Prediction of stability constants for novel chelates design in minor actinides partitioning over lanthanides using density functional theory calculation

Kaneko, Masashi; Sasaki, Yuji; Wada, Eriko*; Nakase, Masahiko*; Takeshita, Kenji*

Chemistry Letters, 50(10), p.1765 - 1769, 2021/10

https://doi.org/10.1246/cl.210402

Density functional theory calculation is applied to predict the stability constants for Eu and Am complexes in aqueous solution for molecular modelling of novel separation agents for minor actinides over lanthanides. Logarithm of experimental stability constants correlates with calculated complex formation enthalpies with high reproducibility (R 0.98). Prediction of stability constants of novel chelates is demonstrated and indicates a potential availability of the derivatives of diethylenetriaminepentaacetic acid type chelate in acidic condition and enhancement of Am selectivity over Eu.

Mechanistic study on the removal of Cs from contaminated soil by rapid ion exchange in subcritical water

Fukuda, Tatsuya*; Takahashi, Ryo*; Hara, Takuhi*; Ohara, Koji*; Kato, Kazuo*; Matsumura, Daiju; Inaba, Yusuke*; Nakase, Masahiko*; Takeshita, Kenji*

Journal of Nuclear Science and Technology, 58(4), p.399 - 404, 2021/04

https://doi.org/10.1080/00223131.2020.1830866

Effects of diluents on the separation of minor actinides from lanthanides with tetradodecyl-1,10-phenanthroline-2,9-diamide from nitric acid medium

Tsutsui, Nao; Ban, Yasutoshi; Suzuki, Hideya*; Nakase, Masahiko*; Ito, Sayumi*; Inaba, Yusuke*; Matsumura, Tatsuro; Takeshita, Kenji*

Analytical Sciences, 36(2), p.241 - 246, 2020/02

https://doi.org/10.2116/analsci.19P275

To investigate the effective separation of actinides (Ans) from lanthanides (Lns), single-stage batch extraction experiments were performed with a novel extractant, tetradodecyl-1,10-phenanthroline-2,9-diamide (TDdPTDA) with various diluents such as 3-nitrobenzotrifluoride (F-3), nitrobenzene, and -dodecane for Am, Cm, and Lns. The extraction kinetics with TDdPTDA was rapid enough to perform the actual extraction flow sheet. The slopes of the distribution ratio versus TDdPTDA concentration and the distribution ratio versus nitric acid concentration were similar for F-3 and nitrobenzene systems but different from -dodecane system. These differences were attributed to the characteristics of the diluents. This study reveals high distribution ratios of Am ( ) and Cm ( ) for TDdPTDA, with the high separation factors (s) of Am from Lns enough for their separation.

Extended X-ray absorption fine structure study on gel/liquid extraction of f-block elements

Nakase, Masahiko*; Kobayashi, Toru; Shiwaku, Hideaki; Kawamura, Takuya*; Takeshita, Kenji*; Yamamura, Tomoo*; Yaita, Tsuyoshi

Progress in Nuclear Science and Technology (Internet), 5, p.56 - 60, 2018/11

https://doi.org/10.15669/pnst.5.56

Gel/liquid extraction was investigated to achieve selective separation of trivalent actinides over lanthanides. In this study, thermosensitive hydrogel including N,N,N',N'-tetraallylpyridine-2,6-dicarboxamine (PDA) was synthesized, and its complexation with lanthanide was investigated by extended X-ray absorption fine structure experiments at SPring-8. The radial structure functions (RSF) of solution with gels with and without ligands at different temperatures showed slight differences. As the temperature increased, the RSF decreased owing to the increase in thermal vibration, but PDA-gel showed a shift in the first peak toward the shorter direction. This shift was attributed to the change in stoichiometry of PDA-Ln(III) complexes or coordination number of water molecules affected by the change of conformation of polymer chains and the hydrophilic/hydrophobic properties in the hydrogel.

Estimation of higher-order eigenvalues from residual of power iteration

Nakase, Masahiko*; Chiba, Go; Saito, Masaki*

no journal, , 

Higher-order eigenvalues can be useful indices for reactor core stability. Usually, higher-order eiganvalues are calculated with the subtraction method in which several numerical techniques are necessary. In this present study, we develop a simple method to estimate higher-order eigenvalues from a residual of power iteration. Through numerical calculations with the IAEA benchmark problem, the present method estimates higher-order eigenvalues up to the 5th order quite well.

Extraction property of tetradodecyl-1,10-phenanthroline-2,9-diamide toward effective separation of minor actinides and lanthanides

Tsutsui, Nao; Nakase, Masahiko*; Ito, Sayumi*; Matsumura, Tatsuro; Takeshita, Kenji*

no journal, , 

To separate minor acitinides from lanthanides in nitric acid, we focused on 1,10-phenanthroline-2,9-diamides (PTDAs) which consist of both soft and hard donor atoms. The present study employed a PTDA having dodecyl groups in N atoms of amides groups, TDdPTDA, and its extraction property toward Am, Cm, and Eu was studied.

Rare earth pattern leading the mutual separation of lanthanides and actinides at the extraction using DGA compound

Sasaki, Yuji; Ban, Yasutoshi; Morita, Keisuke; Matsumiya, Masahiko*; Nakase, Masahiko*

no journal, , 

We focus on the development of simply mutual separation method of trivalent lanthanide (Ln) and actinides (An). The extraction system using extractant and masking agent in both aqueous and organic phases may change the lanthanide pattern greatly, which leads the high separation factor not only Ln and An but also Am and Cm. In this presentation, the results obtained by several extraction system will be discussed.

Extraction separation of minor actinides and lanthanides by 1,10-phenanthroline-2,9-diamide with phenyl group in nitric acid systems

Tsutsui, Nao; Nakase, Masahiko*; Ito, Sayumi*; Ban, Yasutoshi; Matsumura, Tatsuro; Takeshita, Kenji*

no journal, , 

The extraction properties of three 1,10-phenanthroline-2,9-diamide derivatives ( , -diethly- , -bis(4-ethylphenyl)-1,10-phenanthroline-2,9-dicarboxamide (Et(EtPh)PTDA), , -dihexyl- , -bis(4-hexylphenyl)-1,10-phenanthroline-2,9-dicarboxamide (Hex(HexPh)PTDA), and , -didodecyl- , -bis(4-dodecylphenyl)-1,10-phenanthroline-2,9-dicarboxamide (Dd(DdPh)PTDA)) were studied for the separation of minor actinides (Am and Cm) and lanthanide (Eu) using single-stage batch methods. The results demonstrated that the PTDA derivatives extracted Am more efficiently than Eu or Cm. Furthermore, PTDA functionalized with short alkyl chains exhibited higher distribution ratios toward Eu, Am, and Cm when compared with those exhibited with longer chains. It was also revealed that the separation factor of Am with respect to Eu was relatively large, and that the alkyl chain length did not affect the separation factor when the same concentration of PTDA was used.

Development of cyano-group bridge-type coordination polymer with a high sorption characteristic of platinum-group elements for high quality and volume reduction of vitrified objects containing high-level radioactive nuclear wastes, 10; Platinum-group elements sorption studies of aluminum ferrocyanide

Mishima, Ria; Tachioka, Sotaro*; Inaba, Yusuke*; Harigai, Miki*; Matsumura, Tatsuro; Watanabe, Shinta*; Onoe, Jun*; Nakase, Masahiko*; Takeshita, Kenji*

no journal, , 

In Japan, the final disposal of high level liquid waste (HLLW) will be done after vitrification into borosilicate glass and then disposed into deep underground. In this vitrification process, there are some concerns. The first concern is precipitation of platinum group metals (PGMs) in the melter due to their low solubility into borosilicate glass. The second concern is the formation of yellow phase caused by Mo content. The final concern is the generation of huge number of vitrified glasses and the requirement of wide space needed for final disposal. Among many kinds of extractants and adsorbents for separation of such metal ions, metal hexacyanoferrate (HCFs) were reported to have an ability to adsorb PGMs. The objective of this study is to elucidate the adsorption behavior of aluminum hexacyanoferrate (AlHCF) for various metal ions and understand the relation between elution and adsorption. The effect of synthetic and workup conditions on PGM and Mo adsorption from simulated HLLW (sHLLW) was surveyed. Also, the relationship between adsorption of metal ions and elution of the AlHCF was studied. The synthesized AlHCF showed adsorption performance for PGMs and Mo in simulated HLLW. As a result of an adsorption test with a Pd single component solution to investigate the adsorption mechanism, the eluted element ratio was Fe:Al = 1:4 in the Pd adsorption test. However, the element ratio was Fe:Al = 3:4 in the original AlHCF. Therefore, it was suggested the existence of not only Pd adsorption, but also resorption and stabilization mechanisms.

Development of DGA compound and separation of trivalent actinides from lanthanides using organic acid with DTPA-BA

Sasaki, Yuji; Kaneko, Masashi; Matsumiya, Masahiko*; Nakase, Masahiko*; Takeshita, Kenji*

no journal, , 

The history of development of DGA compounds in our laboratory and their extraction ability will be mentioned. In addition, it is effective to separate An from Ln by back-extraction after lumping together extractions of An + Ln, and we can use various aqueous phase in the back-extraction. In this case we use organic acid, thus the results of separation of An and Ln using DTPA-BA dissolved in organic acid will be discussed.