New highly radioactive particles derived from Fukushima Daiichi reactor Unit 1: properties and environmental impacts

DOI: 10.1016/j.scitotenv.2021.145639

Authors: Kazuya Morooka (Kyushu University) , Eitaro Kurihara (Kyushu University) , Masato Takehara (Kyushu University) , Ryu Takami (Kyushu University) , Kazuki Fueda (Kyushu University) , Kenji Horie (National Institute of Polar Research; The Graduate University for Advanced Studies (SOKENDAI)) , Mami Takehara (National Institute of Polar Research) , Shinya Yamasaki (University of Tsukuba) , Toshihiko Ohnuki (Tokyo Institute of Technology) , Bernd Grambow (SUBATECH, IMT Atlantique, CNRS-IN2P3) , Gareth T. W. Law (The University of Helsinki) , Joyce W. I. Ang (The University of Helsinki) , William R. Bower (The University of Helsinki) , Julia Parker (Diamond Light Source) , Rodney Ewings (Stanford University) , Satoshi Utsunomiya (Kyushu University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Science Of The Total Environment

State: Published (Approved)
Published: February 2021
Diamond Proposal Number(s): 21246

Abstract: 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 3.9 km north-northwest of the FDNPP. Two of these particles have the highest particle-associated 134+137Cs activity ever reported for Fukushima (6.1 × 105 and 2.5 × 106 Bq per particle after decay-correction to March, 2011). The new, highly-radioactive particle labeled FTB1 is an aggregate of flaky silicate nanoparticles with an amorphous structure containing ~0.8 wt% Cs, occasionally associated with SiO2 and TiO2 inclusions. FTB1 likely originates from the reactor building, which was damaged by a H2 explosion, after adsorbing volatilized Cs. The 134+137Cs activity in the other highly radioactive particle labeled FTB26 exceeded 106 Bq. FTB26 has a glassy carbon core and a surface that is embedded with numerous micro-particles: Pb–Sn alloy, fibrous Al-silicate, Ca-carbonate or hydroxide, and quartz. The isotopic signatures of the micro-particles indicate neutron capture by B, Cs volatilization, and adsorption of natural Ba. The composition of the micro-particles on FTB26 reflects the composition of airborne particles at the moment of the H2 explosion. Owing to their large size, the health effects of the highly radioactive particles are likely limited to external radiation during static contact with skin; the highly radioactive particles are thus expected to have negligible health impacts for humans. By investigating the mobility of the highly radioactive particles, we can better understand how the radiation dose transfers through environments impacted by Unit 1. The highly radioactive particles also provide insights into the atmospheric conditions at the time of the Unit 1 explosion and the physio-chemical phenomena that occurred during reactor meltdown.

Journal Keywords: Radioactive particle; Unit 1; Fukushima Daiichi Nuclear Power Plant; cesium; boron; isotopic analysis

Subject Areas: Chemistry, Environment


Instruments: I14-Hard X-ray Nanoprobe

Added On: 09/02/2021 13:42

Discipline Tags:

Desertification & Pollution Earth Sciences & Environment Radioactive Materials Natural disaster Chemistry Materials Science Nuclear Waste

Technical Tags:

Diffraction Imaging X-ray Fluorescence (XRF)