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Journal Articles

Magnetization, specific heat, $$^{17}$$O NMR, and $$^{237}$$Np M$"o$ssbauer study of U$$_{0.15}$$Np$$_{0.85}$$O$$_2$$

Martel, L.*; Hen, A.*; Tokunaga, Yo; Kinnart, F.*; Magnani, N.*; Colineau, E.*; Griveau, J.-C.*; Caciuffo, R.*

Physical Review B, 98(1), p.014410_1 - 014410_8, 2018/07

 Percentile:100(Materials Science, Multidisciplinary)

We report a study of the magnetic and electronic properties of the U$$_{0.15}$$Np$$_{0.85}$$O$$_2$$ solid solution, based on dc- and ac- magnetisation, $$^{237}$$Np M$"o$ssbauer spectroscopy, $$^{17}$$O Nuclear Magnetic Resonance (NMR), and specific heat measurements. The compound orders antiferromagnetically at T$$_N$$ = 17 K. The different techniques reveal the complexity of this system with:(1) a spatial distribution of ordered moments, (2) a small Np ordered moment, and (3) an additional specific heat anomaly at 7.4 K, with a residual value at very low temperature and a reduced magnetic entropy. The results are compared to the end-members of the series, UO$$_2$$ and NpO$$_2$$, as well as to the other solid solutions previously reported in this system. We discuss how the properties of U$$_{0.15}$$Np$$_{0.85}$$O$$_2$$ add new input to the trend previously reported for the series, in view of the models that have been previously proposed.

Journal Articles

Distribution behavior of neptunium by extraction with ${it N,N}$-dialkylamides (DEHDMPA and DEHBA) in mixer-settler extractors

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

Solvent Extraction and Ion Exchange, 34(1), p.37 - 47, 2016/01

 Times Cited Count:3 Percentile:80.3(Chemistry, Multidisciplinary)

The extraction properties of ${it N,N}$-di(2-ethylhexyl)-2,2-dimethylpropanamide (DEHDMPA) and ${it N,N}$-di(2-ethylhexyl)butanamide (DEHBA) for Np(V) and Np(VI) were studied by a batch method using various nitrate ion concentrations. The distribution ratios of Np(VI) obtained with DEHDMPA and DEHBA exceeded unity when the nitrate ion concentration was $$>$$3 mol/L. DEHDMPA and DEHBA barely extracted Np(V), and the maximum distribution ratios were 0.4 and 0.2 when DEHDMPA and DEHBA were used as extractants, respectively. A continuous counter-current experiment was performed to evaluate the behavior of Np in a process comprising two cycles. The ratio of Np recovered to the U fraction and U-Pu fraction were 63.7% and 29.1%, respectively. The behavior of Np suggested that the valence state of Np changed from Np(V) to Np(IV) or Np(VI) after the 1st experimental cycle. The recoveries of U and Pu to the U fraction stream and the U-Pu fraction stream were 99.9% and 99.8%, respectively.

Journal Articles

Theoretical and experimental study of the vibrational frequencies of UO$$_{2}$$$$^{2+}$$ and NpO$$_{2}$$$$^{2+}$$ in highly concentrated chloride solutions

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

Journal of Radioanalytical and Nuclear Chemistry, 303(1), p.1015 - 1020, 2015/01

 Times Cited Count:3 Percentile:53.75(Chemistry, Analytical)

The $$nu$$$$_{1}$$ symmetric vibrational frequency of UO$$_{2}$$$$^{2+}$$ in chloride solutions was studied by Raman spectrometry and ab initio calculations. The $$nu$$$$_{1}$$ frequency experimentally obtained decreased with the increase of concentration of Cl in solvent chlorides. This is attributable to that hydration water molecules in the equatorial plane of UO$$_{2}$$$$^{2+}$$ are substituted by Cl$$^{-}$$ ions, which was consistent with the calculation results. The theoretical part was expanded to aqua- and chloro- Np(VI) complexes. The $$nu$$$$_{1}$$ frequencies of neptunyl species computed were acceptable compared with the reported Raman shifts.

Journal Articles

Sorption and migration of neptunium in porous sedimentary materials

Tanaka, Tadao; Mukai, Masayuki; Nakayama, Shinichi

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10

no abstracts in English

Journal Articles

Rapid and quantitative electrolytic preparation and speciation of neptunium ions of various oxidation states using multi-step column electrodes

Aoyagi, Hisao*; Kitatsuji, Yoshihiro; Yoshida, Zenko; Kihara, Sorin*

Analytica Chimica Acta, 538(1-2), p.283 - 289, 2005/05

 Times Cited Count:12 Percentile:60.27(Chemistry, Analytical)

Redox behavior of Np(III), (IV), (V) and (VI) ions in aqueous perchloric, nitric and sulphuric acid solutions was elucidated by using column electrodes connected in series in a flow system. Using a glassy carbon fiber working electrode as the column electrode was found to be very useful for the investigation of current-potential relations of not only reversible redox processes such as Np(VI)/(V) or Np(IV)/(III) but also irreversible processes such as Np(V)/(IV) or Np(V)/(III), the latter not observed by conventional voltammetry which uses a glassy carbon or platinum electrode. Quantitative electrolysis could be executed even if the redox process was completely irreversible by the use of the column electrodes. By taking advantage of column electrode electrolysis, a novel method was developed for the rapid preparation of a neptunium species of a desired oxidation state, including unstable species. The multi-step column electrode system was demonstrated to be useful for the coulometric determination and speciation of Np(IV), (V) and (VI) in aqueous HNO$$_{3}$$ solution as an example.

Journal Articles

Correlation between $$^{237}$$Np M$"o$essbauer parameter and crystal structure of neptunyl compounds

Saeki, Masakatsu

Nippon Kessho Gakkai-Shi, 46(6), p.415 - 420, 2004/12

no abstracts in English

Journal Articles

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

JAEA Reports

Radiochemical studies of iodine, tritium and neptunium

Saeki, Masakatsu

JAERI-Review 2004-011, 54 Pages, 2004/03

JAERI-Review-2004-011.pdf:5.21MB

In this review, experimental results on studies of radioactive iodine, tritium and neptunium are summarized. On studies of radioactive iodine, from various experimental results, the process establishing the formation mechanism of organic iodides was fully described. On the basis of formation mechanism, possibilities for the formation of organic iodides under nuclear reactor accidents and so on were also discussed. On studies of tritium, three topics were concisely described on the isotopic composition of tritium gases, the chemical forms and the diffusivity of tritium in various materials, and the sorption and desorption behaviors of tritium on surfaces of various materials. On the neptunium chemistry, the relationship between the structure of neptunium compound and the Moessbauer isomer shift and experimental results on neptunyl(VI) hydroxides were discussed.

Journal Articles

Complex compound of rare earth elements, Actinides

Saeki, Masakatsu

Dai-5-Han Jikken Kagaku Koza 22; Kinzoku Sakutai, Seni Kinzoku Kurasuta, p.200 - 209, 2004/03

no abstracts in English

Journal Articles

Relationship between M$"o$ssbauer Isomer shifts and Structures of Neptunium compounds

Saeki, Masakatsu; Nakada, Masami; Kitazawa, Takafumi*

KURRI-KR-106, p.38 - 42, 2004/03

no abstracts in English

Journal Articles

An Advanced aqueous reprocessing process for the next generation's nuclear fuel cycle

Mineo, Hideaki; Asakura, Toshihide; Hotoku, Shinobu; Ban, Yasutoshi; Morita, Yasuji

Proceedings of GLOBAL2003 Atoms for Prosperity; Updating Eisenhower's Global Vision for Nuclear Energy (CD-ROM), p.1250 - 1255, 2003/11

An advanced aqueous reprocessing process has been proposed for the next generation fuel cycle. Key technologies applied to the process are: removal of I-129, separation of Np and FP(Tc) separation by selective reduction of Np(VI) and high acid scrubbing of Tc within a single cycle process, MA separation by extraction chromatography and Cs/Sr separation. U separation just after dissolution was supposed to be effective to reduce the required capacity of the following extraction step. Among them Np reduction rate in TBP solution was measured, which was found to be lower than that in aqueous solution. Using an improved flow sheet spent fuel test, based on the Np reduction test, was carried out and about 90% of Np was separated before U and Pu partitioning step.

Journal Articles

Data acquisition for predicting radionuclide migration under deep geological environments

Yamaguchi, Tetsuji; Nakayama, Shinichi

JAERI-Conf 2003-018, p.115 - 116, 2003/10

Effective diffusivity was determined for Np(IV) in bentonite material in presence of carbonate and for Pu(IV) in presence of fulvic acid. Adsorption of actinides onto negatively charged mineral surfaces were investigated under conditions that actinides were predominantly present as anionic complex species. The results of this study will reveal behavior of actinides under various geological environments.

Journal Articles

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

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.

Journal Articles

The Suppression effect of natural barrier for the radionuclide migration under the practice environment

Tanaka, Tadao; Mukai, Masayuki; Maeda, Toshikatsu; Matsumoto, Junko; Ogawa, Hiromichi; Munakata, Masahiro; Kimura, Hideo; Bamba, Tsunetaka; Fujine, Sachio

Genshiryoku eye, 49(2), p.76 - 79, 2003/02

no abstracts in English

JAEA Reports

Records on synthesis of neptunium compounds, recovery and reuse of neptunium by professor N. N. KROT

Saeki, Masakatsu

JAERI-Review 2002-040, 23 Pages, 2003/01

JAERI-Review-2002-040.pdf:1.38MB

Professor Krot stayed at Tokai research establishment, Japan Atomic Energy Research Institute for 45 days from Friday on February 28, 1997 to Thursday on January 16, 1997 by an invitation of the Research group for Moessbauer spectroscopy of actinoids, Advanced science research center. In the mean time, Professor Krot left many memoranda on actinoid research for the research group. This is the translated form of those. The contents are various things, that is, “synthesis of neptunium compounds in valence states of 3, 6 and 7", “method for recovery and reuse of neptunium from compounds in a laboratory", “records of the neptunium compounds synthesized during his stay", and so on. Also, the contents of discussions between Professor Krot and mainly the author is summarized in chronological order.

Journal Articles

Effective diffusivity of neptunium and plutonium in granite from Inada, Ibaraki, Japan under anaerobic conditions

Yamaguchi, Tetsuji; Nakayama, Shinichi; Okamoto, Hisato

Radiochimica Acta, 90(12), p.863 - 868, 2003/01

 Times Cited Count:3 Percentile:73.46(Chemistry, Inorganic & Nuclear)

no abstracts in English

Journal Articles

Magnetic properties of some neptunyl(+1) complexes

Nakamoto, Tadahiro*; Nakada, Masami; Nakamura, Akio

Journal of Nuclear Science and Technology, 39(Suppl.3), p.102 - 105, 2002/11

no abstracts in English

Journal Articles

Study on reduction of neptunium and uranium in nitric acid solution using flow type electrolytic cell, as a basic technique for advanced reprocessing process

Asakura, Toshihide; Uchiyama, Gunzo; Hoshi, Harutaka*; Wei, Y.*; Kumagai, Mikio*

Journal of Nuclear Science and Technology, 39(Suppl.3), p.340 - 342, 2002/11

no abstracts in English

JAEA Reports

Development of nondestructive measurement technique in $$alpha$$-waste including neptunium

Kurosawa, Makoto; Ouchi, Shoichi*; Abe, Jiro; Okane, Shogo; Usui, Takeshi

JAERI-Tech 2002-036, 24 Pages, 2002/03

JAERI-Tech-2002-036.pdf:1.0MB

Method for measurement of plutonium in $$alpha$$-waste using passive $$gamma$$ ray has been adopted at Plutonium Fuel Research Facility. Recently, research of neptunium has been started. It is necessary to evaluate the passive $$gamma$$ ray method for measurement of plutonium in $$alpha$$-waste including plutonium and neptunium together. This report describes the results of comparing the two methods, deduction method and division method. The error of deduction method is about 10 to 15% when the quantity of plutonium is larger than 100 mg in the waste. But the error reaches more than 50% when the quantity of plutonium is less than 10 mg and the ratio of plutonium and neptunium is less than one. On the other hand, the error of division method is about a few to 15% when the quantity of plutonium is larger than 100 mg in the waste. The error is about 30 to 50% when the quantity of plutonium is less than 10 mg, but the error is not affected by the ratio of plutonium and neptunium. By reason of this results, the division method is adopted for measurement of plutonium in $$alpha$$-waste including neptunium.

JAEA Reports

Utilization of actinide as cell active materials, JAERI's nuclear research promotion program, H10-034-1 (Contract research)

Shiokawa, Yoshinobu*; Yamamura, Tomoo*; Watanabe, Nobutaka*; Umekita, Satoshi*

JAERI-Tech 2002-017, 50 Pages, 2002/03

JAERI-Tech-2002-017.pdf:2.69MB

no abstracts in English

132 (Records 1-20 displayed on this page)