During 1-2 May 2022, personnel of the NSC (Objects Shelter) Operation Shop successfully carried out dust-suppression works (feeding of localizing dust-suppressing solution (DSS) AK-510 into the space under the Shelter’s roof) using the Upgraded dust-suppression system.

These works included making the dust-suppression formula and rinsing solution, analyzing the content of Gadolinium in the rinsing solution, testing (determining the viscosity) of dust-suppression solution, feed in of the solution into the working area of the system, washing of pipelines and injectors with the rinsing solution followed by draining of the residues of the composition and rinsing solution into the drain tank. All works have been performed by staff according to the “Operating Instructions for the Upgraded Dust Suppressions System”.

These works serve to limit the dissemination of radioactive substances under the Shelter’s roof space within the dust-suppression system’s area of coverage which lies within the axes 40-53, rows Б-С and covers the space under the roof of the destroyed power unit 4 (Central Hall premises, separator drums boxes etc.) and in between buttresses.

For one dust-suppression session one injection of 5 tons of DSS was carried out for each of the three piping headers.

FYI

As part of the international technical assistance in 2003-2006, upgrade of the dust-suppression system of the Shelter was performed based on the use of the dust-suppression solution with a higher dry residue content, which allows to create a stable film coating that prevents formation of dust.

In 2021, the Institute for NPP Safety Problems (ISP NPP) carried out research work on assessing the condition of the protective polymer coating in the Shelter’s under roof space. According to the conclusions of the Report on Research work "Assessment of the state of protective polymer coating in the Shelter’s under roof space as of 2021" (hereinafter the Report), exceeding of the criteria for assessing the state of the protective polymer coating and of the level of radioactive contamination of the surfaces of the protective polymer coating was not recorded. However, it was recommended in the Report to carry out preventive dust-suppression works no later than first half of May 2022 in order to limit dissemination of radioactive substances, enhance radiation safety during the monitoring of fuel-containing materials inside the Shelter, and conducting pre-design surveys of unstable structures under the development of the NSC CS-2 project. The recommendation has now been implemented.