09 May Initial cleaning of Hot Cells complete

The initial decontamination has removed 85 percent of the radioactivity in the Hot Cell facility. Watch a video demonstrating how the team subsequently removed hotspots in one of the cells.

TThe six interconnected concrete cells in the Hot Cell facility were used to handle radioactive materials from 1964 to 1989. Due to the high radiation level, the initial decontamination was carried out using remote-controlled sandblasting. This process took eighteen months, preceded by several years of planning and preparatory work, including the development of the mechanical arms required.

The walls, floor, and inventory of the cells have been sandblasted with steel particles through a series of holes in the 1.7-meter-thick walls. Once the flakes of contaminated paint accumulated with the used steel particles, the entire mixture was suctioned into a closed system via a vacuum arm and transferred into shielded drums. Typically, two technicians were assigned to the task. A health assistant was stationed nearby to monitor radiation levels, while an engineer supervised all systems from a control room adjacent to the work area.

From July to December 2017, the first three of the six Hot Cells underwent sandblasting. The radioactive contamination was lowest in these cells, so sandblasting commenced here to gain experience with the equipment before proceeding to the remaining three cells, where radiation levels were measured to be higher.

At the beginning of 2018, work began on the fourth cell. This cell and the final two cells had been utilized for various mechanical experiments, including grinding, hence a significant accumulation of radioactive dust was anticipated. However, it was not foreseen that the airborne dust, during extraction, would adhere so tenaciously to the filters. The initial decontamination process had to be paused for five months while supplementary equipment for the filters was developed (read more).

Subsequently, the work proceeded without major challenges, and by the end of the year, the initial decontamination of all six cells was declared complete. Nevertheless, the equipment had not entirely fulfilled its purpose. As demonstrated in the video below, an additional effort was made in January within one cell to remove a few hotspots – small areas or depressions harboring elevated radioactivity.

The radioactive waste from the decontamination process has so far filled 24 drums, which are packed into four containers and placed in interim storage. Measurements indicate that the total radioactivity in the six Hot Cells has been reduced by approximately 85 percent. This implies that in the next phase, personnel will be able to briefly enter the cells to remove inventory and install a robot for remote-controlled intermediate cleaning. Subsequently, it is anticipated that the radiation level inside the cells will be sufficiently low to allow for manual final cleaning.