Numerical reproduction of the seasonal variation in dissolved uranium in Lake Biwa

Saito, Tatsuo; Yamazawa, Hiromi*; Mochizuki, Akihito

Journal of Environmental Radioactivity, 255, p.107035_1 - 107035_14, 2022/12

https://doi.org/10.1016/j.jenvrad.2022.107035

The seasonal variation of dissolved U (DU) in Lake Biwa was reproduced by the following model and parameter research. The introduced models are the water-DU mass balance, and the ion exchange between UO and H on the lakeshore soil. The optimized parameters were the CEC of the lakeshore, TU as the sum of DU and AU (soil adsorbed U), kads and kdes as the first order reaction rate coefficients during rapid soil adsorption and desorption of U, respectively. Tabulated by the chemical equilibria constituting DU and analyzed the contribution of each chemical species, it is shown that the seasonal variation of DU is caused by the seasonal variation of pH. A correction to the ion-exchange equilibrium to shift to first order rate reaction only when the daily AU ratio increased above kads or decreased below kdes, improved the reproducibility of DU measurements and reproduced the delay of the DU peak from the pH peak.

Measurements of thermal-neutron capture cross-section of the Np(n, ) reaction with TC-Pn in KUR

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

KURNS Progress Report 2021, P. 93, 2022/07

https://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2021/ProgRep2021.html

In terms of nuclear transmutation studies of minor actinides in nuclear wastes, the present work selected Np among them and aimed to measure the thermal-neutron capture cross-section of Np using a well-thermalized neutron field by a neutron activation method because there have been discrepancies among reported cross-section data. A Np standard solution was used for irradiation samples. The thermal-neutron flux at an irradiation position was measured with flux monitors: Sc, Co, Mo, Ta and Au. The Np sample was irradiated together with the flux monitors for 30 minutes in the graphite thermal column equipped in the Kyoto University Research Reactor. The similar irradiation was repeated once more to confirm the reproducibility of the results. After irradiation, the Np samples were quantified using 312-keV gamma-ray emitted from Pa in radiation equilibrium with Np. The reaction rates of Np were obtained from the peak net counts of gamma-rays emitted from generated Np, and then the thermal-neutron capture cross-section of Np was found to be 173.84.7 barn by averaging the results obtained by the two irradiations. The present result was in agreement with the reported data given by a time-of-flight method within a limit of uncertainty.

Thermodynamic equilibrium constants for important isosaccharinate reactions; A Review

Rai, D.*; Kitamura, Akira

Journal of Chemical Thermodynamics, 114, p.135 - 143, 2017/11

https://doi.org/10.1016/j.jct.2017.02.012

Isosaccharinic acid is a cellulose degradation product that can form in low-level nuclear waste repositories and is known to form strong complexes with many elements, including actinides, disposed of in these repositories. We (1) reviewed the available data for deprotonation and lactonisation constants of isosaccharinic acid, and the isosaccharinate binding constants for Ca, Fe(III), Th, U(IV), U(VI), Np(IV), Pu(IV), and Am(III), (2) summarized complexation constant values for predicting actinide behavior in geologic repositories in the presence of isosaccharinate, and (3) outlined additional studies to acquire reliable thermodynamic data where the available data are inadequate.

Equilibrium and non-equilibrium charge-state distributions of 2.0 MeV/u carbon ions passing through carbon foils

Imai, Makoto*; Sataka, Masao*; Matsuda, Makoto; Okayasu, Satoru; Kawatsura, Kiyoshi*; Takahiro, Katsumi*; Komaki, Kenichiro*; Shibata, Hiromi*; Nishio, Katsuhisa

Nuclear Instruments and Methods in Physics Research B, 354, p.172 - 176, 2015/07

https://doi.org/10.1016/j.nimb.2014.12.045

Both equilibrium and non-equilibrium charge-state distributions were studied experimentally for 2.0 MeV/u carbon ions after passing through carbon foils. Measured charge-state distribution established the equilibrium at a target thickness of 10 g/cm and this remained unchanged until a maximum target thickness of 98 g/cm. The equilibrium charge-state distribution, the equilibrium mean charge-state, and the width and skewness of the equilibrium distribution were compared with predictions using existing semi-empirical formulae as well as simulation results, including the ETACHA code. It was found that charge-state distributions, mean charge states, and distribution widths for C, C, and C incident ions merged into quasi-equilibrium values at a target thickness of 5.7 g/cm in the pre-equilibrium region and evolved simultaneously to the "real equilibrium" values for all of the initial charge states, including C and C ions. Two kinds of simulation, ETACHA and solution of rate equations taking only single electron transfers into account, were used, and both of them reproduced the measured charge evolution qualitatively. The quasi-equilibrium behavior could be reproduced with the ETACHA code, but not with solution of elementary rate equations.

Investigations of relativistic laser plasma from micron-sized Ar clusters

Fukuda, Yuji; Yamakawa, Koichi

Progress in Ultrafast Intense Laser Science II, p.231 - 251, 2007/00

To better understand a fundamental aspect of the laser cluster interaction, we have carried out systematic investigations of X-ray radiation properties of high-density and high-temperature cluster plasma, created by the action of superintense laser irradiation. The interrelationship between the X-ray radiation properties and ion kinetic energies has been for the first time examined by the simultaneous measurements of X-ray radiation spectra and ion energy spectra. Time scale and mechanism of X-ray emission process have been discussed based on a time-dependent plasma kinetics model. Moreover, in order to demonstrate the practical capability of X-rays thus produced, the pulse X-ray diffraction has been examined from Si crystal with this source.

Variation of current profiles in tokamaks; Formation mechanism and confinement property of current-hole configuration

Takizuka, Tomonori

Purazuma, Kaku Yugo Gakkai-Shi, 79(11), p.1123 - 1129, 2003/11

https://doi.org/10.1585/jspf.79.1123

no abstracts in English

Thick target benchmark test for the code used in the design of high intensity proton accelerator project

Meigo, Shinichiro; Harada, Masahide; Takada, Hiroshi

Proceedings of ICANS-XVI, Volume 3, p.1059 - 1067, 2003/07

In the neutronics design for the J-PARC facilities, transport codes of NMTC/JAM, MCNPX and MARS are used. In order to confirm the predict ability for these codes, it is important to compare with the experiment result. For the validation of the source term of neutron, the calculations are compared with the experimental spectrum of neutrons produced from thick target. Although slightly disagreement exists, NMTC/JAM, MCNPX and MARS are in good agreement with the experiment within by a factor of 2.

Nuclear data evaluation for Np, Am, Am and Am irradiated by neutrons and protons at energies up to 250 MeV

Konobeyev, A. Y.; Fukahori, Tokio; Iwamoto, Osamu

JAERI-Research 2002-032, 36 Pages, 2002/12

JAERI-Research-2002-032.pdf:1.33MB

The evaluation of nuclear data has been performed for Np, Am, Am and . Neutron data were obtained at the energies from 20 to 250 MeV and combined with JENDL-3.3 data at 20 MeV. Evaluation of the proton data has been done from 1 to 250 MeV. The coupled channel optical model was used to obtain angular distributions for elastic and inelastic scattering and transmission coefficients. Pre-equilibrium exciton model and Hauser-Feshbach statistical model were used to describe neutron and charged particles emission from the excited nuclei. These evaluation is the first work for producing the full set of evaluated file up to 250 MeV for Np and americium isotopes.

Axisymmetric tri-magnetic-islands equilibrium of strongly-reversed-shear tokamak plasma; An Idea for the current hole

Takizuka, Tomonori

Purazuma, Kaku Yugo Gakkai-Shi, 78(12), p.1282 - 1284, 2002/12

http://ci.nii.ac.jp/naid/130000133603

An idea of a new equilibrium of a strongly-reversed-shear tokamak plasma with a current hole is proposed. This equilibrium configuration called "Axisymmetric Tri-Magnetic-Islands (ATMI) equilibrium" has three islands, a central-negative-current island and side-positive-current islands, along the R direction and two x-points along the Z direction. The equilibrium is stable with the elongation coils when the current in the ATMI region is limited small.

Development and performance of high speed processing system of magnetohydrodynamic equilibria for discharge analyses on the JT-60 tokamak

Hasegawa, Yukihiro*; Nakamura, Yukiharu; Shirai, Hiroshi; Hamamatsu, Kiyotaka; Harada, Hiro; Kikuchi, Mitsuru; *

Nihon Genshiryoku Gakkai-Shi, 41(1), p.48 - 56, 1999/00

https://doi.org/10.3327/jaesj.41.48

no abstracts in English