報告書番号

282026

タイトル（和文）

放射性核種の地中移行挙動（その３）－土壌・岩石中でのイオン交換反応－

タイトル（英文）

RADIONUCLIDE TRANSFER IN UNDERGROUND MEDIA (3) -ION EXCHANGE REACTIONS IN GEOLOGICAL MATERIALS-

概要 （図表や脚注は「報告書全文」に掲載しております）

原子の施設からの放射性廃棄物の陸地処分技術の安全評価のために，液相における土壌および岩石とＣｏ，Ｍｎ，Ｓｒ，Ｃｓの各イオンとのイオン交換反応による吸着性を検討した。１）土壌・岩石の吸着機構は，低濃度域（Ｅ－３ｍｅｑ／ｍ■以下）ではイオン交換反応が，高濃度域ではＦｒｅｕｎｄｌｉｃｈ型の吸着が支配的である。２）交換性イオンの主体はＣａの２価イオンである。３）イオン交換反応系では分配係数は実験条件により変化するため吸着性の指標としては不適当である。

概要 （英文）

THIS REPORT DESCRIBES ION EXCHANGE REACTIONSOF STRONTIUM,CESIUM,COBALT,AND MANGANESE IN GEOLOGICAL MATERIALS FOR THE PURPOSE OF THE RISK ASSESSMENT OF UNDERGROUND RADIOACTIVE WASTE DISPOSAL. THE COLUMN OR BATCH INVESTIGATIONS WERE CARRIED OUT BY USING CRUSHED AND SIEVED ROCK SAMPLES IN ORDER TO DETERMINE THE ION SELECTIVITY COEFFICIENTS OF CATIONS IN GEOLOGICAL MATERIALS. MAIN RESULTS ARE AS FOLLOWS: 1) TWO COMPETING MECHANISMS ARE FOUND IN THE ADSORPTION PHENOMENA:ION EXCHANGE REACTION AND THE FREUNDLICH TYPE ADSORPTION. THE FORMER MECHANISM IS DOMINANT BELOW THE ION CONCENTRATION OF ABOUT 1.0E-3 MEQ/ML. 2) CALCIUM IS A MAIN EXCHANGEABLE CATION OF GEOLOGICAL MATERIALS,AND THE EXCHANGE RATE AMONG EXCHANGEABLE CALCIUM AND CATIONS IS VERY HIGH. 3) THE DISTRIBUTION COEFFICIENT DEPENDS ON EXPERIMENTAL CONDITIONS:THE PRESENCE OF COMPETING CATIONS AND THE ION CONCENTRATION. THUS,THE COEFFICIENT IS NOT CONSTANT AND NOT SUITABLE FOR THE INDICATOR OF ADSORPTIONEFFECT OF GEOLOGICAL MATERIALS. 4) WITH RESPECT TO THE ION SELECTIVITYCOEFFICIENTS OF CATION IN VARIOUS GEOLOGICAL MATERIALS,STRONTIUM ION IS MORE EXCHANGEABLE THAN COBALT AND MANGANESE IONS,AND THIS TENDENCY ISEXPLAINED BY THE ORDER OF THE RADII OF AQUO-IONS,AS FOR THE MONOVALENTCATION CS+,THE SELECTIVITY COEFFICIENT IS LARGE SCATTERED OF GEOLOGICAL MATERIALS. 5) ADSORPTION AMOUNTS OF THREE CATIONS OF SR,CO AND MN IONS TO THE GEOLOGICAL MATERIAL,WHICH CONTAINS CA ION AS A MAIN EXCHANGEABLE CATION,ARE PREDICTED BY USING SIMULTANEOUS ION EXCHANGE REACTION INMULTI-COMPONENT SYSTEM.CONSEQUENTLY,THE EVALUATED VALUE OF EACH CATIONS IS COMPARABLE TO THE OBSERVED VALUE.

報告者

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