Development of a radioactive waste treatment equipment utilizing microwave heating, 2nd report

The objective of the present study is to establish an incineration technique utilizing microwave heating which enables a high volume reduction of spent ion-exchange resins and filtering media generated at nuclear facilities. The past three years from 1982 to 1985, with the financial aid from the Agency of Science and Technology, brought a great and rapid progress to this project when the heating technique was switched from direct microwave heating to indirect heating by employing a bed of beads of silicon carbide. This material was also used to build a secondary furnace, walls and roster bars, to treat the obnoxious gases and soot arising in the primary incineration process by the radiating heat of this material heated to above 1000 deg C again by microwave energy, but not by the originarily applied direct plasma torch combustion. The incinerator and the secondary furnace were integrated into one unit as the principal treating equipment. This novel approach made possible a well stabilized continuous incineration operation. Further, developmental efforts toward industrial applications were made by setting up a pilot plant with microwave generators, 2 sets of 5 kW of 2450 MHz and 1 set of 25 kW of 915 MHz, and tests were carried out to prove remarkably high volume reduction capability well above roughly 200 on weight basis. For hot test runs, a one - tenth scale pilot test setup was installed at the TOKAI Laboratory of Japan Atmic Energy Research Institute and tested with materials spiked with radioisotopes and also with spent ion-exchange resins stored there. Very satisfactory results were obtained in these proving tests to show the efficient capability of high volume reduction treatment of otherwise stable radioactive waste materials such as spent ion-exchange resins. (author)