Gravitational separation of Cs contaminated soil in Fukushima environment: Density dependence of Cs activity and application to volume reduction.

Behavior of radiocesium in Fukushima after its deposition is mainly controlled by mobility of soil components, of which the density is one of the parameters governing the mobility; however, little information is available on the density of soil components associated with radiocesium in environment. Furthermore, the reduction of the volume of radiocesium-contaminated soil in the interim storage is highly demanded. In this study, we developed a gravitational separation method using a sodium polytungstate (SPT) solution combined with size fractionation to understand the relation between Cs activity and the density of surface soil components and evaluate the feasibility of the method for the volume reduction of the contaminated soil.

Volatilization of BC control rods in Fukushima Daiichi nuclear reactors during meltdown: B-Li isotopic signatures in cesium-rich microparticles.

Boron carbide control rods remain in the fuel debris of the damaged reactors in the Fukushima Daiichi Nuclear Power Plant, potentially preventing re-criticality; however, the state and stability of the control rods remain unknown. Sensitive high-resolution ion microprobe analyses have revealed B-Li isotopic signatures in radioactive Cs-rich microparticles (CsMPs) that formed by volatilization and condensation of Si-oxides during the meltdowns. The CsMPs contain 1518-6733 mg kg of B and 11.

New highly radioactive particles derived from Fukushima Daiichi Reactor Unit 1: Properties and environmental impacts.

A contaminated zone elongated toward Futaba Town, north-northwest of the Fukushima Daiichi Nuclear Power Plant (FDNPP), contains highly radioactive particles released from reactor Unit 1. There are uncertainties associated with the physio-chemical properties and environmental impacts of these particles. In this study, 31 radioactive particles were isolated from surface soils collected 3.

Occurrence of highly radioactive microparticles in the seafloor sediment from the pacific coast 35 km northeast of the Fukushima Daiichi nuclear power plant.

To understand the properties and significance of highly radioactive particles in the marine environment, we have examined seafloor sediment with a radioactivity of ∼1200 Bq/kg (dry weight; after decay correction to March 2011) collected 35 km northeast of the Fukushima Daiichi Nuclear Power Plant (FDNPP). Among the 697 highly radioactive particles separated from the sediment, two particles, D1-MAX and D1-MID, had a total Cs radioactivity of ∼56 and 0.67 Bq (after decay correction to March 2011), respectively.

Particulate plutonium released from the Fukushima Daiichi meltdowns.

Traces of Pu have been detected in material released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March of 2011; however, to date the physical and chemical form of the Pu have remained unknown. Here we report the discovery of particulate Pu associated with cesium-rich microparticles (CsMPs) that formed in and were released from the reactors during the FDNPP meltdowns. The Cs-pollucite-based CsMP contained discrete U(IV)O nanoparticles, <~10 nm, one of which is enriched in Pu adjacent to fragments of Zr-cladding.

Abundance and distribution of radioactive cesium-rich microparticles released from the Fukushima Daiichi Nuclear Power Plant into the environment.

The abundance and distribution of highly radioactive cesium-rich microparticles (CsMPs) that were released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) during the first stage of the nuclear disaster in March 2011 are described for 20 surface soils collected around the FDNPP. Based on the spatial distribution of the numbers (particles/g) and radioactive fraction (RF) of the CsMPs in surface soil, which is defined as the sum of the CsMP radioactivity (in Bq) divided by the total radioactivity (in Bq) of the soil sample, three regions of particular interest have been identified: i.) near-northwest (N-NW), ii.

Dissolution of radioactive, cesium-rich microparticles released from the Fukushima Daiichi Nuclear Power Plant in simulated lung fluid, pure-water, and seawater.

To understand the chemical durability of highly radioactive cesium-rich microparticles (CsMPs) released from the Fukushima Daiichi Nuclear Power Plant in March 2011, we have, for the first time, performed systematic dissolution experiments with CsMPs isolated from Fukushima soils (one sample with 108 Bq and one sample with 57.8 Bq of Cs) using three types of solutions: simulated lung fluid, ultrapure water, and artificial sea water, at 25 and 37 °C for 1-63 days. The Cs was released rapidly within three days and then steady-state dissolution was achieved for each solution type.