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Journal Articles

Measurement of $$^{243}$$Am fission rates in low-enriched uranium region at A-core of KUCA

Oizumi, Akito; Fukushima, Masahiro; Tsujimoto, Kazufumi; Yamanaka, Masao*; Pyeon, C. H.*

KURNS Progress Report 2019, P. 14, 2020/08

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 (FRRs) of Americium-243 ($$^{243}$$Am) to Uranium-235 ($$^{235}$$U) by using a single fission chambers in the KUCA. The result showed that the measured FRR of $$^{243}$$Am/$$^{235}$$U were 0.042 $$pm$$0.002. These measured values will be used for verification of evaluated nuclear data by conducting detailed analyses.

Journal Articles

Sample worth measurements of lead and bismuth in low-enriched uranium region at A-core of KUCA for ADS

Fukushima, Masahiro; Oizumi, Akito; Yamanaka, Masao*; Pyeon, C. H.*

KURNS Progress Report 2019, P. 143, 2020/08

For the design study of ADS, integral experimental data of nuclear characteristics of LBE is necessary to validate cross sections of lead (Pb) and bismuth (Bi). The calculation agree with experiment for the Bi sample worth. On the other hand, the calculation overestimates for the Pb sample worth.

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:0.01(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:57.07(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

Measurement of MA reaction rates under sub-critical condition with spallation neutron source in A-core of KUCA for ADS

Oizumi, Akito; Fukushima, Masahiro; Tsujimoto, Kazufumi; Chiba, Go*; Yamanaka, Masao*; Sano, Tadafumi*; Pyeon, C. H.*

KURNS Progress Report 2018, P. 38, 2019/08

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 (FRRs) of Neptunium-237 ($$^{237}$$Np) or Americium-241 ($$^{241}$$Am) to Uranium-235 ($$^{235}$$U) by using a back-to-back (BTB) fission chamber in the KUCA built as a sub-critical core (k$$_{rm eff}$$ = 0.998) with the nuclear spallation neutron source. The result showed that the measured FRRs of $$^{237}$$Np/$$^{235}$$U and $$^{241}$$Am/$$^{235}$$U were 0.014 $$pm$$0.002 and 0.023 $$pm$$0.005, respectively. These measured values will be used for verification of evaluated nuclear data by conducting detailed analyses.

Journal Articles

Sample worth measurements with systematically changed mixing ratios of lead and bismuth in A-core of KUCA for ADS

Fukushima, Masahiro; Oizumi, Akito; Yamanaka, Masao*; Pyeon, C. H.*

KURNS Progress Report 2018, P. 143, 2019/08

For the design study of ADS, integral experimental data of nuclear characteristics of LBE is necessary to validate cross sections of lead (Pb) and bismuth (Bi). In present study, sample worth measurements were carried out with systematically changed mixing ratios of lead and bismuth, which would be complementary to the previous data of Pb and Bi samples individually measured in FY 2013 and FY 2017, respectively.

Journal Articles

Measurement of MA reaction rates using spallation neutron source

Oizumi, Akito; Fukushima, Masahiro; Tsujimoto, Kazufumi; Yamanaka, Masao*; Sano, Tadafumi*; Pyeon, C. H.*

KURRI Progress Report 2017, P. 50, 2018/08

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 reaction rates of Neptunium-237 ($$^{237}$$Np) and Americium-241 ($$^{241}$$Am) using the nuclear spallation neutron source in the KUCA for 3 hours. The observed distributions of pulse-height of $$^{237}$$Np and $$^{241}$$Am fission reactions were significantly different from the ones generally observed in critical and pulsed neutron source (PNS) experiments because of the influence of the $$gamma$$-ray generated by the nuclear spallation reaction. On the other hand, the capture reaction rate of $$^{237}$$Np was measured in this experiment. The capture reaction rate of the critical experiment which was available to be measured the fission reaction rate of $$^{237}$$Np and $$^{241}$$Am was almost 8 times larger than that of this experiment. Consequently, reducing the influence of the $$gamma$$ generated by the nuclear spallation reaction and extending the duration of the irradiation to 24 or more hours would be necessary for detecting signals of fission reactions under the spallation neutron source.

Journal Articles

Reaction rate analyses of accelerator-driven system experiments with 100 MeV protons at Kyoto University Critical Assembly

Pyeon, C. H.*; Vu, T. M.*; Yamanaka, Masao*; Sugawara, Takanori; Iwamoto, Hiroki; Nishihara, Kenji; Kim, S. H.*; Takahashi, Yoshiyuki*; Nakajima, Ken*; Tsujimoto, Kazufumi

Journal of Nuclear Science and Technology, 55(2), p.190 - 198, 2018/02

 Times Cited Count:13 Percentile:92.61(Nuclear Science & Technology)

At the Kyoto University Critical Assembly, a series of reaction rate experiments is conducted on the accelerator-driven system (ADS) with spallation neutrons generated by the combined use of 100 MeV protons and a lead and bismuth target in the subcritical state. The reaction rates are measured by the foil activation method to obtain neutron spectrum information on ADS. Numerical calculations are performed with MCNP6.1 and JENDL/HE-2007 for high-energy protons and spallation process, JENDL-4.0 for transport and JENDL/D-99 for reaction rates. The reaction rates depend on subcriticality is revealed by the accuracy of the C/E (calculation/experiment) values. Nonetheless, the accuracy of the reaction rates at high-energy thresholds remains an important issue in the fixed-source calculations.

Journal Articles

Progress in long-pulse production of powerful negative ion beams for JT-60SA and ITER

Kojima, Atsushi; Umeda, Naotaka; Hanada, Masaya; Yoshida, Masafumi; Kashiwagi, Mieko; Tobari, Hiroyuki; Watanabe, Kazuhiro; Akino, Noboru; Komata, Masao; Mogaki, Kazuhiko; et al.

Nuclear Fusion, 55(6), p.063006_1 - 063006_9, 2015/06

 Times Cited Count:29 Percentile:89.03(Physics, Fluids & Plasmas)

Significant progresses in the extension of pulse durations of powerful negative ion beams have been made to realize the neutral beam injectors for JT-60SA and ITER. In order to overcome common issues of the long pulse production/acceleration of negative ion beams in JT-60SA and ITER, the new technologies have been developed in the JT-60SA ion source and the MeV accelerator in Japan Atomic Energy Agency. As for the long pulse production of high-current negative ions for JT-60SA ion source, the pulse durations have been successfully increased from 30 s at 13 A on JT-60U to 100 s at 15 A by modifying the JT-60SA ion source, which satisfies the required pulse duration of 100 s and 70% of the rated beam current for JT-60SA. This progress was based on the R&D efforts for the temperature control of the plasma grid and uniform negative ion productions with the modified tent-shaped filter field configuration. Moreover, the each parameter of the required beam energy, current and pulse has been achieved individually by these R&D efforts. The developed techniques are useful to design the ITER ion source because the sustainment of the cesium coverage in large extraction area is one of the common issues between JT-60SA and ITER. As for the long pulse acceleration of high power density beams in the MeV accelerator for ITER, the pulse duration of MeV-class negative ion beams has been extended by more than 2 orders of magnitude by modifying the extraction grid with a high cooling capability and a high-transmission of negative ions. A long pulse acceleration of 60 s has been achieved at 70 MW/m$$^{2}$$ (683 keV, 100 A/m$$^{2}$$) which has reached to the power density of JT-60SA level of 65 MW/m$$^{2}$$.

Oral presentation

The Estimation of a prompt neutron decay constant using linear combination method

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

no journal, , 

no abstracts in English

Oral presentation

Sample worth measurement with systematically changed mixing ratio of Lead and Bismuth in KUCA

Oizumi, Akito; Yamanaka, Masao*; Fukushima, Masahiro; Pyeon, C. H.*

no journal, , 

Sample reactivity worths of Lead (Pb) and Bismuth (Bi), which are a coolant candidate for the accelerator driven system (ADS), have been independently measured for the integral evaluations of their cross sections in the relatively hard neutron spectrum in the Kyoto University Critical Assembly (KUCA), respectively. There is a difference between C/E values of Pb and Bi which are obtained by comparing experimental analysis values using the Monte Carlo calculation code MCNP with the JENDL-4.0 nuclear data library with the measured values. In this experiment, in order to complement the measured values of simple substances of Pb and/or Bi, the sample reactivity worth measurements with systematically changed mixing ratio of them were carried out under the same conditions as the past experiments in the KUCA. First, the reproducibility of past experiments was confirmed from the measurement result of Pb simple substance (Pb100%). In addition, it was confirmed that the new measured values different in the lead volumetric filling ratio obtained in this experiment supplement between the measured values of simple substances of Pb (Pb100%) and Bi (Pb0%) in the past. In the future, the analyses of these series of experiments and the evaluations of C/E values will be carried out by using nuclear data libraries of JENDL, ENDF, and JEFF. By using the sensitivity analysis, we will identify the nuclides and their reactions responsible for the differences between the experimental and measured values and among the each nuclear data library.

Oral presentation

Investigation of nuclear data accuracy for commercial grade accelerator-driven system to transmute minor actinides

Sugawara, Takanori; Kashima, Takao; Gabrielli, F.*; Rineiski, A.*; Yamanaka, Masao*

no journal, , 

The benchmark problem for JAEA-ADS was proposed in IAEA CRP (Coordinated Research Program) on ADS (Accelerator-Driven System). The purpose of this benchmark problem is to obtain fundamental knowledge of calculation accuracy for the neutronics design of a commercial grade ADS at the present time. In this benchmark problem, the calculations of a criticality and a burnup behaviour for JAEA-ADS were proposed and three institutes aimed the problem. The sensitivity and uncertainty analyses were also performed to know the current situation of covariance data prepared in nuclear data libraries. Through the benchmark calculations, it was confirmed that the prediction accuracy of the criticality and the transmutation amount for the ADS had the problem.

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