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Journal Articles

The Effects of plutonium content and self-irradiation on thermal conductivity of mixed oxide fuel

Ikusawa, Yoshihisa; Morimoto, Kyoichi; Kato, Masato; Saito, Kosuke; Uno, Masayoshi*

Nuclear Technology, 205(3), p.474 - 485, 2019/03

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

This study evaluated the effects of plutonium content and self-irradiation on the thermal conductivity of mixed-oxide (MOX) fuel. Samples of UO$$_{2}$$ fuel and various MOX fuels were tested. The MOX fuels had a range of plutonium contents, and some samples were stored for 20 years. The thermal conductivity of these samples was determined from thermal diffusivity measurements taken via laser flash analysis. Although the thermal conductivity decreased with increasing plutonium content, this effect was slight. The effect of self-irradiation was investigated using the stored samples. The reduction in thermal conductivity caused by self-irradiation depended on the plutonium content, its isotopic composition, and storage time. The reduction in thermal conductivity over 20 years' storage can be predicted from the change of lattice parameter. In addition, the decrease in thermal conductivity caused by self-irradiation was recovered with heat treatment, and recovered almost completely at temperatures over 1200 K. From these evaluation results, we formulated an equation for thermal conductivity that is based on the classical phonon-transport model. This equation can predict the thermal conductivity of MOX fuel thermal conductivity by accounting for the influences of plutonium content and self-irradiation.

Journal Articles

Self-radiation effects and glassy nature of magnetic transition in AmO$$_2$$ revealed by $$^{17}$$O-NMR

Tokunaga, Yo; Nishi, Tsuyoshi; Nakada, Masami; Ito, Akinori*; Sakai, Hironori; Kambe, Shinsaku; Homma, Yoshiya*; Honda, Fuminori*; Aoki, Dai*; Walstedt, R. E.*

Physical Review B, 89(21), p.214416_1 - 214416_8, 2014/06

 Times Cited Count:7 Percentile:57.95(Materials Science, Multidisciplinary)

The magnetic phase transition near $$T_0=8.5$$ K in AmO$$_2$$ has been investigated microscopically by means of $$^{17}$$O NMR. To avoid complexities arising from sample aging associated with the alpha decay of $$^{243}$$Am, all measurements have been performed within 40 days after sample synthesis. Even during such a short period, however, a rapid change of NMR line shape has been observed at 1.5 K, suggesting that the ground state of AmO$$_2$$ is very sensitive to disorder. We have also confirmed the loss of $$^{17}$$O NMR signal intensity over a wide temperature range below $$T_0$$, and more than half of oxygen nuclei are undetectable at 1.5 K. This behavior reveals the persistence of slow and distributed spin fluctuations down to temperatures well below $$T_0$$. In the paramagnetic state, strong NMR line broadening and spatially inhomogeneous spin fluctuations have been observed. The results are all indicative of short-range, spin-glass-like character for the magnetic transition in this system.

Journal Articles

Studies on self-irradiation damage of curium-doped titanate ceramics containing high-level nuclear waste

Hakushi Gakui Rombun, 00(00), p.1 - 265, 1997/00

no abstracts in English

JAEA Reports

Evaluation of dose contribution of self-irradiation and cosmic-ray to glass dosemeter for environmental radiation measurement

Sakamoto, Ryuichi; Nagaoka, Toshi; Saito, Kimiaki; Tsutsumi, Masahiro; Moriuchi, Shigeru

JAERI-M 94-060, 21 Pages, 1994/03

JAERI-M-94-060.pdf:0.98MB

no abstracts in English

Oral presentation

Self-radiation effects on the electronic ground state of AmO$$_2$$ studied by $$^{17}$$O-NMR

Tokunaga, Yo; Nishi, Tsuyoshi; Nakada, Masami; Ito, Akinori*; Sakai, Hironori; Kambe, Shinsaku; Homma, Yoshiya*; Honda, Fuminori*; Aoki, Dai*; Walstedt, R. E.*

no journal, , 

We will present the result of our recent NMR study performed to elucidate the origin of magnetic phase transition near $$T_0=8.5$$ K in AmO$$_2$$. To avoid complexities arising from sample aging associated with the alpha decay of $$^{243}$$Am, all measurements have been performed within 40 days after sample synthesis. Even during such a short period, however, a rapid change of NMR line shape has been observed at 1.5 K, suggesting that the ground state of AmO$$_2$$ is very sensitive to disorder. We have also confirmed the loss of $$^{17}$$O NMR signal intensity over a wide temperature range below $$T_0$$, and more than half of oxygen nuclei are undetectable at 1.5 K. This behavior reveals the persistence of slow and distributed spin fluctuations down to temperatures well below $$T_0$$. The results are all indicative of short-range, spin-glass-like character for the magnetic transition in this system.

Oral presentation

Self-irradiation effect on thermal conductivity of Zr$$_{0.70}$$Pu$$_{0.25}$$Cm$$_{0.05}$$N

Nishi, Tsuyoshi; Hayashi, Hirokazu; Hatakeyama, Yuichi; Kurata, Masaki

no journal, , 

no abstracts in English

Oral presentation

Evaluation and formulation of MOX fuel thermal conductivity

Ikusawa, Yoshihisa; Morimoto, Kyoichi; Kato, Masato; Uno, Masayoshi*

no journal, , 

The thermal conductivity of oxide fuel is one of the most important properties, since it affects temperature distribution in fuel during irradiation. It is well known that thermal conductivity strongly depends on the oxide-metal ratio (O/M) and burnup of the oxide fuel, and there have been many studies of UO$$_{2}$$ fuel. On the other hand, the thermal conductivity of uranium-and-plutonium-mixed oxide (MOX) fuel is more complex than UO$$_{2}$$ fuel because it is influenced by plutonium content and alpha damage in addition to the aforementioned factors. We have measured the thermal conductivity of various MOX fuels, such as stored samples, irradiated samples, and, several different plutonium content samples. In addition, plutonium content, alpha damage, and burnup effects on MOX fuel thermal conductivity were investigated from the result of these measurements.

Oral presentation

R&D on nitride fuel cycle for MA transmutation to enhance safety and economy, 3; Lattice and bulk expansion of nitride fuel pellet by self-irradiation damage

Takano, Masahide; Takaki, Seiya

no journal, , 

In the fuel containing minor actinides with high concentrations, lattice defects and He atoms accumulates quickly due to the self-irradiation damage of alpha-decay. The lattice expansion arising from the defects accumulation is well-known phenomenon, however, the knowledge relating to the bulk expansion have not been obtained yet. In this work we prepared a nitride fuel pellet containing $$^{244}$$Cm as a main alpha-emitter, and obtained data on the relationship between lattice and bulk expansion as a function of storage duration at room temperature.

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