Phase analysis of simulated nuclear fuel debris synthesized using UO 2 , Zr, and stainless steel and leaching behavior of the fission products and matrix elements

• Published in: Nuclear engineering and technology Vol. 55; no. 4; pp. 1300 - 1309
• Main Authors: Ryutaro Tonna, Takayuki Sasaki, Yuji Kodama, Taishi Kobayashi, Daisuke Akiyama, Akira Kirishima, Nobuaki Sato, Yuta Kumagai, Ryoji Kusaka, Masayuki Watanabe
• Format: Journal Article
• Language: Korean
• Published: 2023
• Subjects: Static leaching; Simulated fuel debris; Fission product; Fukushima Daiichi nuclear power station; Alloy
• ISSN: 1738-5733; 2234-358X

Simulated debris was synthesized using UO2, Zr, and stainless steel and a heat treatment method under inert or oxidizing conditions. The primary U solid phase of the debris synthesized at 1473 K under inert conditions was UO2, whereas a (U, Zr)O2 solid solution formed at 1873 K. Under oxidizing conditions, a mixture of U3O8 and (Fe, Cr)UO4 phases formed at 1473 K, whereas a (U, Zr)O2+x solid solution formed at 1873 K. The leaching behavior of the fission products from the simulated debris was evaluated using two methods: the irradiation method, for which fission products were produced via neutron irradiation, and the doping method, for which trace amounts of non-radioactive elements were doped into the debris. The dissolution behavior of U depended on the properties of the debris and aqueous solution for immersion. Cs, Sr, and Ba leached out regardless of the primary solid phases. The leaching of high-valence Eu and Ru ions was suppressed, possibly owing to their solid-solution reaction with or incorporation into the uranium compounds of the simulated debris.