Uptake selectivity for different types of zeolites in the presence of boric acid - 15244

The development of selective adsorbents is very important subject for the effective multi-nuclide decontamination related to the severe accident of Fukushima NPP-1. Many removal methods have been developed to separate nuclide from decontaminated solutions containing multi-nuclide so far. From the standpoint of cost efficiency, stability for usage and safety handling, the decontamination methods using inorganic adsorbents are one of the most effective methods for the selective decontamination system. Thus, many researches related to inorganic adsorbents have been carried out after the accident; actually, in Fukushima NPP-1, zeolites are used to remove radioactive nuclides from decontaminated water as a main adsorbent in the circulating injection cooling system. However, the adsorption characteristics of zeolites in the presence of boric acid have not been clarified in detail. As for the decontamination in PWR[1], the adsorption properties should be examined in the presence of highly concentrated boric acid. Based on this background, the final objective of this study is to develop the decontamination methods in PWR-NPP by using various zeolites for multi-nuclide. In this study, the adsorption properties for eight kinds of zeolites (Zeolite A, Zeolite X, Zeolite Y, Zeolite L, Chabazite, Synthetic Mordenite, Natural Mordenite and Clinoptilolite) are evaluated in the presence of boric acid and seawater. The present study deals with (1) selective adsorption properties for single nuclide ion (¹³⁷Cs⁺, ⁶⁰Co²⁺, ⁸⁵Sr²⁺ and ¹⁵²Eu³⁺), (2) preparation of Ag-loaded Natural Mordenite (Ag-NM) and uptake properties of I- ions, and (3) multi-nuclide decontamination properties of 26 elements (typical elements in Advanced Liquid Processing System (ALPS) in Fukushima NPP-1) for the above zeolites. (authors)