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Nakamura, Shoji; Endo, Shunsuke; Kimura, Atsushi; Shibahara, Yuji*
KURNS Progress Report 2020, P. 94, 2021/08
The present study selected Np among radioactive nuclides and aimed to converge a contradiction between reported thermal-neutron capture cross sections. Neutron irradiation was carried out using the graphite thermal column equipped with the Kyoto University Research Reactor. A solution equivalent to 950 Bq order of radioactivity was pipetted out of a Np standard solution and dropped onto a fiber filter, which was then dried with an infrared lamp to prepare a Np sample. The Np sample was quantified using 312-keV gamma ray emitted from Pa in a radiation equilibrium with Np. To monitor a thermal-neutron flux component at an irradiation position, the Np sample was irradiated together with several stable nuclides as neutron flux monitors: Sc, Co, Mo, Ta and Au. The reaction rate of Np was obtained from gamma-ray yields given by Np and Pa, and then the thermal-neutron capture cross section of Np was derived.
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
Times Cited Count:5 Percentile:25.26(Materials Science, Multidisciplinary)We report a study of the magnetic and electronic properties of the UNpO solid solution, based on dc- and ac- magnetisation, Np Mssbauer spectroscopy, O Nuclear Magnetic Resonance (NMR), and specific heat measurements. The compound orders antiferromagnetically at T = 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 and NpO, as well as to the other solid solutions previously reported in this system. We discuss how the properties of UNpO add new input to the trend previously reported for the series, in view of the models that have been previously proposed.
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:9 Percentile:31.99(Chemistry, Multidisciplinary)The extraction properties of -di(2-ethylhexyl)-2,2-dimethylpropanamide (DEHDMPA) and -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.
Fujii, Toshiyuki*; Uehara, Akihiro*; Kitatsuji, Yoshihiro; Yamana, Hajimu*
Journal of Radioanalytical and Nuclear Chemistry, 303(1), p.1015 - 1020, 2015/01
Times Cited Count:6 Percentile:45.29(Chemistry, Analytical)The symmetric vibrational frequency of UO in chloride solutions was studied by Raman spectrometry and ab initio calculations. The 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 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 frequencies of neptunyl species computed were acceptable compared with the reported Raman shifts.
Kato, Chiaki; Motooka, Takafumi; Numata, Masami; Endo, Shinya; Yamamoto, Masahiro
Structural Materials for Innovative Nuclear Systems (SMINS), p.439 - 447, 2008/07
Corrosion of a nuclear fuel reprocessing plant is also important problem in either current or an advanced nuclear fuel reprocessing system. In this process, nitric acid solution is used to dissolve spent nuclear fuels and solvent extraction method is used to separate U, Pu and actinoid elements. It will be much severer corrosive environment. In this paper, an effect of neptunium ions on corrosion of ultra low carbon Type 304 stainless steel was investigated. The corrosion tests were conducted in 9 kmol/m nitric acid solution adding neptunium ions. The results show that neptunium ions promote inter-grainier corrosion of SUS304ULC in nitric acid solution and corrosion rate in heat-transfer condition is larger than that in immersed condition. It is estimated that the oxidise potential of nitric ions increases under heat-transfer condition more than immersion condition in boiling solution. Furthermore, the effect of -ray irradiation used Co is examined. -ray irradiation decreases corrosion rates and the reason is discussed.
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
Aoyagi, Hisao*; Kitatsuji, Yoshihiro; Yoshida, Zenko; Kihara, Sorin*
Analytica Chimica Acta, 538(1-2), p.283 - 289, 2005/05
Times Cited Count:15 Percentile:41.49(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 solution as an example.
Saeki, Masakatsu
Nihon Kessho Gakkai-Shi, 46(6), p.415 - 420, 2004/12
no abstracts in English
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
Saeki, Masakatsu
JAERI-Review 2004-011, 54 Pages, 2004/03
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.
Saeki, Masakatsu
Dai-5-Han Jikken Kagaku Koza 22; Kinzoku Sakutai, Seni Kinzoku Kurasuta, p.200 - 209, 2004/03
no abstracts in English
Saeki, Masakatsu; Nakada, Masami; Kitazawa, Takafumi*
KURRI-KR-106, p.38 - 42, 2004/03
no abstracts in English
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.
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.
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.
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
Saeki, Masakatsu
JAERI-Review 2002-040, 23 Pages, 2003/01
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.
Yamaguchi, Tetsuji; Nakayama, Shinichi; Okamoto, Hisato
Radiochimica Acta, 90(12), p.863 - 868, 2003/01
Times Cited Count:4 Percentile:29(Chemistry, Inorganic & Nuclear)no abstracts in English
Nakamoto, Tadahiro*; Nakada, Masami; Nakamura, Akio
Journal of Nuclear Science and Technology, 39(Suppl.3), p.102 - 105, 2002/11
no abstracts in English
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