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Journal Articles

Theoretical calculation of neutron cross sections for $$^{90,91,92,94,96}$$Zr in the incident energy range between 200 keV and 20 MeV

Ichihara, Akira

Journal of Nuclear Science and Technology, 55(9), p.1087 - 1098, 2018/09

 Percentile:100(Nuclear Science & Technology)

Toward the revision of JENDL-4.0, neutron cross sections of $$^{90,91,92,94,96}$$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 $$^{90}$$Zr$$(n,2n)$$$$^{89m}$$Zr, $$^{91}$$Zr$$(n,x)$$$$^{90m}$$Y and $$^{91}$$Zr$$(n,nalpha)$$$$^{87m}$$Sr were well reproduced by the present calculation.

Journal Articles

Evaluation of neutron resonance parameters for Zr isotopes

Ichihara, Akira

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, $$^{93}$$Zr is a long-lived fission product (LLFP) with a half-life of 1.61$$times$$10$$^{6}$$ 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 $$^{93}$$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 Articles

Status of the JENDL project

Iwamoto, Osamu; Shibata, Keiichi; Iwamoto, Nobuyuki; Kunieda, Satoshi; Minato, Futoshi; Ichihara, Akira; Nakayama, Shinsuke

EPJ Web of Conferences (Internet), 146, p.02005_1 - 02005_6, 2017/09

 Percentile:100

Journal Articles

Calculation of cross sections for metastable state production in the $$(n,gamma)$$, $$(n,n')$$, $$(n,2n)$$ and $$(n,3n)$$ reactions of $$^{93}$$Nb

Ichihara, Akira

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

 Times Cited Count:2 Percentile:76.09(Nuclear Science & Technology)

Toward the revision of $$^{93}$$Nb data in JENDL-4.0, we calculated cross sections for metastable state production in the $$(n,gamma)$$, $$(n,n')$$, $$(n,2n)$$ and $$(n,3n)$$ 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 $$^{93}$$Nb$$(n,n')$$$$^{93m}$$Nb cross section was in good agreement with the experiments in the incident energies below 10 MeV, in comparison with JENDL/A-96.

Journal Articles

Evaluation of neutron cross sections of $$^{93}$$Nb in the energy range between 10$$^{-5}$$ eV and 20 MeV

Ichihara, Akira

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 $$^{93}$$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 $$(n,gamma)$$, $$(n,n')$$, $$(n,2n)$$, $$(n,3n)$$, $$(n,alpha)$$ and $$(n,nalpha)$$ without spoiling the cross sections.

Journal Articles

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

 Times Cited Count:9 Percentile:32.2(Optics)

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 $$^{7}$$Li$$^{35}$$CL and $$^{7}$$Li$$^{37}$$Cl to demonstrate the applicability of our method. Nearly 20% of $$^{7}$$Li$$^{37}$$Cl in the lowest rovibrational state is dissociated in the designed pulse fields, while the dissociation probability is negligible in $$^{7}$$Li$$^{35}$$Cl. This method is expected to be applicable to other diatomic molecules, and to molecular ensembles whose rotational states spread in energy.

Journal Articles

Quantum control of isotope-selective rovibrational excitation of diatomic molecules in the thermal distribution

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

Optical Review, 22(1), p.153 - 156, 2015/02

 Times Cited Count:5 Percentile:52.57(Optics)

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.

Journal Articles

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

Isotope-selective dissociation of the lithium chloride (LiCl) molecule was investigated by quantum mechanical calculations. $$^7$$Li$$^{35}$$Cl 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 $$^7$$Li$$^{35}$$Cl. $$^7$$Li$$^{37}$$Cl 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 $$^7$$Li$$^{35}$$Cl was dissociated. The dissociation probability of $$^7$$Li$$^{37}$$Cl was less than 2%t.

Journal Articles

Quantum control of molecular rotational excitation

Ichihara, Akira

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$$^2$$ 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.

JAEA Reports

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage, 2; Progress report on NUMO-JAEA collaborative research in FY2012 (Joint research)

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

JAEA-Research-2013-037.pdf:42.0MB

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.

Journal Articles

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

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.

Journal Articles

Theoretical study on isotope-selective excitation of diatomic molecules by a terahertz frequency comb

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 $$^7$$Li$$^{35}$$Cl molecule was excited selectively in gaseous mixture of $$^7$$Li$$^{35}$$Cl and $$^7$$Li$$^{37}$$Cl by adjusting pulse parameters. Moreover, the wave packet calculations were performed to investigate the dissociation process. More than half of $$^7$$Li$$^{35}$$Cl in the rovibrational state (v=0, J=150) were dissociated by the second pulse.

JAEA Reports

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage; Progress report on NUMO-JAEA collaborative research in FY2011 (Joint research)

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-Research-2012-032.pdf:33.68MB

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.

Journal Articles

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

Journal Articles

Quantum optimal control for the full ensemble of randomly oriented molecules having different field-free Hamiltonians

Kurosaki, Yuzuru; Ichihara, Akira; Yokoyama, Keiichi

Journal of Chemical Physics, 135(5), p.054103_1 - 054103_6, 2011/08

 Times Cited Count:3 Percentile:87.35(Chemistry, Physical)

Journal Articles

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

 Times Cited Count:8 Percentile:42.17(Physics, Multidisciplinary)

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 $$^{235}$$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.

Journal Articles

Evaluation of neutron nuclear data on bromine and krypton isotopes for JENDL-4.0

Shibata, Keiichi; Ichihara, Akira; Kunieda, Satoshi

Journal of Nuclear Science and Technology, 48(3), p.429 - 439, 2011/03

 Times Cited Count:1 Percentile:86.64(Nuclear Science & Technology)

Neutron nuclear data on $$^{79,81}Br$$ and $$^{78,80,82,83,84,85,86}Kr$$ have been evaluated for the evaluated nuclear data library JENDL-4.0 in the energy region from $$rm{10^{-5}}$$ 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.

JAEA Reports

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 $$56 leq A leq 238$$. 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.

Journal Articles

JENDL-4.0; A New library for nuclear science and engineering

Shibata, Keiichi; Iwamoto, Osamu; Nakagawa, Tsuneo*; Iwamoto, Nobuyuki; Ichihara, Akira; Kunieda, Satoshi; Chiba, Satoshi; Furutaka, Kazuyoshi; Otsuka, Naohiko*; Osawa, Takaaki*; et al.

Journal of Nuclear Science and Technology, 48(1), p.1 - 30, 2011/01

 Times Cited Count:851 Percentile:0.01(Nuclear Science & Technology)

The fourth version of Japanese Evaluated Nuclear Data Library has been produced. In the new library, much emphasis is placed on the improvements of fission product and minor actinoid data. Two nuclear model codes were developed to evaluate the cross sections of fission products and minor actinoids. Coupled-channel optical model parameters, which can be applied to wide mass and energy regions, were obtained for nuclear model calculations. Thermal cross sections of actinoids were determined by considering recent experimental data or by the systematics of neighboring nuclei. A simultaneous evaluation was performed for the fission cross sections of important uranium and plutonium isotopes above 10 keV. The data on FP were re-evaluated, and new evaluations were performed for 30 nuclides. The data on light elements and structural materials were partly re-evaluated. The new library was released as JENDL-4.0 in May 2010.

Journal Articles

Calculation of neutron nuclear data on rubidium and strontium isotopes for JENDL-4

Shibata, Keiichi; Ichihara, Akira; Kunieda, Satoshi

Journal of Nuclear Science and Technology, 47(11), p.1055 - 1064, 2010/10

Neutron nuclear data on $$^{85,86,87}$$Rb and $$^{84,86,87,88,89,90}$$Sr have been calculated for the evaluated nuclear data library JENDL-4. Simultaneously calculated are the total, elastic and inelastic scattering, ($$n$$,$$gamma$$), ($$n$$,$$p$$), ($$n$$,$$d$$), ($$n$$,$$t$$), ($$n$$,$$rm{^{3}He}$$), ($$n$$,$$alpha$$), ($$n$$,$$np$$), ($$n$$,$$nd$$), ($$n$$,$$n$$$$alpha$$), ($$n$$,2$$n$$), ($$n$$,3$$n$$) reaction cross sections, the angular distributions of emitted particles, and the energy distributions of emitted particles and $$gamma$$-rays. The statistical model was applied to calculate these quantities. 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 calculations are consistent with available experimental data. The calculated results are compiled into JENDL-4.

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