Theoretical evaluation of neutron thermal scattering laws of heavy water for JENDL-5

Ichihara, Akira; Abe, Yutaka*

JAEA-Conf 2022-001, p.175 - 180, 2022/11

https://doi.org/10.11484/jaea-conf-2022-001

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.

Survey of computational methods of cross sections for thermal neutron scattering by liquids

Ichihara, Akira

JAEA-Review 2019-046, 36 Pages, 2020/03

JAEA-Review-2019-046.pdf:1.55MB

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.

Evaluation of neutron resonance parameters for Zr isotopes

Ichihara, Akira

JAEA-Conf 2017-001, p.103 - 108, 2018/01

https://doi.org/10.11484/jaea-conf-2017-001

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.

Calculation of cross sections for metastable state production in the , , and reactions of Nb

Ichihara, Akira

Journal of Nuclear Science and Technology, 53(12), p.2049 - 2055, 2016/12

https://doi.org/10.1080/00223131.2016.1192005

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.

Isotope-selective dissociation of diatomic molecules by terahertz optical pulses

Ichihara, Akira; Matsuoka, Leo*; Segawa, Etsuo*; Yokoyama, Keiichi

Physical Review A, 91(4), p.043404_1 - 043404_7, 2015/04

https://doi.org/10.1103/PhysRevA.91.043404

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.

Theoretical study on isotope-selective dissociation of the lithium chloride molecule using a designed terahertz-wave field

Ichihara, Akira; Matsuoka, Leo; Kurosaki, Yuzuru; Yokoyama, Keiichi

JPS Conference Proceedings (Internet), 1, p.013093_1 - 013093_4, 2014/03

https://doi.org/10.7566/JPSCP.1.013093

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.

An Analytic formula for describing the transient rotational dynamics of diatomic molecules in an optical frequency comb

Ichihara, Akira; Matsuoka, Leo*; Kurosaki, Yuzuru; Yokoyama, Keiichi

Chinese Journal of Physics, 51(6), p.1230 - 1240, 2013/12

https://doi.org/10.6122/CJP.51.1230

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.

Theoretical study for laser isotope separation of heavy-element molecules in a thermal distribution

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

JENDL-4.0; A New library for innovative nuclear energy systems

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

https://doi.org/10.3938/jkps.59.1046

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.

Deduced soft-rotator model Hamiltonian parameters and collective properties of medium-to-heavy even-even nuclei

Kunieda, Satoshi; Chiba, Satoshi; Shibata, Keiichi; Ichihara, Akira; Iwamoto, Osamu; Iwamoto, Nobuyuki; Fukahori, Tokio; Sukhovitskij, E.*

JAEA-Research 2010-053, 59 Pages, 2011/02

JAEA-Research-2010-053.pdf:1.24MB

The soft-rotator model Hamiltonian parameters were deduced for 63 even-even medium and heavy nuclei in a mass range . We obtained those values by the combination of the low-lying level structure and the coupled-channels proton scattering analyses. It was found that the values of the effective quadrupole and octupole deformations obtained were consistent with those derived from experimental data. Besides, the equilibrium ground-state quadrupole deformation parameters were also in reasonable accord with the theoretical mass-models results for deformed heavy nuclei. In this report, we present a complete set of the Hamiltonian parameters for each nucleus. The obtained values of the parameters often varied with the constituent neutron and/or proton numbers anomalously. On the other hand, some clear systematic trends were seen among the major Hamiltonian parameters.