• Nuclear Engineering and Technology
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• v.42 no.5
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• pp.552-561
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• 2010

This study investigates the solubility of neptunium (Np) in the deep natural groundwater of the Korea Atomic Energy Research Institute Underground Research Tunnel (KURT). According to a Pourbaix diagram (pH-$E_h$ diagram) that was calculated using the geochemical modeling program PHREEQC 2.0, the redox potential and the carbonate ion concentration both control the solubility of neptunium. The carbonate effect becomes pronounced when the total carbonate concentration is higher than $1.5\;{\times}\;10^{-2}$ M at $E_h$ = -200 mV and the pH value is 10. Given the assumption that the solubility-limiting stable solid phase is $Np(OH)_4(am)$ under the reducing condition relevant to KURT, the soluble neptunium concentrations were in the range of $1\;{\times}\;10^{-9}$ M to $3\;{\times}\;10^{-9}$ M under natural groundwater conditions. However, the solubility of neptunium, which was calculated with the formation constants of neptunium complexes selected in an OECD-NEA TDB review, strongly deviates from the value measured in natural groundwater. Thus, it is highly recommended that a prediction of neptunium solubility is based on the formation constants of ternary Np(IV) hydroxo-carbonato complexes, even though the presence of those complexes is deficient in terms of the characterization of neptunium species. Based on a comparison of the measurements and calculations of geochemical modeling, the formation constants for the "upper limit" of the Np(IV) hydroxo-carbonato complexes, namely $Np(OH)_y(CO_3)_z^{4-y-2z}$, were appraised as follows: log $K^{\circ}_{122}\;=\;-3.0{\pm}0.5$ for $Np(OH)_2(CO_3)_2^{2-}$, log $K^{\circ}_{131}\;=\;-5.0{\pm}0.5$ for $Np(OH)_3(CO_3)^-$, and log $K^{\circ}_{141}\;=\;-6.0{\pm}0.5$ for $Np(OH)_4(CO_3)^{2-}$.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.307-307
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• 1999

• Journal of the Korean Society of Radiology
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• v.5 no.4
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• pp.217-221
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• 2011

$^{237}Np$ is very important material in the fission products of nuclear reactors. Resonance integral(RI) tests of this material is necessary to check between the experiments and the evaluated data. Such feedback to the evaluated data is very important to correct data and improve of codes. The RI for the $^{237}Np(n,{\gamma})^{238}Np$ reaction were measured by using the 46-MeV electron linear accelerator (linac) at the Research Reactor Institute, Kyoto University (KURRI). The measurement was performed in the energy region from 0.005 eV and 10 keV. RI obtained as 804.7 barns, compared with those of the evaluated data in JENDL-4.0 and Mughabghab.

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.475-478
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• 2008

• Nuclear Engineering and Technology
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• v.13 no.3
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• pp.139-144
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• 1981

Plutionum, neptunium, and uranium isotopes which were produced in the interaction of $^{136}$ Xe and $^{244}$ Pu are separated and determined their cross sections. The cross sections are: $\sigma$($^{245}$ Pu)=66 mb, $\sigma$($^{243}$ Pu)=57 mb, $\sigma$($^{246}$ Pu)=6.0 mb, $\sigma$($^{239}$ Np)=15 mb, $\sigma$($^{240}$ U)=12 mb, $\sigma$($^{245}$ U)=6.4 mb respectively.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.317-317
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• 2002

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.342.1-342
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• 2002

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2011.10a
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• pp.109-110
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• 2011

• Bulletin of the Korean Chemical Society
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• v.26 no.11
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• pp.1692-1694
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• 2005

Spent nuclear fuel is reprocessed commercially by the chemical process to recover U and Pu. Recently, new salt-free reagents to separate plutonium and neptunium from uranium suitable for use in a single cycle flowsheet have been developed. Acetohydroxamic acid $(CH_3CONHOH)$ has been taken much interest in as a complexing agent capable of selective stripping of tetravalent actinides from U(VI) when actinides are present in the solvent stream of the advanced PUREX process. Additionally acetohydroxamic acid will rapidly reduce Np(VI) to inextractable Np(V) thus allowing the separation of Np from U. In this study, the rate equation for the reduction of Np(VI) to Np(V) in nitric acid aqueous solution has been determined as: $-[NpO_2^{2+}]$/dt = $k[NpO_2^{2+}]$[AHA] with k = 191.2 ${\pm}$ 11.2 $M^{-1}s^{-1}$ at 25 ${\pm}$ 0.5 ${^{\circ}C}$ and $[HNO_3]$ = 1.0 M. Comparison with other reductants available in the literature, acetohydroxamic acid is a strong one for $NpO_2^{2+}$.

• Economic and Environmental Geology
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• v.24 no.3
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• pp.227-232
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• 1991

Since "Gyeonsang Formation" has been introduced 90 years ago by B.Koto(1903), it was newly found within the lower Chomgog Formation ore mineralized zone. The mineralized zone occurs along the stratigraphic unit there. The ore minerals are mainly composed of hematite, ilmenite and magnetite. The molybdenum (2.100-3.100ppm?), copper and zinc are the accessories. There are also traces of cadmium, gadolinium, neptunium, ruthenium and tin. The ore mineralized zone shows about 1 km of apparent thickness with 10 to 12 degrees of plunging on the surface and extends 12 km along its strike in the U-Bo sheet(Chwae et al., 1990). The mineralized zone could be valuable to correlate the stratigraphic sequence between the Uisong and Mirryang subbasins, if giving consideration of the Palgongsan lineament (Chang, 1975).