Characteristics of Cesium Adsorption by Alginate Bead Adsorbent with Layer-by-Layer Synthesis of Prussian Blue

Objectives : The purpose of this study was to develop an adsorbent to which Prussian blue (PB) is stably immobilized to remove radioactive cesium (Cs).Methods : Prussian blue-Alginate (PA) bead and Prussian blue-Alginate with Layer-by-layer synthesis (PAL) bead were synthesized by immobilizing PB respectively.Results and Discussion : As a results of XRD and FT-IR analysis, PB was successfuuly immobilized in alginate bead and PA, PAL bead. SEM (EDS) and TG analysis data were confirmed that the PB content of the PAL bead to which the LBL synthesis method was applied was improved by 6.31%. It was confirmed that the Cs adsorption capacity was improved through the LBL assembly process. The maximum adsorption amount (qm) of PA bead was 25.783 mg/g, and PAL bead was mg/g. In addition, as a result of UV-vis analysis of washing water after synthesis of PA bead and PAL bead, it was confirmed that the PB desorption of the PAL bead was lower indicating that the stability was also improved by LBL synthesis.Conclusions : We developed an adsorbent which prussianblue immobilized on alginate bead for selective removal cesium in aqueous solution. PB was immobilized by LBL synthesis method qm of PAL beads was 28.294 mg/g. It was expected to applied effectively and stably to radioactive cesium contaminated water.

Monitoring of Radioactive Cesium in Wild Boars Captured Inside the Difficult-To-Return Zone in Fukushima Prefecture Over a Five-Year Period

Following the Fukushima Daiichi Nuclear Power Plant accident in 2011, tissue samples from wild boar (Sus scrofa) outside the evacuation zone (difficult-to-return zone, DRZ) tended to show high concentrations of cesium-137 (137Cs). Understanding the 137Cs dynamics of wild boar populations inside the DRZ is necessary because they affect 137Cs dynamics and wild boar management in areas outside the DRZ. Since few detailed, long-term studies have been conducted inside the DRZ, we measured 137Cs concentrations in 221 wild boar muscle samples obtained from wild boar caught inside the DRZ and surrounding areas over a five-year period. Our results showed that the 137Cs concentration in wild boar from inside the DRZ were higher than those in wild boar outside this zone. No significant difference was observed between muscle and soil 137Cs levels, but significant correlations were observed between muscle 137Cs concentrations and body length and body weight in the low-concentration season, but not between all seasons and the high-concentration seasons. It is considered that the size effects observed during the low-concentration season may be due to factors related to metabolism and changes in food habit. This is the first long-term survey of 137Cs in wild boar inside the DRZ.

Use of Clay Minerals to Control Radioactive Cesium Leaching from Municipal Solid Waste Incineration Ash in Fukushima Prefecture in Summer and Winter

Radioactive cesium (r-Cs) released from the 2011 Fukushima Daiichi Nuclear Power Plant attaches to vegetation/soil and is collected as municipal solid waste (MSW) for incineration, being concentrated in incineration ash (bottom ash [BA], fly ash [FA], and chelate-treated FA [TFA]). r-Cs in FA and TFA can easily leach upon contact with moisture. It is important to prevent further contamination, as r-Cs has negative effects on ecosystems and the human body. Naturally available clay minerals, considered effective for capturing r-Cs, are a good alternative. Here, we sampled ash from MSW incineration facilities in Fukushima in August 2016 and February 2017. We used energy dispersive X-ray fluorescence spectroscopy and Ge semiconductor detector to determine elemental composition and r-Cs concentration in the samples and conducted leaching tests. We also determined the extent of leaching suppression by zeolite, acidic clay, and vermiculite. Chloride contents and r-Cs leaching rates were higher in FA and TFA than in BA, regardless of the season. Prior direct addition and mixing of clay minerals (5 to 20 wt.%) effectively prevented r-Cs leaching. This study is the first to examine r-Cs leaching inhibition by clay mineral direct addition and mixing to MSW incineration ash.

Wireless Backpack System for Detection of Radioactive Cesium on Contaminated Soil Using Portable Plastic Scintillator with Efficient Readout Device

The miniaturization and usability of radiation detectors make it increasingly possible to use mobile instruments to detect and monitor gamma radiations. Here, a Bluetooth-based mobile detection system for integrated interaction in a backpack was designed and implemented to smart equipment for the detection of radioactive cesium on contaminated soil. The radiation measurement system was demonstrated in the form of a backpack using a quantum dot (QD)-loaded plastic scintillator manufactured and prepared directly in this study, and it can be measured by a person in the wireless framework of integrated interaction. The QD-loaded plastic scintillator was measured after setting the distance from the contaminated soil to 20, 50, and 100 mm. As a result, the detection efficiency of the commercial plastic scintillator (EJ-200) was calculated to be 11.81% and that of the QD-loaded plastic scintillator was 15.22%, which proved the higher detection efficiency performance than the commercial plastic scintillator. The measurement result was transmitted to a personal computer using Bluetooth as a portable system. In the future, this wireless system design could be expanded as a wireless communication system equipped with a global positioning system to detect and measure radioactively contaminated environments.