Structure, stability, and actinide leaching of simulated nuclear fuel debris synthesized from UO2, Zr, and stainless-steel

Akira Kirishima, Daisuke Akiyama, Yuta Kumagai, Ryoji Kusaka, Masami Nakada, Masayuki Watanabe, Takayuki Sasaki, Nobuaki Sato

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

To evaluate the chemical structure and stability of nuclear fuel debris comprising UO2, Zr, and stainless-steel (SUS) generated during the Fukushima Daiichi Nuclear Power Plant accident in Japan in 2011, the simulated debris of a UO2–SUS–Zr system and those of other fundamental-component-containing systems were synthesized and characterized. The simulated debris was synthesized by heat treatment at 1600 °C under inert (Ar) or oxidative (Ar + 2% O2) atmospheres for 1–12 h. 237Np and 241Am tracers were doped for leaching tests from the simulated debris. The simulated debris was characterized using X-ray diffraction, scanning electron microscopy–energy-dispersive X-ray spectroscopy, Raman spectroscopy, and Mössbauer spectroscopy, and the results revealed that the major uranium phase of the UO2–SUS–Zr debris comprised a Zr(IV)-and-Fe(II)-containing UIVO2 solid-solution, regardless of the treatment conditions. The results of a long-term immersion test of the simulated debris in pure water and seawater revealed that the macroscale crystal structure of the simulated debris was chemically durable under wet conditions for at least a year. Furthermore, the leaching test results indicated that the leaching ratios of U, Np, and Am from the UO2–SUS–Zr debris were small and lower than 0.08% for all the experiments in this study.

Original languageEnglish
Article number153842
JournalJournal of Nuclear Materials
Volume567
DOIs
Publication statusPublished - 2022 Aug 15

Keywords

  • Actinides
  • Alloys
  • Chemical stability
  • Fuel debris
  • Fukushima Daiichi nuclear power plant accident
  • Oxides

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