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Konno, Chikara
JAEA-Conf 2026-001, p.115 - 120, 2026/06
The US nuclear safety analysis code system SCALE6.2 is also widely used in Japan, but the bundled AMPX continuous energy libraries are produced only from the US nuclear data library ENDF/B. Thus I produced an AMPX continuous energy library of JENDL-5 with the AMPX-6 code bundled in SCALE6.2. In this nuclear data processing I found out that several produced AMPX continuous energy files of the thermal scattering law data in JENDL-5 had strange cross section data. I examined reasons why the strange cross section data were produced in detail and specified that an inadequate processing method of the thermal scattering law data in AMPX-6 caused the strange cross section data. I improved AMPX-6 and obtained adequate AMPX continuous energy files of the JENDL-5 thermal scattering law data.
Nakayama, Shinsuke
JAEA-Conf 2026-001, p.22 - 27, 2026/06
This talk will introduce and discuss the current status and issues of the evaluation of thermal scattering laws (TSL) in the development of the Japanese Evaluated Nuclear Data Library, JENDL. In thermal neutron reactors, the TSL of the moderator has a significant impact on core calculations. In the JENDL series, the latest version, JENDL-5, is the first to include an original evaluation of TSL. In this evaluation, the TSL of water, a typical moderator, and hydrogen-containing organic compounds such as methane, which is used as a moderator in neutron sources, were evaluated based on molecular dynamics calculations. However, data for crystalline materials was obtained from the ENDF/B-VIII.0 library. Crystalline materials are often used as moderators in thermal neutron reactors. Such examples are graphite in high-temperature gas-cooled reactors and molten salt reactors, and calcium hydride (CaH
) in small reactors. Under these circumstances, we have started to establish a method for evaluating the TSL of crystalline materials with the aim of enhancing the TSL data in JENDL. As a result, we have obtained results that reproduce the experimental values of neutron scattering at J-PARC well for graphite and CaH by using an evaluation method based on first-principles calculations. In addition, further improvements are underway for the TSL of light water. In order to improve reliability under high-temperature and high-pressure conditions such as reactor operation conditions, we are developing a method for evaluating TSL using molecular dynamics calculations with potentials based on first-principles calculations, which are considered to have high predictability for changes in temperature and pressure. We will also discuss the progress of evaluating TSL for light water using this method.
Konno, Chikara
JAEA-Conf 2026-001, p.28 - 33, 2026/06
Activation analyses are essential in planning and execution of reactor decommissioning, where the ORIGEN-2 and ORIGEN-S codes are often used in Japan. This presentation points out problems in these codes and introduces the ORIGEN code, which is bundled in the US nuclear safety analysis code system SCALE6.2 or later. ORIGEN solves most of the problems but SCALE6.2 bundles only the libraries from the nuclear data library ENDF/B-VII.0 or later. Thus I produced new libraries for the ORIGEN code from JENDL-5. I also present remarks on calculations with the two-dimensional Sn code DORT which is often used to calculate neutron spectra for activation analyses.
Iwamoto, Hiroki
JAEA-Conf 2026-001, p.34 - 37, 2026/06
Nuclear data are essential for the research and development of nuclear energy systems and accelerator facilities, and applications involving radioactive isotopes. However, the increasing complexity of theoretical models and the demands of large-scale computations have made sustainable nuclear data evaluation challenging with limited human resources. To overcome these difficulties and continue providing reliable nuclear data, it is crucial to advance nuclear data evaluation methods. In this talk, I will explore possible solutions to these issues through Bayesian machine learning, using examples from our recent work.
Lee, J.; Rossi, F.; Hironaka, Kota; Koizumi, Mitsuo; Shiba, Tomooki
JAEA-Conf 2026-001, p.44 - 48, 2026/06
Sakai, Seiya*; Otsu, Hideaki*; Iwamoto, Osamu; Iwamoto, Nobuyuki; Nakayama, Shinsuke; Kikunaga, Hidetoshi*; Fukahori, Tokio
JAEA-Conf 2026-001, p.85 - 90, 2026/06
