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Abe, Takumi; Suzuki, Taiga*; Okamura, Tomohiro*; Nakase, Masahiko*
Annals of Nuclear Energy, 232, p.112224_1 - 112224_7, 2026/07
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Bachmann, A. M.*; Nishihara, Kenji; Richards, S.*; Abe, Takumi; Feng, B.*
Progress in Nuclear Science and Technology (Internet), 8, p.11 - 16, 2025/09
Nishihara, Kenji; Oizumi, Akito; Hino, Tetsushi*; Soneda, Hideo*
Progress in Nuclear Science and Technology (Internet), 7, p.305 - 310, 2025/03
Hitachi-GE is conducting research and development of new fuel design named resource-renewable boiling water reactor-backfit (RBWR-BF) to enhance plutonium utilization in BWRs. In this study, the effects of installing RBWR-BF were estimated using the NMB code, a nuclear fuel cycle simulator, under the assumption of a future nuclear energy utilization scenario based on light water reactor (LWR) in Japan. As a result, it was shown that burden of MOX loading to LWRs can be minimized and fissionability of remaining plutonium in 2100 was improved by RBWR-BF introduction from 2040.
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
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.
Okamura, Tomohiro*; Nishihara, Kenji; Katano, Ryota; Oizumi, Akito; Nakase, Masahiko*; Asano, Hidekazu*; Takeshita, Kenji*
JAEA-Data/Code 2021-016, 43 Pages, 2022/03
JAEA-Data-Code-2021-016.pdf:3.06MB
The quantitative prediction and analysis of the future nuclear energy utilization scenarios are required in order to establish the advanced nuclear fuel cycle. However, the nuclear fuel cycle consists of various processes from front- to back-end, and it is difficult to analyze the scenarios due to the complexity of modeling and the variety of scenarios. Japan Atomic Energy Agency and Tokyo Institute of Technology have jointly developed the NMB code as a tool for integrated analysis of mass balance from natural uranium needs to radionuclide migration of geological disposal. This user manual describes how to create a database and scenario input for the NMB version 4.0.
Okamura, Tomohiro*; Oizumi, Akito; Nishihara, Kenji; Nakase, Masahiko*; Takeshita, Kenji*
JAEA-Data/Code 2020-023, 32 Pages, 2021/03
JAEA-Data-Code-2020-023.pdf:1.67MB
Nuclear Material Balance code (NMB code) have been developed in Japan Atomic Energy Agency. The NMB code will be updated with the function of mass balance analysis at the backend process such as reprocessing, vitrification and geological disposal. In order to perform its analysis with high accuracy, it is necessary to expand the number of FP nuclides calculated in the NMB code. In this study, depletion calculation by ORIGEN code was performed under 3 different burn-up conditions such as spent uranium fuel from light water reactor, and nuclides were selected from 5 evaluation indexes such as mass and heat generation. In addition, the FP nuclides required to configure a simple burnup chain with the same calculation accuracy as ORIGEN in the NMB code was selected. As the result, two lists with different number of nuclides, such as "Detailed list" and a "Simplified list", were created.
Nishihara, Kenji
JAEA-Data/Code 2020-005, 48 Pages, 2020/07
JAEA-Data-Code-2020-005.pdf:2.95MB
JAEA-Data-Code-2020-005-appendix(CD-ROM).zip:3.62MB
In order to discuss the technological development and human resource development necessary for the future nuclear fuel cycle, various quantitative analyzes were conducted assuming a wide range of future nuclear power generation scenarios. In the evaluation of quantities, the future power generation of LWR and fast reactor, the amount of spent fuel reprocessing, etc. were assumed, and the amount of uranium demand, the accumulation of spent fuel, plutonium, vitrified waste etc. were estimated.
Nishihara, Kenji
no journal, ,
In order to discuss the technological development and human resource development necessary for the future nuclear fuel cycle at the research committee on "Feasibility of Nuclear Fuel Cycle," various quantitative analyzes were conducted assuming a wide range of future scenarios. In the evaluation of quantities, the future power generation of LWR and fast reactor, the amount of spent fuel reprocessing, etc. were assumed, and the amount of uranium demand, the accumulation of spent fuel, plutonium, vitrified waste etc. were estimated.
Nishihara, Kenji; Takeshita, Kenji*; Shimada, Takashi*; Aizawa, Naoto*; Nakase, Masahiko*; Wada, Satoshi*; Wakasaki, Shingo*; Matsui, Minefumi*; Yasunaga, Yoshiaki*; Okamura, Tomohiro*; et al.
no journal, ,
This study presents benchmark activities conducted by a research committee of the Atomic Energy Society of Japan to enhance the reliability of nuclear fuel cycle simulators. Standard reactor libraries and phased benchmark scenarios were developed and applied to stepwise validation exercises. The results clarify consistency of simulators on burnup calculation and impact of human error. The results for 11 large-scale scenarios are also provided for future activity.
Nishihara, Kenji; Abe, Takumi
no journal, ,
In order to study the future nuclear power generation and nuclear fuel cycle including geological disposal in Japan, various quantity evaluation codes are used to calculate the time variation of the quantities. The NMB code published by Tokyo Institute of Technology and JAEA was used to evaluate various quantities using the example of the Ikata Nuclear Power Plant, and the code was validated. Simple future projections were also made.
Nishihara, Kenji
no journal, ,
no abstracts in English
Ono, Koki*; Okamura, Tomohiro*; Abe, Takumi; Nishihara, Takahiro*; Nakase, Masahiko*; Nishihara, Kenji; Suzuki, Taiga*
no journal, ,
no abstracts in English
Takeshita, Kenji*; Matsumura, Tatsuro
no journal, ,
no abstracts in English
Dwijayanto, A. P.*; Nishihara, Kenji; Okamura, Tomohiro*; Nakase, Masahiko*
no journal, ,
NMB4 is a nuclear fuel cycle simulator capable of modelling various nuclear fuel cycle scenarios from front-end to back-end. However, its capability to simulate a Molten Chloride Fast Reactor (MCFR), a subset of Molten Salt Reactor (MSR), had yet to be tested. Verifying NMB4 capability to model MCFR fuel cycle in a nuclear energy system is crucial for determining the limit of applicability and future development of the NMB4 simulator. A mass balance comparison between the NMB4 nuclear fuel cycle simulator and the Monte Carlo code Serpent-2 was then performed. A long-lived marine-based MCFR core with minimal reprocessing was modeled in a Monte-Carlo code as the closest scheme with the depletion capability supported by NMB4. From the results, NMB4 was found to generate an acceptable mass balance compared to Serpent-2, and a simple case study using a marine-based MCFR was subsequently simulated to analyse the mass balance and the disposal area required in a once-through cycle. Several discrepancies in code verification have been discussed, and future developments are suggested.
