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Journal Articles

Sensitivity coefficient evaluation of an accelerator-driven system using ROM-Lasso method

Katano, Ryota; Yamamoto, Akio*; Endo, Tomohiro*

Nuclear Science and Engineering, 196(10), p.1194 - 1208, 2022/10

 Times Cited Count:0 Percentile:0.02(Nuclear Science & Technology)

In this study, we propose the ROM-Lasso method that enables efficient evaluation of sensitivity coefficients of neutronics parameters to cross-sections. In the proposed method, a vector of sensitivity coefficients is expanded by subspace bases, so-called Active Subspace (AS) based on the idea of Reduced Order Modeling (ROM). Then, the expansion coefficients are evaluated by the Lasso linear regression between cross-sections and neutronics parameters obtained by the random sampling. The proposed method can be applied in the case where the adjoint method is difficult to be applied since the proposed method uses only forward calculations. In addition, AS is an effective subspace that can expand the vector of sensitivity coefficients with the lower number of dimension. Thus, the number of unknows is reduced from the original number of input parameters and the calculation cost is dramatically improved compared to the Lasso regression without AS. In this paper, we conducted ADS burnup calculations as a verification. We have shown how AS bases are obtained and the applicability of the proposed method.

Journal Articles

Proposal and application of ROM-Lasso method for sensitivity coefficient evaluation

Katano, Ryota; Yamamoto, Akio*; Endo, Tomohiro*

Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) (Internet), p.2032 - 2041, 2022/05

We have proposed the ROM-Lasso method to perform an efficient evaluation of the sensitivity coefficients of ADS core parameters to cross sections without major modification of the core analysis system. In the ROM-Lasso method, the sensitivity coefficient vector is expanded via the subspace bases so-called Active Subspace (AS), and the effective number of unknowns is reduced. Then, the expansion coefficients are determined via the penalized linear regression with the core parameters obtained by the random sampling, and the sensitivity coefficient vector is estimated. Owing to the AS, the required number of the core calculations is dramatically reduced in the ROM-Lasso method. In this work, we take the sensitivity coefficient evaluation of the coolant void reactivity at the end of the cycle for example and demonstrate how estimation accuracy depends on the number of samples and the AS.

JAEA Reports

Determination of accelerator parameters for subcriticality measurement of accelerator-driven system before operation

Katano, Ryota; Nishihara, Kenji; Kondo, Yasuhiro; Meigo, Shinichiro

JAEA-Research 2021-016, 16 Pages, 2022/03

JAEA-Research-2021-016.pdf:1.65MB

It has to be confirmed that the accelerator-driven system (ADS), which is dedicated to transmuting minor actinides, is subcritical in any state by measurements. In the previous research, we have proposed a procedure in which the core safely and efficiently approaches the target subcriticality before the operation. In this procedure, the reference value of the subcriticality at the initial state is measured by the area ratio method capable of the absolute value measurement. The area ratio method uses a pulsed neutron source. However, specific and practical parameters of the accelerator for the area ratio method have not been determined. In this study, we determined the accelerator parameters with the consideration of the uncertainties derived by the dead-time of the detector and the statistical error of the count ratio. In addition, we estimate the coating amount of the sample nuclide in the assumption of the use of the fission chambers.

JAEA Reports

User manual of 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.

Journal Articles

Subcriticality determination methodology during fuel loading of accelerator-driven system

Katano, Ryota

Journal of Nuclear Science and Technology, 59(3), p.368 - 381, 2022/03

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

We propose a subcriticality determination methodology to be applied during fuel loading of an accelerator-driven system (ADS). In this methodology, subcriticality is determined via the area ratio method (via the proton accelerator) in the first step and by the neutron source multiplication method (through the spontaneous fission neutrons of minor actinides) in subsequent steps; then, the number of fuel assemblies to be loaded in the next step is predicted. We performed a numerical simulation of the proposed methodology, and the estimated subcriticalities agreed well with those obtained by eigenvalue calculations. We also conducted an uncertainty assessment of the proposed methodology and deduced a value of 1000 pcm for the $$k_{eff}$$ uncertainty. The proposed methodology can be a candidate for practical subcriticality monitoring for ADS.

JAEA Reports

Radiation shielding analysis of the upper structure of an accelerator-driven system

Iwamoto, Hiroki; Meigo, Shinichiro; Nakano, Keita; Yee-Rendon, B.; Katano, Ryota; Sugawara, Takanori; Nishihara, Kenji; Sasa, Toshinobu; Maekawa, Fujio

JAEA-Research 2021-012, 58 Pages, 2022/01

JAEA-Research-2021-012.pdf:7.23MB

A radiation shielding analysis was performed for the structure located above the spallation target of an accelerator-driven system (ADS), assuming one cycle of an 800 MW thermal and 30 MW beam power operation. In this analysis, the Monte Carlo particle transport code PHITS and the activation analysis code DCHAIN-PHITS were used. The structures to be analyzed are a beam duct above the target, a beam transport room located above the ADS reactor vessel, beam transport equipment, and the room ceiling. For each structure, the radiation doses and radioactivities during and after the operation were estimated. Furthermore, the shielding structure of the ceiling was determined. As a result, it was found that the radiation dose at the site boundary would be sufficiently lower than the legal limit by applying the determined shielding structure. Moreover, under the condition of this study, it was shown that the effective dose rate around the beam transport equipment positioned above the target after the operation exceeded 10 mSv/h, and that the maintenance and replacement of the equipment in the room would require remote handling.

Journal Articles

NMB4.0: Development of integrated nuclear fuel cycle simulator from the front to back-end

Okamura, Tomohiro*; Katano, Ryota; Oizumi, Akito; Nishihara, Kenji; Nakase, Masahiko*; Asano, Hidekazu*; Takeshita, Kenji*

EPJ Nuclear Science & Technologies (Internet), 7, p.19_1 - 19_13, 2021/11

Nuclear Material Balance code version 4.0 (NMB4.0) has been developed through collaborative R&D between Tokyo Institute of Technology and JAEA. Conventional nuclear fuel cycle simulation codes mainly analyze actinides and are specialized for front-end mass balance analysis. However, quantitative back-end simulation has recently become necessary for considering R&D strategies and sustainable nuclear energy utilization. Therefore, NMB4.0 was developed to realize the integrated nuclear fuel cycle simulation from front- to back-end. There are three technical features in NMB4.0: 179 nuclides are tracked, more than any other code, throughout the nuclear fuel cycle; the Okamura explicit method is implemented, which contributes to reducing the numerical cost while maintaining the accuracy of depletion calculations on nuclides with a shorter half-life; and flexibility of back-end simulation is achieved. The main objective of this paper is to show the newly developed functions, made for integrated back-end simulation, and verify NMB4.0 through a benchmark study to show the computational performance.

Journal Articles

Measurement of $$^{237}$$Np and $$^{243}$$Am fission reaction rates in lead region at A-core of KUCA

Oizumi, Akito; Katano, Ryota; Kojima, Ryohei; Fukushima, Masahiro; Tsujimoto, Kazufumi; Pyeon, C. H.*

KURNS Progress Report 2020, P. 104, 2021/08

In the nuclear transmutation system such as ADS, the nuclear data validation of MA is required to reduce the uncertainty caused by the nuclear data of MA. This study aims to measure the fission reaction rate ratios (FRRRs) of Neptunium-237 ($$^{237}$$Np) or Americium-243 ($$^{243}$$Am) to Uranium-235 ($$^{235}$$U) by using a single fission chambers in the KUCA. The results showed that the measured FRRRs of $$^{237}$$Np/$$^{235}$$U and $$^{243}$$Am/$$^{235}$$U were 0.048$$pm$$0.003 and 0.042$$pm$$0.004, respectively. The measured values will be used for verification of evaluated nuclear data by conducting detailed analyses.

Journal Articles

Measurement of prompt neutron decay constant with spallation neutrons at Kyoto University Critical Assembly using linear combination method

Katano, Ryota; Yamanaka, Masao*; Pyeon, C. H.*

Journal of Nuclear Science and Technology, 57(2), p.169 - 176, 2020/02

 Times Cited Count:1 Percentile:16.22(Nuclear Science & Technology)

We proposed the linear combination method as a subcriticality measurement method which estimates the prompt neutron decay constant ($$alpha$$) correlated with the subcriticality using measurement results obtained at multiple detector positions. In the previous study, we confirmed applicability of the linear combination method through the pulsed neutron experiment with DT neutron source at Kyoto University Critical Assembly (KUCA). In this study, we conduct the pulsed neutron source experiment with spallation neutrons at KUCA and confirm the robustness of the linear combination to neutron sources.

Journal Articles

Application of linear combination method to pulsed neutron source measurement at Kyoto University Critical Assembly

Katano, Ryota; Yamanaka, Masao*; Pyeon, C. H.*

Nuclear Science and Engineering, 193(12), p.1394 - 1402, 2019/12

 Times Cited Count:4 Percentile:54.72(Nuclear Science & Technology)

The author proposed the linear combination method as a subcriticality measurement method which estimates the prompt neutron decay constant (alpha) correlated with the subcriticality using measurement results obtained at multiple detector positions. In this study, we conduct the pulsed neutron experiment at Kyoto University Critical Assembly (KUCA) and measure alpha by the linear combination method using measured neutron counts. Through experiment, we experimentally show that the linear combination method can reduce the higher-mode effect compared to the conventional method. In addition, experimentally show that the linear combination has capability of the different mode extraction.

Journal Articles

Design of accelerator-driven system consistent to partitioning technology

Sugawara, Takanori; Ban, Yasutoshi; Katano, Ryota; Tateno, Haruka; Nishihara, Kenji

Proceedings of International Conference on the Management of Spent Fuel from Nuclear Power Reactors 2019 (Internet), 9 Pages, 2019/06

The JAEA has proposed the double-strata strategy which will introduce a dedicated minor actinide (MA) transmutation cycle using an accelerator-driven system (ADS). In the previous study, the ideal fuel condition was supposed in the neutronics design of the ADS. For example, impurities such as rare earth (RE) nuclides which would accompany with MA, were not assumed. However, these nuclides would accompany with the ADS fuel and the capture reaction of these nuclides deteriorates the neutron economy of the ADS core. This study investigates a new fuel composition based on the SELECT (Solvent Extraction from Liquid-waste using Extractants of CHON-type for Transmutation) process proposed by JAEA. By performing the neutronics calculation of the ADS with the new fuel composition, a feasibility of the new fuel composition will be investigated.

Journal Articles

Area ratio method via linear combination of the neutron counts in pulsed neutron experiment

Katano, Ryota

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 6 Pages, 2019/05

no abstracts in English

Journal Articles

Estimation method of prompt neutron decay constant reducing higher order mode effect by linear combination

Katano, Ryota

Nuclear Science and Engineering, 193(4), p.431 - 439, 2019/04

 Times Cited Count:5 Percentile:63.49(Nuclear Science & Technology)

We proposed "linear combination method" to reduce the higher order mode effect on the prompt neutron decay constant measured by the pulsed neutron experiment. When the spatial higher order mode effect is taken into account, the time evolution of the neutron counts after the pulsed neutron injection is given by linear combination of multiple exponential functions. However, the measurement results by the conventional method include the systematic error derived from the higher order mode effect because the conventional method fit the neutron counts with a single exponential function. The proposed method extract the single exponential function of the fundamental mode by linear combination of the neutron counts at multiple detectors, thus the proposed method reduces the higher order mode effect. As the verification, we applied the proposed method to the numerical simulation. The results indicate that the proposed method can reduce the higher order mode effect by linear combination.

Journal Articles

Journal Articles

Estimation of sensitivity coefficient based on lasso-type penalized linear regression

Katano, Ryota; Endo, Tomohiro*; Yamamoto, Akio*; Tsujimoto, Kazufumi

Journal of Nuclear Science and Technology, 55(10), p.1099 - 1109, 2018/10

 Times Cited Count:3 Percentile:38.13(Nuclear Science & Technology)

In this study, we propose the penalized regression "adaptive smooth-lasso" for the estimation of sensitivity coefficients of the neutronics parameters. The proposed method estimates the sensitivity coefficients of the neutronics parameters using the variation of the microscopic cross sections and the neutronics parameter obtained by random sampling. The proposed method utilizes only the forward calculations. Thus, the proposed method can be applied for the complex reactor analysis for which the application of the adjoint method is difficult. In this study, we proposed a penalty term considering the characteristics of the sensitivity coefficients of the neutronics parameter to the microscopic multi-group cross sections. Through verification calculation, we show that the proposed method achieves high accuracy with less computational cost compared to the method based on random sampling proposed in the previous studies.

Journal Articles

Impact of impurity in transmutation cycle on neutronics design of revised accelerator-driven system

Sugawara, Takanori; Katano, Ryota; Tsujimoto, Kazufumi

Annals of Nuclear Energy, 111, p.449 - 459, 2018/01

 Times Cited Count:10 Percentile:80.31(Nuclear Science & Technology)

This study aims to review the ADS design based on the outcome for the last dozen years and to investigate the impact of impurities in the transmutation cycle on the ADS neutronics design. The impact of impurities in the transmutation cycle is investigated for the reviewed reference design. For the uranium from the partitioning, the accompaniment of 20 wt.% U against the Pu weight is acceptable although the MA transmutation amount will be decreased slightly. For the rare earth (RE) from the partitioning, the accompaniment of 5 wt.% RE against the MA weight is allowable. In the reprocessing, the decontamination factor, DF=10 for RE is enough from the viewpoint of the neutronics design. The impact of the fuel composition accuracy is also investigated. The uncertainty of the ZrN ratio against the MA fuel should be less than 0.2% to minimize a surplus proton beam current due to the uncertainty.

JAEA Reports

Effect of experiments using Transmutation Physics Experimental Facility on the reduction of uncertainties in reactor physics parameters of an accelerator-driven system

Iwamoto, Hiroki; Nishihara, Kenji; Katano, Ryota*; Fukushima, Masahiro; Tsujimoto, Kazufumi

JAEA-Research 2014-033, 82 Pages, 2015/03

JAEA-Research-2014-033.pdf:6.53MB

The effect of experiments using Transmutation Physics Experimental Facility (TEF-P) is analysed from the viewpoint of the reduction of uncertainties in reactor physics parameters (criticality and coolant void reactivity) of an accelerator-driven system (ADS). The analysis is conducted by the nuclear-data adjustment method using JENDL-4.0 on the assumption that ve types of reactor physics experiments (a total of 44 experiments) are performed in TEF-P: (1) criticality experiment, (2) lead void reactivity experiment, (3) reaction rate ratio experiment, (4) sample reactivity experiment, and (5) fuel replacement reactivity experiment. As the result, 1.0% of uncertainty in criticality is found to be reduced to approximately 0.4%, and effective experiments for the reduction of uncertainty in criticality and coolant void reactivity are shown to be fuel replacement reactivity experiments and lead void reactivity experiments, respectively. Although these effects depend largely on the composition and amount of minor-actinide (MA) fuels, it is found that a combination of different types of experiments and database of existing experiments is effective in reducing the uncertainties.

Oral presentation

Reduction of uncertainties in reactor physics parameters of an accelerator-driven system by minor-actinide loaded experiments at J-PARC

Iwamoto, Hiroki; Nishihara, Kenji; Katano, Ryota*; Fujimoto, Atsushi*

no journal, , 

no abstracts in English

Oral presentation

Development of generalized area ratio method for subcriticality measurement

Katano, Ryota; Nishihara, Kenji; Tsujimoto, Kazufumi; Endo, Tomohiro*

no journal, , 

no abstracts in English

Oral presentation

Impact of impurity in transmutation cycle on neutronics design of accelerator-driven system

Sugawara, Takanori; Katano, Ryota; Tsujimoto, Kazufumi

no journal, , 

This study aims to investigate the impact of impurities in the transmutation cycle on the ADS neutronics design. For the uranium from the partitioning, the accompaniment of 20 wt.% U against the Pu weight is acceptable although the MA transmutation amount will be decreased slightly. For the rare earth (RE) from the partitioning, the accompaniment of 5 wt.% RE against the MA weight is allowable. In the reprocessing, the decontamination factor, DF=10 for RE is enough from the viewpoint of the neutronics design.

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