Implementation of ideal cascade model for uranium enrichment to nuclear fuel cycle simulator

Abe, Takumi; Suzuki, Taiga*; Okamura, Tomohiro*; Nakase, Masahiko*

Annals of Nuclear Energy, 232, p.112224_1 - 112224_7, 2026/07

https://doi.org/10.1016/j.anucene.2026.112224

Conceptual design of pilot ADS

Nishihara, Kenji; Fukushima, Masahiro; Abe, Takumi; Katano, Ryota; Yee-Rendon, B.; Iwamoto, Hiroki; Sugawara, Takanori; Obayashi, Hironari; Saito, Shigeru

JAEA-Research 2025-013, 125 Pages, 2026/03

JAEA-Research-2025-013.pdf:4.68MB

A conceptual design for a pilot Accelerator Driven subcritical System (ADS) was developed as a precursor to a commercial ADS aimed at partitioning and transmutation of minor actinides. The output of the pilot ADS was set at 200 MW. Based on safety assessment results, the design incorporates deep subcriticality and safety rods. Core design, accelerator design, target design, and in-vessel equipment design were performed, clarifying the specific concept.

Evaluation of Aluminum Hexacyanoferrate utilization for PGM and Mo removal from simulated high-level-raffinates in reprocessing for repository area minimization

Nakase, Masahiko*; Mishima, Ria; Abe, Takumi; Okamura, Tomohiro*; Asano, Hidekazu*

Annals of Nuclear Energy, 224, p.111569_1 - 111569_14, 2025/12

https://doi.org/10.1016/j.anucene.2025.111569

Impact of fast reactor fuel type on backend processes in the nuclear fuel cycle

Takeshita, Kenji*; Okamura, Tomohiro*; Nakase, Masahiko*; Abe, Takumi; Nishihara, Kenji

Progress in Nuclear Science and Technology (Internet), 8, p.52 - 57, 2025/09

https://doi.org/10.15669/pnst.8.52

Investigation of measurement accuracy of burnup reactivity of accelerator-driven system during normal operation

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.

Scenario analysis of future nuclear energy use in Japan, 1; Methodology of nuclear fuel cycle simulator: NMB4.0

Abe, Takumi; Oizumi, Akito; Nishihara, Kenji; Nakase, Masahiko*; Asano, Hidekazu*; Takeshita, Kenji*

Progress in Nuclear Science and Technology (Internet), 7, p.299 - 304, 2025/03

https://doi.org/10.15669/pnst.7.299

Currently, much research continues on stable energy sources that do not emit CO in order to achieve a carbon-neutral and sustainable society. Nuclear energy is one of the such sources, and various new reactors and reprocessing technologies are being developed. In order to implement the nuclear fuel cycle with these technologies, a nuclear fuel cycle simulator is required to quantitatively evaluate various quantities, such as the distribution of nuclear fuel materials and the scale of waste loading. For this purpose, NMB4.0 was developed in collaboration with Tokyo Institute of Technology and Japan Atomic Energy Agency. This code calculates the material balance of 179 nuclides including actinides and fission products (FPs) from the front-end to the back-end and simulates the nuclear fuel cycle in an integrated manner. Unlike other nuclear fuel cycle simulators, the code is capable of performing precise back-end analyses such as the number of radioactive wastes and the scale of the geological repository considering heat generation of waste package under diverse nuclear energy scenario, and is an open source code that runs on Microsoft Excel. By these features, it is possible to quantitatively study nuclear energy utilization strategies with various stakeholders. The presentation will detail the numerical model used in NMB4.0.

The Impact of nuclear fuel cycle operation factor uncertainty on nuclear power plant operation

Abe, Takumi; Nishihara, Kenji

Proceedings of International Conference on Nuclear Fuel Cycle (GLOBAL2024) (Internet), 4 Pages, 2024/10

The robustness of whole of a nuclear fuel cycle (NFC) can be evaluated by a simulation of future operation factors (OFs) of the NFC facilities and mass flow analysis coupled with the simulated OF. In this study, the impact of a reprocessing plant OF on a fast reactor OF was quantified.

Initial verification of Cyclus and NMB fuel cycle simulators

Bachmann, A. M.*; Richards, S.*; Feng, B.*; Nishihara, Kenji; Abe, Takumi

Proceedings of International Conference on Nuclear Fuel Cycle (GLOBAL2024) (Internet), 4 Pages, 2024/10

This work demonstrates the value of code verification as an initial step in utilizing fuel cycle simulation. Cyclus and NMB are open-source fuel cycle simulators that provide computational modeling of nuclear fuel cycle alternatives and were chosen by Argonne National Laboratory and Japan Atomic Energy Agency (JAEA), respectively, for a multi-year collaboration on fuel cycle benchmarks. Both are relatively new and can be improved after conducting a rigorous code-to-code comparison. Initial verification of these simulators was performed using a set of hypothetical scenarios for once-through and multi-recycle fuel cycles. The results of this work identify how differences in scenario definitions and the modeling methodologies of the two simulators lead to differences in results in material inventories, mass flows, and other important metrics for fuel cycle assessments.

A Science-based mixed oxide property model for developing advanced oxide nuclear fuels

Kato, Masato; Oki, Takumi; Watanabe, Masashi; Hirooka, Shun; Vauchy, R.; Ozawa, Takayuki; Uwaba, Tomoyuki; Ikusawa, Yoshihisa; Nakamura, Hiroki; Machida, Masahiko

Journal of the American Ceramic Society, 107(5), p.2998 - 3011, 2024/05

https://doi.org/10.1111/jace.19609

Development of irradiation capsules with adjusting neutron spectrum

Fuyushima, Takumi; Takabe, Yugo; Sayato, Natsuki; Kimura, Akihiro; Takemoto, Noriyuki

The IV International Scientific Forum "Nuclear Science and Technologies"; AIP Conference Proceedings 3020, p.040007_1 - 040007_6, 2024/01

https://doi.org/10.1063/5.0192860

We studied irradiation tests of structural materials simulating fast reactor conditions in JMTR. We fabricated capsules that can simulate fast reactor irradiation in JMTR by using He/dpa ratio as index. To simulate fast reactor, cadmium, which shield thermal neutrons, was placed inside the capsule to adjust the neutron spectrum. According to the result of irradiation tests by neutron spectrum adjusting capsule, we confirmed that it can simulate the He/dpa ratio of fast reactor. Currently, since it is impossible to conduct irradiation tests in Japan, a plan is underway to partly replace the irradiation function of JMTR with overseas reactors. The alternative irradiation will be carried out by succeeding and developing the irradiation technology accumulated in the JMTR, and as a part of this, a trial of such irradiation in which the neutron spectrum is adjusted is under consideration.