화학공학소재연구정보센터
Journal of the Korean Industrial and Engineering Chemistry, Vol.11, No.7, 767-772, November, 2000
LiCl 용융염계에서 제올라이트 4A의 이온교환특성에 관한 연구
A Study of the Ion-exchange Properties of Zeolite 4A in LiCl Molten Salt
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초록
사용후 핵연료 차세대관리공정의 금속전환공정에서 발생되는 LiCl 폐용융염은 알카리 및 알카리토금속, 일부 RE 원소를 포함하고 있다. LiCl 용융염의 재순환을 위해서는 고방열성 물질인 Cs과 Sr을 반드시 제거하여야 한다. 본 연구에서는 고온에서 비교적 안정한 제올라이트 4A의 이온교환특성을 이용하여 LiCl 폐용융계의 Cs과 Sr 원소를 선택적으로 제거하는 방안을 설정하고, 이에 대한 이온교환특성을 고찰하였다. 제올라이트 4A는 고온의 LiCl 용융염계에서 Cs과 Sr원소와 이온교환특성을 나타내고, 2∼4 h 이후에는 평형상태에 도달하였다. 제올라이트 4A는 제올라이트 격자구조내의 양이온과 LiCl 용융염의 Li 양이온과 이온교환이 우선진행되고, 2단계에서는 용질의 양이온과 이온교환되는 메카니즘을 나타내고 있다. 특히 순수 LiCl 용융염계에서 제조된 염내포 제올라이트는 10∼11.5개의 염분자를 내포하고, LiCl 용융염계의 Cs 및 Sr 원소와의 이온교환특성이 매우 양호하였다.
An advanced spent fuel management process that is based on Li reduction of the spent oxide fuel to metallic form generates waste LiCl salt containing the alkali, alkaline-earth and some of the rare-earth fission products. The recycling of the LiCl waste salt to the process stream needs periodic removal of the Cs and Sr, which generate high radioactive decay heat. In this study, zeolite 4A was selected as an absorbent for removal of Cs and Sr element in LiCl molten salt phase, and the ion-exchange characteristics were investigated. Batch tests have shown that zeolite 4A has the desirable properties for selective removal of Cs and Sr elements by the ion-exchange process. Uptake of Cs and Sr elements in LiCl molten salt reaches nearly a constant value after 2 to 4 h of contact. We have formed salt occluded zeolite from LiCl molten salt, and studied its ion exchange and salt occlusion properties experimentally. The results indicate that zeolite 4A occluded between 10 and 11.5 salt molecules, and the salt occluded zeolite was found to be the most effective molecular sieve for sorbing Cs and Sr in LiCl waste salt.
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