Development of the vitrification process of high-level liquid waste in the engineering test facility

The engineering test facility has been constructed to establish the vitrification process for high level liquid wastes (HLLW). Two campaigns with the simulated HLLW containing 3 mol/l of nitric acid have been conducted to confirm the facility performance and to grasp the operation mode. The facility includes a pretreatment system, an off-gas treatment system, Joule heated ceramic melters and a canister-handling system. In two campaigns, approximately 50 m3 of the simulated HLLW were treated, and 18.5 tons of the borosilicate glass containing about 30 percent of the waste oxides were produced. The maximum gas evolution rate during denitration is dependent on the feed rate of formic acid and the quantity of waste solution. The data in the engineering scale experiment were in good agreement with those in the laboratory scale experiment. Various heating tests were performed for the melters. Investigation was made on the corrosion of the electrodes and refractories. The corrosion of the molybdenum electrodes was observed. The analysis of the particulates deposited inside the off-gas lines showed that the chemical composition of the particulates generated during slurry feeding agreed well with the composition of glass product and particulates during the operation held in the melters. The removal efficiency of NO2 was measured. (Kato, T.)