Identification of carbon in the insoluble cesium rich microparticle using electron microscopy

Abstract

Estimating the formation mechanisms of insoluble radioactive cesium particles (Type A) released into the environment at the time of the Fukushima Daiichi NPS accident is useful for clarifying the accident progression. The authors pointed out that the origin of Type A may be that the Unit 3 HEPA filter (glass fiber: GF) was melted and atomized during a hydrogen explosion. In that case, carbon in the activated carbon filter or GF binder is likely to be present with the Type A particles. However, in conventional observations, it has been difficult to identify carbon because carbon tape has been used for fixing particles. In this study, carbon was tried to be identified using an electron probe microanalyzer (EPMA) and a sample table other than carbon tape. As a result, the carbon content of Type A was similar to that of GF, which is considered to be of binder origin. This is consistent with the hypothesis by the authors. While paying close attention to the relationship between carbon information and other constituent elements, we will work on further elucidation of the formation process.