DEVELOPMENT OF ISOTOPE MICRO-IMAGING APPARATUS FOR DEBRIS ANALYSIS OF FDNPP

抄録

For the decommissioning of Fukushima Daiichi Nuclear Power Station (1F), it is necessary to analyze the state and element composition including radio isotopes of the debris. Both radiation measurement and ICP-MS analysis are excellent methods for elucidating radioactive species and composition. Both the methods are limited to be applicable to bulk samples. As for microscopic analysis, it is very difficult to analyze simultaneously isotope ratios, element distribution, and mixing states. Existing surface analysis methods, such as SEM-EDX, TEM-EDX, TEM-EELS, are generally reliable for element analysis and quantification. However, they cannot perform isotope-selective analysis. In order to elucidate the properties of debris with high accuracy is useful to evaluate the risk of re-criticality. Moreover, the evaluation of fission products needs to understand the distribution and dynamics in the reactor.

It is an extremely difficult task to realize the analysis of solid-local isotope ratios and trace elements. There are few options other than mass spectrometry to isolate and detect isotopes of target elements, and solid-local isotope analysis is limited to secondary ion mass spectrometry (SIMS). However, in SIMS, the problem of isobaric interference may occur, and it is not possible to accurately analyze the isotope of interest. Therefore, we are developing an isotope micro-imaging technique. This isotope micro-imaging technique is based on SIMS, but element-selective ionization with resonance laser ionization is newly employed, called R-SNMS. We have performed the analysis of radioactive Cs imaging for a small particle. In this paper, we report on the micro-imaging of each isotope of Nd from a simulated debris sample made of stable isotopes, assuming an analysis of 148Nd, which is important for understanding the burnup of fuel debris.