Probabilistic fracture mechanics benchmarking study of PASCAL-SP code with xLPR code regarding primary water stress corrosion cracking

Mano, Akihiro; Yamaguchi, Yoshihito; Katsuyama, Jinya

International Journal of Pressure Vessels and Piping, 222, p.105792_1 - 105792_11, 2026/08

https://doi.org/10.1016/j.ijpvp.2026.105792

A probabilistic fracture mechanics (PFM) analysis code, PASCAL-SP, has been developed by the Japan Atomic Energy Agency (JAEA) to evaluate the failure probability of piping within nuclear power plants while considering age-related degradations such as stress corrosion cracking and fatigue for both pressurized water reactor and boiling water reactor environments. To strengthen the confidence in the results of PASCAL-SP, a benchmarking study was performed with the PFM analysis code, xLPR, which was developed by the U.S.NRC in collaboration with EPRI. In this benchmarking study, deterministic and probabilistic analyses are performed using common analysis conditions. This paper presents the details of these conditions and comparisons of the results between the two aforementioned codes. Both codes were found to provide nearly the same results in both deterministic and probabilistic analyses for a dissimilar metal weld subjected to primary water stress corrosion cracking.

Real-time inversion of radioactive source distribution using air dose rate measurements via least absolute shrinkage and selection operator method

Shi, W.*; Machida, Masahiko; Okamoto, Koji*; Luo, X.*; Feng, W.*; Liu, X.*

Reliability Engineering & System Safety, 272, Part1, p.112538_1 - 112538_18, 2026/08

http://doi.org/10.1016/j.ress.2026.112538

The reliability of emergency response in severe nuclear accidents critically depends on robust real-time monitoring of radioactive source distributions. However, this safety function is challenged by physical constraints that create monitoring blind spots and by the inadequacy of static methods in tracking dynamic releases. To enhance the reliability and robustness of source term estimation, this study proposes a dynamic reconstruction framework based on LASSO regression with temporal regularization. A sliding-window time-penalty mechanism is introduced, imposing -norm constraints on inter-step source variations to ensure physical continuity. The contribution matrix and measurement vector are normalized to counteract biases from radiation shielding and time-varying intensities. Validation using a two-room model with internal shielding, with PHITS Monte Carlo simulation, demonstrates accurate reconstruction of dynamic sources from remote measurements. Temporal regularization enhances situational awareness by suppressing spatial aliasing: at sliding-window width (no regularization), hotspot locations fluctuate significantly, with quantitative mean absolute error fluctuations at around , whereas yields improved spatial consistency and the fluctuation quantities decrease to the range. Comparative analysis identifies as optimal in balancing accuracy and computational cost. This work establishes a more reliable pathway for dynamic hazard assessment, enabling accurate localization and intensity tracking under challenging conditions. The proposed framework provides a decision-support tool enhancing the resilience and safety of emergency management in nuclear facilities.

Trade-off between adsorption capacity and binding strength regulates carbon stabilization in mineral-associated organic matter

Sun, R.; Abe, Yukiko; Atarashi-Andoh, Mariko; Koarashi, Jun

Soil Biology & Biochemistry, 218, p.110150_1 - 110150_12, 2026/07

https://doi.org/10.1016/j.soilbio.2026.110150

The role of minerals in soil carbon sequestration has been increasingly recognized. However, the mechanism by which mineral-associated organic matter (MAOM) resists microbial decomposition remains an open question. We prepared MAOM on amorphous allophane and crystalline kaolinite with different organic matter (OM) proxies, characterized the affinity strength of these associations using isothermal titration calorimetry and X-ray photoelectron spectroscopy, and quantified their microbial mineralization through aerobic incubation. We found that amorphous allophane displayed greater OM adsorption capacity due to its higher specific surface area; in contrast, crystalline kaolinite exhibited stronger binding with OM, consistent with its predominant inner-sphere complexation. Furthermore, lower MAOM mineralization was found corresponding to higher Langmuir affinity. This inverse relationship was more pronounced than the correlation with the amount of OM adsorbed by minerals. These findings suggest that the overall MAOM stability is controlled by a balance between binding strength and adsorption capacity. Namely, stronger binding affinity enhances microbial resistance of MAOM, while the abundance of mineral sites determines the amount of MAOM accessible for microbial decomposition. This study presents a novel mechanistic understanding of the MAOM dynamics and refines the prevailing perspective on MAOM persistence.

Analysis of fracture conditions of Cr-coated Zr alloy claddings under LOCA conditions calculated using FEMAXI fuel performance code

Luu, V. N.; Taniguchi, Yoshinori; Udagawa, Yutaka; Tasaki, Yudai; Katsuyama, Jinya

Annals of Nuclear Energy, 230, p.112114_1 - 112114_14, 2026/06

https://doi.org/10.1016/j.anucene.2026.112114

Bayesian approach to model temperature dependence of Charpy absorbed energy and uncertainty evaluation of ductile-to-brittle transition temperature for reactor pressure vessel steel

Takamizawa, Hisashi; Nishiyama, Yutaka

Journal of Pressure Vessel Technology, 148(3), p.031501_1 - 031502_12, 2026/06

https://doi.org/10.1115/1.4070725

Embrittlement of reactor pressure vessel (RPV) steel caused by neutron irradiation has been evaluated using ductile-to-brittle transition temperature (DBTT) derived from surveillance tests (Charpy impact tests) during plant operation. For reliable structural integrity assessment of the RPV, incorporating adequate safety margins which take into account uncertainties inherent in surveillance Charpy impact tests is needed. In this study, a model to evaluate temperature dependence of Charpy absorbed energy variability using approximately 1,900 datasets of unirradiated and irradiated materials manufactured in Japan and United States was developed. Next, probability distribution of Charpy ductile-to-brittle transition temperature at a 41J energy level () was evaluated by estimating the probability distribution of Charpy test data using Monte Carlo sampling and Bayesian inference. From the detailed evaluation of the relationship between the number of specimens and uncertainty, uncertainty of was found to be almost the same in materials manufactured in Japan and U.S., and unchanged with neutron irradiation (no clear change in material inhomogeneity). Regarding product form on the other hand, uncertainty of for base metal and weld metal was almost the same, but the heat affected zone was shown to have large uncertainty.

Interpretation of lanthanoid oxide and hydroxide solubilities based on their bulk and surface properties

Kobayashi, Taishi*; Moniruzzaman, M.*; Motokawa, Ryuhei; Sasaki, Takayuki*

Applied Geochemistry, 202, p.106780_1 - 106780_11, 2026/05

https://doi.org/10.1016/j.apgeochem.2026.106780

Quantitative evaluation of confined water distribution in ionomers within catalyst layers of fuel cells

Iwase, Hiroki*; Arima-Osonoi, Hiroshi*; Harada, Masashi*; Kumada, Takayuki

Hamon, 36(2), p.84 - 88, 2026/05

no abstracts in English

Chemical kinetic uncertainty quantification for Reynolds-Averaged Navier-Stokes simulations of turbulent premixed combustion

Motegi, Kosuke; Shiotsu, Hiroyuki; Matsumoto, Toshinori; Hibiki, Takashi*; Shibamoto, Yasuteru

International Journal of Heat and Mass Transfer, 258, p.128275_1 - 128275_15, 2026/05

https://doi.org/10.1016/j.ijheatmasstransfer.2025.128275

Development of quick neutron spectrum reconstruction module based on POD for burnup calculation of fast reactor

Aizawa, Naoto*; Watanabe, Tomoaki; Chiba, Go*; Tada, Kenichi; Fujita, Tatsuya*; Yamamoto, Akio*

Nuclear Engineering and Technology, 58(5), p.104176_1 - 104176_16, 2026/05

https://doi.org/10.1016/j.net.2026.104176

Design of a storage ring based on a fixed-field alternating-gradient configuration with an internal target for heavy-ion beams with stochastic charge state conversions

Ishi, Yoshihiro*; Uesugi, Tomonori*; Mori, Yoshiharu*; Nishio, Katsuhisa

Physical Review Accelerators and Beams (Internet), 29(5), p.050101_1 - 050101_14, 2026/05

https://doi.org/10.1103/th5l-mq3q