Estimation of continuous distribution of iterated fission probability using an artificial neural network with Monte Carlo-based training data

Tuya, D.; Nagaya, Yasunobu

Journal of Nuclear Engineering (Internet), 4(4), p.691 - 710, 2023/11

https://doi.org/10.3390/jne4040043

The Monte Carlo method is used to accurately estimate various quantities such as k-eigenvalue and integral neutron flux. However, when a distribution of a quantity is desired, the Monte Carlo method does not typically provide continuous distribution. Recently, the functional expansion tally and kernel density estimation methods have been developed to provide continuous distribution. In this paper, we propose a method to estimate a continuous distribution of a quantity using artificial neural network (ANN) model with Monte Carlo-based training data. As a proof of concept, a continuous distribution of iterated fission probability (IFP) is estimated by ANN models in two systems. The IFP distributions by the ANN models were compared with the Monte Carlo-based data and the adjoint angular neutron fluxes by the PARTISN code. The comparisons showed varying degrees of agreement or discrepancy; however, it was observed that the ANN models learned the general trend of the IFP distributions.

Cavitation damage prediction in mercury target for pulsed spallation neutron source using Monte Carlo simulation

Wakui, Takashi; Takagishi, Yoichi*; Futakawa, Masatoshi

Materials, 16(17), p.5830_1 - 5830_16, 2023/09

https://doi.org/10.3390/ma16175830

Cavitation damage on the mercury target vessel is induced by proton beam injection in mercury. The prediction method of the cavitation damage using Monte Carlo simulations was proposed taking into account of the uncertainties of the position of cavitation bubbles and impact pressure distributions. The distribution of impact pressure attributed to individual cavitation bubble collapsing was assumed to be the Gaussian distribution, and the probability distribution of the maximum value of impact pressures was assumed to be three kinds of distributions; the delta function, the Gaussian and Weibull distributions. Two parameters were estimated using Bayesian optimization by comparing the distribution of the cavitation damage obtained from experiment with that of accumulated plastic strain obtained from the simulation. It was found that the results obtained using the Weibull distribution reproduced the actual cavitation erosion phenomenon better than the other results.

Cavitation damage prediction in mercury target for pulsed spallation neutron sources by Monte Carlo simulation

Wakui, Takashi; Takagishi, Yoichi*; Futakawa, Masatoshi; Tanabe, Makoto*

Jikken Rikigaku, 23(2), p.168 - 174, 2023/06

Cavitation damage on the inner surface of the mercury target for the spallation neutron source occurs by proton bombarding in mercury. The prediction method of the cavitation damage using Monte Carlo simulations was suggested taking variability of the bubble core position and impact pressure distribution into account. The impact pressure distribution was estimated using the inverse analysis with Bayesian optimization was conducted with comparison between cavitation damage distribution obtained from experiment and the cumulative plastic strain distribution obtained from simulation. The average value and spread of maximum impact pressure estimated assuming the Gaussian distribution were 3.1 GPa and 1.2 m, respectively. Simulation results reproduced experimental results and it can be said that this evaluation method is useful.

Insight on the mechanical properties of hierarchical porous calcium-silicate-hydrate pastes according to the Ca/Si molar ratio using synchrotron X-ray scattering and nanoindentation test

Im, S.*; Jee, H.*; Suh, H.*; Kanematsu, Manabu*; Morooka, Satoshi; Choe, H.*; Nishio, Yuhei*; Machida, Akihiko*; Kim, J.*; Lim, S.*; et al.

Construction and Building Materials, 365, p.130034_1 - 130034_18, 2023/02

https://doi.org/10.1016/j.conbuildmat.2022.130034

Evaluation of power distribution calculation of the very high temperature reactor critical assembly (VHTRC) with Monte Carlo MVP3 code

Simanullang, I. L.*; Nakagawa, Naoki*; Ho, H. Q.; Nagasumi, Satoru; Ishitsuka, Etsuo; Iigaki, Kazuhiko; Fujimoto, Nozomu*

Annals of Nuclear Energy, 177, p.109314_1 - 109314_8, 2022/11

https://doi.org/10.1016/j.anucene.2022.109314

Analysis of pulverization property of the collision-plate-type jet mill

Kawaguchi, Koichi; Segawa, Tomoomi; Ishii, Katsunori

Funtai Kogakkai-Shi, 59(6), p.283 - 290, 2022/06

https://doi.org/10.4164/sptj.59.283

In the Japan Atomic Energy Agency, in order to effectively use the out-of-standard pellets in the fuel manufacturing process for high-speed furnaces, we are developing techniques for crushing and reusing them with raw material powder. By analyzing in detail the particle size distribution before and after grinding, it was shown that the grinding powder is composed of three different component particles having different characteristics of the particle size distribution. In addition, we examined the method of predicting pulverized powder particle size distribution from the supply powder particle size distribution.

Annual report of Engineering Services Department on JFY2020

Engineering Services Department

JAEA-Review 2021-054, 85 Pages, 2022/01

JAEA-Review-2021-054.pdf:95.12MB

The Engineering Services Department is in charge of operation and maintenance of utility facilities (water distribution systems, electricity supply systems, steam generation systems and drain water systems etc.) in whole of the institute. And also is in charge of operation and maintenance of specific systems (power receiving and transforming facilities, an emergency electric power supply system, an air/liquid waste treatment system, a compressed air supply system) in nuclear reactor facilities, nuclear fuel treatment facilities and usual facilities or buildings. In addition, the department is in charge of maintenance of buildings, design and repair of electrical/mechanical equipments. This annual report describes summary of activities, operation and maintenance data and technical developments of the department carried out in JFY 2020. We hope that this report may help to future work.

Stoichiometry between humate unit molecules and metal ions in supramolecular assembly induced by Cu and Tb measured by gel electrophoresis techniques

Nakano, Sumika*; Marumo, Kazuki*; Kazami, Rintaro*; Saito, Takumi*; Haraga, Tomoko; Tasaki-Handa, Yuiko*; Saito, Shingo*

Environmental Science & Technology, 55(22), p.15172 - 15180, 2021/11

https://doi.org/10.1021/acs.est.1c03993

Humic acid (HA) can strongly complex with metal ions to form a supramolecular assembly via coordination binding. However, determining the supramolecular size distribution and stoichiometry between small HA unit molecules constituting HA supramolecule and metal ions has proven to be challenging. Here, we investigated the changes in the size distributions of HAs induced by Cu and Tb ions using a unique polyacrylamide gel electrophoresis (PAGE) for the separation and quantification of HA complexes and metal ions bound, followed by UV-Vis spectroscopy and EEM-PARAFAC. It was found that the supramolecular behaviors of Cu and Tb complexes with HA collected from peat and deep groundwater (HHA) differed. Our results suggest that this supramolecular stoichiometry is related to the abundance of sulfur atoms in the elemental composition of HHA. Our results provide new insights into HA supramolecules formed via metal complexation.

HTTR burnup characteristic analysis with detailed axial burning region using MVP-BURN

Ikeda, Reiji*; Ho, H. Q.; Nagasumi, Satoru; Ishii, Toshiaki; Hamamoto, Shimpei; Nakano, Yumi*; Ishitsuka, Etsuo; Fujimoto, Nozomu*

JAEA-Technology 2021-015, 32 Pages, 2021/09

JAEA-Technology-2021-015.pdf:2.74MB

Burnup calculation of the HTTR considering temperature distribution and detailed burning regions was carried out using MVP-BURN code. The results show that the difference in k, as well as the difference in average density of some main isotopes, is insignificant between the cases of uniform temperature and detailed temperature distribution. However, the difference in local density is noticeable, being 6% and 8% for U and Pu, respectively, and even 30% for the burnable poison B. Regarding the division of burning regions to more detail, the change of k is also small of 0.6%k/k or less. The small burning region gives a detailed distribution of isotopes such as U, Pu, and B. As a result, the effect of graphite reflector and the burnup behavior could be evaluated more clearly compared with the previous study.

Analytical study on removal mechanisms of cesium aerosol from a noble gas bubble rising through liquid sodium pool, 2; Effects of particle size distribution and agglomeration in aerosols

Miyahara, Shinya*; Kawaguchi, Munemichi; Seino, Hiroshi; Atsumi, Takuto*; Uno, Masayoshi*

Proceedings of 28th International Conference on Nuclear Engineering (ICONE 28) (Internet), 6 Pages, 2021/08

https://doi.org/10.1115/ICONE28-63286

In a postulated accident of fuel pin failure of sodium cooled fast reactor, a fission product cesium will be released from the failed pin as an aerosol such as cesium iodide and/or cesium oxide together with a fission product noble gas such as xenon and krypton. As the result, the xenon and krypton released with cesium aerosol into the sodium coolant as bubbles have an influence on the removal of cesium aerosol by the sodium pool in a period of bubble rising to the pool surface. In this study, cesium aerosol removal behavior due to inertial deposition, sedimentation and diffusion from a noble gas bubble rising through liquid sodium pool was analyzed by a computer program which deals with the expansion and the deformation of the bubble together with the aerosol absorption considering the effects of particle size distribution and agglomeration in aerosols. In the analysis, initial bubble diameter, sodium pool depth and temperature, aerosol particle diameter and density, initial aerosol concentration in the bubble were changed as parameter, and the results for the sensitivities of these parameters on decontamination factor (DF) of cesium aerosol were compared with the results of the previous study in which the effects of particle size distribution and agglomeration in aerosols were not considered. From the results, it was concluded that the sensitivities of initial bubble diameter, the aerosol particle diameter and density to the DF became significant due to the inertial deposition of agglomerated aerosols. To validate these analysis results, the simulation experiments have been conducted using a simulant particles of cesium aerosol under the condition of room temperature in water pool and air bubble systems. The experimental results were compared with the analysis results calculated under the same condition.