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Journal Articles

A Negative probability table problem of heating number in FENDL-3.1d ACE file

Konno, Chikara; Kwon, Saerom*

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.320 - 325, 2020/10

We found out that p-table data in the FENDL-3.1d ACE file included negative values for 33 nuclei. Thus, we studied why p-tables for heating number included negative. As a result, it was found out that partial KERMA factors became too large because the energy-balance was broken in the 33 nuclei and that FENDL-3.1d adopted kinematics KERMA factors. Then NJOY could not process adequately the 33 nuclei data, which led to negative p-tables for heating number. We prosed two solutions for this issue, produced new ACE files of FENDL-3.1d with the above two methods and confirmed that the new ACE files had no negative p-tables of the heating number.

Journal Articles

Benchmarks of depletion and decay heat calculation between MENDEL and MARBLE

Yokoyama, Kenji; Lahaye, S.*

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.109 - 116, 2020/10

CEA/DEN/DM2S/SERMA and JAEA/NSEC are working on benchmarks for burnup, isotopic concentrations and decay heat calculations in the collaboration framework between both organisms. Both actors of this benchmark are independently developing their own simulation code systems for computing quantities of interest in nuclear fuel cycle domain: MENDEL in CEA and MARBLE in JAEA. The purpose of the benchmark is to verify each system by comparing both calculation results on specific applications. MENDEL uses a several solvers for the resolution of Bateman equation. Runge-Kutta method or Chebyshev Rational Approximation method (CRAM) are used for irradiation computations. An analytical solver can also be used for decay calculations. MARBLE can use Krylov subspace method or CRAM method. As the first phase of the benchmark, we compared the calculated results of decay heat and isotropic concentrations following by a Pu-239 fast fission pulse. We applied nuclear data from three libraries: (1) JEFF-3.1.1, (2) JENDL/DDF-2015 + JENDL/FPY-2011, and (3) ENDF/B-VII.1. Nuclear data and burnup chain were generated from these libraries independently on each system. We confirmed that the results for both systems were in very good agreement with each other. Numerical results were also compared to experimental data. As the second phase of the benchmark, we are proceeding with a burnup calculation benchmark of MENDEL and MARBLE using the nuclear data and burnup chain provided by ORLIBJ33, which is a set of cross-section data based on JENDL-3.3 for ORIGEN-2 code system. We will also compare with calculation results by the ORIGEN-2 code with ORLIBJ33. Since the series of ORLIB, that is, ORLIBJ32, ORLIBJ33, and ORLIBJ40, have been widely used especially in Japan for many years, the comparison with ORLIB is effective for confirming the performance of MENDEL and MARBLE.

Journal Articles

Study of shields against D-T neutrons for Prompt Gamma-ray Analysis apparatus in Active-N

Furutaka, Kazuyoshi; Toh, Yosuke

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.297 - 304, 2020/10

Journal Articles

An Investigation on the control rod homogenization method for next-generation fast reactor cores

Takino, Kazuo; Sugino, Kazuteru; Oki, Shigeo

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.92 - 96, 2020/10

Journal Articles

Applications of radiocesium migration models to Fukushima environmental issues: Numerical analysis of radiocesium transport in temperature-stratified reservoirs by 3D-Sea-SPEC

Yamada, Susumu; Machida, Masahiko; Kurikami, Hiroshi

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.140 - 146, 2020/10

no abstracts in English

Journal Articles

Interactive in-situ steering and visualization of GPU-accelerated simulations using particle-based volume rendering

Kawamura, Takuma; Hasegawa, Yuta; Idomura, Yasuhiro

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.187 - 192, 2020/10

In order to realize the atmospheric dispersion prediction of pollutants, a fluid simulation by adaptive mesh refinement (AMR) optimized for GPU supercomputer has been developed, and interactive visualization and parameter steering of the simulation results are needed. In this study, we extend particle-based in-situ visualization method for structured grids into AMR, and enables in-situ steering of the simulation parameters by utilizing an in-situ control mechanism via files. By combining the developed method with plume dispersion simulation in urban areas running on a GPU platform, it was shown that human-in-the-loop pollution source search is possible without enormous parameter scanning.

Journal Articles

A Comparative study of sampling techniques for dynamic probabilistic risk assessment of nuclear power plants

Kubo, Kotaro; Zheng, X.; Tanaka, Yoichi; Tamaki, Hitoshi; Sugiyama, Tomoyuki; Jang, S.*; Takata, Takashi*; Yamaguchi, Akira*

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.308 - 315, 2020/10

Dynamic probabilistic risk assessment (PRA) is a method for improving the realism and completeness of conventional PRA. However, enormous calculation costs are incurred by these improvements. One solution is to select an appropriate sampling method. In this paper, we applied the Monte Carlo, Latin hypercube, grid-point, and quasi-Monte Carlo sampling methods to the dynamic PRA of a simplified accident sequence and compared the results for each method. Quasi-Monte Carlo sampling was found to be the most effective method in this case.

Journal Articles

Validation study of finite element thermal-hydraulics analysis code SPIRAL to a large-scale wire-wrapped fuel assembly at low flow rate condition

Yoshikawa, Ryuji; Imai, Yasutomo*; Kikuchi, Norihiro; Tanaka, Masaaki; Gerschenfeld, A.*

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.73 - 80, 2020/10

A finite element thermal-hydraulics simulation code SPIRAL has been developed in Japan Atomic Energy Agency (JAEA) to analyze the detailed thermal-hydraulics phenomena in a fuel assembly (FA) of Sodium-cooled Fast Reactors (SFRs). The numerical simulation of a large-scale sodium test for 91-pin bundle (GR91) at low flow rate condition was performed for the validation of SPIRAL with the hybrid k-e turbulence model to take into account the low Re number effect near the wall in the flow and temperature fields. Through the numerical simulation, specific velocity distribution affected by the buoyancy force was shown on the top of the heated region and the temperature distribution predicted by SPIRAL agreed with that measured in the experiment and the applicability of the SPIRAL to thermal-hydraulic evaluation of large-scale fuel assembly at low flow rate condition was indicated.

Journal Articles

Quantitative evaluation of effects of isomorphic substitutions on delamination energies of clay minerals

Yamaguchi, Akiko; Asano, Ikumi*; Kitagawa, Yuri*; Meng, C.*; Nakao, Atsushi*; Okumura, Masahiko

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.127 - 130, 2020/10

no abstracts in English

Journal Articles

Image-based view selection for shape comparison of mode water regions in virtual reality spaces

Yano, Midori; Ito, Takayuki*; Tanaka, Yusuke*; Matsuoka, Daisuke*; Araki, Fumiaki*; Czauderna, T.*; Stephens, K.*

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.201 - 208, 2020/10

Visual analysis plays an important role in understanding and evaluating the climate models, their variables, and their outputs because complex processes are required for the tuning of the climate models. Virtual Reality (VR) technologies are effective for 3D visualization and have been recently employed for visual analysis of more various scientific data. However, researchers may have some problematic situations while using VR space depending on user operations and target geometries. Here, we propose an image-based view selection method to solve these situations and understand differences in ocean states between simulations and observations based on shapes of mode water regions. This view selection takes evaluation criteria for shape comparison of mode water regions generated from simulations and observations into account. This paper introduces two example cases applying this view selection and discusses on a degree of shape matching of mode water regions of each case.

Journal Articles

Communication-avoiding Krylov solvers for extreme scale nuclear CFD simulations

Idomura, Yasuhiro; Ina, Takuya*; Ali, Y.*; Imamura, Toshiyuki*

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.225 - 230, 2020/10

A new communication avoiding (CA) Krylov solver with a FP16 (half precision) preconditioner is developed for a semi-implicit finite difference solver in the Gyrokinetic Toroidal 5D full-f Eulerian code GT5D. In the solver, the bottleneck of global collective communication is resolved using a CA-Krylov subspace method, while the number of halo data communication is reduced by improving the convergence property using the FP16 preconditioner. The FP16 preconditioner is designed based on the physics properties of the operator and is implemented using the new support for FP16 SIMD operations on A64FX. The solver is ported on Fugaku (A64FX) and Summit (V100), which respectively show $$sim$$63x and $$sim$$29x speedups in socket performance compared to the conventional non-CA Krylov solver on JAEA-ICEX (Haswell).

Journal Articles

Intuitive interactions for immersive data exploration of numerical simulation results

Tabata, Ginga*; Sakamoto, Naohisa*; Kawamura, Takuma

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.193 - 200, 2020/10

In interactive visualization/analysis, interactive operation of visualization results on the screen is an important technology that is directly linked to knowledge extraction. On the conventional 2D display, interactive operations such as moving the viewpoint and adjusting the visualization parameters were performed using the mouse. Then, the virtual reality (VR) technology such as CAVE system and head mounted display (HMD) is used for visualization and analysis, and the development of technology for interactively operating visualization result data in VR space has become one of the important issues in the visualization field. In this paper, we propose a technique to capture a real hand gesture by Leap Motion and intuitively change the viewpoint movement and visualization parameters in VR space by HMD. We asked four people to test the developed technology, and obtained a result that it was easy to change the viewpoint from the questionnaire on the operation feeling.

Journal Articles

Performance portable implementation of a kinetic plasma simulation mini-app with a higher level abstraction and directives

Asahi, Yuichi; Latu, G.*; Bigot, J.*; Grandgirard, V.*

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.218 - 224, 2020/10

Performance portability is expected to be a critical issue in the upcoming exascale era. We explore a performance portable approach for a fusion plasma turbulence simulation code employing the kinetic model, namely the GYSELA code. For this purpose, we extract the key features of GYSELA such as the high dimensionality (more than 4D) and the semi-Lagrangian scheme, and encapsulate them into a mini-application which solves the similar but a simplified Vlasov-Poisson system as GYSELA. We implement the mini-app with OpenACC, OpenMP4.5 and Kokkos, where we suppress unnecessary duplications of code lines. Based on our experience, we discuss the advantages and disadvantages of OpenACC, OpenMP4.5 and Kokkos, from the view point of performance portability, readability and productivity.

Journal Articles

Ensemble wind simulations using a mesh-refined lattice Boltzmann method on GPU-accelerated systems

Hasegawa, Yuta; Onodera, Naoyuki; Idomura, Yasuhiro

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.236 - 242, 2020/10

The wind condition and the plume dispersion in urban areas are strongly affected by buildings and plants, which are hardly described in the conventional mesoscale simulations. To resolve this issue, we developed a GPU-based CFD code using a mesh-refined lattice Boltzmann method (LBM), which enables real-time plume dispersion simulations with a resolution of several meters. However, such high resolution simulations are highly turbulent and the time histories of the results are sensitive to various simulations conditions. In order to improve the reliability of such chaotic simulations, we developed an ensemble simulation approach, which enables a statistical estimation of the uncertainty. We examined the developed code against the field experiment JU2003 in Oklahoma City. In the comparison, the wind conditions showed good agreements, and the average values of the tracer gas concentration satisfied the factor 2 agreements between the ensemble simulation data and the experiment.

Journal Articles

GPU-acceleration of locally mesh allocated two phase flow solver for nuclear reactors

Onodera, Naoyuki; Idomura, Yasuhiro; Ali, Y.*; Yamashita, Susumu; Shimokawabe, Takashi*; Aoki, Takayuki*

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.210 - 215, 2020/10

This paper presents a GPU-based Poisson solver on a block-based adaptive mesh refinement (block-AMR) framework. The block-AMR method is essential for GPU computation and efficient description of the nuclear reactor. In this paper, we successfully implement a conjugate gradient method with a state-of-the-art multi-grid preconditioner (MG-CG) on the block-AMR framework. GPU kernel performance was measured on the GPU-based supercomputer TSUBAME3.0. The bandwidth of a vector-vector sum, a matrix-vector product, and a dot product in the CG kernel gave good performance at about 60% of the peak performance. In the MG kernel, the smoothers in a three-stage V-cycle MG method are implemented using a mixed precision RB-SOR method, which also gave good performance. For a large-scale Poisson problem with $$453.0 times 10^6$$ cells, the developed MG-CG method reduced the number of iterations to less than 30% and achieved $$times$$ 2.5 speedup compared with the original preconditioned CG method.

Journal Articles

Molecular dynamics study of phosphorus migration in $$Sigma$$5 grain boundary of $$alpha$$-iron

Ebihara, Kenichi; Suzudo, Tomoaki

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.65 - 69, 2020/10

Phosphorus (P) is known as one of the elements which cause the grain boundary (GB) embrittlement in steels and its GB segregation is promoted by the increase of vacancies and self-interstitial atoms due to irradiation. Thus we have been developing the rate-theory model for estimating GB P segregation under several temperatures and irradiation conditions. Because the model does not include the trapping and de-trapping processes properly, however, the model cannot calculate GB P coverage which is measured by experiments. As for the de-trapping process, so far, we have considered the migration of a P atom in the GB region of $$Sigma$$3 symmetrical tilt GB using molecular dynamics (MD). In the current study, we also simulated the P migration in $$Sigma$$5 GB using MD and compared the result with that of $$Sigma$$3. As a result, at 800K, it was found that a P atom cannot migrate in $$Sigma$$5 without vacancies while a P atom can migrate between iron atoms in $$Sigma$$3.

Journal Articles

Estimation of air dose rate using measurement results of monitoring posts in Fukushima Prefecture

Seki, Akiyuki; Mayumi, Akie; Wainwright-Murakami, Haruko*; Saito, Kimiaki; Takemiya, Hiroshi; Idomura, Yasuhiro

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.158 - 164, 2020/10

We developed a method to estimate the temporal change of the air dose rate at the location with sparse (in time) measurements by using the continuous measurement data from the nearby monitoring post. This method determines an observation model from the correlation between sparse data at the target location and dense data at the monitoring post based on a hierarchical Bayesian model. The developed method was validated against the air dose rate measured at the monitoring posts in Fukushima prefecture from 2012 to 2017. The results showed that the developed method can predict the air dose rate at almost all target locations with an error rate of less than 10%.

Journal Articles

Machine-learning molecular dynamics study of thermal properties of CaF$$_2$$

Nakamura, Hiroki; Machida, Masahiko

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.104 - 108, 2020/10

Journal Articles

JAEA activities related to the use of computer programs and databases in the nuclear field

Suzuki, Yoshio; Otani, Takayuki; Sakamoto, Kensaku; Takakura, Masahiro*; Kuwabara, Yasuhiro*

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.287 - 294, 2020/10

HPC Technology Promotion Office, Center for Computational Science and e-systems (CCSE) of Japan Atomic Energy Agency (JAEA) is responsible for the administration of computer programs (CPs) and databases (DBs) developed in JAEA to disseminate R&D results in JAEA to the outside and improve R&D efficiency. The information of these CPs and DBs can be found using Program and Database retrieval System (PRODAS) (https://prodas.jaea.go.jp), which is developed by our team. Those in Japan can also obtain CPs and DBs in the nuclear field possessed in OECD NEA Data Bank (NEADB), Radiation Safety Information Computational Center (RSICC) in the United States, and International Atomic Energy Agency (IAEA). In this paper, the recent situation of possession and dispatch of CPs and DBs developed within JAEA and the frameworks to obtain and provide CPs and DBs in nuclear field worldwide are presented.

Oral presentation

A Computational approach for an object situated alone in infinitely expanded radiation field by Monte Carlo codes using reflection boundaries

Furuta, Takuya; Takahashi, Fumiaki

no journal, , 

The conventional approach to compute radiation dose for an object in infinitely expanded radiation field by Monte Carlo codes is very inefficient because extremely large is necessary to approximately consider the infinitely expanded radiation field and the probability an initiated radiation to hit the target object is tiny. We therefore proposed an approach to efficiently compute radiation dose in the target object by considering radiation transport in a computational volume of the size slightly larger than the object using reflection boundaries. Firstly radiation transport enclosed in the computational area by the reflection boundaries at the borders was computed without setting the object and the position and momentum of the radiations were recorded just after the reflections. Secondly radiation dose exposure to the object from radiations originated inside and radiations incoming to the area from exterior was computed by setting the object and removing reflection boundaries. The radiation records in the first step are simulating the incoming radiations from infinitely expanded radiation field and thus the radiation dose of the object in infinitely expanded radiation field can be evaluated. The required computational time of our approach was a hundred times shorter than that of the conventional approach. We demonstrate the validity of our approach showing several example applications in this presentation.

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