Abstract
Characterizing fuel debris (FD) is critical for decommissioning the Fukushima Daiichi Nuclear Power Station (FDNPS). Samples collected from inside the reactor building through various methods provide valuable insights into the properties of FD. However, localized isotope data from these samples have not been previously reported. In this study, we present the first global report of isotope imaging and ratio data for the FDNPS particle obtained using our novel high-spatial-resolution secondary ion mass spectrometry (SIMS) technique developed for FD analysis. The method successfully mapped the spatial distributions of uranium, a key nuclear fuel component, and boron-10 (10B), a control rod material, within the particle. In addition, the spatial distributions and isotope ratios of B and lithium (Li) in the particles provide definitive evidence that 10B (n, α) 7Li reactions occur in the control rod during normal reactor operation. These findings provide new insights into the FD composition and underscore the effectiveness of SIMS for the detailed characterization of FD.
Data availability
The data that support the findings of this study were obtained from samples provided by Tokyo Electric Power Company Holdings, Inc. Restrictions apply to the availability of these data, which were used under license for the current study, and thus they are not publicly available. Data are, however, available from the authors upon reasonable request and with permission of Tokyo Electric Power Company Holdings, Inc.
Code availability
No custom code was used in this study. Data analyses were performed using standard software and custom scripts for image processing, which are available from the corresponding author upon reasonable request.
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Acknowledgements
This work was supported by the JAEA Nuclear Energy S&T and Human Resource Development Project through concentrating wisdom (Grant Number JPJA21P21465814). The authors would like to thank Enago (www.enago.jp) for the English language review.The authors wish to acknowledge the contributions of Dr. Masabumi Miyabe, who contributed to validation of the obtained data and passed away before the completion of this manuscript.
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T.Y. carried out the investigation, performed formal analysis, prepared visualizations, and wrote the original draft of the manuscript. T.S. developed the methodology and supervised the overall project. K.M. and Y.S. were responsible for funding acquisition, provided resources, contributed to validation of part of the data, and assisted with writing – review and editing. H.T. and Y.I. contributed to validation of the obtained data. M.H. and M.M. provided the analysis samples and contributed to validation and critical review of the manuscript. All authors discussed the results and approved the final version of the manuscript.
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Yoshida, T., Maeda, K., Sekio, Y. et al. Spatially resolved isotopic analysis of a uranium-bearing particle from inside the Fukushima Daiichi unit 2 reactor using high-resolution SIMS. Sci Rep (2026). https://doi.org/10.1038/s41598-026-40875-y
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DOI: https://doi.org/10.1038/s41598-026-40875-y
