Hiroyuki Tsuchiya

Decontamination of Uranium-Contaminated Mild Steel by Melt Refining

Melt refining as a means of uranium decontamination of metallic wastes was examined. Samples of mild steel, contaminated with uranium, were melted by adding SiO/sub 2/-CaO-Al/sub 2/O/sub 3/ ternary system fluxes. Various melting temperatures and times were used, and the uranium concentrations in the resulting ingots were determined. Flux, and hence slag, composition was found to influence the level of decontamination, but melting temperature and time had little effect. Using the most effective flux composition (10 SiO/sub 2/-50 CaO-40 Al/sub 2/O/sub 3/), uranium concentration was lowered from a contamination level of 500 to 0.027 ppm, a value nearly that of the initial steel before contamination. When the ionic character of slag was defined using basicity (the mole ratio of basic oxide (CaO) to acidic oxide (SiO/sub 2/ + Al/sub 2/O/sub 3/)), the optimum decontamination value was found near a basicity of 1.6. The slag anions of silicate or aluminate seemed to affect the uranium decontamination.

Application of cryogenic distillation to Krypton-85 recovery

Abstract Fundamental and pilot experiments were carried out to develop a 85 Kr recovery system for nuclear power and fuel reprocessing plants. It consisted of a pretreatment unit to remove oxygen (O 2 ), acetylene (C 2 H 2 ) and nitrogen oxides (NO x ) from the inlet gas, a cryogenic distillation unit to remove and concentrate 85 Kr, and a storage unit for recovered 85 Kr.

Development of a sponge metal catalyst for a recombiner

Fundamental and pilot plant experiments have been carried out to develop a new recombiner catalyst with high catalytic activity and less deterioration at high temperature. The catalyst is prepared by electroplating palladium over a chromium layer, which in turn has been plated onto a sponge nickel metal surface. The optimal Cr/Ni ratio and palladium content are 2% and 0.6 mg/cm/sup 2/, respectively. The catalytic activity of the new catalyst is about ten times more than presently available metallic catalysts.

Properties of a radioactive waste pellet package using cement-glass

This paper reports on radioactive waste slurry generated from nuclear power plants which is dried and compressed into pellets. These pellets are dropped in a polymer-impregnated concrete (PIC) barrier and solidified with cement-glass, which is a mixture of sodium silicate and cement. The mechanical strength of the PIC barrier is about three times higher than that of ordinary portland cement because of added steel fibers. The leaching ration form the package is experimentally studied using {sup 14}C, {sup 60}Ci, {sup 85}Sr, {sup 99}Tc, {sup 125}I, and {sup 134}Cs. Because of the low porosity of the PIC barrier, the leaching rate is controlled and increases in proportion to immersion time. The maximum leaching ratio from a 200-l package is estimated to be 0.004/yr.