Occurrence of highly radioactive microparticles in the seafloor sediment from the pacific coast 35 km northeast of the Fukushima Daiichi nuclear power plant
Journal
Chemosphere
Journal Volume
267
Start Page
128907
ISSN
0045-6535
Date Issued
2021-03
Author(s)
Ikenoue, Takahito
Takehara, Masato
Morooka, Kazuya
Kurihara, Eitaro
Takami, Ryu
Ishii, Nobuyoshi
Kudo, Natsumi
Abstract
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. These particles were characterized with a variety of electron microscopic techniques, including transmission electron microscopy. The 134Cs/137Cs radioactivity ratio of D1-MAX, 1.04, was comparable to that calculated for Unit 2 or 3. D1-MAX consisted mainly of a Cs-rich microparticle (CsMP) with a silica glass matrix. The data clearly suggested that D1-MAX resulted from a molten core–concrete interaction during meltdowns. In contrast, D1-MID was an aggregate of plagioclase, quartz, anatase, and Fe-oxide nanoparticles as well as clay minerals, which had adsorbed soluble Cs. D1-MID was likely a terrestrial particle that had been transported by wind and/or ocean currents to a site 35 km from the FDNPP. The radioactive fractions of D1-MAX and D1-MID were 15% and 0.36%, respectively, of the total radioactivity in the bulk sediment. These highly radioactive particles have a great impact on the movement of radioactive Cs in the marine environment by carrying condensed Cs radioactivity with various colloidal and desorption properties depending on the host phase.
Subjects
Cesium Radioisotopes
Fukushima Nuclear Accident
Japan
Nuclear Power Plants
Radiation Monitoring
Radioactivity
Water Pollutants
Radioactive
Cesium
Feldspar
High resolution transmission electron microscopy
Iron oxides
Marine power plants
Nuclear energy
Nuclear fuels
Ocean currents
Radiation
Sediments
Silica
Sols
Titanium dioxide
cesium 134
cesium 137
iron oxide nanoparticle
silicon dioxide
titanium dioxide
cesium
Decay correction
Desorption properties
Fukushima dai-ichi nuclear power plants
Marine environment
Microscopic techniques
Radioactive particles
Seafloor sediments
Silica glass matrix
autoradiography
energy dispersive X ray spectroscopy
Fukushima nuclear accident
gamma spectrometry
high resolution transmission electron microscopy
limit of detection
marine environment
nuclear power plant
ocean current
particulate matter
radioactivity
seashore
sediment
surface property
transmission electron microscopy
wind
radiation monitoring
water pollutant
Nuclear power plants
SDGs
Publisher
Elsevier BV
Type
journal article