[en] Characterization of fuel debris is required to develop fuel debris removal tools for decommissioning Fukushima Daiichi nuclear power plant (1F). Especially, knowledge about the characteristics of molten core-concrete interaction (MCCI) product is needed because of the limited information available at present. Samples from a large-scale MCCI test performed under quenching conditions, VULCANO VW-U1 were analyzed to evaluate the characteristics of the surface of MCCI product. Four samples were selected from test sections at different locations. As a result, the characteristics of the samples were found to be similar. Several corium phases, such as cubic-(U,Zr)O₂ and tetragonal ZrO₂, were detected by X-ray diffraction (XRD), but concrete-based phases, such as the crystalline SiO₂ phase, were not detected by XRD because the quantity of the SiO₂ phase was too small to be measured. The Vickers hardness of each phase in these samples was higher than that of previously analyzed samples in another VULCANO test campaign, VBS-U4. Based on a comparison between MCCI product generated under quenching condition, such as VW-U1, and gently cooled MCCI product, such as VBS-U4, the MCCI product generated under quenching condition is more homogeneous, and its hardness is higher than that of the gently cooled MCCI product. (author)

[en] Whereas the measurement of Beta radioactivity has a crucial role in the control of the environment, but also in numerous industrial branches, in medicine, and in fundamental and applied research, this book, written by experts in beta metrology and in nuclear and atomic data, aims at gathering theoretical as well as practical data regarding the measurement of the activity of radionuclides which are disintegrated under the influence of a beta radiation or due to some nuclear transitions inducing electron emissions. After a brief historical recall, the authors propose an overview of natural and artificial sources of beta radiation, and of radionuclides of interest. Theoretical aspects of beta disintegration are then addressed, as well as the role of other electronic radiations, and radiation-matter interaction phenomena. The next chapter describes the preparation of standard sources and samples (solid sources, liquid scintillators, scintillating balls). Techniques and devices of measurement of the beta radiation are addressed: proportional counter, beta liquid scintillation, Cherenkov counting, beta spectrometers. Issues related to the expression of results and measurement uncertainty are discussed. A comparison of non radiometric measurement techniques is reported (various mass spectrometry), as well as measurement examples. The last chapter addresses issues related to quality assurance of beta measurement