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Journal Articles

Thorium oxide dissolution in HNO$$_{3}$$-HF mixture; Kinetics and mechanism

Simonnet, M.; Barr$'e$, N.*; Drot, R.*; Le Naour, C.*; Sladkov, V.*; Delpech, S.*

Radiochimica Acta, 107(4), p.289 - 297, 2019/04

 Percentile:100(Chemistry, Inorganic & Nuclear)

Journal Articles

Extraction behavior of rutherfordium as a cationic fluoride complex with a TTA chelate extractant from HF/HNO $$_{3}$$ acidic solutions

Yokoyama, Akihiko*; Kitayama, Yuta*; Fukuda, Yoshiki*; Kikunaga, Hidetoshi*; Murakami, Masashi*; Komori, Yukiko*; Yano, Shinya*; Haba, Hiromitsu*; Tsukada, Kazuaki; Toyoshima, Atsushi*

Radiochimica Acta, 107(1), p.27 - 32, 2019/01

 Percentile:100(Chemistry, Inorganic & Nuclear)

Journal Articles

Online chemical adsorption studies of Hg, Tl, and Pb on SiO$$_{2}$$ and Au surfaces in preparation for chemical investigations on Cn, Nh, and Fl at TASCA

Lens, L.*; Yakushev, A.*; D$"u$llmann, Ch. E.*; Asai, Masato; Ballof, J.*; Block, M.*; David, H. M.*; Despotopulos, J.*; Di Nitto, A.*; Eberhardt, K.*; et al.

Radiochimica Acta, 106(12), p.949 - 962, 2018/12

 Percentile:100(Chemistry, Inorganic & Nuclear)

Online gas-solid adsorption studies with single atom quantities of Hg, Tl, and Pb on SiO$$_{2}$$ and Au surfaces were carried out using short-lived radioisotopes with half-lives in the range of 4-49 s. This is a model study to measure adsorption enthalpies of superheavy elements Cn, Nh, and Fl. The short-lived isotopes were produced and separated by the gas-filled recoil separator TASCA at GSI. The products were stopped in He gas, and flushed into gas chromatography columns made of Si detectors whose surfaces were covered by SiO$$_{2}$$ or Au. The short-lived Tl and Pb were successfully measured by the Si detectors with the SiO$$_{2}$$ surface at room temperature. On the other hand, the Hg did not adsorb on the SiO$$_{2}$$ surface, but adsorbed on the Au surface. The results demonstrated that the adsorption properties of short-lived Hg, Tl, and Pb could be studied with this setup, and that this method is applicable to the experiment for Cn, Nh, and Fl.

Journal Articles

A Thermodynamic model for the solubility of HfO$$_{2}$$(am) in the aqueous K$$^{+}$$ - HCO$$_{3}$$$$^{-}$$ - CO$$_{3}$$$$^{2-}$$ - OH$$^{-}$$ - H$$_{2}$$O system

Rai, D.*; Kitamura, Akira; Rosso, K.*

Radiochimica Acta, 105(8), p.637 - 647, 2017/08

Solubility of HfO$$_{2}$$(am) was determined as a function of KHCO$$_{3}$$ concentrations ranging from 0.001$$^{-1}$$ to 0.1$$^{-1}$$. The solubility of HfO$$_{2}$$(am) increased dramatically with the increase in KHCO$$_{3}$$ concentrations, indicating that Hf(IV) makes strong complexes with carbonate. Thermodynamic equilibrium constants for the formation of Hf-carbonate complexes were determined using both the Pitzer and SIT models. The dramatic increase in Hf concentrations with the increase in KHCO$$_{3}$$ concentrations can best be described by the formation of Hf(OH-)$$_{2}$$(CO$$_{3}$$)$$_{2}$$$$^{2-}$$ and Hf(CO$$_{3}$$)$$_{5}$$$$^{6-}$$. The log$$_{10}$$ K$$^{0}$$ values for the reactions [Hf$$^{4+}$$ + 2 CO$$_{3}$$$$^{2-}$$ +2 OH$$^{-}$$ $$leftrightarrow $$ Hf(OH)$$_{2}$$(CO$$_{3}$$)$$_{2}$$$$^{2-}$$] and [Hf$$^{4+}$$ + 5 CO$$_{3}$$$$^{2-}$$ $$leftrightarrow $$ Hf(CO$$_{3}$$)$$_{5}$$$$^{6-}$$], based on the SIT model, were determined to be 44.53 $$pm$$ 0.46 and 41.53 $$pm$$ 0.46, respectively.

Journal Articles

Issues concerning the determination of solubility products of sparingly soluble crystalline solids; Solubility of HfO$$_{2}$$(cr)

Rai, D.*; Kitamura, Akira; Rosso, K. M.*; Sasaki, Takayuki*; Kobayashi, Taishi*

Radiochimica Acta, 104(8), p.583 - 592, 2016/08

 Times Cited Count:3 Percentile:42.29(Chemistry, Inorganic & Nuclear)

Solubility studies were conducted with HfO$$_{2}$$(cr) solid as a function of acid concentrations. These studies involved (1) using two different amounts of the solid phase, (2) acid washing the bulk solid phase, (3) preheating the solid phase to 1400 $$^{circ}$$C, and (4) heating amorphous HfO$$_{2}$$(am) suspensions to 90 $$^{circ}$$C to ascertain whether the HfO$$_{2}$$(am) converts to HfO$$_{2}$$(cr) and to determine the solubility from the oversaturation direction. Based on the results of these treatments it is concluded that the HfO$$_{2}$$(cr) contains a small fraction of less crystalline, but not amorphous, material [HfO$$_{2}$$(lcr)] and this, rather than the HfO$$_{2}$$(cr), is the solubility-controlling phase in the range of experimental variables investigated in this study. The solubility data are interpreted using both the Pitzer and SIT models. The log$$_{10}$$ of the solubility product of HfO$$_{2}$$(cr) is estimated. The observation of a small fraction of less crystalline higher solubility material is consistent with the general picture that mineral surfaces are often structurally and/or imperfect leading to a higher solubility than the bulk crystalline solid. This study stresses the urgent need, during interpretation of solubility data, of taking precautions to make certain that the observed solubility behavior for sparingly-soluble solids is assigned to the proper solid phase.

Journal Articles

Decomposition studies of group 6 hexacarbonyl complexes, 1; Production and decomposition of Mo(CO)$$_6$$ and W(CO)$$_6$$

Usoltsev, I.*; Eichler, R.*; Wang, Y.*; Even, J.*; Yakushev, A.*; Haba, Hiromitsu*; Asai, Masato; Brand, H.*; Di Nitto, A.*; D$"u$llmann, Ch. E.*; et al.

Radiochimica Acta, 104(3), p.141 - 151, 2016/03

 Times Cited Count:8 Percentile:10.94(Chemistry, Inorganic & Nuclear)

Conditions of the production and decomposition of hexacarbonyl complexes of short-lived Mo and W isotopes were investigated to study thermal stability of the heaviest group 6 hexacarbonyl complex Sg(CO)$$_6$$. A tubular flow reactor was tested to decompose the hexacarbonyl complexes and to extract the first bond dissociation energies. A silver was found to be the most appropriate reaction surface to study the decomposition of the group 6 hexacarbonyl. It was found that the surface temperature at which the decomposition occurred was correlated to the first bond dissociation energy of Mo(CO)$$_6$$ and W(CO)$$_6$$, indicating that the first bond dissociation energy of Sg(CO)$$_6$$ could be determined with this technique.

Journal Articles

An In-situ X-ray absorption spectroelectrochemical study of the electroreduction of uranium ions in HCl, HNO$$_3$$, and NaCO$$_3$$ solutions

Uehara, Akihiro*; Fujii, Toshiyuki*; Yamana, Hajimu*; Okamoto, Yoshihiro

Radiochimica Acta, 104(1), p.1 - 9, 2016/01

 Times Cited Count:2 Percentile:57.25(Chemistry, Inorganic & Nuclear)

The spectroelectrochemical cell was fabricated for in-situ X-ray absorption fine structure (XAFS) measurement. The XAFS spectra of U L$$_3$$-edge were monitored in electrolyte solutions during the electrochemical reduction. Tetravalent uranium was electrochemically prepared from hexavalent uranium and the extended X-ray absorption fine structure (EXAFS) was analyzed. The U$$^{4+}$$ formed in 0.1M HNO$$_3$$ was partially re-oxidized to UO$$_2$$$$^{2+}$$ by NO$$_3$$$$^-$$ in the solution. The UO$$_2$$$$^+$$ carbonates were prepared during electrolysis.

Journal Articles

An Attempt to select thermodynamic data and to evaluate the solubility of radioelements with uncertainty under HLW disposal conditions

Yamaguchi, Tetsuji; Takeda, Seiji; Nishimura, Yuki; Iida, Yoshihisa; Tanaka, Tadao

Radiochimica Acta, 102(11), p.999 - 1008, 2014/11

 Times Cited Count:1 Percentile:85.45(Chemistry, Inorganic & Nuclear)

An attempt was made to select thermodynamic data with uncertainties and to evaluate the solubility of radioelements with uncertainties considering variation in groundwater chemistry. The thermodynamic data was selected by reviewing the JAEA-TDB released in 2012. Data for Nb, Pd and Pa were revised from the viewpoint of the consistency of the data selection process. Data for Se, U and Pa were revised from the viewpoint of the conservativeness. Up-to-date ternary calcium-metal(IV)-OH complexes were adopted for Zr, Th, U, Np and Pu. A Monte Carlo-based probabilistic calculation code, PA-SOL, was used for probabilistic analysis of the solubility.

Journal Articles

Spectroscopic study of Np(V) oxidation to Np(VI) in 3 mol/dm$$^{3}$$ nitric acid at elevated temperatures

Ban, Yasutoshi; Hakamatsuka, Yasuyuki; Tsutsui, Nao; Urabe, Shunichi; Hagiya, Hiromichi; Matsumura, Tatsuro

Radiochimica Acta, 102(9), p.775 - 780, 2014/09

 Times Cited Count:2 Percentile:73.24(Chemistry, Inorganic & Nuclear)

Optical absorption spectra of Np in 3 mol/dm$$^{3}$$ nitric acid at elevated temperatures were measured using an optical glass cell with a water jacket having a light path of 1 cm, and molar extinction coefficients of Np(VI), $$varepsilon$$$$_{T}$$, were obtained at various temperature. The values of $$varepsilon$$$$_{T}$$ was found to decrease with increasing the temperature, and could be described by the equation $$varepsilon$$$$_{T}$$ = -0.14${it T}$+85.5, where ${it T}$ is the temperature. Oxidation of Np(V) to Np(VI) in 3 mol/dm$$^{3}$$ nitric acid at elevated temperatures was observed using the optical glass cell. Oxidation of Np(V) proceeded as pseudo-first order with respect to Np(V) concentration. The rate equation in the temperature range of 336-362 K was obtained as follows: -d[Np(V)]$$_{t}$$/dt = 2.2$$times$$10$$^{7}$$ exp[-65$$times$$10$$^{3}$$/(${it RT}$)][Np(V)]$$_{t}$$, where ${it R}$ and [Np(V)]$$_{t}$$ indicate the gas constant and Np(V) concentration at time ${it t}$, respectively.

Journal Articles

Thermodynamic model for the solubility of Ba(SeO$$_{4}$$, SO$$_{4}$$) precipitates

Rai, D.*; Felmy, A. R.*; Moore, D. A.*; Kitamura, Akira; Yoshikawa, Hideki; Doi, Reisuke; Yoshida, Yasushi*

Radiochimica Acta, 102(8), p.711 - 721, 2014/08

 Times Cited Count:1 Percentile:85.45(Chemistry, Inorganic & Nuclear)

The solubility of Ba(SeO$$_{4}$$, SO$$_{4}$$) precipitates was determined as a function of the BaSeO$$_{4}$$ mole fractions, ranging from 0.0015 to 0.3830, and time with an equilibration period extending to as long as 302 days. Equilibrium/steady state conditions in this system are reached in $$leq$$ 65 days. Pitzer's ion interaction model was used to calculate solid and aqueous phase activity coefficients. Thermodynamic analyses showed that the data do not satisfy Gibbs-Duhem equation, thereby demonstrating that a single-solid solution phase does not control both the selenate and sulfate concentrations. Our extensive data with [Ba], [SeO$$_{4}$$], and [SO$$_{4}$$] can be explained with the formation of an ideal BaSeO$$_{4}$$ solid solution phase that controls the selenium concentrations and a slightly disordered/less-crystalline BaSO$$_{4}$$(s) that controls the sulfate concentrations. In these experiments the BaSO$$_{4}$$ component of the solid solution phase never reaches thermodynamic equilibrium with the aqueous phase. Thermodynamic interpretations of the data show that both the ideal BaSeO$$_{4}$$ solid solution phase and less-crystalline BaSO$$_{4}$$(s) phase are in equilibrium with each other in the entire range of BaSeO$$_{4}$$ mole fractions investigated in this study.

Journal Articles

Thermodynamic model for the solubility of BaSeO$$_{4}$$(cr) in the aqueous Ba$$^{2+}$$-SeO$$_{4}$$$$^{2-}$$-Na$$^{+}$$-H$$^{+}$$-OH$$^{-}$$-H$$_{2}$$O system; Extending to high selenate concentrations

Rai, D.*; Felmy, A. R.*; Moore, D. A.*; Kitamura, Akira; Yoshikawa, Hideki; Doi, Reisuke; Yoshida, Yasushi*

Radiochimica Acta, 102(9), p.817 - 830, 2014/04

 Percentile:100(Chemistry, Inorganic & Nuclear)

The aqueous solubility of BaSeO$$_{4}$$(cr) was studied in Na$$_{2}$$SeO$$_{4}$$ solutions ranging in concentration from 0.0001 to 4.1$$^{-1}$$ and maintained in a N$$_{2}$$ atmosphere at room temperature (296 $$pm$$ 2 K). The studies were conducted from both the undersaturation and oversaturation directions, with equilibration periods ranging from 3 to 596 days. The equilibrium in this system was reached rather rapidly ($$leq$$ 3 days). The SIT and Pitzer's ion-interaction models were used to interpret these data and the predictions based on both of these models agreed closely with the experimental data.

Journal Articles

Production of $$^{256}$$Lr in the $$^{249,250,251}$$Cf + $$^{11}$$B, $$^{243}$$Am + $$^{18}$$O, and $$^{248}$$Cm + $$^{14}$$N reactions

Sato, Nozomi; Sato, Tetsuya; Asai, Masato; Toyoshima, Atsushi; Tsukada, Kazuaki; Li, Z.*; Nishio, Katsuhisa; Nagame, Yuichiro; Sch$"a$del, M.; Haba, Hiromitsu*; et al.

Radiochimica Acta, 102(3), p.211 - 219, 2014/03

 Times Cited Count:6 Percentile:43.1(Chemistry, Inorganic & Nuclear)

Production cross-sections of the isotope $$^{256}$$Lr in the $$^{249,250,251}$$Cf + $$^{11}$$B, $$^{243}$$Am + $$^{18}$$O, and $$^{248}$$Cm + $$^{14}$$N reactions were measured using a He/KCl gas-jet transport system and a rotating wheel $$alpha$$-particle detection apparatus. The $$alpha$$-particle energy of $$^{256}$$Lr was distributed from 8.3 to 8.7 MeV and its half-life, $$T_{1/2}$$, was measured to be $$28 pm 1$$ s. The maximum cross sections in the $$^{249}$$Cf($$^{11}$$B, 4$$n$$)$$^{256}$$Lr and $$^{243}$$Am($$^{18}$$O, 5$$n$$)$$^{256}$$Lr reactions were determined to be $$122 pm 6$$ nb at the beam energy of 63 MeV and $$26 pm 3$$ nb at 96 MeV, respectively. In the $$^{248}$$Cm($$^{14}$$N, 6$$n$$)$$^{256}$$Lr reaction, the cross section was measured to be $$27 pm 1$$ nb at 91 MeV.

Journal Articles

Precise age determination of a single plutonium particle using inductively coupled plasma mass spectrometer

Miyamoto, Yutaka; Esaka, Fumitaka; Suzuki, Daisuke; Magara, Masaaki

Radiochimica Acta, 101(11), p.745 - 748, 2013/11

 Times Cited Count:8 Percentile:29.95(Chemistry, Inorganic & Nuclear)

Age-dating of single plutonium particles with diameters of 1 $$mu$$m was demonstrated using eight particles. The precision and accuracy of the Pu age were improved through the addition of an $$^{243}$$Am spike to the sample solutions and by the trace chemical separation of the Pu and Am. The determined age in this work was in good agreement with the expected age with high accuracy and precision. The age with this technique was more precise than that determined using the common technique without an Am spike.

Journal Articles

New alkyl-pyridinedicarboxyamides as extractants for separation of trivalent minor actinides from fission products by extraction chromatography

Arisaka, Makoto; Watanabe, Masayuki; Kimura, Takaumi

Radiochimica Acta, 101(11), p.711 - 717, 2013/11

 Times Cited Count:2 Percentile:72.96(Chemistry, Inorganic & Nuclear)

Four new alkyl-pyridinedicarboxyamides (R-PDA; R = butyl, octyl, decyl, dodecyl) were synthesized and used as extractants for partitioning minor actinides from high level radioactive waste using extraction chromatography. The R-PDAs were successfully impregnated into XAD resins (Amberlite). The prepared adsorbents, R-PDA/XAD, exhibited moderate adsorptions of both Am(III) and Eu(III), and separation between Am(III) and Eu(III), over a high HNO$$_{3}$$ concentration range (3-5 M). Deterioration of the prepared adsorbent as a result of contact with HNO$$_{3}$$ solution was prevented by using R-PDAs containing longer alkyl groups. The equilibrium data for Eu(III) were analyzed using Langmuir and Freundlich isotherm models. The adsorption of Eu(III) ions onto the R-PDA/XAD was fitted better to the Langmuir isotherm than to the Freundlich isotherm. The maximum adsorption capacity was determined to be 24.2 mg Eu/g (R-PDA/XAD).

Journal Articles

Spectroscopic study of Pu(IV) oxidation to Pu(VI) in 3 mol/dm$$^{3}$$ nitric acid at 373 K

Ban, Yasutoshi; Morita, Yasuji

Radiochimica Acta, 100(12), p.879 - 883, 2012/12

 Times Cited Count:2 Percentile:74.11(Chemistry, Inorganic & Nuclear)

Optical absorption spectra of Pu(IV) in 3 mol/dm$$^{3}$$ (M) nitric acid at 373 K were measured using an optical quartz cell equipped with a thin-film heater. Pu(IV) was oxidized to Pu(VI) by heating at 373 K, and the concentrations of Pu(IV) and Pu(VI) gradually decreased and increased, respectively, with the heating time. The ratio of Pu(IV) oxidized to Pu(VI) was 37% at a heating time of 394 min, and no Pu(III) or Pu(V) characteristic peaks were observed throughout the experiment. The oxidation rate of Pu(IV) in 3 M nitric acid at 373 K could be described by the equation -d[Pu(IV)]$$_{t}$$/d$$t$$ =$$k_{1}^{'}$$[Pu(IV)]$$_{t}$$-$$k_{2}^{'}$$[Pu(VI)]$$_{t}$$, where [Pu(IV)]$$_{t}$$ and [Pu(VI)]$$_{t}$$ were the concentrations of Pu(IV) and Pu(VI) at a heating time of t min. The apparent rate constants for Pu(IV) oxidation ($$k_{1}^{'}$$) and Pu(VI) reduction ($$k_{2}^{'}$$) at 373 K were calculated to be 2.3$$times$$10$$^{-3}$$min$$^{-1}$$ and 3.4$$times$$10$$^{-3}$$min$$^{-1}$$, respectively.

Journal Articles

Effect of crystal size on purity of uranyl nitrate hexahydrate crystalline particles grown in nitric acid medium

Nakahara, Masaumi; Nomura, Kazunori

Radiochimica Acta, 100(11), p.821 - 826, 2012/11

 Percentile:100(Chemistry, Inorganic & Nuclear)

A relationship between crystal size and decontamination factor of impurities for uranyl nitrate hexahydrate crystals was examined with a dissolver solution of irradiated fast reactor fuel. The large crystal size reduced the specific surface area of the crystals which in turn decreased the adhesion of liquid impurities on the surface of the crystals. Therefore, high decontamination factors of liquid impurities were achieved. However, the uranyl nitrate hexahydrate crystal size did not affect the decontamination of solid impurities in the experiments.

Journal Articles

Two-mode fission; Experimental verification and characterization of two fission-modes

Nagame, Yuichiro; Nakahara, Hiromichi*

Radiochimica Acta, 100(8-9), p.605 - 614, 2012/08

 Times Cited Count:5 Percentile:48.35(Chemistry, Inorganic & Nuclear)

Journal Articles

Chemistry of superheavy elements

Sch$"a$del, M.

Radiochimica Acta, 100(8-9), p.579 - 604, 2012/08

 Times Cited Count:21 Percentile:8.06(Chemistry, Inorganic & Nuclear)

The chemistry of superheavy elements is summarized. After giving an overview over historical developments, nuclear aspects about synthesis of these elements and their nuclear decay properties are briefly mentioned. Specific requirements to cope with the one-atom-at-a-time situation in automated chemical separations and recent developments are presented. Current developments and future prospects of chemical separations behind physical recoil separators are discussed in detail. The status of our current knowledge about the chemistry of rutherfordium (Rf, element 104), dubnium (Db, element 105), seaborgium (Sg, element 106), bohrium (Bh, element 107), hassium (Hs, element 108), copernicium (Cn, element 112), and element 114 is discussed from an experimental point of view. Recent results are emphasized and compared with empirical extrapolations and with fully-relativistic theoretical calculations, especially also under the aspect of the architecture of the Periodic Table.

Journal Articles

Sulfate complexation of element 104, Rf, in H$$_{2}$$SO$$_{4}$$/HNO$$_{3}$$ mixed solution

Li, Z.*; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Sato, Nozomi; Kikuchi, Takahiro; Nagame, Yuichiro; Sch$"a$del, M.; Pershina, V.*; et al.

Radiochimica Acta, 100(3), p.157 - 164, 2012/03

 Times Cited Count:8 Percentile:32.85(Chemistry, Inorganic & Nuclear)

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