RadChem 2018

"Dry” decontamination by films and pastes

18 May 2018, 14:30

16m

Marble Hall (Casino Conference Centre)

Verbal Chemistry of Nuclear Fuel Cycle, Radiochemical Problems in Nuclear Waste Management NFC 6

Speaker

Dr Nadzeya Varonik (Joint Institute for Power and Nuclear Research – Sosny of the National Academy of Sciences of Belarus)

Description

This study was aimed to development and application of polymer composite formulations for “dry” decontamination of the spent nuclear fuel storage of mobile NPP “PAMIR” with gas-cooled nuclear reactor using heat carrier N${}_2$O${}_4$.
Polymer composite formulations for “dry” decontamination and their operation characteristics (decontamination efficiency, consumption rate), and at evaluating the chemical resistance and radionuclide fixation strength in the “dry” decontamination waste obtained using the new decontaminating pastes were developed. Polymer composite formulations for decontamination were developed on the basis of a polyvinyl alcohol solution as a binder with active additives (HNO${}_3$, HBF${}_4$, 1-hydroxyethane-1,1-diphosphonic acid and its triammonium salt, and a synthetic detergent) and fillers (natural rottenstone; rottenstone modified with nickel ferrocyanides; clinoptilolite modified with iron(III) and calcium chlorides, sodium phosphate, and potassium ferrocyanide; hydrolytic lignin). The developed polymer composite materials (pastes) exhibit high decontaminating ability (DF=10${}^2$–10${}^3$) and low adhesion to the tested surfaces of stainless and carbon steels (including painted surfaces), plastic compound, self-leveling floors, and Teflon surface. The ${}^{137}$Cs leach rates from dry decontamination wastes were determined by long-term leaching test in accordance with GOST (State Standard) 29114–91. Results show that rottenstone modified with nickel ferrocyanide fixes strongly (up to 99 %) cesium radionuclides in the solid waste from decontamination with pastes.
The current work directions deal with implementation of decontaminating gels on decommissioning of the spent nuclear fuel storage pools, spacing grids of storage pools and further release of decommissioning material and waste from regulatory control.
Total square of decontaminated equipment was 62,4 m${}^2$, decontaminating gel consumption for 2-lauer coating – 1,2 kg/m${}^2$. DF = 10${}^1$–6•10${}^2$, formed solid waste was 0,3 kg/m${}^2$.
The developed formulations ensure reliable, efficient, and safe storage of radioactive waste from “dry” decontamination of the external surfaces of the equipment and premises with the new formulations.