Decontamination technologies for contaminated water in Fukushima Daiichi Nuclear Power Station

Contaminated water in Fukushima Daiichi nuclear power station had been decontaminated. Cesium adsorbing devices using zeolite (KURION) and zeolite/silico titanate/filter (SARRY) were installed just after the accident for contaminated water with radioactive materials, seawater and turbine oils and had removed more than 30% of cesium inventory in the core. Multi-nuclide removal equipment using coagulating sedimentation and absorbing tower (ALPS) was installed about two years later for RO (Reverse Osmosis) concentrated seawater to remove strontium and other nuclides. The author measured performance of adsorption equilibrium of zeolite for simulated contaminated water and clarified the amount of cesium adsorption was decreased one tenth or hundredth due to effects of sea salts. Small column test showed zeolite had enough strength and adsorption rate at the same linear velocity with real system. Cesium adsorbing device was obliged to operate remotely with difficult operation monitoring and so simulation code of cesium adsorption device was developed to show decontamination performance and used for operational optimization. (T. Tanaka)