-10 well, located northeast of the SO, an increase in the concentration of tritium from 3-5 to 30 Bq/1 is observed. Outside the “Arch”, by separate observation wells, the mineralization and ion concentration increase is 1.4-5 times, possibly due to the contact of the concrete of the pile foundation of the “Arch” with underground waters. The tritium concentrations in the block waters that associated with the facilities, located under reactor increased of 3 to 5 times. An increase in tritium concentrations may be associated with an increase in the density of neutron fluxes in rooms under reactor after the “Arch” was drawn. Increased mineralization leads to an increase in the solubility of block water, which in turn can lead to an additional transfer of radionuclides from the active precipitate into the water of the precipitating clusters. Increasing the volume activities of radionuclides by evaporation and increasing the solubility of block water can lead to the formation of radioactively contaminated water masses, which at the concentration levels of radionuclides will refer to highly active liquid radioactive waste.

Keywords: “Arch” influence, industrial site of Chornobyl NPP, underground and block waters, radionuclides, basic ions, pH, migration, pile foundation.

References

1. Institute for Safety Problems of Nuclear Power Plants (2017). Radiohydroecological monitoring in the area of the Shelter object. Stage 2. Conducting a radiohydroecological monitoring for the second stage of 2017. Final research report. Contract no. 373/16 of 06.04.2017. Chornobyl, ISP NPP, 200 p. (in Russ.)

2. Panasiuk M. I., Lytvyn I. A. (2017). [Patterns of uranium distribution in the groundwater of the ChNPP site], Yad-ernafizyka ta enerhetyka [Nuclear Physics and Energy], vol. 18, no. 1, pp. 56-62. (in Ukr.)

3. Matrosov D., Shevchenko A., Nosovskyi A., Panasiuk M. (2018). Data analysis of radiation and hydroecological monitoring of ground waters located at the industrial site of Chornobyl NPP. Proceedings of the XII International Scientific Conference “Monitoring of Geological Processes and Ecological Condition of the Environment” (Kyiv, November 13-16, 2018). Doi: 10.3997/2214-4609.201803172.

4. Panasiuk M. I., Lytvyn I. A., Liushnya E. P., Al-fyoroff A. M., Levin G. V., Shestopalov V. M. (2015). Soils and Ground Water’s Radioactive Contamination into the Local Zone of the “Shelter” Object and Industrial Site of Chernobyl NPP. Proceedings of the 7th International Conference on Uranium Mining and Hydrogeology “Uranium — Past and Future Challenges” (Freiberg, Germany, September, 2014), pp. 657-664.

5. Korneev A. A., Krinitsyn A. P., Strikhar’ O. L., Shcherbin V. N. (2002). [Liquid radioactive waste inside the Shelter object]. Radiokhimiya [Radiochemistry], vol. 44, no. 6, pp. 545-552. (in Russ.)

6. Vysotskii E. D., Godun R. L., Doroshenko A. A. (2018). Dynamics of neutron activity and sub-specificity of a nuclear-dangerous cluster under the conditions of the “NSC — Shelter object” complex. Problemy bezpeky atom-nykh elekrostantsiy i Chornobylya [Problems of Nuclear Power Plants’ Safety and of Chornobyl], vol. 30, pp. 78-86. (in Russ.)

Full Text (PDF)


Published
2019-11-31

If the article is accepted for publication in the journal «Industrial Heat Engineering» the author must sign an agreement on transfer of copyright. The agreement is sent to the postal (original) or e-mail address (scanned copy) of the journal editions.

Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a  Creative Commons Attribution License International CC-BY that allows others to share the work with an acknowledgement of the work’s authorship and initial publication in this journal.