Open AccessProblematic Issues Regarding the Quantity and Properties of Vitrified High-Level Waste Returning to Ukraine
Author(s) -
Yu. Olkhovyk
Publication year - 2019
Publication title -
âderna ta radìacìjna bezpeka
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.221
H-Index - 5
ISSN - 2073-6231
DOI - 10.32918/nrs.2019.2(82).05
Subject(s) - leaching (pedology) , crystallization , high level waste , materials science , radioactive waste , spent nuclear fuel , homogeneity (statistics) , radionuclide , amorphous solid , sodium cooled fast reactor , environmental science , waste management , chemical engineering , chemistry , nuclear chemistry , computer science , nuclear physics , physics , organic chemistry , machine learning , soil science , engineering , soil water
Safety justification of long-term storage and further disposal of vitrified high-level waste returning to Ukraine shall be based on reliable information about their physical and chemical characteristics, which include not only the radionuclide composition, but also the estimated evolution of Na-Al-P glass properties in the conditions of potential longterm effect of unfavorable factors. The paper indicates an inconsistency of dose coefficients, which according to the Energoatom standards shall be used to calculate the amount of high-level waste returning to Ukraine after storage and processing of VVER-440 spent nuclear fuel, with the regulatory requirements of the country supplying vitrified high-level waste. The quantitative assessment of transuranium radionuclides and technetium 99 entering the glass matrix also requires a critical review. The research considered the possibility of uncertainty related to the structural homogeneity of a glass matrix due to the underestimation of cracking and crystallization processes that occur in the package in sodium-aluminophosphate glass cooling. The presence of a large number of rare-earth oxides in sodium-aluminophosphate glass contributes to its crystallization in slow cooling with monazite formation. These phenomena can lead to a partial conversion of amorphous glass into a crystalline phase accompanied by 1-2 order increase in the velocity of leaching of elements. When developing technical requirements for vitrified high-level waste returning to Ukraine, it is necessary to insist on the provision of experimentally determined parameters of the structural homogeneity of glass blocks. There is a need for obtaining experimentally defined parameters of radiation resistance of a sodium-aluminophosphate matrix under the influence of a dose that can be accumulated over a period of 100 years using accelerated self-radiation methods.