JOPSS - Search Results

Journal Articles

Symmetry lowering in NpO; $^{17}$ O-NMR study

Tokunaga, Yo; Homma, Yoshiya*; Kambe, Shinsaku; Aoki, Dai*; Sakai, Hironori; Yamamoto, Etsuji; Nakamura, Akio; Shiokawa, Yoshinobu; Walstedt, R. E.; Yasuoka, Hiroshi

Physica B; Condensed Matter, 359-361, p.1096 - 1098, 2005/04

https://doi.org/10.1016/j.physb.2005.01.297

Times Cited Count：7 Percentile：32.63(Physics, Condensed Matter)

In order to elucidate the nature of the exotic ordered phase of NpO below = 26 K, we have initiated the first $^{17}$ O-NMR measurements. From the temperature dependence of the $^{17}$ O-NMR spectrum, the occurrence of two inequivalent oxygen sites has been confirmed below . This finding verifies the lowering of symmetry in the ordered state of NpO.

Journal Articles

Phase transition of NpO $_{2}$ at 25K

Masaki, Nobuyuki; Nakada, Masami; Tsutsui, Satoshi; Nakamura, Akio; Yamashita, Toshiyuki

Physica B; Condensed Matter, 281-282, p.256 - 257, 2000/06

https://doi.org/10.1016/S0921-4526(99)00953-9

Times Cited Count：4 Percentile：27.02(Physics, Condensed Matter)

no abstracts in English

JAEA Reports

Migration behavior of actinide colloids in near-field

Nagasaki, Shinya*

JNC TJ8400 2000-004, 32 Pages, 2000/02

JNC-TJ8400-2000-004.pdf:0.69MB

Equilibrium and kinetics of sorption of NpO $_{2}^{+}$ on illite were investigated at pH = 6 by using the differential pulse anodic stripping voltammetry method and the spectroscopic method, respectively. It was found that the sorption isotherm obtained was fitted better by the Langmuir-Freundlich type equation than by the Langmuir equation. The heterogeneity coefficient was 0.89 0.05 and the half width at half maximum (HWHM) of affinity spectrum was 0.19 log unit, indicating that the surfacc of illite used has a low degree of heterogeneity. The kinetic spectra indicated that the sorption of NpO $_{2}^{+}$ occurs only at the outer surfacc. The mean HWHM of the kinetic spectra was 0.18 log unit. This also proves that the sorption kinetics of NpO $_{2}^{+}$ on the illite used is controlled by the same heterogeneity of the sorption sites. From the dependence of mean rate constants on temperature, a mean apparent activation enthalpy and a mean apparent activation entropy were evaluated at 373 kJ/mol and - 69 7 J/Kmol, respectively. This value of enthalpy suggests that the sorption is not controlled by diffusion through the hydrodynamic film around the illite. Equilibrium and kinetics of sorption of NpO $_{2}^{+}$ and Np(V) carbonate complexes (mainly NpO $_{2}$ CO $_{3}$ ) on Na-montmorillonite were also examined by using same technique.