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

Abstract

Abstract:In aerial radiation monitoring (ARM), the air dose rate cannot be appropriately estimated under snowy conditions due to attenuation of gamma rays by the snow layer. A technique to address this issue is required for ARM to obtain enough signals for air dose rates. To develop this technique, we investigated the relationship between snow depth and ARM measurement results using ARM, laser imaging detection and ranging, and ground measurement before and after snowfall. From the measured data, the results obtained using three different correction factors were examined and compared. An appropriate correction improved the underestimation of the air dose rate. However, further improvement in the accuracy of the analysis requires accurate estimation of the snow water equivalent.

Estimation of the Vertical Distribution of Radiocesium in Soil on the Basis of the Characteristics of Gamma-Ray Spectra Obtained via Aerial Radiation Monitoring Using an Unmanned Helicopter

“…The temporal variation of the dose rate distribution around FDNPP has been continuously monitored by the Nuclear Regulation Authority in Japan and the Japan Atomic Energy Agency (JAEA) to evaluate the short half-life decay of radionuclides resulting from the decontamination efforts [ 4 ]. The analytical schema of ARM using a manned helicopter has been improved in response to geographical and weather conditions [ 5 , 6 ]. ARM using an unmanned helicopter is suitable for small-scale monitoring and evaluation of the local distribution of radionuclides and dose rate above the ground within a narrow area because as per Japanese Aviation Law, a manned helicopter cannot fly at altitudes lower than 150 m. ARM using an unmanned helicopter allows for low-altitude evaluation of the detailed deposition of radionuclides on surface soil.…”