Tadashi Yanagi

Sorption behavior of cesium, strontium and americium ions on clay materials.

The sorption behavior of Cs, Sr and Am ions on loams, which is widely distributed in Tohoku district of Japan, was studied under static and flowing conditions. The measurements of ion distribution ratios, which span a range of nearly three orders of magnitude, were fitted to Freundlich or Langmuir isotherms and the sorption parameters of isotherm equations were determined. It was found that the sorption of these ions on loams is due to the ionic exchange with Na, Ca and Mg ions of the loams. Analyzing the breakthrough curve of Cs ion sorption on a loam sorbent yielded 0.2 s−1 and 0.32 em for values of the overall mass transfer coefficient and of the length of adsorption zone, respectively.

Leaching behavior of crystalline phosphate waste forms

Abstract Some synthetic monazite-type solids loaded with a simulated high-level radioactive waste of simplified composition were studied for their leaching behavior in distilled water by means of leachate solution analyses using atomic absorption method. The results obtained from Soxhlet-type experiments showed that the matrix leach rate of the solids were at least 100 to 1000 times lower than that of the currently investigated borosilicate glass, even though the selective release of sodium ion from the solids was observed. Zirconium phosphate type solids were also tested to study their ability for immobilizing alkali and alkaline earth metal ions. The obtained results indicated this type of solid looks good as a waste form for these ions. However, there still remains a problem on the simultaneous synthesis of both types of solids.

Leach Rates of Composite Waste Forms of Monazite- and Zirconium Phosphate-Type

Leaching behavior of simultaneously synthesized composite waste form of monazite- and zirconium phosphate-type was investigated by making use of simulated high level waste (HLW). The obtained results showed that the leach rates of the composite forms are very low compared to that of the borosilicate glass waste form, indicating that the composite is regarded as being significant to immobilize HLW grossly like vitrification.

Leach Rates and Thermal Properties of Lead-Iron Phosphate Glass Waste Forms

Lead-iron phosphate (LIP) glasses loaded with a simulated high-level nuclear waste were studied on their leach rates and thermal properties. The obtained results showed that the phosphate glass matrix consisting of lead monoxide, phosphorus pentoxide and ferric oxide of 56:35:9w/0 is able to vitrify the waste, pretreated with formic acid to remove Zr, to about 15 w/0 at 950°C. The leach rate of the vitrified waste glass was in the order of 10−7 g/cm2.d at 110°C, which is low compared with that of the borosilicate glass waste form. Increasing the phosphorus pentoxide content of the matrix to higher than 35% enabled it to produce the glass form with the waste near 20 w/0 at 950°C, but this increase rendered the glass waste form more soluble than the former. Thermal properties such as thermal expansion coefficient, critical cooling rate for vitrification and temperatures of glass transition, softening and maximum rate of crystallization were measured and discussed. Removing Na ions from wastes improves consi...

Ion sputtering technique for making thin titanium film of a tritium target

Abstract The applicability of an ion sputtering technique has been examined for the making of titanium coatings that bond tightly to copper substrates. The usual scratching test and the scanning electron microscopic observation revealed that the adhesion of RF-sputtered titanium coating to copper was higher than those of DC-sputtered and of vacuum evaporated coatings. To reduce the hydriding effect which causes a considerable decrease in the adherence of the coating, an attempt to make a composite layer of titanium and copper at the interface was also carried out.

Application of a Continuous Channel Electron Multiplier for Measuring Gaseous Tritium at Low Pressures

Some fundamental studies on the application of a continuous channel electron multiplier (channeltron) for monitoring gaseous tritium present in an evacuated vessel at low pressures below 10(-4) Torr were carried out. The results showed that at the tritium pressures lower than 10(-6) Torr the tritium counting rate measured by the channeltron increased linearly, in practice, with increasing tritium pressure, as was expected by assuming that the interactions between beta-particle emitted from tritium and the vessel wall and gaseous molecules during the migration of beta-particle to the channeltron can be ignored. However, in the range of pressures over 10(-5) Torr the measured tritium counting rate was found to be getting smaller than the expected with increase in tritium pressure. This is presumably due to the absorption and scattering of beta-particles by gaseous tritium.

Behaviors of Impurities in Liquid Sodium, (II): Effect of Oxygen on Behavior of Hydrogen in Liquid Sodium

The behavior of hydrogen in liquid sodium containing relatively large amounts of oxygen were investigated with the aid of the hydrogen sensor of niobium membrane. The partial pressure of the hydrogen in liquid sodium at hot zone of a cold-trapped natural circulation sodium loop was measured as functions of temperatures of the cold trap and the hot zone of the loop. It was observed that at constant cold trap temperature the partial pressure of hydrogen in sodium increases with increasing the hot zone temperature. This study also showed that, keeping the temperature of hot zone constant, a logarithmic plot of hydrogen concentration calculated from the equilibrium hydrogen partial pressure vs. the reciprocal temperature of cold trap yields a straight line whose slope is nearly equal to that on the solubility of sodium hydroxide in sodium. Finally, it was observed that the permeation of hydrogen in sodium through a niobium membrane is a process controlled by diffusion. But the permeability for hydrogen in nio...

Studies of focusing chromatography on its scale-up and effect of ionic strength

さきにロ紙片(2×22cm)を用いて行なう従来の分析用焦点クロマトグラフ法により,諸種放射化学的物質分離の有効な実験例を得た.本研究では,人絹用パルプ・シートを用いて大型化し,従来のものに比して多量の試料を用いた分離法を確立するため,まず金属イオンの焦点化に及ぼす基礎的因子はいかなるものかを解明することを目的とした.すなわちイオン強度,電極室のpHの変化,電位こう配,錯化剤濃度および通電時間などについて検討した.それぞれ10-3Mの銅イオン,ニッケルイオンの共存溶液より,銅イオン,ニッケルイオンの分離を行なうにあたり,トリポリリン酸ナトリウムを錯化剤として用いる場合を例にとって検討を加えた.その結果,試料溶液の帯域のイオン強度を隣接する帯域のそれに比して小にすれば分離に良好な結果を得ることができることを知った.なお錯化剤には,分離のための至適濃度が存在することが判明した.また錯化剤の濃度こう配のほかに,電位こう配,pHこう配,イオン強度のこう配などの各こう配と焦点化の問題についても知見を得ることができた.