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Journal Articles

Development of a DDA+PGA-combined non-destructive active interrogation system in "Active-N"

Furutaka, Kazuyoshi; Ozu, Akira; Toh, Yosuke

Nuclear Engineering and Technology, 55(11), p.4002 - 4018, 2023/11

https://doi.org/10.1016/j.net.2023.07.015

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

JAEA Reports

Mesh effect around burnable poison rod of cell model for HTTR fuel block

Fujimoto, Nozomu*; Fukuda, Kodai*; Honda, Yuki*; Tochio, Daisuke; Ho, H. Q.; Nagasumi, Satoru; Ishii, Toshiaki; Hamamoto, Shimpei; Nakano, Yumi*; Ishitsuka, Etsuo

JAEA-Technology 2021-008, 23 Pages, 2021/06

JAEA-Technology-2021-008.pdf:2.62MB

The effect of mesh division around the burnable poison rod on the burnup calculation of the HTTR core was investigated using the SRAC code system. As a result, the mesh division inside the burnable poison rod does not have a large effect on the burnup calculation, and the effective multiplication factor is closer to the measured value than the conventional calculation by dividing the graphite region around the burnable poison rod into a mesh. It became clear that the mesh division of the graphite region around the burnable poison rod is important for more appropriately evaluating the burnup behavior of the HTTR core..

JAEA Reports

Report of summer holiday practical training 2019; Feasibility study on nuclear battery using HTTR core; Feasibility study for nuclear design, 2

Ishitsuka, Etsuo; Nakashima, Koki*; Nakagawa, Naoki*; Ho, H. Q.; Ishii, Toshiaki; Hamamoto, Shimpei; Takamatsu, Kuniyoshi; Kenzhina, I.*; Chikhray, Y.*; Matsuura, Hideaki*; et al.

JAEA-Technology 2020-008, 16 Pages, 2020/08

JAEA-Technology-2020-008.pdf:2.98MB

As a summer holiday practical training 2019, the feasibility study for nuclear design of a nuclear battery using HTTR core was carried out, and the $^{235}$ U enrichment and burnable poison of the fuel, which enables continuous operation for 30 years with thermal power of 5 MW, were studied by the MVP-BURN. As a result, it is clear that a fuel with $^{235}$ U enrichment of 12%, radius of burnable poison and natural boron concentration of 1.5 cm and 2wt% are required. As a next step, the downsizing of core will be studied.

Journal Articles

Validation of MOSRA-SRAC for burnup of a BWR fuel assembly

Kojima, Kensuke

Proceedings of International Conference on the Physics of Reactors; Unifying Theory and Experiments in the 21st Century (PHYSOR 2016) (USB Flash Drive), p.3283 - 3292, 2016/05

The MOSRA system has been developing to improve the applicability of the neutronic characteristic analyses. The cell calculation module MOSRA-SRAC is a core module of MOSRA, and applicability tests for realistic problems are required. As a test, MOSRA-SRAC is validated by comparison with measured values. As the measurement, the post irradiation examination SFCOMPO 99-5 is chosen. In the examination, the compositions of major heavy metal and fission product nuclides in a UO $_{2}$ -Gd $_{2}$ O $_{3}$ fuel rod pulled from the 88 BWR fuel assembly used in TEPCO's Fukushima-Daini-2 were measured. The result shows good agreement between calculated and measured value. For uranium and plutonium nuclides, calculated values agree within 5% except for $^{238}$ Pu. $^{238}$ Pu composition is overestimated by 30%, and the overestimation is caused by the unclearness of the void faction history of the fuel rod. For fission products, calculated values agree within approximately 10%.

Journal Articles

Deterioration of pulse characteristics and burn-up effects with an engineering model in Japanese spallation neutron source

Harada, Masahide; Watanabe, Noboru; Teshigawara, Makoto; Kai, Tetsuya; Maekawa, Fujio; Kato, Takashi; Ikeda, Yujiro

LA-UR-06-3904, Vol.2, p.700 - 709, 2006/06

Pulse characteristics data for every neutron beam line are indispensable in designing devices for neutron scattering experiments of JSNS. A detailed model was built and pulse characteristics of each beam line were estimated using the PHITS code and the MCNP-4C code. These results have been disclosed on the J-PARC homepage since September 2004. Due to changes of moderator shapes in a progress of manufacture design, we observed from the calculation that pulse structures of decoupled moderators were deteriorated, especially, those of pulse tail. We found that this deterioration was caused by leakage neutron from gaps between decouplers and absorbing liners of the reflector. For a final stage of the manufacture design, we carefully tried to find other factors which deteriorated the pulse characteristics. Furthermore, pulse structures of poisoned and unpoisoned decoupled moderators were evaluated with the consideration of heterogeneous burn-up and leakage neutron spectra including high-energy region up to GeV were estimated for each neutron beam hole.

Journal Articles

Nuclear design

Fujimoto, Nozomu; Nojiri, Naoki; Ando, Hiroei*; Yamashita, Kiyonobu*

Nuclear Engineering and Design, 233(1-3), p.23 - 36, 2004/10

https://doi.org/10.1016/j.nucengdes.2004.07.008

Times Cited Count：13 Percentile：63.95(Nuclear Science & Technology)

In the nuclear design of the HTTR, the reactivity balance is planned so that the design requirements are fully satisfied. Moreover, the reactivity coefficients are evaluated to confirm the safety characteristics of the reactor. The power distribution in the core was optimized by changing the uranium enrichment to maintain the fuel temperature at less than the limit (1600 $^{circ}$ C). Deviation from the optimized distribution due to the burnup of fissile materials was avoided by flattening time-dependent changes in local reactivities. Flattening was achieved by optimizing the specifications of the burnable poisons. The original nuclear design model had to be modified based on the first critical experiments. The Monte Carlo code MVP was also used to predict criticality of the initial core. The predicted excess reactivities are now in good agreement with the experimental results.

Journal Articles

Validation of the nuclear design code system for the HTTR using the criticality assembly VHTRC

Fujimoto, Nozomu; Nojiri, Naoki; Yamashita, Kiyonobu*

Nuclear Engineering and Design, 233(1-3), p.155 - 162, 2004/10

https://doi.org/10.1016/j.nucengdes.2004.08.005

Times Cited Count：2 Percentile：17.18(Nuclear Science & Technology)

The HTTR uses low-enriched uranium fuel with burnable poison rod. For validation of the nuclear design code system for the HTTR, a critical assembly of VHTRC had been constructed. The calculation uncertainties of effective multiplication factor, neutron flux distribution, burnable poison reactivity worth, and control rod worth, temperature coefficients were evaluated. Calculation accuracy of a Monte Carlo code is also evaluated.

JAEA Reports

Behavior of the regulating control rod on automatic power control mode in operation of JMTR

Nagao, Yoshiharu; Miyazawa, Masataka; Komukai, Bunsaku; Fujiki, Kazuo

JAERI-Tech 2003-067, 33 Pages, 2003/07

JAERI-Tech-2003-067.pdf:1.63MB

no abstracts in English

Journal Articles

Optimization of poisoned and unpoisoned decoupled moderators in JSNS

Harada, Masahide; Teshigawara, Makoto; Watanabe, Noboru; Kai, Tetsuya; Ikeda, Yujiro

Proceedings of ICANS-XVI, Volume 2, p.697 - 706, 2003/07

For two decoupled moderators in JSNS, optimization studies were performed by model calculations using NMTC/JAM and MCNP-4C codes. The model was based on a realistic Target-Moderator-Reflector Assembly. We assumed a para-hydrogen ratio of 100%. The shape of poisoned and unpoisoned moderators is a canteen type with dimensions of 13126.2 cm. A decoupling energy of about 1 eV was adopted to meet the user's requests. As a decoupler material we selected silver-indium-cadmium alloy. It was found that for the decoupled moderators, especially the poisoned moderator, pulse broadening due to a finite beam-extraction angle () was very serious. Therefore, for the poisoned and the unpoisoned moderators were limited to be 7.5 $^{circ}$ and 17.5 $^{circ}$ , respectively. Cadmium (Cd) was selected as a poison material due to higher cut-off energy than gadolinium and higher peak intensity with narrower pulse width. The poison plate will be placed at 25 mm from the viewed surface which meets the user's requirements.

JAEA Reports

Revaluation of JACS code system benchmark analyses of the heterogeneous system; Fuel rods in U+Pu nitric acid solution system

Takada, Tomoyuki; Miyoshi, Yoshinori; Katakura, Junichi

JAERI-Tech 2003-036, 80 Pages, 2003/03

JAERI-Tech-2003-036.pdf:3.67MB

In order to perform accuracy evaluation of the critical calculation by the combination of multi-group constant library MGCL and 3-dimensional Monte Carlo code KENO-IV among critical safety evaluation code system JACS, benchmark calculation was carried out from 1980 in 1982. Some cases where the neutron multiplication factor calculated in the heterogeneous system in it was less than 0.95 were seen. In this report, it re-calculated by considering the cause about the heterogeneous system of the U+Pu nitric acid solution systems containing the neutron poison shown in JAERI-M 9859. The present study has shown that the keff value less than 0.95 given in JAERI-M 9859 is caused by the fact that the water reflector below a cylindrical container was not taken into consideration in the KENO-IV calculation model. By taking into the water reflector, the KENO-IV calculation gives a keff value greater than 0.95 and a good agreement with the experiment.

JAEA Reports

Super safe small reactor RAPID-L conceptual design and R&D, JAERI's nuclear research promotion program, H11-002 (Contract research)

Kobe, Mitsuru*; Tsunoda, Hirokazu*; Mishima, Kaichiro*; Kawasaki, Akira*; Iwamura, Takamichi

JAERI-Tech 2003-016, 68 Pages, 2003/03

JAERI-Tech-2003-016.pdf:4.37MB

The 200 kWe uranium nitride fueled lithium cooled fast reactor "RAPID-L" combined with thermoelectric power conversion system that can be operated unmanned without refueling for up to ten years has been demonstrated. The RAPID refueling concept enables quick and simplified refueling, and achieves plant design lifetime over 20 years. A significant advantage of the RAPID-L design, which does not require the use of control rods - is the introduction of the innovative reactivity control systems: lithium expansion module (LEM), lithium injection module (LIM) and lithium release module (LRM). LEM is the most promisiong candidate for improving inherent reactivity feedback. LEMs could realize burnup compensation. LIMs assure sufficient negative reactivity feedback in unprotected transients. LRMs enable an automated reactor startup by detecting the hot standby temperature of the primary coolant. All these systems use $^{6}$ Li as liquid poison and are actuated by highly reliable physical properties (volume expansion of $^{6}$ Li for LEM, and freeze seal melting for LIM and LRM).