AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Dust and Radioactivity Concentrations Emitted from Radiocesium-contaminated Soil during Decontamination Work by a Heavy Vehicle
MAROMU YAMADA, Mitsutoshi Takaya, Norio Tsujimura, Tadayoshi Yoshida, Seiichiro Kanno, Yasushi Shinohara, Kenji Nakamura, Shigeki Koda, Japan National Institute of Occupational Safety and Health
Abstract Number: 650 Working Group: Aerosol Exposure
Abstract It is necessary to estimate the internal exposure to radiocesium-containing dust associated with the decontamination work after the accident at the Fukushima Daiichi Nuclear Power Station (NPS). However, the size distribution of the dust and the radiocesium concentrations emitted during the decontamination work are unknown. The aim of this study was therefore to clarify the relationship between the size distribution of airborne dust and the 137Cs concentration by field observation and a laboratory experiment. The observation was carried out at the Joban highway located about 7 km from the NPS, on May 30, 2014. The contaminated surface soil was removed by a heavy vehicle (W200Hi, Wirtgen). The inhalable dust was collected on filters (T60A20) with IOM samplers (SKC Inc.) in the personal breathing zone (PBZ) of three workers. Additionally, the dust was collected at a fixed point with an Andersen sampler (Tokyo Dylec Corp.) that is able to collect nine different sizes of particles. The filters were weighed by an ultra-microbalance to determine the dust concentration (mg/m$^3). The airborne $^(137)Cs concentrations (Bq/m$^3) were subsequently quantified with a Ge semiconductor detector (installed at the Japan Atomic Energy Agency). Additionally, to complete the samples that were below the detection limit of $^(137)Cs, we conducted dust resuspension experiments in our laboratory with a dust feeder (DF-3, Shibata), using the contaminated soils collected at the observation site. The results indicated that the $^(137)Cs concentrations in the PBZ were from 0.10 to 0.44 Bq/m$^3. The internal exposure was estimated at approximately 0.9×10$^(-5) to 4.1×10$^(-5) mSv/day, assuming that the working time was eight hours and the respiration volume was 1.8 m$^3/hr. The size-segregated samples from the Andersen sampler showed that the $^(137)Cs concentration per unit weight increased with the decreasing of the diameter of the particles.