Alternative reductants for foam control during vitrification of high-iron High Level Waste (HLW) feeds

0570896 - ÚSMH 2024 RIV NL eng J - Journal Article
Rigby, J.C. - Dixon, D.R. - Kloužek, Jaroslav - Pokorný, Richard - Thompson, P.B.J. - Scrimshire, A. - Kruger, A.A. - Bell, A.M. T. - Bingham, P.A.
Alternative reductants for foam control during vitrification of high-iron High Level Waste (HLW) feeds.
Journal of Non-Crystalline Solids. Roč. 608, MAY 15 2023 (2023), č. článku 122240. ISSN 0022-3093. E-ISSN 1873-4812
Institutional support: RVO:67985891
Keywords : Cold cap * Vitrification * Redox * Multivalent species * Secondary foaming
OECD category: Ceramics
Impact factor: 3.5, year: 2022
Method of publishing: Open access
https://doi.org/10.1016/j.jnoncrysol.2023.122240

Foaming during vitrification of radioactive waste in Joule-Heated Ceramic Melters (JHCM) is exacerbated by trapping of evolving gases, such as CO2, NOx and O2, beneath a viscous reaction layer. Foaming restricts heat transfer during melting. Sucrose is employed as the baseline additive at the Hanford site in Washington State, USA to reduce foaming. Alternative carbon-based reductant additives were explored in simulated, inactive Hanford high-iron HLW-NG-Fe2 feeds, for both their effect on foaming and to give insight to the behaviour of multivalent species in glass melts under different redox conditions. Graphite, coke (93% C), formic acid and HEDTA additives were compared with sucrose, and a feed with no additive. Graphite and coke additions proved most effective in reducing the maximum foam volume by 51 +/- 3% and 54 +/- 2%, respectively, compared with 24 +/- 5% for sucrose. Lower foaming could result in more efficient vitrification in JHCMs. Reductants also affected redox ratios in the multivalent species present in the feed. The order of reduction, Mn3+/Mn2+ > Cr6+/Cr3+ > Ce3+/Ce4+ > Fe3+/Fe2+ was as predicted on the basis of their redox potentials. There is less reduction overall, particularly in the Fe3+> Fe2+, than predicted by the calculations, attributed to the oxygenated atmosphere of the experiments.
Permanent Link: https://hdl.handle.net/11104/0342964