[en] Volatility of ¹³⁷Cs and ⁹⁰Sr from simulated high-level waste glass was examined in a closed system. The sample containing ¹³⁷Cs or ⁹⁰Sr was placed in a double-crucible, heated at a given temperature for 3 days and cooled to room temperature. Then the activity of ¹³⁷Cs or ⁹⁰Sr of the crucible was measured. Volatility of ¹³⁷Cs at 800⁰C was measured to be about 2 x 10^-2 g/cm².day. The amount of the leakage of ¹³⁷Cs from the inner crucible to the outer crucible was very small. Volatility of ¹³⁷Cs at 400⁰C was about 1.6 x 10^-6 g/cm².day, which was almost the same as that of ⁹⁰Sr at 400⁰C. This may indicate that fine particles adhering to the surface of the sample are the main cause of air contamination when the temperature is less than 400⁰C. Part of the ¹³⁷Cs that was deposited on the surface of the outer crucible (stainless steel) dissolved in water at room temperature, which means that ¹³⁷Cs deposited on a stainless steel surface may be easily removed by a decontamination process

[en] Application of the energy dispersive x-ray fluorescence technique to a sedimentation method for particle size analysis has been studied. Two types of apparatuses are proposed which enable to determine the size distribution for each component of a powder mixture, in wide ranges of particle size and atomic number, using a small quantity of sample. Examples are given of the analysis of airborne particulates and rock powder

[en] A simple method for preparing a pollucite ¹³⁷Cs γ-ray source pellet is presented. An original pellet forming commercial synthetic (NH₄-Na)A zeolite is calcined at 600⁰C for 2 h, and impregnated with ¹³⁷CsNO₃ solution of appropriate radioactive concentration, followed by heating at 1100⁰C for 2 h, for synthesizing the pollucite and sintering the source pellet. The pellet thus obtained with bulk density of about 2.4 g cm^-3 and specific activity up to about 12 Ci g^-1, has prominent properties such as high resistivity for heating and insolubility to water. (author)

[en] Deep underground disposal is one of the most considerable options for high level radioactive waste management. The waste material will be surrounded by an engineered barrier that consists of canister, overpack and buffer material. In this barrier, a large amount of iron will be dissolved from canister and overpack for long term because these kinds of barrier are iron-based metal. Radionuclides released from the waste material will be adsorbed on corrosion products (iron compounds) that are produced from a precipitation process of dissolved FE(II)/Fe(III) ion. Then, adsorption behavior of radionuclides on iron compounds has been studied. These investigations were conducted using with individual iron compounds. In real situation, however, some kinds of the compound are mixed, and a dehydration and/or crystallization process of the amorphous iron compound is in progress. Then, it is important to study the adsorption behavior of elements under the realistic complex condition. Osada et al. analyzed the corrosion products on the carbon steel surface in wet bentonite from 40 to 90 deg C, and they were α-FeO(OH) (goethite) and γ-FeO(OH) (lepidocrocite). These kinds of corrosion product will be produced by the alternation of the amorphous iron precipitates to the crystalline iron products by the dehydration process. Then, as one of the alternation process of iron compound, the crystallization of amorphous ferrihydrite into crystalline goethite was taken into account in this paper. The adsorption behavior of strontium, cesium and lithium was studied under this crystallization process. After the adsorption experiment, a sequential extraction was applied to study a degree of association between these elements and iron compounds. (authors). 4 figs., 1 tab., 19 refs

[en] A simple closed column system was developed to study migration of bicarbonate and carbonate ¹⁴C in a soil layer. Experimental data for glass beads having less ¹⁴C adsorption was used to test the system in keeping a mass balance of ¹⁴C. Migration behavior of bicarbonate and carbonate ¹⁴C in a tuffaceous sandy soil was investigated by this column system in the pH range from 8 to 12. The ¹⁴C was delayed to tritiated water, and the retardation became stronger in order, pH 12 < pH 10 < pH 8. This is considered to be due to pH-dependent adsorption of bicarbonate and carbonate ions onto the soil sample

No abstract available

[en] Thermal shock resistance of a simulated high-level waste glass was examined by water quenching in the range of the temperature difference up to 600⁰C. The observation of cracks revealed that there existed two critical temperature differences. One was the threshold temperature difference of 74⁰C above which surface cracks appeared. The other was the temperature difference of 600⁰C at which cracks were propagated markedly and the specimen broke down into many pieces. In the range of the temperature difference of 74⁰C to 600⁰C, the surface area of cracks on the surface of the quenched specimens increased with increasing temperature difference. However, the fractional release of sodium and cesium from the quenched specimens was almost constant in the range of the temperature difference up to 500⁰C, and it increased markedly at the temperature difference of 600⁰C. These facts indicate that sodium and cesium do not leach out from the cracks when the separation of fracture surfaces is small

[en] The application of a ⁵⁵Fe X-ray source for particle size analysis is proposed in combination with a small sedimentation cell of 3 mm X-ray path length, X-ray detector and beam scanning device. Feasibility tests of the method showed good agreement with results by other methods and also with the certificated values of a standard powder sample. The analyser is applicable to particulate materials in the range 0.2 to 50 μm and of elements of atomic number higher than magnesium. (author)

[en] Sorption of strontium on an amorphous ferrihydrite has been studied under a proceeding of its crystallization to goethite. Sorption fraction of strontium decreased from approximately 100% to 60% during the crystallization. A sequential extraction technique was applied to study a degree of binding of strontium on the amorphous ferrihydrite and the crystalline goethite. Its result suggested that most of strontium sorbed on the iron(III) compounds was reversible form, but some amount of strontium once sorbed on the amorphous ferrihydrite was transferred into an irreversible form on the crystalline goethite during the crystallization. The model calculation was carried out to study the redistribution behavior of strontium during the crystallization. From this calculation, it is likely that strontium sorbed on the amorphous ferrihydrite was trapped into the crystalline goethite when the amorphous ferrihydrite was once dissolved to be crystallized to goethite. (author) 9 figs., 3 tabs., 20 refs

[en] As the first step to elucidate fixation mechanism of transuranic elements with iron compounds, coprecipitation experiments of neodymium with iron were conducted. By X-ray diffractometry (XRD) analyses, resulting comprecipitate phases were found to be different according to the molar Nd/(Nd + Fe) ratios in the initial solutions, i.e. a) goethite and hematite (the ratios of 0 - 10 %), b) amorphous materials (15 - 30 %) and c) neodymium hydroxides (50 - 100 %). In the b) region, DTA and XRD analyses indicated the neodymium fixation as the amorphous Nd-bearing iron hydroxides. In the a) region, IR analyses pointed out the possibility of neodymium fixation in the goethite-like structure. (author)