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Journal Articles

Evaluation of thermal neutron scattering law of nuclear-grade isotropic graphite

Nakayama, Shinsuke; Iwamoto, Osamu; Kimura, Atsushi

EPJ Web of Conferences, 294, p.07001_1 - 07001_6, 2024/04

https://doi.org/10.1051/epjconf/202429407001

Graphite is a candidate of moderator in innovative nuclear reactors such as molten salt reactors. Scattering of thermal neutrons by the moderator material has a significant impact on the reactor core design. To contribute to the development of innovative nuclear reactors, an evaluation method of thermal neutron scattering law for reactor grade graphite was studied. The inelastic scattering component due to lattice vibration was evaluated based on the phonon density of states computed with first-principles lattice dynamics simulations. The simulations were performed for ideal crystalline graphite. The coherent elastic scattering component due to crystal structure was evaluated based on neutron transmission and scattering experiments recently performed in the J-PARC/MLF facility. In comparison with the neutron transmission experiments, it was found that the quantification of small-angle neutron scattering due to structures larger than crystal, such as pores in graphite, is important. Based on the above methods, thermal neutron scattering law data for reactor-grade graphite at room temperature were evaluated.

Journal Articles

Linearization of thermal neutron scattering cross section to optimize the number of energy grid points

Tada, Kenichi

Proceedings of 12th International Conference on Nuclear Criticality Safety (ICNC2023) (Internet), 8 Pages, 2023/10

The number of energy grids of the thermal neutron scattering law data has a large impact on the data size of a cross section file of continuous energy Monte Carlo calculation codes. The optimization of the number of energy grids is an effective way to reduce the data size. This study developed the linearization method of the thermal neutron scattering cross section to optimize the number of energy grids and the linearization function was implemented in the nuclear data processing code FRENDY. The linearization process which is used in the resonance reconstruction and the Doppler broadening was adopted. The criticality benchmarks which use ZrH as the moderator were calculated to estimate the impact of the difference of the energy grids on neutronics calculations. The calculation results indicate that the linearization of the thermal neutron scattering cross section improves the prediction accuracy of neutronics calculations.

Journal Articles

Preliminary analyses of modified STACY core configuration using serpent with JENDL-5

Kawaguchi, Maho*; Shiba, Shigeki*; Iwahashi, Daiki*; Okawa, Tsuyoshi*; Gunji, Satoshi; Izawa, Kazuhiko; Suyama, Kenya

Proceedings of 12th International Conference on Nuclear Criticality Safety (ICNC2023) (Internet), 8 Pages, 2023/10

The Nuclear Regulation Authority (NRA) has been working on an experimental approach for evaluating the criticality of fuel debris produced by the Fukushima Daiichi Nuclear Power Plant (FDNP) accident since 2014, collaborating with the Japan Atomic Energy Agency (JAEA). As part of the approach, JAEA has modified the STAtic experiment Critical facilitY (STACY) for critical experiments to evaluate characteriscs of pseudo-fuel debris. As the preliminary analyses, we verified critical characteristics with major nuclear data libraries for the proposed core configuration patterns. The three-dimensional continuous-energy Monte Carlo neutron and photon transport code, SERPENT-V2.2.0 was used with the latest JENDL, JENDL-5. As a result, larger multiplication factors of JENDL-5 across the modified STACY core configuration patterns were evaluated in comparison to the other libraries. And, $^{1}$ H scattering and $^{238}$ U fission sensitivity coefficients of JENDL-5 were different from those of the other libraries. Comparing among analyses with those libraries, the updated S(, ) of JENDL-5 might affect the result of critical characteristics in the critical analyses for the modified STACY core configuration.

Journal Articles

Thermal-neutron capture cross-section measurement of $^{237}$ Np using graphite thermal column

Nakamura, Shoji; Endo, Shunsuke; Kimura, Atsushi; Shibahara, Yuji*

KURNS Progress Report 2020, P. 94, 2021/08

https://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2020/ProgRep2020.html

The present study selected $^{237}$ Np among radioactive nuclides and aimed to converge a contradiction between reported thermal-neutron capture cross sections. Neutron irradiation was carried out using the graphite thermal column equipped with the Kyoto University Research Reactor. A solution equivalent to 950 Bq order of radioactivity was pipetted out of a $^{237}$ Np standard solution and dropped onto a fiber filter, which was then dried with an infrared lamp to prepare a $^{237}$ Np sample. The $^{237}$ Np sample was quantified using 312-keV gamma ray emitted from $^{233}$ Pa in a radiation equilibrium with $^{237}$ Np. To monitor a thermal-neutron flux component at an irradiation position, the $^{237}$ Np sample was irradiated together with several stable nuclides as neutron flux monitors: $^{45}$ Sc, $^{59}$ Co, $^{98}$ Mo, $^{181}$ Ta and $^{197}$ Au. The reaction rate of $^{237}$ Np was obtained from gamma-ray yields given by $^{238}$ Np and $^{233}$ Pa, and then the thermal-neutron capture cross section of $^{237}$ Np was derived.

Journal Articles

Neutron moderation, 1; Research reactor as neutron source

Arai, Masaji

Hamon, 28(2), p.99 - 102, 2018/05

https://doi.org/10.5611/hamon.28.2_99

A thermal neutron reactor operates by the fission of uranium, a nuclear reaction which produces neutrons of energies in the range of MeV. This is far too high an energy to be useful for neutron scattering experiments. Therefore in a research reactor which has neutron beam utilization there are moderators arranged around the primary source to slow down the source neutrons to useful energies. Additionally almost major research reactors include at least one cold neutron source, a special moderator maintained at cryogenic temperature, where neutrons can equilibrate to lower average energies.

JAEA Reports

Characteristics of thermal neutron calibration fields using a graphite pile

Uchida, Yoshiaki*; Saegusa, Jun; Kajimoto, Yoichi; Tanimura, Yoshihiko; Shimizu, Shigeru; Yoshizawa, Michio

JAERI-Tech 2005-012, 31 Pages, 2005/03

JAERI-Tech-2005-012.pdf:4.58MB

no abstracts in English

Journal Articles

Nondestructive elemental analysis using neutron

Matsue, Hideaki; Tanji, Akira; Miyata, Satoru; Yasuda, Ryo; Matsubayashi, Masahito; Nakanishi, Tomoko

Dai-5-Kai Hoshasen Ni Yoru Hihakai Hyoka Shimpojiumu Koen Rombunshu, p.45 - 48, 2005/02

no abstracts in English

Journal Articles

The Recommended k $_{0}$ -factors for neutron-induced prompt -ray analysis and the prompt -ray emission probabilities

Matsue, Hideaki; Yonezawa, Chushiro

Journal of Radioanalytical and Nuclear Chemistry, 262(1), p.49 - 55, 2004/07

https://doi.org/10.1023/B:JRNC.0000040853.53889.34

Times Cited Count：9 Percentile：52.57(Chemistry, Analytical)

The recommended k $_{0}$ factors for 81 -lines of 24 elements, which are useful for neutron induced prompt -ray analysis (PGA) and are not influenced by neutron spectrum difference, were obtained from the k $_{0}$ factors measured with the cold and thermal guided neutron beams of JRR-3M by statistical calculation. The prompt -ray emission probabilities were derived from the recommended k $_{0}$ -factors using atomic weight, isotopic abundance and thermal neutron cross-section of other nuclear constants consisting the k $_{0}$ factors, for which one can obtain accurate data. The derived -ray emission probabilities for the light elements (H to Ca) well agreed within 10% with those of the ENSDF, which reflect recent data, which the agreements for heavy elements (Ti to Pb) were 40% with those of the ENSDF, which are still composed of old data.

Journal Articles

Development of thermal neutron focusing device using supermirrors

Osakabe, Toyotaka; Soyama, Kazuhiko; Suzuki, Koji*; Miyo, Tatsuya*

Hamon, 14(1), p.84 - 87, 2004/01

https://doi.org/10.5611/hamon.14.84

The neutron-focusing is an indispensable technical element in the experments under extreme condition with tiny samples. In this article, the development of the thermal neutron focusing device is reported. The device has 18 pieces of the 3Q $_{c}$ NiC/Ti neutron supermirrors with the shape of a circle. The extension of the end of each mirror meets at a focal point (sample position). Neutrons are repeatedly reflected with the same angle by the inner side of the circle and arrive at the sample position. The test results show that the integrated intensity increases by a factor of 2 or more for the neutron wavelength of 2.36AA .

Journal Articles

Quantitative assessment of interfering nuclear reactions of matrix elements in neutron activation analysis

Miyamoto, Yutaka

Hoshaka Bunseki Handobukku, 7 Pages, 2004/00

no abstracts in English

Journal Articles

Inelasticity effect on neutron scattering intensities of the null-H $_{2}$ O

Kameda, Yasuo*; Sasaki, Motoya*; Usuki, Takeshi*; Otomo, Toshiya*; Ito, Keiji*; Suzuya, Kentaro; Fukunaga, Toshiharu*

Journal of Neutron Research, 11(3), p.153 - 163, 2003/09

https://doi.org/10.1080/10238160310001657817

We describe results of time-of-flight (TOF) neutron diffraction of the liquid water null-H $_{2}$ O in order to investigate the effect of both the scattering angle and the neutron flight path ratio to the observed self-scattering intensities. An empirical inelasticity correction procedure is proposed using the self-scattering intensity observed for the null-H $_{2}$ O.

Journal Articles