Photochemical separation of elements in high level radioactive liquid waste

Matsuda, Shohei; Yokoyama, Keiichi

Isotope News, (786), p.6 - 9, 2023/04

no abstracts in English

Oxygen potential and self-irradiation effects on fuel temperature in Am-MOX

Ikusawa, Yoshihisa; Hirooka, Shun; Uno, Masayoshi*

2018 GIF Symposium Proceedings (Internet), p.321 - 327, 2020/05

Research and development of Minor actinides (MAs) bearing MOX fuel for fast reactor has been proceeding from the viewpoint of reducing radioactive waste. In order to develop, MA bearing MOX, it is indispensable to clarify the influence of MA addition on irradiation behavior. The addition of Americium (Am) to MOX affects vapor pressure and thermal conductivity, which are important properties from the perspective of evaluating fuel temperature. This is because vapor pressure affects fuel restructuring, and thermal conductivity affects fuel temperature distribution. Focusing on these physical properties, this study evaluates the influence of Am on fuel temperature using irradiation behavior analysis code to contribute to the development of MA-bearing MOX fuel. An increase in Am content decreases the thermal conductivity and increases the oxygen potential of oxide fuel. Because vapor pressure increases with increasing Am content, pore migration is accelerated, and the central void diameter increases with increasing Am content. As a result, after formation of the central void, the influence of Am content on the fuel center temperature is mild. Alpha particles generated by radioactive decay of transuranium elements cause lattice defects in the oxide fuel pellets. It is well known that this phenomenon, which is called self-irradiation, affects thermal conductivity. Since americium is the typical alpha radioactive nucleus, to evaluate fuel temperature of Am-MOX is necessary to take account of the influence of self-irradiation damage on thermal conductivity. Self-irradiation decreases thermal conductivity, and as the Am content increases, the rate of decrease in thermal conductivity is accelerated. Because it recovers with temperature rise, the decrease in thermal conductivity due to self-irradiation damage has very little effect on fuel center temperature. These results suggest that Am-MOX fuel could be irradiated under the same conditions as conventional MOX fuel.

Minor actinides separation by -hexaoctyl nitrilotriacetamide (HONTA) using mixer-settler extractors in a hot cell

Ban, Yasutoshi; Suzuki, Hideya*; Hotoku, Shinobu; Tsutsui, Nao; Tsubata, Yasuhiro; Matsumura, Tatsuro

Solvent Extraction and Ion Exchange, 37(7), p.489 - 499, 2019/11

https://doi.org/10.1080/07366299.2019.1693486

A continuous counter-current experiment to separate minor actinides (MAs: Am and Cm) was performed with -hexaochyl nitrilotriacetamide (HONTA) as an extractant. Nitric acid of 0.08 M (mol/dm) containing MAs and rare earths (REs) recovered from high-level waste was used as the Feed, and the experiment was conducted for 14 h. The ratios of Am and Cm recovered into the MA fraction measured 94.9% and 78.9%, respectively. HONTA hardly extracted Y, La, and Eu in the Feed (99.9% for Y, 99.9% for La, and 96.7% for Eu), most of which were distributed to the RE fraction. A portion of Nd was extracted by HONTA, and consequently the ratio of Nd in the RE fraction was 83.5%. The concentrations of MAs and some REs in each stage were calculated using a simulation code, and the results are consistent with the experimental values. This code indicates that the ratios of MAs in the MA fraction and REs in the RE fraction could be 99% by optimizing separation conditions.

Extraction of trivalent rare earths and minor actinides from nitric acid with -tetradodecyldiglycolamide (TDdDGA) by using mixer-settler extractors in a hot cell

Ban, Yasutoshi; Suzuki, Hideya; Hotoku, Shinobu; Kawasaki, Tomohiro*; Sagawa, Hiroshi*; Tsutsui, Nao; Matsumura, Tatsuro

Solvent Extraction and Ion Exchange, 37(1), p.27 - 37, 2019/00

https://doi.org/10.1080/07366299.2019.1586347

A continuous counter-current experiment using TDdDGA was performed using mixer-settler extractors installed in a hot cell. Nitric acid containing minor actinides (MAs: Am and Cm), rare earths (REs: Y, La, Nd, and Eu), and other fission products (Sr, Cs, Zr, Mo, Ru, Rh, and Pd) was fed to the extractor. TDdDGA effectively extracted MAs and REs from the feed, while other fission products were barely extracted. The extracted MAs and REs were back-extracted by bringing them in contact with 0.02 mol/dm nitric acid, and they were collected as the MA-RE fraction. The proportions of MA and RE in the MA-RE fraction were 98% and 86%, respectively. These results demonstrated the applicability of TDdDGA as an extractant for MAs and REs.

Fabrication and short-term irradiation behaviour of Am-bearing MOX fuels

Kihara, Yoshiyuki; Tanaka, Kosuke; Koyama, Shinichi; Yoshimochi, Hiroshi; Seki, Takayuki; Katsuyama, Kozo

NEA/NSC/R(2017)3, p.341 - 350, 2017/11

https://www.oecd-nea.org/pt/iempt14/

In order to investigate the effect of the addition of americium to MOX fuels on the irradiation behaviour, the "Am-1" program is being conducted at the JAEA. The Am-1 program consists of two short-term irradiation tests of 10-min and 24-h irradiation periods, and a steady-state irradiation test. The short-term irradiation tests and their post irradiation examinations (PIEs) have been successfully completed. To date, the data for PIE of the Am-MOX fuels focused on the microstructural evolution and redistribution behaviour of Am at the initial stage of irradiation have been obtained and reported. In this paper, the results obtained from the Am-1 program are reviewed and detailed descriptions of the fabrication and inspection techniques for the Am-MOX fuels prepared for the program are provided. PIE data for the Am-MOX fuels at the initial stage of irradiation have been accumulated. In this paper, unpublished PIE data for the Am-MOX fuels are also presented.

Separation of minor actinides and lanthanides from nitric acid solution by R-BTP extraction resin

Hoshi, Harutaka*; Wei, Y.*; Kumagai, Mikio*; Asakura, Toshihide; Morita, Yasuji

Recent Advances in Actinide Science, p.596 - 598, 2006/06

Recently, extraction selectivity for trivalent minor actinides (MA = Am and Cm) over lanthanides (Ln) has been found in some extractants containing soft donor, such as S or N, ligands. Kolarik et al. reported that a new N-donor ligand 2,6-bis(5,6-dialkyl-1,2,4-triazine-3-yl)-pyridine (R-BTP) shows high selectivity for MA (III) over Ln(III) [1]. However, protonation of R-BTP results in its acidic hydrolysis in acidic medium. Stability in acidic solution was improved by substitution of long normal chain or branched chain [2]. In this work, separation of MA(III) and Ln(III) from nitric acid solution was studied by using novel R-BTP impregnated resin. Branched R-BTP resin had high affinity for Am from up to 4 M HNO solution and its distribution coefficient was over 10.

Separation of trivalent actinides from lanthanides by using R-BTP resins and stability of R-BTP resin

Hoshi, Harutaka*; Wei, Y.*; Kumagai, Mikio*; Asakura, Toshihide; Morita, Yasuji

Journal of Alloys and Compounds, 408-412, p.1274 - 1277, 2006/02

https://doi.org/10.1016/j.jallcom.2005.04.128

For the development of advanced aqueous reprocessing system, it is one of the most important subjects to separate minor trivalent actinides (MA = Am and Cm). Recently, extraction selectivity for MA(III) over Ln(III) has been found in some extractants containing soft donor, such as S or N, ligands. Kolarik et al. reported that a new N-donor ligand 2,6-bis(5,6-dialkyl-1,2,4-triazine-3-yl)-pyridine (R-BTP) shows high selectivity for MA (III) over Ln(III). The novel silica-based extraction resins were prepared by impregnating some R-BTP molecules into a macroreticular styrene-divinylbenzene copolymer which is immobilized in porous silica particles with a mean diameter of 50 m. Separation of simulated high level liquid waste solution containing Ln(III) and trace amount of Am(III) was studied. Am(III) was mutually separated from Ln(III) through a packed column with R-BTP impregnating resin, very high decontamination factor ( 10) for Am, and all the elements were recovered quantitatively.

Status of fuel transmutation programmes in Japan and France; Lessons drawn from results

Arai, Yasuo; Pillon, S.*

Proceedings of International Conference ATALANTE 2004 Advances for Future Nuclear Fuel Cycles (CD-ROM), 9 Pages, 2004/06

no abstracts in English

Migration models of neptunium and americium in groundwater under the present condition of humic substances

Tanaka, Tadao; Sakamoto, Yoshiaki; Sawada, Hiroshi; Ogawa, Hiromichi

JAERI-Conf 2003-010, p.134 - 141, 2003/09

https://jopss.jaea.go.jp/pdfdata/JAERI-Conf-2003-010.pdf

We have performed migration experiments of Np(V) and Am(III) for crushed granite, under the coexistent condition with humic acid substance. As for Np, the periodical concentration changes in the breakthrough curve and the migration velocity of Np passed through the column were not affected by the coexistence of the humic substance. As for Am, on the other hand, the periodical concentration changes in the breakthrough curve were affected by the humic substance concentration. The migration behavior of Am passed through the present column system could be expressed by a migration model taking account of the non-equilibrium state.

The Sorption database of radionuclides for cementitious materials

Kato, Hiroshige*; Mine, Tatsuya*; Mihara, Morihiro; Oi, Takao; Honda, Akira

JNC TN8400 2001-029, 63 Pages, 2002/01

JNC-TN8400-2001-029.pdf:1.81MB

Cementitious materials will be used for the TRU waste repository as a component of engineered barrier system. The distribution coefficients which represent the retardation of radionuclides migration for the cementitious materials would be one of the important parameter for the safety assessment. The much information of radionuclide sorption onto the cementitious materials has been accumulated through the study in the world. Therefore it is necessary to compile the information and Kd of the radionuclides reported in previous studies. In this report, the Kd of the important radionuclides, such as C, Ni, Se, Sr, Zr, Nb, Mo, Tc, Sn, I, Cs, Sm, Pb, Ra, Ac, Th, Pa, U, Np, Pu, Am, Cm, for the cementitious materials were compiled as the Sorption Database (SDB). For radionuclides to be sensitive to the redox potential, e.g. Se, Tc, Pa, U, Pu and Np, some Kds measured under the controlled atmosphere had been reported, and few Kds measured under the controlled redox potential had been reported. For Se, Mo, Sm, Cm and Ac, the distribution coefficients had not been reported, therefore distribution coefficients of Se and Mo for OPC (Ordinary Portland Cement) pastes were measured by batch sorption experiments and these data were added into the SDB.