Development of vitrification of HLLW by Joule-heated ceramic melter. Process testing and components examination of the equipment.


In order to establish the vitrification process for high level liquid wastes, the development of Joule-heated ceramic melters has been performed for three years. This ceramic melter can convert continuously the mixture of nuclear wastes and glass into stable glass products. In order to perform the process testing with simulated calcined wastes and simulated denitrated liquid wastes, an engineering scale melter was made, and five running tests were carried out for about 300 days. The service life of the refractories and electrodes was evaluated from the results of these tests. The improvement of the glass flowing-out system was made in this period. The ceramic melter consists of the melting cavity, the riser and the forehearth for glass refining. Electrofused and cast refractories of ZrO sup 2 -SiO sup 2 -Al sup 2 O sup 3 were used for the walls and bottoms in contact with glass. Two pairs of metallic molybdenum electrodes are in the melting cavity, a pair of molybdenum electrodes are in the riser, and a pair of SnO sup 2 electrodes are in the forehearth. The total holding capacity is about 200 litre. The start-up, steady operation, feeding in slurry state, flowing-out of glass and stopping are explained. The melter can be operated safely for more than two years. (Kako, I.). Torata,-Shin-ichiro; Kawanishi,-Nobuo; Nagaki,-Hiroshi; Tsunoda,-Naomi (Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan). Tokai Works)