Collaboration with Dr. Efrem Sh. Soukhovitsukii; Our fortuitous experiences on optical model analysis, his contribution to nuclear data activities of Japan and a posthumous study on light-nuclei

Kunieda, Satoshi; Iwamoto, Osamu; Fukahori, Tokio; Chiba, Satoshi*

European Physical Journal A, 59(1), p.2_1 - 2_8, 2023/01

https://doi.org/10.1140/epja/s10050-022-00907-3

Optical model or coupled-channels calculation serves as an entrance to sophisticated calculation of nuclear data. It was a great contribution of Dr. Efrem Sh. Soukhovitsukii who has developed an excellent computation scheme which takes account of the low-lying collective nuclear structure in terms of the soft-rotator + vibrational model, and integrated it into the coupled-channels calculation. In Japan, we had a fortuitous experience with him in parametrization of the optical model potential (OMP) and to employ this methodology in nuclear data evaluation for JENDL. Firstly, we summarize our collaborative works with him in this paper. Secondly, let us have a discussion on a new parameterization of OMP which we obtained for light nuclei within his framework, quite recently. It was found that values of the potential parameters themselves are rather similar among different nuclei while the nuclear deformation describes one of the main characteristics of each isotopes.

EXFOR-based simultaneous evaluation of neutron-induced uranium and plutonium fission cross sections for JENDL-5; Inputs and outputs

Otsuka, Naohiko*; Iwamoto, Osamu

JAEA-Data/Code 2022-005, 102 Pages, 2022/10

JAEA-Data-Code-2022-005.pdf:2.18MB
JAEA-Data-Code-2022-005-appendix(CD-ROM).zip:3.85MB

The neutron-induced fission cross sections were simultaneously evaluated for the JENDL-5 library for U and Pu from 10 keV to 200 MeV and for U and Pu from 100 keV to 200 MeV. Evaluation was performed by least-squares fitting of Schmittroth's roof function to the logarithms of the experimental cross sections and cross section ratios in the EXFOR library. A simultaneous evaluation code SOK was used with its extension to data in arbitrary unit. This report describes (1) construction of the experimental database, (2) selection of data points from TUD-KRI collaboration, (3) comparison with the evaluated cross sections in recent major libraries, and (4) impact of the U datasets published in 1970s.

Calculation of recoil nucleus spectrum in the presence of multi-particle emission in nuclear reaction with Monte Carlo method as an extension of CCONE code

Iwamoto, Osamu

Journal of Nuclear Science and Technology, 59(10), p.1232 - 1241, 2022/10

https://doi.org/10.1080/00223131.2022.2038300

Calculation of deuteron-induced reaction cross-sections for nuclear transmutation of long-lived fission products

Nakayama, Shinsuke; Furutachi, Naoya; Iwamoto, Osamu; Watanabe, Yukinobu*

NEA/NSC/R(2020)4 (Internet), p.345 - 349, 2022/10

Long-lived fission products (LLFPs) generated in nuclear reactors are strongly desired to be converted to stable or short-lived nuclides. Recently, it has been considered to transmute LLFPs by spallation reactions with high energy particles, and some experimental studies revealed that spallation reaction cross-sections induced by deuteron are larger than proton-induced ones. These results suggest the possibility that nuclear transmutation of LLFPs using deuteron beams is more efficient than one using proton beams. On the other hand, we have been developing a code system dedicated for deuteron-induced reactions, called DEURACS. DEURACS has been originally developed to contribute to the design of deuteron accelerator neutron sources. In the present study, we apply DEURACS to calculation of deuteron-induced spallation reactions on LLFPs. Through comparison with measured data, the applicability of DEURACS will be discussed.

Completion of JENDL-5 and prospects for its application to numerical analysis, 1; Overview of JENDL-5

Iwamoto, Osamu

Kaku Deta Nyusu (Internet), (132), p.1 - 8, 2022/06

no abstracts in English

Theoretical study of deuteron-induced reactions in the nuclear data field

Nakayama, Shinsuke; Iwamoto, Osamu; Watanabe, Yukinobu*; Ogata, Kazuyuki*

Few-Body Systems, 63(1), p.4_1 - 4_6, 2022/03

https://doi.org/10.1007/s00601-021-01712-2

Intensive neutron sources using deuteron accelerators have been proposed for not only science and engineering fields but also medical applications. For the engineering design of such facilities, accurate and comprehensive nuclear data of deuteron-induced reactions are indispensable. However, it is difficult to meet the requirement by employing experimental data alone. Thus, theoretical model calculations play a key role in completing the necessary nuclear data by interpolation and extrapolation of experimental data. Under the above situations, we have been developing a code system dedicated for deuteron-induced reactions, called DEURACS. In the present work, calculations using DEURACS are compared with available experimental data and validation of the present modelling in DEURACS is discussed. Moreover, the importance of consideration of the breakup processes for accurate prediction of deuteron-induced reactions is also presented.

G-HyND: A Hybrid nuclear data estimator with Gaussian processes

Iwamoto, Hiroki; Iwamoto, Osamu; Kunieda, Satoshi

Journal of Nuclear Science and Technology, 59(3), p.334 - 344, 2022/03

https://doi.org/10.1080/00223131.2021.1971120

A hybrid nuclear data estimator (G-HyND) based on a machine learning technique with Gaussian processes (GP) was developed. G-HyND estimates cross-sections from a hybrid training dataset composed of an experimental dataset and an analytical dataset based on a nuclear physics model, and generates the cross-section datasets including the dataset's uncertainty information. It was demonstrated that an experimental dataset and a physics model-based analytical dataset perform a complementary role in nuclear data generation, and that the generated nuclear data from the hybrid training dataset are more reasonable than only those from the experimental dataset. Furthermore, solutions for two inherent GP problems, i.e., overfitting and computational cost, are presented within the G-HyND framework.

Am neutron capture cross section in the keV region using Si and Fe-filtered neutron beams

Rovira Leveroni, G.; Kimura, Atsushi; Nakamura, Shoji; Endo, Shunsuke; Iwamoto, Osamu; Iwamoto, Nobuyuki; Katabuchi, Tatsuya*; Kodama, Yu*; Nakano, Hideto*

Journal of Nuclear Science and Technology, 11 Pages, 2022/00

https://doi.org/10.1080/00223131.2022.2116496

Report of 33rd Meeting of the Working Party on International Nuclear Data Evaluation Co-operation (WPEC)

Iwamoto, Osamu; Iwamoto, Nobuyuki; Kimura, Atsushi; Tada, Kenichi

Kaku Deta Nyusu (Internet), (130), p.9 - 15, 2021/10

The 33rd annual meeting and the subgroup meeting of the Working Party on International Nuclear Data Evaluation Co-operation (WPEC) under the Nuclear Energy Agency of the Organization for Economic Co-operation and Development (OECD/NEA) was held via a web meeting system from 10 to 14 in May in 2021. The activities about nuclear data measurement and evaluation of each region or country were reported at the annual meeting, and the SG activities were discussed at the subgroup meetings. The summary of these meetings are reported.

Neutron capture cross sections of curium isotopes measured with ANNRI at J-PARC

Kawase, Shoichiro*; Kimura, Atsushi; Harada, Hideo; Iwamoto, Nobuyuki; Iwamoto, Osamu; Nakamura, Shoji; Segawa, Mariko; Toh, Yosuke

Journal of Nuclear Science and Technology, 58(7), p.764 - 786, 2021/07

https://doi.org/10.1080/00223131.2020.1864492