The phenomenon of swelling during the glassification of HAW-MTR radioactive waste
A study has been carried out on the foaming effect which occurs during the calcination of MTR type waste materials, in order to improve the in-pot vitrification technology. Foaming was accompanied by swelling and growth-expansion phenomena, and was influenced by the initial composition of the waste and by the operating parameters in the applied vitrification process (in particular the heating conditions). The waste studied was made of a mixture of alkaline sludges and zeolites coming from the treatment of simulated high aluminium content nitric liquid waste (the so-called "alkaline declassification" process), and the vitrifying additives. During the heat treatment of the samples, attention has been focussed on: - softening temperature; - thermal decomposition, examined by differential thermogravimetric analysis; - residual nitrate ion and released gas composition, and - iron oxidation state after heat treatment in air and in nitrogen. The foaming effect on the calcined material occurred in the temperature range 923-1023 K and it is due to gas release at temperatures higher than the softening temperature of the calcined material. The most effective remedy in minimising foaming was found to be the addition of organic substances, such as sugar, to the material to be calcined.
Bibliographic Reference: Article: Energia Nucleare, Vol. 8 (1991) No. 1, pp. 29-35
Record Number: 199111320 / Last updated on: 1994-12-02
Original language: it
Available languages: it