Estimation of the activity median aerodynamic diameter of plutonium particles using image analysis

ABSTRACT

The aerodynamic radioactive median diameter (AMAD) and the absorption type are necessary information for internal exposure assessment. In 2017, at a plutonium-handling facility in the Oarai site of the Japan Atomic Energy Agency, an accidental contamination occurred, and five workers were contaminated with radioactive materials, including plutonium. In this study, some smear papers and a dust sampling filter were measured with the imaging plate, and some particles were observed with an electron microscope. The minimum AMADs for the two absorption types of plutonium were estimated for the conservative dose assessment. Two AMADs were calculated for Type M as plutonium nitrate and Type S as plutonium dioxide. Excluding the extremely large particle found in a smear sample, the AMAD estimation results showed that the minimum AMADs of plutonium nitrate from smear papers were 4.3–11.3 μm, while those of plutonium dioxide were 5.6–14.4 μm. Moreover, the minimum AMAD of plutonium nitrate from a dust sampling filter was 3.0 μm, while that of plutonium dioxide was 3.9 μm.

Graphical Abstract

KEYWORDS:

• Autoradiography
• imaging plate
• plutonium
• particle size
• AMAD
• internal exposure
• SEM
• EDS
• WDS

Acknowledgments

The authors would like to thank individual members of JAEA concerned with this study for their efforts and cooperation, and Akira Endo, Fumiaki Takahashi, and Kentaro Manabe of JAEA for their helpful support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Ethical issues

The ‘Study on the clinical course and exposure dose of workers in the contaminated accident at Japan Atomic Energy Agency’ has been conducted in accordance with the research protocols reviewed by the ethical review committee at National Institutes for Quantum Science and Technology (QST).

$\cdot$Research protocol (No. 17–018), National Institute of Radiological Sciences, QST

$\cdot$Research protocol (No. 18–006), Nuclear Fuel Cycle Engineering Laboratories, JAEA

$\cdot$Research protocol (No. 18–007), Oarai Research and Development Institute, JAEA