Carrying-out of whole nuclear fuel materials in Plutonium Research Building No.1

Inagawa, Jun; Kitatsuji, Yoshihiro; Otobe, Haruyoshi; Nakada, Masami; Takano, Masahide; Akie, Hiroshi; Shimizu, Osamu; Komuro, Michiyasu; Oura, Hirofumi*; Nagai, Isao*; et al.

JAEA-Technology 2021-001, 144 Pages, 2021/08

JAEA-Technology-2021-001.pdf:12.98MB

Plutonium Research Building No.1 (Pu1) was qualified as a facility to decommission, and preparatory operations for decommission were worked by the research groups users and the facility managers of Pu1. The operation of transportation of whole nuclear materials in Pu1 to Back-end Cycle Key Element Research Facility (BECKY) completed at Dec. 2020. In the operation included evaluation of criticality safety for changing permission of the license for use nuclear fuel materials in BECKY, cask of the transportation, the registration request of the cask at the institute, the test transportation, formulation of plan for whole nuclear materials transportation, and the main transportation. This report circumstantially shows all of those process to help prospective decommission.

Optical properties of trinuclear citrate complexes containing 4f and 5f block metals

Aoyagi, Noboru; Palladino, G.*; Nagasaki, Shinya*; Kimura, Takaumi

Bulletin of the Chemical Society of Japan, 91(6), p.882 - 890, 2018/06

https://doi.org/10.1246/bcsj.20170419

The speciation and coordination geometries of M(III)-citrate complexes in aqueous solutions, where M denotes Eu, Tb, Lu, or Cm, are studied using potentiometric titration, nuclear magnetic resonance spectroscopies. Their photophysical properties are also characterized by time-resolved fluorescence spectra. The formation constants of mononuclear, dinuclear, and trinuclear Lu-citrate species were determined by potentiometric titration in 3.00 M NaClO aqueous media. Terminal carboxylic conformation in trinuclear complexes comprised both the five- and six-membered rings at different exchanging rates. Hydration states evaluated for Eu ions are the chemical formula of [Eu(Cit) (H O) ] and [Eu(OH)(Cit)(HO)]. These complexes in aqueous solution have geometrical similarity to the crystal structures in the literature. Furthermore, the entity of the hetero-trinuclear complex induces the intramolecular energy transfer from Tb to Eu. The incorporation of Cm into these homo/hetero-trinuclear citrate complexes proved to be a successful trial to probe the formation of actinide polymer at a trace level.

Electrochemistry at liquid/liquid interface

Kitatsuji, Yoshihiro

Bunseki, 2015(6), p.239 - 244, 2015/06

AA2014-0843.pdf:3.48MB

https://cir.nii.ac.jp/crid/1050564287525685120

Electrochemical studies of ion transfer and charge transfer at liquid/liquid interface reported between 2012 and 2014 were surveyed. They were categorized by method of measurement. The merit of the method, improvement, species of application were described. Applied research such as analyses of redox inactive species, sensitive analyses based on adsorption at the interface and developments of new functional materials had been widely carried out.

Corrosion of uranium and plutonium dioxides in aqueous solutions

Otobe, Haruyoshi; Kitatsuji, Yoshihiro; Kurata, Masaki; Takano, Masahide

Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 11 Pages, 2014/10

The chemical and transport behaviors of Pu and U in the corroded debris must be understood for the criticality safety control of Pu and U in the debris, especially for the removal operations and storage. Therefore, the chemical changes of UO and PuO powders, disks and U and Pu metal disks in HO aqueous solution have been checked, where HO is formed by the radiolysis of HO. As a result, UO changed to hydrated uranium peroxide, whereas the PuO remained unchanged. U metal was more reactive with HO aqueous solution than Pu metal. The chemical changes of the mixed UO/PuO powders in HO aqueous solution have been investigated. The dried slurry of the middle zone of HO aqueous solution was mainly composed of hydrated uranium peroxide, whereas the dried powder of the bottom zone was mainly composed of PuO.

Self-radiation effects and glassy nature of magnetic transition in AmO revealed by 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

https://doi.org/10.1103/PhysRevB.89.214416

The magnetic phase transition near K in AmO has been investigated microscopically by means of O NMR. To avoid complexities arising from sample aging associated with the alpha decay of 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 is very sensitive to disorder. We have also confirmed the loss of O NMR signal intensity over a wide temperature range below , 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 . 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.

Studies on solution chemistry of actinides and lanthanides by time-resolved laser-induced fluorescence spectroscopy

Kimura, Takaumi

Hosha Kagaku, (29), p.26 - 33, 2014/04

http://www.radiochem.org/rad-nw/rad_nw29.pdf

no abstracts in English

Mssbauer and magnetic study of neptunyl(+1) complexes

Nakamoto, Tadahiro*; Nakamura, Akio; Takeda, Masuo*

Mssbauer Spectroscopy; Applications in Chemistry, Biology, and Nanotechnology, p.95 - 114, 2013/10

https://doi.org/10.1002/9781118714614.ch05

Flow electrolysis of U, Np and Pu ions utilizing electrocatalysis at a column electrode with platinized glassy carbon fiber working electrode

Kitatsuji, Yoshihiro; Kimura, Takaumi; Kihara, Sorin*

Electrochimica Acta, 74, p.215 - 221, 2012/07

https://doi.org/10.1016/j.electacta.2012.04.055

Redox reactions of U, Np and Pu ions of various oxidation states were investigated by flow electrolysis at a column electrode (CE) equipped with a platinized glassy carbon (GC) fiber working electrode (Pt/GC-WE), and compared with those observed at the CE with an ordinary activated GC fiber working electrode (GC-WE). Since the overpotential for the reduction of NpO and PuO were decreased when Pt/GC-WE was employed, the one-electron reduction of NpO to Np followed by that of Np to Np and the one-step three-electron reduction of PuO to Pu proceeded at the CE with Pt/GC-WE, different from the reduction processes of NpO and PuO at the CE with GC-WE. A rapid and precise method for the preparation of U, Np and Pu ion of a desired oxidation state was proposed by taking advantage of the unique characteristics of the CE with Pt/GC-WE.

Standard Gibbs free energies for transfer of actinyl ions at the aqueous/organic solution interface

Kitatsuji, Yoshihiro; Okugaki, Tomohiko*; Kasuno, Megumi*; Kubota, Hiroki*; Maeda, Koji*; Kimura, Takaumi; Yoshida, Zenko; Kihara, Sorin*

Journal of Chemical Thermodynamics, 43(6), p.844 - 851, 2011/06

https://doi.org/10.1016/j.jct.2010.12.023

Standard Gibbs energies for transfer (G) of actinyl ions (AnO; z = 2 or 1; An: U, Np or Pu) between an aqueous solution and an organic solution were determined based on distribution method combined with voltammetry for ion transfer at the interface of two immiscible electrolyte solutions. The organic solutions examined were nitrobenzene, 1,2-dichloroethane, benzonitrile, acetophenone and 2-nitrophenyl octyl ether. Irrespective of the type of organic solutions, G of UO, NpO and PuO were nearly equal to each other and slightly larger than that of Mg. The G of NpO was extraordinary large compared with those of ordinary monovalent cations. The dependence of G of AnO on the type of organic solutions was similar to that of H or Mg. The G of An and An were also discussed briefly.

Reduction behavior of neptunium(V) at a gold or platinum electrode during controlled potential electrolysis and procedures for electrochemical preparations of neptunium(IV) and (III)

Kitatsuji, Yoshihiro; Kimura, Takaumi; Kihara, Sorin*

Journal of Electroanalytical Chemistry, 641(1-2), p.83 - 89, 2010/03

Unique current-time relations were observed during the controlled potential electrolysis for the reduction of Np(V) to Np(IV) or Np(III) at a Au or Pt electrode. The reduction process of Np(V) was elucidated based on bulk electrolysis and voltammetry: Though Np(V) is not reduced directly at a Au electrode, it is reduced by chemical reaction with Np(III) which is produced by the electrode reduction of Np(IV). The reduction of Np(V) at a Pt electrode is initiated by the electrocatalytic reduction to Np(IV) with the hydrogen atom which is produced by the electrode reduction of H and adsorbed on the Pt electrode surface. The Np(IV) produced functions as an electron transfer mediator to reduce Np(V) similarly to the reaction at a Au electrode. The above described catalytic reduction processes of Np(V) were elucidated with the aid of digital simulation. Methods useful for the preparation of Np(IV) and Np(III) by bulk electrolysis were proposed based on the experimental results.