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Journal Articles

Systematics and uncertainties of Hamiltonian parameters of soft-rotator model for actinides and their implications for nuclear data calculations

Chiba, Satoshi; Koura, Hiroyuki; Maruyama, Toshiki; Kunieda, Satoshi; Soukhovitskij, E. Sh.*

Proceedings of International Conference on Nuclear Data for Science and Technology (ND 2007), Vol.1, p.305 - 308, 2008/06

 Times Cited Count:0 Percentile:100

A coupled-channel (CC) method based on the soft-rotator model (SRM) wave functions, SRM-CC, has been recognized as a powerful tool to calculate, estimate and evaluate the nucleon-induced cross sections. It is because that this method can take account of the information from the nuclear structure and reaction studies simultaneously. For example, the coupling strengths required in the coupled-channel calculation is determined from analyses of low-lying collective level structure of target nuclei. However, nobody has looked into so far how the uncertainties of the SRM parameters affects the calculated cross section data. In this work, collective level structure of 19 even-even actinide nuclei are analyzed in terms of the soft-rotator model (SRM). Hamiltonian parameters of SRM to describe the low-lying level scheme and their uncertainties are obtained. Systematic trends are found for major Hamiltonian parameters as a function of ground-state quadrupole deformation which are important to estimate low-lying level structure of other e-e nuclei for which level structure is unknown or only partly known. Then, those parameters and their uncertainties are used to calculate neutron cross sections and their covariance of actinides in terms of SRM-CC. Furthermore, effects of side-band coupling is investigated. Especially, effects of coupling are noticeable for low-energy observables, e.g., strength functions. Such saturated calculations are not possible in RRM (rigid rotor model)-CC approach, making SRM-CC an effective method for investigations of reaction mechanisms and nuclear data evaluation.

Journal Articles

Accelerator-based facility design in association with nuclear data

Takada, Hiroshi

Proceedings of International Conference on Nuclear Data for Science and Technology (ND 2007), Vol.1, p.23 - 28, 2008/05

In the design study of a large accelerator facility using high energy and high intensity beam accelerator as examples of J-PARC and SNS, it is required to seek the best neutronic performance and assure engineering feasibilities such as heat removal from the target and its surroundings, capability on installation and assembling, material selection to have enough life-time under radiation environment for reasonable operation duration. It is also important to design sophisticated maintenance scheme to treat highly activated components, and optimal radiation shield around accelerator components and secondary beam lines. High energy nuclear data file and accumulation of new experimental data are indispensable to improve or to know the prediction accuracy of neutronics design by a computer simulation using a model independent of the nuclear data. In this paper, roles of nuclear data in design of accelerator facilities is presented.

Journal Articles

Problem on unresolved resonance data in recent nuclear data libraries

Konno, Chikara; Nakagawa, Tsuneo; Ochiai, Kentaro; Sato, Satoshi; Yamauchi, Michinori

Proceedings of International Conference on Nuclear Data for Science and Technology (ND 2007), Vol.1, p.713 - 716, 2008/05

A leakage neutron spectrum from a niobium sphere of 0.5 m in radius with a 20 MeV neutron in the center, which was calculated with ANISN, MCNP and JENDL-3.3, had a large strange bump around 100 keV, which originated from the unresolved resonance data. We checked cross section data of (n,$$gamma$$) reaction and elastic scattering in $$^{93}$$Nb with and without self-shielding correction by using a multigroup library of JENDL-3.3. The self-shielding correction of the unresolved resonances seems to be too large even around the upper energy of the unresolved resonance region. It is considered that the average reduced neutron widths or the upper energy of the unresolved resonance region in $$^{93}$$Nb have any problems. It is found out that many nuclei with unresolved resonance data in JENDL-3.3 and ENDF/B-VI have the similar problem. The unresolved resonance data in JENDL-3.3 and ENDF/B-VI should be revised by considering self-shielding correction in the next version.

Journal Articles

Experimental study on breakup reaction of beryllium and carbon induced with 14-MeV neutrons based on emitted charged-particle measurements

Kondo, Keitaro; Murata, Isao*; Ochiai, Kentaro; Miyamaru, Hiroyuki*; Kubota, Naoyoshi*; Konno, Chikara; Nishitani, Takeo

Proceedings of International Conference on Nuclear Data for Science and Technology (ND 2007), Vol.1, p.407 - 410, 2008/05

Beryllium and carbon are candidate materials of fusion reactors and the $$^{9}$$Be(n,2n+2$$alpha$$) and $$^{12}$$C(n,n'+3$$alpha$$) reactions are important from engineering requirements. In order to estimate double-differential cross sections (DDX) for emitted particles, we have to accurately grasp details of the reaction mechanism. Understanding of the reaction mechanism is also interesting from a viewpoint of nuclear physics. Recently we developed a new spectrometry system with a pencil-beam DT neutron source. Using the system, we carried out detailed measurements of DDX for $$alpha$$-particles emitted from beryllium and carbon. The reaction mechanism was investigated by a Monte Carlo calculation of DDX. For the $$^{9}$$Be(n,2n+2$$alpha$$) reaction, the result suggests importance of the contribution from the $$^{9}$$Be(n,$$alpha$$)$$^{6}$$He*(Ex$$geq$$1.8MeV) reaction. For the $$^{12}$$C(n,n'+3$$alpha$$) reaction, the contribution from the $$^{12}$$C(n,$$alpha$$)$$^{9}$$Be*(Ex$$geq$$2.43MeV) reaction was appeared and its ratio was investigated to explain the shape of DDX for neutrons in lower energy.

Journal Articles

Systematical nucleon-induced optical model analysis for medium and heavy nuclei with coupled-channel framework

Kunieda, Satoshi; Chiba, Satoshi; Shibata, Keiichi; Ichihara, Akira; Sukhovitskij, E.*

Proceedings of International Conference on Nuclear Data for Science and Technology (ND 2007), Vol.1, p.227 - 230, 2008/05

The optical model analyses were carried out for nucleon-induced reactions on medium and heavy nuclei from 1 keV to 200 MeV. The coupled-channels method based on the rigid-rotator model was employed as an initial approach. It was found that the coupled-channels analyses were indispensable to obtain a global formulation of optical potential. In addition to this, the coupled-channels calculations based on the soft-rotator model was applied to analyses for various even-even fission product isotopes. They reproduced measured cross sections better than the rigid-rotator model in many cases. Though the latter is our ongoing study, we show the advantage of coupled-channels calculations and the applicability of the soft-rotator model in this conference.

Journal Articles

Measurement of total $$gamma$$ absorption for high energy $$gamma$$ rays

Kitatani, Fumito; Harada, Hideo; Hara, Kaoru; Utsunomiya, Hiroaki*; Goko, Shinji*; Kaihori, Takeshi*; Toyokawa, Hiroyuki*

Proceedings of International Conference on Nuclear Data for Science and Technology (ND 2007), Vol.1, p.123 - 126, 2008/05

Total $$gamma$$ absorption cross sections are most important data used in various fields related to the application of $$gamma$$ rays. However, the measurements of the total $$gamma$$ absorption cross section were difficult for high energy $$gamma$$ rays since there were no suitable $$gamma$$ ray sources. Recently, the nuclear photo-absorption measurement system using the laser-Compton backscattering (LCS) $$gamma$$ rays and the high-resolution high-energy photon spectrometer (HHS) were developed. We have utilized the system to measure the total $$gamma$$ absorption cross section, that is, the sum of the atomic and nuclear interactions. The total $$gamma$$ absorption cross sections at 10 MeV for Al and Cu have been measured with the system. The preliminary results show that the obtained values agree fairly with the theoretical.

Journal Articles

High resolution spectroscopy of the giant resonance in the $$^{16}$$O($$gamma$$,abs) reaction

Harada, Hideo; Kitatani, Fumito; Hara, Kaoru; Utsunomiya, Hiroaki*; Goko, Shinji*; Kaihori, Takeshi*; Toyokawa, Hiroyuki*

Proceedings of International Conference on Nuclear Data for Science and Technology (ND 2007), Vol.1, p.499 - 502, 2008/05

The characteristics of the nuclear photo-absorption spectroscopy using the laser Compton scattering (LCS) photons and the high-resolution high-energy photon spectrometer (HHS) are presented in this paper. The maximum energy of a LCS photon was increased up to 30 MeV, and the response functions of the HHS were improved. By taking advantage of these achievements, the $$^{16}$$O($$gamma$$,abs) cross section was measured in the giant resonance region, that is, 20 to 25 MeV. The preliminary result with the energy resolution of about 0.1% is presented and compared with the preceding data.

Journal Articles

Performance of a 4$$pi$$ Ge spectrometer for neutron capture cross section measurements

Oshima, Masumi; Hori, Junichi*; Harada, Hideo; Furutaka, Kazuyoshi; Koizumi, Mitsuo; Kitatani, Fumito; Toh, Yosuke; Kimura, Atsushi; Nakamura, Shoji; Igashira, Masayuki; et al.

Proceedings of International Conference on Nuclear Data for Science and Technology (ND 2007), Vol.1, p.603 - 606, 2008/05

Neutron capture cross sections of minor actinides and long-lived fission products are important for the R&D of innovative nuclear reactors. However, those data are rather poor both in quality and in quantity at present. Thus, we have started projects for neutron cross section measurements. We will construct an innovative $$gamma$$-ray spectrometer consisting of Ge crystals and BGO shields. The neutron cross section measurements will be done at KUR linac and JAEA JRR-3M facilities, which will be extended at the high-intensity neutron source at J-PARC.

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