Ichihara, Akira; Abe, Yutaka*
JAEA-Conf 2022-001, p.175 - 180, 2022/11
Thermal neutron scattering law data were calculated for the heavy water molecule toward the fifth version of the Japanese evaluated nuclear data library, JENDL-5. The scattering laws for deuterium and oxygen atoms were computed using the molecular dynamics simulations. The simulations have been performed in the temperature range from 283.6 K to 600 K. The scattering law data have been evaluated in the neutron incident energies between 0.01 meV and 10 eV. With the obtained scattering laws, we calculated the cross sections for the heavy water molecule, and confirmed that the experimental data at room temperature were well reproduced. Moreover, in the computed temperature range, the cross sections were almost consistent with the ENDF/B-VIII.0 evaluations.
JAEA-Review 2019-046, 36 Pages, 2020/03
Toward the revision of JENDL-4.0, we conducted a literature survey on how to compute the cross section of thermal neutrons scattered by a liquid. This report summarizes the computational methods for evaluating thermal neutron cross sections with molecular dynamics simulations. The cross section can be expressed with a function called as scattering law. For light and heavy water, the scattering law data instead of the cross sections have been provided in nuclear databases. In this report we review the formulations of the scattering laws. The scattering laws can be derived from both the intermediate scattering function and the space-time correlation function. Features of the derived scattering laws are briefly explained. It is shown that the scattering law data can be evaluated using a molecular dynamics simulation of the liquid that is the target of thermal neutrons.
Journal of Nuclear Science and Technology, 55(9), p.1087 - 1098, 2018/09
Toward the revision of JENDL-4.0, neutron cross sections of Zr were calculated in the energy range between 200 keV and 20 MeV. The calculation was carried out by using nuclear reaction models such as the spherical optical model, the distorted wave Born approximation, preequilibrium models, and the multi-step statistical model. The obtained results were almost consistent with the experimental data. The cross sections were also estimated for the metastable states which had not been considered in the JENDL-4.0 evaluation. The experimental cross sections for the reactions ZrZr, ZrY and ZrSr were well reproduced by the present calculation.
JAEA-Conf 2017-001, p.103 - 108, 2018/01
In the Nuclear Data Center of Japan Atomic Energy Agency (JAEA-NDC), we are engaged in the evaluation activity for the next version of the Japanese Evaluated Nuclear Data Library, JENDL-4.0. Zirconium is an important structural material in nuclear reactors, and zircaloys are being employed in fuel rods. Also, Zr is a long-lived fission product (LLFP) with a half-life of 1.6110 years. At present we are investigating resonance parameters of Zr isotopes using experimental data published after the evaluation of JENDL-4.0. Through this work, a negative resonance of Zr in JENDL-4.0 was removed to reproduce the J-PARC/MLF/ANRRI experiment. The resonance parameters for other natural Zr isotopes will be altered by adopting the data obtained at CERN n-TOF experiments.
Journal of Nuclear Science and Technology, 53(12), p.2049 - 2055, 2016/12
Toward the revision of Nb data in JENDL-4.0, we calculated cross sections for metastable state production in the , , and reactions in the incident energy range from 7 keV to 20 MeV. The cross sections were computed on the basis of nuclear reaction models (the spherical optical model, the multi-step statistical model, preequilibrium models, and the distorted-wave Born approximation). By adjusting the parameters in nuclear spin densities and the number of discrete states, we could obtain the metastable state production cross sections which were almost consistent with the measured data. The obtained NbNb cross section was in good agreement with the experiments in the incident energies below 10 MeV, in comparison with JENDL/A-96.
JAEA-Conf 2016-004, p.141 - 146, 2016/09
This year we started a new activity for the next version of Japanese evaluated nuclear data library, JENDL-4.0. The next JENDL is planned to contribute to the transmutation of nuclear wastes. The evaluation activity will be focused on structural materials in the nuclear power plants, and the isomer production data will be supplemented to the library. In this work, we re-evaluated the nuclear data of Nb. We altered the resolved resonance parameters in the energy range between 2.6 and 7.0 keV. The agreement with experimental data was slightly improved in the average capture cross section. Cross sections above the RR region were re-calculated using the comprehensive nuclear data evaluation code CCONE. We adjusted the spin cutoff parameters of level densities to reproduce the measured isomer production ratios in the reactions , , , , and without spoiling the cross sections.
Ichihara, Akira; Matsuoka, Leo*; Segawa, Etsuo*; Yokoyama, Keiichi
Physical Review A, 91(4), p.043404_1 - 043404_7, 2015/04
We propose a new method for isotope-selective dissociation of diatomic molecules in the gas phase by using two kinds of terahertz-pulse fields. The first field consists of a train of pulses, which composes a frequency comb, excites the selected isotope into highly-rotationally excited state. The second intense pulse field dissociates the excited molecule by further rotational excitations. We performed wave-packet computations using the lithium chlorides LiCL and LiCl to demonstrate the applicability of our method. Nearly 20% of LiCl in the lowest rovibrational state is dissociated in the designed pulse fields, while the dissociation probability is negligible in LiCl. This method is expected to be applicable to other diatomic molecules, and to molecular ensembles whose rotational states spread in energy.
Ichihara, Akira; Matsuoka, Leo*; Kurosaki, Yuzuru; Yokoyama, Keiichi
Optical Review, 22(1), p.153 - 156, 2015/02
We propose a method to excite the rovibrational states of diatomic molecules in the gas-phase isotope-selectively by optical pulses. In this method, the rotational state of the selected isotope molecule is excited by the terahertz frequency comb, and the vibrational state of high J molecule is excited via the fundamental transitions in the P-branch by using the second pulse. The applicability of the proposed method is demonstrated by computer simulations using the LiCl molecules in the thermal distribution at 70 K.
Ichihara, Akira; Matsuoka, Leo; Kurosaki, Yuzuru; Yokoyama, Keiichi
JPS Conference Proceedings (Internet), 1, p.013093_1 - 013093_4, 2014/03
Isotope-selective dissociation of the lithium chloride (LiCl) molecule was investigated by quantum mechanical calculations. LiCl in the initial rovibrational state (v=0,J=0) was excited by an optical frequency comb whose spectral frequencies were tuned to the rotational transition frequencies of LiCl. LiCl was not highly excited by the comb because of the difference of the transition frequencies. The time evolution of rovibrational population was evaluated using the close-coupling method during the comb irradiation. The dissociation process in the second pulse was calculated by the wave packet method. The amplitudes of close-coupling were employed as the input of the wave packet computation. The dissociation probability was estimated by absorbing wave packet using a damping function. By the optical pulses adopted, about 60% of LiCl was dissociated. The dissociation probability of LiCl was less than 2%t.
Shototsu, 11(1), P. 5, 2014/01
With the recent progress of developments of laser devices, pulses with the intensity higher than 100 MeV/cm have been generated in the THz region. As an application of the THz pulses, there is rotational excitation of a diatomic molecule by a frequency comb. This article mentions the excitation process briefly. First, interaction between the molecule and the laser field is introduced. The frequency comb is given in a form of a periodic delta function. Then we explain that the molecule can be excited into a high rotational state by tuning spectral frequencies of the comb to rotational transition frequency of the molecule. Finally, the computational result for the LiCl molecule is given in order to demonstrate the rotational excitation process induced by the frequency comb.
Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Hayano, Akira; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Oda, Chie; Kitamura, Akira; Osawa, Hideaki; et al.
JAEA-Research 2013-037, 455 Pages, 2013/12
Following FY2011, JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, the tree diagram of methodology of groundwater travel time has been extended for crystalline rock, in addition, tree diagram for sedimentary rock newly has been organized. With regard to (2) study on scenario development, the existing approach has been improved in terms of a practical task, and applied and tested for near field focusing on the buffer. In addition, the uncertainty of some important processes and its impact on safety functions are discussed though analysis. With regard to (3) study on setting radionuclide migration parameters, the approaches for parameter setting have been developed for sorption for rocks and solubility, and applied and tested through parameter setting exercises for key radionuclides.
Ichihara, Akira; Matsuoka, Leo*; Kurosaki, Yuzuru; Yokoyama, Keiichi
Chinese Journal of Physics, 51(6), p.1230 - 1240, 2013/12
We derived an analytic expression for evaluating the transient rotational dynamics of diatomic molecules in an optical frequency comb which is tuned to induce a series of pure rotational transitions. The formulation is based on the quantum delta-kicked rotor model, and the orthogonality of delta functions at different time is assumed. The formulation is performed with the matrix decomposition technique. We derived the probability amplitude composed of term corresponding to a Bessel function of the first kind and other oscillating terms. The time dependence of obtained transition probability is shown as a staircase function.
Ichihara, Akira; Matsuoka, Leo; Kurosaki, Yuzuru; Yokoyama, Keiichi
Proceedings of 10th Conference on Lasers and Electro-Optics Pacific Rim and 18th OptoElectronics and Communications Conference and Photonics in Switching 2013 (CLEO-PR & OECC/PS 2013) (USB Flash Drive), 2 Pages, 2013/06
Computer simulations were performed for studying isotope-selective excitation of lithium chloride using a terahertz frequency comb. The time evolution of rovibrational population was calculated by the close-coupling method. The LiCl molecule was excited selectively in gaseous mixture of LiCl and LiCl by adjusting pulse parameters. Moreover, the wave packet calculations were performed to investigate the dissociation process. More than half of LiCl in the rovibrational state (v=0, J=150) were dissociated by the second pulse.
Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Hayano, Akira; Mitsui, Seiichiro; Taniguchi, Naoki; Oda, Chie; Kitamura, Akira; Osawa, Hideaki; et al.
JAEA-Research 2012-032, 298 Pages, 2012/09
JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation phase. The topics and the conducted research are follows; (1) Study on selection of host rock: in terms of hydraulic properties, items for assessing rock property, and assessment methodology of groundwater travel time has been organized with interaction from site investigation. (2) Study on development of scenario: the existing approach has been embodied, in addition, the phenomenological understanding regarding dissolution of and nuclide release from vitrified waste, corrosion of the overpack, long-term performance of the buffer are summarized. (3) Study on setting nuclide migration parameters: the approach for parameter setting has been improved for sorption and diffusion coefficient of buffer/rock, and applied and tested for parameter setting of key radionuclides. (4) Study on ensuring quality of knowledge: framework for ensuring quality of knowledge has been studied and examined aimed at the likely disposal facility condition.
Matsuoka, Leo; Ichihara, Akira; Hashimoto, Masashi; Yokoyama, Keiichi
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 7 Pages, 2011/12
Kurosaki, Yuzuru; Ichihara, Akira; Yokoyama, Keiichi
Journal of Chemical Physics, 135(5), p.054103_1 - 054103_6, 2011/08
Shibata, Keiichi; Iwamoto, Osamu; Nakagawa, Tsuneo; Iwamoto, Nobuyuki; Ichihara, Akira; Kunieda, Satoshi; Chiba, Satoshi; Katakura, Junichi; Otsuka, Naohiko*
Journal of the Korean Physical Society, 59(2), p.1046 - 1051, 2011/08
In JENDL-4, much emphasis is placed on the improvements of FP and MA data. For achieving this, new nuclear model codes POD and CCONE were developed, since experimental data are very scarce for those nuclei. The global coupled-channel optical model parameters, which were obtained in the wide mass region, were used for the evaluation of cross sections. Thermal cross sections of actinides were determined by carefully examining available experimental data. Special care was taken for the resonance region of U in order to reproduce measured criticalities and Na-void reactivities for U fueled fast-neutron cores. As for FP, resolved resonance parameters were updated for more than 100 nuclei. The cross sections of above the resonance region were evaluated by using the POD and CCONE codes. Fission product yield data were obtained from the ENDF/B-VII.0 data with some modifications. The new library, which contains neutron data for 406 nuclei, will be made available in 2010.
Shibata, Keiichi; Ichihara, Akira; Kunieda, Satoshi
Journal of Nuclear Science and Technology, 48(3), p.429 - 439, 2011/03
Neutron nuclear data on and have been evaluated for the evaluated nuclear data library JENDL-4.0 in the energy region from eV to 20 MeV. The resolved resonance parameters were adjusted so as to reproduce the recommended or measured thermal capture cross sections for some isotopes. The statistical model was applied to calculate the cross sections above the resolved resonance region. In the calculations, coupled-channel optical model parameters were used for neutrons. Preequilibrium and direct-reaction processes were taken into account in addition to the compound process. The present evaluation is consistent with available experimental data. The evaluated results were compiled into JENDL-4.0.