Strontium adsorption characteristics of natural Zeolites for permeable reactive barrier in Fukushima Daiichi nuclear power station

Abstract

Laboratory experiments and model estimates were carried out to evaluate the effectiveness of sorbent for construction of the Permeable Reactive Barrier (PRB) at downstream of H4 tank area in Fukushima-Daiichi Nuclear Power Station in September 2014. Measurement of cation exchange capacity and X-ray diffraction analyses of crystal structures were carried out for natural zeolites. The Sr adsorption isotherms were measured for these zeolites contacted with  water containing Sr or the simulated groundwater containing Na, K, Ma, Ca, and Sr. According to these equilibrium characteristics, Akita-Futastui zeolite was selected as candidate. The zeolite was served for the column tests to obtain Sr breakthrough curves with different conditions such as particle size of zeolite, Darcy Flux, Sr concentration in the simulated groundwater, and mixed bed with gravel. From the breakthrough curves, kinetic properties such as the film mass transfer coefficient and the effective intraparticle diffusivity were derived by fitting with adsorption model. Based on these kinetic properties, Sr breakthrough curves were estimated for the simulated groundwater containing 0.3 ppm Sr passed at 10 cm∙day-1 through 1.5 m thick PRB with zeolite and gravel. The breakthrough points for the PRB with 33 wt.% zeolite was evaluated as more than 70 years.