Masaaki Kaneko

Contribution to Understanding Iodine Sorption Mechanism onto Mixed Solid Alumina Cement and Calcium Compounds

An experimental study on the iodine sorption mechanism onto mixed solid alumina cement and calcium compounds was carried out. The solids were prepared by mixing the alumina cement with Ca(OH)2 and/or CaSO4·2H2O. Batch experiments were performed for iodine sorption onto the solid and iodine desorption from the solid that was obtained after a sorption experiment. In order to clarify the hydrates in the solids, X-ray diffraction measurement and scanning electron microscopic observation were adopted. The iodine sorption onto the solid proceeded to replace the OH- in 4CaO·Al2O3·13H2O by I- in solution to form the new hydrate, 3CaO·Al2O3·CaI2·12H22O. The results of sorption and desorption experiments showed that the iodine sorption proceeded reversibly and was independent of concentration of iodine up to 1×10-2 mole/dm in solution.

Iodine Sorption onto Mixed Solid Alumina Cement and Calcium Compounds

A substance for solidifying waste containing 129I is sought that effectively sorbs iodine to inhibit its release from repository into the environment. Three candidate media—commercial alumina cement mixed with calcium sulfate and/or calcium hydroxide—were investigated. The criterion applied for evaluating iodine sorption performance was the distribution coefficient Kd of iodine between solid and solution in an emulsion of sodium iodide solution and powder prepared from the alumina cement/calcium compound mixture, which was molded, cured and ground. Batch sorption experiments were performed on different combinations of the above-mentioned calcium compounds added to alumina cement. The solidified substance was also examined for mechanical strength. The highest iodine sorption performance was obtained with calcium sulfate added to alumina cement to a SC4/Ca mole ratio of 0.16, which ensured a Kd value raised to a level of not lower than 0.2 m3/kg from the (1.8–3.2)x10-3 m3/kg obtainable with alumina cement before calcium compound addition. The enhancement of iodine sorption with addition of calcium sulfate is attributed to formation in the substance of monosulfate (3CaO·Al2O3·CaSO412H2O) or tetracalcium aluminate hydrate (4CaO·Al2O3·XH2O (X=13 to 19)).

Development of Cement Solidification Process for Sodium Borate Waste Generated From PWR Plants

A cement solidification process for treating sodium borate waste produced in pressurized water reactor (PWR) plants was studied. To obtain high volume reduction and high mechanical strength of the waste, simulated concentrated borate liquid waste with a sodium / boron (Na/B) mole ratio of 0.27 was dehydrated and powdered by using a wiped film evaporator. To investigate the effect of the Na/B mole ratio on the solidification process, a sodium tetraborate decahydrate reagent with a Na/B mole ratio of 0.5 was also used. Ordinary portland cement (OPC) and some additives were used for the solidificaiton. Solidified cement prepared from powdered waste with a Na/B mole ratio 0.24 and having a high sillica sand content (silica sand/cement>2) showed to improved uniaxial compressive strength.Copyright

Solidification of Simulated Liquid Waste of Primary Loop Resin Elution Process of PWR

Primary loop resin waste is eluted by sulfuric acid in The Kansai Electic Company Mihama, Takahama and Ohi nuclear power station. Waste solution from this elution process is planned to be solidified by cement. This study bring out a range of chemical composition and crud concentration of waste solution from this elution process, and examine the properties of alumina cement solidification process and solidified material. Test for sulfate ion, borate, lithium, ammonium ion was carried out. Volume reduction ratio of over 0.5 was achieved for 5 to 25wt% of sulfate ion and <5,000ppm of borate. Lithium ion restrained the solidification delay by borate. Also, ammonium ion shows no significant effect. Based on this study, we concluded that the aluminum cement is applicable to all range of composition of waste solution from the resin elution process. This study is a part of committed work of The Kansai electric company.© 2010 ASME