Axial variations of oxide layer growth and hydrogen uptake of BWR fuel claddings under steam starvation conditions

Sakamoto, Kan*; Adachi, Mika*; Tokushima, Kazuyuki*; Aomi, Masaki*; Shibata, Hiroki; Nagae, Yuji; Kurata, Masaki

Zirconium in the Nuclear Industry; 20th International Symposium (ASTM STP 1645), p.411 - 432, 2023/11

https://doi.org/10.1520/STP164520220043

Study on chemical interaction between UO and Zr at precisely controlled high temperatures

Shirasu, Noriko; Sato, Takumi; Suzuki, Akihiro*; Nagae, Yuji; Kurata, Masaki

Journal of Nuclear Science and Technology, 60(6), p.697 - 714, 2023/06

https://doi.org/10.1080/00223131.2022.2138602

Interaction tests between UO and Zr were performed at precisely controlled high temperatures between 1840 and 2000 C to understand the interaction mechanism in detail. A Zr rod was inserted in a UO crucible and then heat-treated at a fixed temperature in Ar-gas flow for 10 min. After heating in the range of 1890 to 1930 C, the Zr rod was deformed to a round shape, in which the post-analysis detected the significant diffusion of U into the Zr region and the formation of a dominant -Zr(O) matrix and a small amount of U-Zr-O precipitates. The abrupt progress of liquefaction was observed in the sample heated at around 1940 C or higher. The higher oxygen concentration in the -Zr(O) matrix suppressed the liquefaction progress, due to the variation in the equilibrium state. The U-Zr-O melt formation progressed by the selective dissolution of Zr from the matrix, and the selective diffusion of U could occur via the U-Zr-O melt.

An Investigation of the microstructure and phase composition of the Zr bearing metallic debris in a bypass channel of a BWR fuel after the exothermic reaction in the CLADS-MADE-04 test

Pshenichnikov, A.; Kurata, Masaki; Nagae, Yuji

Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 4 Pages, 2022/10

The CLADS-MADE-04 is the next test in the series aiming at understanding of the melt propagation behaviour in the lower core region. In this contribution, recent results of the post-test analysis including microstructure of metallic debris investigated by Electron Probe Micro Analyzer (EPMA) are discussed. During the test, melting of the control blade happened with sudden wave of strong heat release relatively slowly (several cm/min) spread from the hottest area downwards along the degrading control blade and channel box consuming the walls made of Zircaloy-4. A significant damage happened with the sample supporting plate as well. The investigation of microstructure of such metallic debris would allow understanding of a mechanism of enhanced local core degradation. The nature of strong heat release and possibility of spreading to the surrounding materials is to be confirmed after thorough phase identification by EPMA. The difference between Fe-B eutectic debris and Zr-Fe eutectic debris will be outlined. It is especially important for understanding of the lower core plate melt-through and a possibility of a Zr-Fe molten material progression into the lower plenum.

Ten years of Fukushima Dai-ichi post-accident research on the degradation phenomenology of the BWR core components

Pshenichnikov, A.; Shibata, Hiroki; Yamashita, Takuya; Nagae, Yuji; Kurata, Masaki

Journal of Nuclear Science and Technology, 59(3), p.267 - 291, 2022/03

https://doi.org/10.1080/00223131.2021.1985647

A BWR control blade degradation observed in situ during a CLADS-MADE-02 test under Fukushima Dai-Ichi Unit 3 postulated conditions

Pshenichnikov, A.; Kurata, Masaki; Nagae, Yuji

Journal of Nuclear Science and Technology, 58(9), p.1025 - 1037, 2021/09

https://doi.org/10.1080/00223131.2021.1906777

Comparison of the observed Fukushima Dai-ichi Unit 2 debris with simulated debris from the CLADS-MADE-01 control blade degradation test

Pshenichnikov, A.; Nagae, Yuji; Kurata, Masaki

Journal of Nuclear Science and Technology, 58(4), p.416 - 425, 2021/04

https://doi.org/10.1080/00223131.2020.1856734

Segregation behavior of Fe and Gd in molten corium during solidification progress

Sudo, Ayako; Meszaros, B.*; Poznyak, I.*; Sato, Takumi; Nagae, Yuji; Kurata, Masaki

Journal of Nuclear Materials, 533, p.152093_1 - 152093_8, 2020/05

https://doi.org/10.1016/j.jnucmat.2020.152093

Raman characterization of the simulated control blade debris to understand the boric compounds transformations during severe accidents

Pshenichnikov, A.; Nagae, Yuji; Kurata, Masaki

Mechanical Engineering Journal (Internet), 7(2), p.19-00477_1 - 19-00477_8, 2020/04

https://doi.org/10.1299/mej.19-00477

Oxidation of silicon carbide in steam studied by laser heating

Pham, V. H.; Nagae, Yuji; Kurata, Masaki; Furumoto, Kenichiro*; Sato, Hisaki*; Ishibashi, Ryo*; Yamashita, Shinichiro

Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.670 - 674, 2019/09

Characterization of the Fukushima Dai-ichi Unit 2 sediments / debris based on the on-site video investigations in comparison to the debris obtained after integral CLADS-MADE-01 test

Pshenichnikov, A.; Kurata, Masaki; Nagae, Yuji

Dai-24-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (USB Flash Drive), 4 Pages, 2019/06