The Effect of Sealing of the NSC Enclosing Perimeter
on the Surface Contamination of the External
Surfaces of the Shelter Object Roof and Assessment
of the Possibility of Their Deactivation

L. I. Pavlovskyi1, D. V. Gorodetskyi1, Ye. A. Menshenin1,
O. O. Odintsov1, L. A. Palamar1, O. P. Solоnenko2

1 Institute for Safety Problems of Nuclear Power Plants,
NAS of Ukraine, Kirova st., 36a, Chornobyl, 07270, Ukraine
2 State Specialized Enterprise “Chornobyl Nuclear Power
Plant”, P.O. B. 11, Slavutych, 07100, Ukraine

DOI: doi.org/10.31717/2311-8253.22.3.4

Abstract

After the sealing of the enclosing perimeter of the New Safe Confinement — Shelter object (NSC-SO) complex (at the end of 2017), unorganized emissions of radioactive aerosols from the Shelter object were dispersed in the environment. Currently, in the closed volume under the NSC arch, a significant amount of dust is settling and accumulating, which is characterized by a high content of radionuclides. In particular, these processes are manifested on the roofs of the Shelter object, where the mass of dust has already reached 15 g/m2 . At the same time, since the sealing of the containment circuit of the NSC-SO complex, the density of total surface contamination by the sum of alpha- and beta-active nuclides has increased by 9.3 times, and the non-fixed form of surface contamination has increased by 5.7 times. According to our data, the formation of dust is the result of the deposition of a construction dust mixture, as evidenced by its significant content of calcium — up to 72% and heavy metals — up to 28% by mass, as well as radioactive aerosols of unorganized emissions from the SO. Currently, the activity of dust on the surface of the roof structures of the Shelter object is up to 580 kBq/kg of α-active, as well as up to 19,300 kBq/kg of beta- and gamma-active nuclides, which allows it to be classified as medium-active radioactive waste. It was established that the use of a vacuum cleaner (dust suction power ≥13 kPa) for the dry decontamination of the surfaces of the metal structures of the SO roofs allows removing from 79 to 98% of the activity of nonfixed surface pollution, which can provide a significant improvement in the radiation situation during the dismantling work of unstable constructions of the SO. At the same time, it is advisable to use autonomous models of vacuum cleaners for decontamination of places where metal structures are cut. For decontamination of arge surface areas of structural fragments that will be transported to the storage site, models of vacuum cleaners with high production capacity are needed to perform this operation as quickly as possible, which will ensure a reduction in the dose of exposure to the working personnel.

Keywords: ChNPP, NSC-SO, unfixed radioactive surface contamination, dry decontamination.

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Published
2023-04-25

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