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Oizumi, Akito; Sagara, Hiroshi*
Annals of Nuclear Energy, 223, p.111677_1 - 111677_12, 2025/12
This study aims to provide a new rational physical protection (PP) design method by using 
(
) and to design a rational PP system for a site of the transuranium fuel cycle with accelerator-drive systems (ADSs cycle) using the new method. First, the new rational PP design method with different PP design requirements for each was generalized based on the definitions of a national standard method defined by the US Department of Energy, the joint US-Japan study, and the International Atomic Energy Agency. A new PP categorization of Uranium (U), including U-234, which is abundant in the ADS cycle, was also developed based on . Second, a PP design was conducted for a general BWR site with MOX fuel and the ADS cycle site by using the new rational method. It was clarified that the highest overall of the items within the ADS cycle site was lower than that of the MOX fuel assembly within the BWR site. The BWR site was determined to be Category I requiring the inner area. The PP design requirement level of the ADS cycle site was determined to be Category II, which does not require an inner area, while the ADS cycle site would have been classified as Category I if the PP design had been conducted using the conventional method.
Motegi, Kosuke; Shibamoto, Yasuteru; Hibiki, Takashi*
International Journal of Heat and Mass Transfer, 252, p.127451_1 - 127451_16, 2025/12
Otsuka, Naohiko*; Devi, V.*; Iwamoto, Osamu
Applied Radiation and Isotopes, 225, p.111903_1 - 111903_18, 2025/11
Times Cited Count：0
Cl
Aoki, So; Abe, Yosuke; Abe, Hiroshi*; Watanabe, Yutaka*; Yamamoto, Masahiro*
Corrosion Science, 255, p.113119_1 - 113119_10, 2025/10
This study aimed to visualise the distribution of chloride in the corroded crevice of stainless steel and to evaluate the chloride content quantitatively. Crevice corrosion tests were carried out using Cl, a radioactive isotope of chloride, as a tracer in NaCl test solutions. After crevice corrosion tests, stainless steel specimens were placed on an imaging plate. The imaging plate was sensitised by 
-ray emitted by Cl adhering to the crevice. As a result, the chloride distribution in the corroded area inside the crevice was visualised. A calibration curve for the amount of Cl was obtained from the relationship between the time of photosensitivity to -ray emitted by Cl and the luminance of the imaging plate. The chloride content in the corroded crevice was quantitatively evaluated based on the calibration curve. These visualisation and quantitative evaluation methods were also applied to tests in which specimens were left in pure water after crevice corrosion tests, and the behaviour of chloride in crevice corrosion was discussed.
Rizaal, M.; Nakajima, Kunihisa; Suzuki, Eriko; Miwa, Shuhei
Annals of Nuclear Energy, 218, p.111433_1 - 111433_10, 2025/08
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Yamashita, Susumu
JAEA-Data/Code 2025-003, 262 Pages, 2025/07
JAEA-Data-Code-2025-003.pdf:9.4MB
A multi-phase, multi-component, detailed thermal-hydraulic code JAEA Utility Program for Interdisciplinary Thermal-hydraulics Engineering and Research (JUPITER) has been developed to simulate the thermal-hydraulic behavior in nuclear reactors under steady-state and severe accident conditions in a mechanism-based manner. JUPITER can faithfully reproduce thermal hydraulics based on the governing equations. In addition, eutectic reactions at dissimilar metal contact surfaces and oxidation reactions between steam and zirconium alloys, which are important phenomena in severe accidents, can be analyzed. It is also applicable to porous media flow, which is often used for flow phenomena in fine particles. In this report, the governing equations and physical models of JUPITER and its numerical methods are outlined, and an input manual for JUPITER is presented as an appendix.
Yamashita, Susumu
JAEA-Data/Code 2025-002, 243 Pages, 2025/07
JAEA-Data-Code-2025-002.pdf:9.37MB
A multi-phase, multi-component, detailed thermal-hydraulic code JAEA Utility Program for Interdisciplinary Thermal-hydraulics Engineering and Research (JUPITER) has been developed to simulate the thermal-hydraulic behavior in nuclear reactors under steady-state and severe accident conditions in a mechanism-based manner. JUPITER can faithfully reproduce thermal hydraulics based on the governing equations. In addition, eutectic reactions at dissimilar metal contact surfaces and oxidation reactions between steam and zirconium alloys, which are important phenomena in severe accidents, can be analyzed. It is also applicable to porous media flow, which is often used for flow phenomena in fine particles. In this report, the governing equations and physical models of JUPITER and its numerical methods are outlined, and an input manual for JUPITER is presented as an appendix.
Soma, Yasutaka; Komatsu, Atsushi; Kaji, Yoshiyuki; Yamamoto, Masahiro*; Igarashi, Takahiro
Corrosion Science, 251, p.112897_1 - 112897_15, 2025/07
Times Cited Count：1 Percentile：0.00(Materials Science, Multidisciplinary)Experimental and modeling studies of the oxygen ingression at the crevices of stainless steels were conducted in high-temperature water (288
C). The limiting distance of oxygen ingression, 
, was defined as the point beyond which the primary surface oxide changed (hematite 
magnetite), regardless of crevice gap, oxygen concentration, and time. In situ measurements revealed increased electrical conductivity around the position indicating ion enrichment due to a differential oxygen concentration cell. increased with increasing crevice gap, oxygen concentration, and immersion time. Modeling study suggested that oxide layer growth reduced anodic dissolution and slowed oxygen consumption, allowing oxygen ingression with time.
Sato, Tatsuhiko
Radioisotopes, 74(2), p.183 - 188, 2025/07
no abstracts in English
Yanagisawa, Hiroshi; Motome, Yuiko
JAEA-Research 2025-001, 99 Pages, 2025/06
JAEA-Research-2025-001.pdf:1.98MB
The detailed computational models for nuclear criticality analyses on the first startup cores of NSRR (Nuclear Safety Research Reactor), which is categorized as a TRIGA-ACPR (Annular Core Pulse Reactor), were created for the purposes of deeper understandings of safety inspection data on the neutron absorber rod worths of reactivity and improvement of determination technique of the reactivity worths. The uncertainties in effective neutron multiplication factor (k
) propagated from errors in the geometry, material, and operation data for the present models were evaluated in detail by using the MVP version 3 code with the latest Japanese nuclear data library, JENDL-5, and the previous versions of JENDL libraries. As a result, the overall uncertainties in k for the present models were evaluated to be in the range of 0.0027 to 0.0029 
k. It is expected that the present models will be utilized as the benchmark on k for TRIGA-ACPR. Moreover, it is confirmed that the overall uncertainties were sufficiently smaller than the values of absorber rod worths determined in NSRR. Thus, it is also considered that the present models are applicable to further analyses on the absorber rod worths in NSRR.
Ogawa, Tatsuhiko
Annals of Nuclear Energy, 216, p.111256_1 - 111256_12, 2025/06
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)A novel robust method has been developed to simulate the performance of composite neutron sources composed of an alpha-emitting actinide and a light nucleus with low neutron separation energy. This method is based on the JENDL-5 cross-section data library and the Monte-Carlo radiation transport code PHITS. In contrast to previously devised methods, this approach can predict various quantities of the sources, such as actinide grain size dependence, absolute neutron emission intensity, energy spectra of neutrons and parasitic photons, neutron multiplicity, and time structure, with little approximation. The accurate calculation of stopping power of alpha rays in actinide grains and light elements, as well as the use of (
,n) reaction evaluated cross sections, which is one of the unique features of PHITS Ver.3.34 and its later versions, are the essences of the method. This method allows for the calculation of quantities important for practical applications, such as detection signal frequency, coincidence event rate, and the impact of parasitic gamma-rays.
Kondo, Ryoichi; Yamamoto, Akio*; Endo, Tomohiro*
EPJ Nuclear Sciences & Technologies (Internet), 11, p.21_1 - 21_9, 2025/06
The flux distribution tallies using the proper orthogonal decomposition (POD) called "the POD tallies" have been developed in our previous study. The POD tallies can achieve dimensionality and statistical uncertainty reduction for a finely discretized flux distribution. Some characteristics of the POD tallies, which are left by our previous work, are revealed in the present study. Firstly, the POD tallies with the track length estimator are newly implemented. Since the statistical uncertainty of the POD tallies is reduced compared with the cell tallies, the POD tallies with the track length estimator can obtain the most precise result among the present implantations. Secondly, the basis vectors obtained by the deterministic and the stochastic methods are compared. The statistical uncertainty of the snapshot data invokes the degradation of the extracted basis vectors. This result indicates that the deterministic method might be more efficient for the snapshot calculation. Finally, the impact of the covariances of expansion coefficients on the statistical uncertainty of expanded flux distribution is investigated. The reconstructed statistical uncertainty considering only the variances of the expansion coefficients differs from the reference. This result reveals that the covariances of the expansion coefficients are important to estimate the statistical uncertainty of the local flux in the flux distribution.
-rays emitted from 
S(n,)
S reaction with polarized neutronsEndo, Shunsuke; Fujioka, Hiroyuki*; Ide, Ikuo*; Iinuma, Masataka*; Iwamoto, Nobuyuki; Iwamoto, Osamu; Kameda, Kento*; Kawamura, Shiori*; Kimura, Atsushi; Kitaguchi, Masaaki*; et al.
EPJ Web of Conferences, 329, p.05003_1 - 05003_3, 2025/06
no abstracts in English
Hf(n,)
Hf reaction measurementKawamura, Shiori*; Endo, Shunsuke; Iwamoto, Osamu; Iwamoto, Nobuyuki; Kimura, Atsushi; Kitaguchi, Masaaki*; Nakamura, Shoji; Okudaira, Takuya*; Rovira Leveroni, G.; Shimizu, Hirohiko*; et al.
EPJ Web of Conferences, 329, 05002_1 Pages, 2025/06
no abstracts in English
-Ps) in fluorinated polymers and silica glassKobayashi, Yoshinori*; Sato, Kiminori*; Yamawaki, Masato*; Michishio, Koji*; Oka, Toshitaka; Washio, Masakazu*
Journal of Physics; Conference Series, 3029, p.012001_1 - 012001_7, 2025/06
Nakamura, Shoji; Endo, Shunsuke; Rovira Leveroni, G.; Kimura, Atsushi; Shibahara, Yuji*
KURNS Progress Report 2024, P. 31, 2025/06
no abstracts in English
Fukushima, Masahiro; Ando, Masaki; Nagaya, Yasunobu
Nuclear Science and Engineering, 199(6), p.1029 - 1043, 2025/06
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Hartzell, S.*; Furutani, K. M.*; Parisi, A.*; Sato, Tatsuhiko; Kase, Yuki*; Deglow, C.*; Friedrich, T.*; Beltran, C. J.*
Radiation (Internet), 5(2), p.21_1 - 21_24, 2025/06
Saga, Kaname
JAEA-Review 2025-003, 23 Pages, 2025/05
JAEA-Review-2025-003.pdf:1.08MB
Diagnosis and treatment using radioisotopes (RI) in the medical field contribute to improving people's welfare. However, almost all medical RI distributed in Japan are imported from overseas. As a result, geopolitical influences and natural disasters lead to difficulties for importing them. Based on these backgrounds, in Japan, a specialized subcommittee on the production and utilization of medical radioisotopes was established within the Atomic Energy Commission, and in May 2022, it formulated the "Action Plan for Promotion of Production and Utilization of Medical Radioisotopes." Japan Atomic Energy Agency (JAEA) launched the NXR Development Center in FY2024 to separate and recycle valuable elements contained in high-level liquid waste (HLLW). The advantages of using HLLW are that it contains a wide variety of nuclides and in large quantities. Therefore, this report focused on the RI contained in HLLW and evaluated whether it can be supplied for medical use. Specifically, the target supply amount of Sr-90, the parent nuclide of Y-90 approved as a RI for medical use, and the amount of Sr-90 in HLLW were estimated. Based on the estimation, the feasibility of separating medical RI from HLLW in a reprocessing research facility was evaluated. As a result, the HLLW possibly contains an amount of RI equivalent to the domestic medical demand. Although it depends on the RI concentration in the HLLW, a small volume of HLLW, ranging from a few hundred milliliters to a few liters, could potentially produce an amount of medical RI equivalent to domestic demand. In addition, the equipment already installed in research facilities, such as NUCEF at JAEA, may be sufficient to produce the medical RI. It may be possible to meet domestic medical demand for Sr-90, as a source of Y-90, by processing a few hundred milliliters to a few liters of HLLW using an existing research facility.
Katano, Ryota; Abe, Takumi; Cibert, H.*
JAEA-Research 2024-019, 22 Pages, 2025/05
JAEA-Research-2024-019.pdf:1.03MB
An accelerator-driven system (ADS) dedicated to transmutation of minor actinides (MAs) is driven in subcritical states. It is important for establishment of the subcriticality control of ADS to predict the burnup reactivity. To validate the prediction accuracy, the burnup reactivity, especially at the first cycle, must be measured with sufficient accuracy. In this study, we focus on Current-To-Flux (CTF) method. We have simulated the burnup reactivity monitoring during the ADS normal operation with the CTF method by performing fixed-source-burnup calculations using a continuous energy Monte Carlo code SERPENT2 with some tallies that models in-core fission chambers and have estimated its measurement uncertainty. We have clarified that the 10% biases of measure burnup reactivities appear independently of the burnup duration and their detector position dependence is particularly small in the outer region of the system.
