The aerial radiation monitoring in Japan after the Fukushima Daiichi nuclear power plant accident

Abstract

The ambient dose-rate and the deposition of radioactive cesium was measured by using helicopters in the whole area of Japan to investigate the influence of the radioactivity that discharged into the atmosphere due to the disaster of the Fukushima Daiichi NPP (Nuclear Power Plant), Tokyo Electric Power Company (TEPCO), occurred by the East Japan earthquake and tsunami on March 11, 2011. As a result, the deposition of radioactive cesium on the ground was obtained, and it was clarified that range of Cs spread had been almost limited from the southern part of Iwate Prefecture to Kanto areas. The variation distribution of the dose-rate in Japan was also revealed in this measurement.

Atmospheric radioactivity over Tsukuba, Japan: a summary of three years of observations after the FDNPP accident

“…Introduction There are several reports containing estimates of the radioactive contamination from the FDNPP accident, presented in the form of mapped images produced from the results of investigations of radionuclides in the soil (e.g., MEXT 2011a ; Sanada et al 2014;Torii et al 2013) and in the form of air dose rate figures produced from aircraft observations. Among the radionuclides, radioSr is an important indicator of contamination.…”

“…The present simple estimation shows that more than a decade would be necessary for the 137 Cs atmospheric deposition level to return to pre-accident levels territories (Hirose 2012;Kinoshita et al 2011;Morino et al 2011;Terada et al 2012;Tsuruta et al 2014) has been well depicted by many researchers. The pattern of domestic pollution of the land by local fallout was made fairly clear by the creation of a contamination map based on many university investigations (Kinoshita et al 2011;Tanihata 2013) and airborne surveys by Japan's MEXT and the USA's NASA/DOE (MEXT and USDOE 2011; Sanada et al 2014;Torii et al 2013;USDOE 2013). The transport of the radioactive plume and its subsequent deposition over the capital area (the Kanto Plain; Amano et al 2012;Haba et al 2012;Tsuruta et al 2014) has been reported and monitored in Tsukuba (Doi et al 2013;Kanai 2012).…”

Investigation of Snow Cover Effects and Attenuation Correction of Gamma Ray in Aerial Radiation Monitoring

“…From the spectrum, the net count rate, Cnet (count per second), was obtained by subtracting the background count caused by cosmic rays. The background caused by cosmic rays, CCR, was obtained using the cosmic-ray index, ICR, [1] as shown in Figure 3. To calculate the ICR, we collected a spectrum at a higher altitude of 1000 m above the ground or above the sea.…”

“…These parameters were obtained from the test line measurement [1]. The measurement system mounted inside the helicopter was fabricated by Radiation Solutions Inc. (Mississauga, ON, Canada).…”

“…Immediately after the FDNPS accident, aerial radiation monitoring (ARM) began by the U.S. Department of Energy and the Japanese Ministry of Education, Culture, Sports Science and Technology to assess the air dose rate from deposited radioactive nuclides and to quantify the activity concentration [1][2][3]. The ARM has continued until the present time by the Nuclear Regulation Authority in Japan and the Japan Atomic Energy Agency [4].…”