Abstract: In treatment of aqueous solutions and suspensions of radioactive waste through a step of drying and pulverizing the aqueous solutions and suspensions and a successive step of compressing and solidifying the resulting powders of radioactive waste, a step of measuring a water content of the powders is provided between the step of drying and pulverizing and the step of compressing and solidifying. When the measured water content of the powders fails to satisfy a predetermined water content, the powders are eliminated from a system of the treatment without passing through the step of compressing and solidifying.

Abstract: A vent gas containing radioactive iodine and methyliodide is effectively decontaminated by chemically adsorbing the iodine contained in the vent gas onto an activated carbon layer at first, then physically adsorbing the methyl iodide contained in the vent gas onto another activated carbon layer separately disposed from the former activated carbon layer, and retaining the radioactive iodine and radioactive methyl iodide on the respective activated carbon layers for a definite period of radioactive decay.

Abstract: A thin-film field-emission electron source having an emitter within a minute cavity in a conductive substrate, an insulating layer covering the surface of the substrate except for the portion of the cavity, and a first anode layer on the insulating layer, wherein the substrate and the emitter are comprised as one body, and the insulating layer and the first anode layer overhang the cavity, except directly over the emitter.This electron source may be manufactured by the method comprising the steps of i) forming a sandwich structure of the substrate-insulating layer-first anode layer, ii) forming a closed loop opening at a predetermined position on the surface of the first anode layer, iii) etching the insulating layer with the use of the first anode layer as a mask and iv) forming an emitter and a cavity by etching the substrate with the use of the insulating layer as a mask.