Thermal-neutron capture cross-section measurement of Np using graphite thermal column

Nakamura, Shoji; Endo, Shunsuke; Kimura, Atsushi; Shibahara, Yuji*

KURNS Progress Report 2020, P. 94, 2021/08

https://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2020/ProgRep2020.html

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.

Distribution behavior of neptunium by extraction with -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

https://doi.org/10.1080/07366299.2015.1130423

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.

Effect of neptunium ions on corrosion of ultra low carbon type 304 stainless steel in nitric acid solution

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.

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

https://doi.org/10.1016/j.aca.2005.02.035

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.

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

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

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.

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.

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.

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

http://www.tandfonline.com/doi/abs/10.1080/00223131.2002.10875418

no abstracts in English