Synergistic solvent extraction of lanthanide ions with mixtures of D2EHPA and MIDPA in phosphonium-based ionic liquids

Matsumiya, Masahiko*; Nomizu, Daiki*; Tsuchida, Yusuke*; Sasaki, Yuji

Hydrometallurgy, 199, p.105539_1 - 105539_8, 2021/02

https://doi.org/10.1016/j.hydromet.2020.105539

The synergistic solvent extraction of lanthanide(III) with mixtures of di-(2-ethylhexyl)phosphoric acid (D2EHPA, A) and monoisodecyl phosphoric acid (MIDPA, B) in phosphonium-based ionic liquid was investigated. In the case of D2EHPA or MIDPA single extractant system, Ln(III) (Ln = Pr and Nd) was extracted as [LnAHA] or [LnBHB], respectively, the extracted species of Tb(III) or Dy(III) were determined by slope analysis. According to the equilibrium constants (, and ) and the formation constants (, and ), it was found that the extracted complex [TbHAB or [DyHAB] was more stable than [LnAHA] or [LnBHB]. The synergistic extraction effects were investigated to study the possibility of separating Dy(III) from Pr(III) and Nd(III) according to their separation factors.

Melting behavior and thermal conductivity of solid sodium-concrete reaction product

Kawaguchi, Munemichi; Miyahara, Shinya; Uno, Masayoshi*

Journal of Nuclear Science and Technology, 56(6), p.513 - 520, 2019/06

https://doi.org/10.1080/00223131.2019.1599744

This study revealed melting points and thermal conductivities of four samples generated by sodium-concrete reaction (SCR). We prepared the samples using two methods such as firing mixtures of sodium and grinded concrete powder, and sampling depositions after the SCR experiments. In the former, the mixing ratios were determined from the past experiment. The latter simulated the more realistic conditions such as the temperature history and the distribution of Na and concrete. The thermogravimetry-differential thermal analyzer (TG-DTA) measurement showed the melting points were 865-942C, but those of the samples containing metallic Na couldn't be clarified. In the two more realistic samples, the compression moldings in a furnace were observed. The observation revealed the softening temperature was 800-840C and the melting point was 840-850C, which was 10-20C lower than the TG-DTA results. The thermodynamics calculation of FactSage 7.2 revealed the temperature of the onset of melting was caused by melting of the some components such as NaSiO and/or NaSiO. Moreover, the thermal conductivity was =1-3W/m-K, which was comparable to xNaO-1-xSiO (x=0.5, 0.33, 0.25), and those at 700C were explained by the equation of .

Thermodynamic study of gaseous CsBO by Knudsen effusion mass spectrometry

Nakajima, Kunihisa; Takai, Toshihide; Furukawa, Tomohiro; Osaka, Masahiko

Journal of Nuclear Materials, 491, p.183 - 189, 2017/08

https://doi.org/10.1016/j.jnucmat.2017.05.001

One of the main chemical forms of cesium in the gas phase during severe accidents of light water reactor is expected to be cesium metaborate, CsBO, by thermodynamic equilibrium calculation considering reaction with boron. But accuracy of the thermodynamic data of gaseous metaborate, CsBO(g), has been judged as poor quality. Thus, Knudsen effusion mass spectrometric measurement of CsBO was carried out to obtain reliable thermodynamic data. The evaluated values of standard enthalpy of formation of CsBO(g), H(CsBO,g), by the 2nd and 3rd law treatments are -700.710.7 kJ/mol and -697.010.6 kJ/mol, respectively, and agree with each other within the errors, which suggests our data are reliable. Further, it was found that the existing data of the Gibbs energy function and the standard enthalpy of formation agreed well with the values evaluated in this study, which indicates the existing thermodynamic data are also reliable.

Evaluation of uncertainty associated with parameters for long-term safety assessments of geological disposal

Yamaguchi, Tetsuji; Minase, Naofumi; Iida, Yoshihisa; Tanaka, Tadao; Nakayama, Shinichi

JAERI-Conf 2005-007, p.150 - 155, 2005/08

https://jopss.jaea.go.jp/pdfdata/JAERI-Conf-2005-007.pdf

no abstracts in English

Proceedings of the 2nd Workshop on Molten Salts Technology and Computer Simulation

Okamoto, Yoshihiro; Minato, Kazuo

JAERI-Conf 2003-005, 186 Pages, 2003/06

JAERI-Conf-2003-005.pdf:10.42MB

Applications of molten salts technology to separation and synthesis of materials have been widely studied. Especially, much attention is given to the pyrochemical reprocessing of spent nuclear fuels. Computer simulation technique is expected to play an important role for supporting experimental works and predicting unknown physical properties in the molten salts application studies. Research group for Actinides Science, Department of Materials Science, Japan Atomic Energy Research Institute (JAERI), together with Reprocessing and Recycle Technology Division, Atomic Energy Society of Japan, organized the 2nd Workshop on Molten Salts Technology and Computer Simulation at Tokai Research Establishment, JAERI on December 3, 2002. Many molten salts researchers in Japan participated in the workshop and many useful presentations and discussions were performed.

Thermodynamic study on redox reactions of boiling nitric acid solutions

Kato, Chiaki; Kiuchi, Kiyoshi; Sugimoto, Katsuhisa*

Zairyo To Kankyo, 52(1), p.44 - 52, 2003/01

http://joi.jlc.jst.go.jp/JST.Journalarchive/jcorr1991/52.44

In order to understand corrosion of metals in nitric acid solutions, it is necessary to know the generation mechanism of high equilibrium potential in the solutions, especially under boiling conditions. The Raman spectroscopic analysis showed that the existing amount of un-dissociated HNO increased with increasing nitric acid concentration and solution temperature. The existing amount of NO also increased by thermal decomposition. The thermodynamic calculation showed that the important nitrogen oxides in nitric acid solutions are HNO, NO, HNO, NO, and NO. The equilibrium potential of nitric acid solutions is, however, mainly decided by the HNO/HNO equilibrium. The thermodynamic calculation also suggested that the increased oxidization potential on the heat-transfer surface is attributed to the reduction of nitrous acid concentration by the thermal decomposition of nitrous acid on the surface and the continuous removal of decomposition product from the solutions by boiling bubbles.

Evaluation on chemical state of irradiated rock-like oxide fuels by nuclear and chemical modeling

Nitani, Noriko; Kuramoto, Kenichi; Yamashita, Toshiyuki; Omichi, Toshihiko*

Progress in Nuclear Energy, 38(3-4), p.435 - 438, 2001/02

https://doi.org/10.1016/S0149-1970(00)00153-0

no abstracts in English

Sorption studies of plutonium on geological materials - year 2

J. A. BERRY*; M. BROWNSWORD*; D. J. ILETT*; Linklater, C. M.*; Mason, C.*; TWEED, C. J.*

JNC TJ8400 2000-060, 60 Pages, 2000/02

JNC-TJ8400-2000-060.pdf:2.95MB

Batch sorption experiments have been carried out to investigate the sorption behaviour of plutonium onto basalt and sandstone from the appropriate rock-equilibrated waters under different redox eonditions. Redox Potentials in solution were controlled by the addition of two reducing agents and one oxidising agent. Thermodynamic chemical modelling was undertaken to interpret the results. The sorption models were based on iron oxide. They adequately reproduced the data for sorption of plutonium onto sandstone, but tended to underpredict sorption onto basalt.

Models of Cement-Water Interaction and a Compilation of a Associated Thermodynamic Data

Savage, D.*; Lemke, K.*; Sasamoto, Hiroshi; Shibata, Masahiro; Arthur, R. C,*; Yui, Mikazu

JNC TN8400 2000-004, 30 Pages, 2000/01

JNC-TN8400-2000-004.pdf:1.26MB

Modeling approaches that have been proposed for cement-water system are reviewed in this report, and relevant supporting thsrmodynamic data are compiled. The thermodynamic data include standard molal thermodynamic properties of minerals and related compounds comprising cements, and equilibrium constants for associated hydrolysis reactions. Similar data for minerals that are stable in hyperalkaline geologic environments (e.g., zeolites) are also included because these minerals could be formed as hyperalkaline fluids emanating from cementitious matelials in a repository for radioactive wastes interact with the surrounding host rock. Standard molal properties (i.e., standard molal Gibbs free energies and enthalpies of formation and standard molal entropies), and/or equilibrium constants for associated hydrolysis reactions, are included for. (1)cement minerals and related compounds (Reardon, 1992; Glasser et al., 1999) (2)calcium-silicate hydrate minerals (Sarkar et al., 1982), and (3)zeolites (calorimetric and estimated values from various sources) All these data are accepted at face value, and it is therefore cautioned that the data, considered as a whole, may not be internally consistent. It is also important to note that the accuracy of these data have not been evaluated in the present study. Several models appropriate for cement-water systems have been proposed in recent years. Most are similar in the sense that they represent empirical fits to laboratory data for the CSH gel-water system, and therefore not thermodynamically defensible. An alternative modeling approach based on thermodynamic principles of solid-solution behavior appropriate for CSH gel has recently been proposed, however. It is reviewed in the present study, and evaluated in relation to experimental results obtained by JNC on cement-water interactions. The solid-solution model is based upon a thermodynamically- and structually-justifiable description of CSH gel in terms of a non-ideal ...

JNC Thermodynamic Database for Performance Assessment of High-level Radioactive Waste Disposal System

Yui, Mikazu; ; Shibata, Masahiro

JNC TN8400 99-070, 106 Pages, 1999/11

JNC-TN8400-99-070.pdf:2.93MB

This report is a summary of status, frozen datasets, and future tasks of the JNC thermodynamic database (JNC-TDB) for assessing performance of high-level radioactive waste in geological environments. The JNC-TDB development was carried out after the first progress report on geological disposal research in Japan (H3). In the development, thermodynamic data (equilibrium constants at 25 C, I=0) for important radioactive elements were selected/determined based on original experimental data using different models (e.g., SIT, Pitzer). As a result, the reliability and traceability of the data for most of the important elements were improved over those of the PNC-TDB used in H-3 report. For detailed information of data analysis and selections for each element, see the JNC technical reports listed in this document.