Code Coupling Research Articles

Burnup-control drum coupling characteristics investigation of lead–bismuth eutectic-cooled solid reactor

As an advanced research tool, neutronics and thermal-hydraulics coupling have a wide range of promising applications in the field of nuclear energy. This paper develops a burnup-control drum coupling code based on the Monte Carlo code RMC and the computational fluid dynamics (CFD) program STAR-CCM +. The dynamic adjustment of the control drums' position and more realistic prediction of reactor neutronics and thermal-hydraulics is achieved by updating the nuclide density, solving the control drum value function and updating the neutronics model in the process of burnup calculation. The core of a lead–bismuth-cooled solid reactor was also studied to investigate the neutronics and thermal-hydraulics properties of the solid core when the effective multiplication factor was kept at about 1.0, and the core's power and temperature variation patterns during the lifetime were obtained. The results of the study show that the simulation of the coupling code achieves the design purpose. In addition, the solid core's maximum fuel and cladding temperatures decrease with the deepening of the burnup.

Finite-Length Analysis for Spatially Coupled LDPC Codes Based on Base Matrix.

Spatially coupled low density parity check (SC-LDPC) are prominent candidates for future communication standards due to their "threshold saturation" properties. To evaluate the finite-length performance of SC-LDPC codes, a general and efficient finite-length analysis from the perspective of the base matrix is proposed. We analyze the evolution of the residual graphs resulting at each iteration during the decoding process based on the base matrix and then derive the expression for the error probability. To verify the effectiveness of the proposed finite-length analysis, we consider the SC-LDPC code ensembles constructed by parallelly connecting multiple chains (PC-MSC-LDPC). The analysis results show that the predicted error probabilities obtained by using the derived expression for the error probability match the simulated error probabilities. The proposed finite-length analysis provides a useful engineering tool for practical SC-LDPC code design and for analyzing the effects of the code parameters on the performances.

Water Chemistry Impact on Activated Corrosion Products: An Assessment on Tokamak Reactors

Activated Corrosion Product (ACP) formation and deposition pose a critical safety issue for nuclear fusion reactors. The working fluid transports the ACPs towards regions accessible by worker personnel, i.e., the steam generator. The code OSCAR-Fusion has been developed by the CEA (France) to evaluate the ACP generation and transport in closed water-cooled loops for fusion application. This work preliminary assesses the impact of water chemistry on the transport, precipitation, and deposition of corrosion products for the EU-DEMO divertor Plasma Facing Unit Primary Heat Transfer System. Sensitivity analyses and uncertainty quantification are needed due to the multi-physics phenomena involved in ACP formation and transport. The OSCAR-Fusion/RAVEN code coupling developed by the Sapienza University of Rome and ENEA are used. This work presents the perturbation results of different parameters chosen for a closed water-cooled loop considering a continuous scenario of 1888 days. The aim of this work is to preliminarily assess the variation of build-up of ACPs, perturbing the alkalizing agent concentration into the coolant, and the corrosion and release rates of different materials. The assessment of ACP formation deposition and transport is fundamental for source term identification, reduction of radiation exposure assessment, maintenance plan definition, design optimization, and waste management.

A New Calculation Strategy for Molten Salt Reactor Neutronic–Thermal-Hydraulic Analysis Implemented with APOLLO3® and TRUST/TrioCFD

Molten salt nuclear reactors (MSRs) constitute a promising technology to produce safe, reliable, abundant low-carbon energy. To design MSR systems and perform safety analyses on them, numerical simulation is a powerful tool. Here, we implemented a coupling between several solvers of the deterministic neutronics code APOLLO3® (the MINARET SN transport and the MINOS diffusion and SPn-simplified transport solvers) and the computational fluid dynamics (CFD) code TRUST/TrioCFD, both developed at the French Alternative Energies and Atomic Energy Commission (CEA). The code coupling is orchestrated using the dedicated C3PO library of the open-source SALOME platform. A new code-coupling strategy is employed whereby the delayed neutron precursor concentrations are computed by the CFD code, which eases the use of traditional deterministic neutronics codes. We verified the correctness of our implementation by performing a numerical benchmark dedicated to fast spectrum MSRs originally devised by the French National Center for Scientific Research. The numerical results we obtained are in excellent agreement with those obtained by recent MSR-dedicated multiphysics simulation tools. This study provides a new convenient neutronic–thermal-hydraulic coupling strategy for MSR core simulation.

Multi-physical fuel performance modeling of U-50Zr helical cruciform fuel based on fluid-thermal-structure coupling methodology

Helical cruciform fuel (HCF) has the potential to improve the power density and safe margins of nuclear reactors. However, the four-petaled twisting profile of HCF contributes to completely different fuel performance against traditional rods, so the fluid–solid coupled analysis on HCF is significant. In this paper, one fluid–solid interaction coupling code was developed for data communications and mesh mappings between the CFD and FEM solvers. The fluid-thermal-structure coupling simulation on HCF was carried out under in-pile conditions, and the multi-physical coupled fuel performance was analyzed. Under the non-irradiated condition, the maximum fuel temperature was predicted to be 598.8 K due to high heat transfer capacity, and the mechanical contact effect would lead to the stress concentration of 207.4 MPa at the blade zones. In the long-time irradiated stage, the swelling would result in fuel deformation and fluid channel compression, which could further affect the flow velocity and heat transfer behaviors. In addition, the principal plastic strain was estimated to be 0.086 at 4.83% FIMA burnup, which remains a tough challenge for the HCF application.

Fast reactor multi-scale and multi-physics modelling at NRG

With the increase in computational power and capacity, and the advancements being made in numerical modeling, it has become possible to model the various physical phenomena that take place in nuclear reactors with more and more detail and accuracy. This includes phenomena related to structural mechanics, fluid dynamics and reactor physics amongst others. Additionally, there has been an increased interest to simulate these combined, interacting phenomena simultaneously by coupling various numerical tools. This coupling of different codes is currently a topic high on the research and development agenda of the international nuclear community. It is also a focus point within the research done at NRG in the national PIONEER research program funded by the Dutch ministry of economic affairs.This focus has resulted in two branches of research at NRG: multi-scale modeling of the complete primary system of a nuclear reactor by coupling a 3D Computational Fluid Dynamics (CFD) code with a 1D System Thermal Hydraulics (STH) code, and multi-physics modelling through the coupling of dedicated and advanced thermal-dynamics, structural mechanics and reactor physics solvers. The paper presents simulation results of both branches applied to fast reactors. As both fields of research require the coupling of codes, it has led to the creation of an independent, external, Fortran-based coupling tool named myMUSCLE (MultiphYsics MUltiscale Simulation CoupLing Environment) that arranges the efficient and robust coupling of the different codes. The paper presents the proof-of-principle and first validation of the myMUSCLE tool under development. Additionally, results obtained with MUSCLE-Foam will be presented, which is a new multi-physics code being developed at NRG that includes several reactor physics as well as structural mechanics solvers.

Multiphysics analysis of fuel fragmentation, relocation, and dispersal susceptibility–Part 1: Overview and code coupling strategies

The US nuclear energy industry is investigating strategies to increase the reactor operating cycle to 24 months, resulting in peak rod average burnups exceeding the current limit of 62 GWd/tU. This increase will in turn increase the probability of fuel fragmentation, relocation, and dispersal (FFRD) in the event of a loss-of-coolant accident (LOCA). This effort couples multiple codes to (1) evaluate full-core power histories for high-burnup fuel operated in a Westinghouse 4-loop pressurized water reactor, (2) model a postulated large-break LOCA, and (3) calculate the mass of fuel susceptible to FFRD. This paper, the first of three describing the work, focuses on code coupling strategies and FFRD susceptibility calculations. The other two companion papers focus on code-specific designs and analyses.Three codes were used in this work. VERA was used to calculate steady-state power histories, TRACE was used to model the transient thermal hydraulics, and BISON was used to model steady-state and transient fuel performance and cladding failure. Several fuel pulverization models were used to calculate FFRD susceptibility in failed rods. Depending on the cladding failure/fuel pulverization model combination, the core-wide FFRD susceptibility during the postulated LOCA range from 0 to over 5,000 kg.

Criticality Evaluation During Fuel Debris Particle Sedimentation Using Coupled DEM-MPS Code

From the viewpoint of criticality management in the fuel debris retrieval operation at the Fukushima Daiichi Nuclear Power Station, it is important in criticality safety analyses to consider the behavior of fuel debris particles as they fall into the water, given that the neutron moderation condition of the fuel debris can dramatically change. In this study, we evaluated a reactivity insertion while fuel debris particles dropped into the water. Specifically, we considered the effects of the fuel debris particle-size distribution in either an erroneous operation or a postulated accident in the fuel debris retrieval operation. Three types of fuel debris particle-size distribution were assumed: monodisperse, uniform, and Rosin-Rammler. The behaviors of the fuel debris particles during sedimentation were evaluated using the coupled Distinct Element Method–Moving Particle Simulation (DEM-MPS) code. The multiplication factors corresponding to the behaviors of the falling fuel debris were calculated by a continuous-energy Monte Carlo code MVP3.0 with JENDL-4.0. Consequently, the multiplication factors changed with the particle motions during the sedimentation, and the trends of the multiplication factors differed between the particle-size distributions. Especially, the 2-cm monodisperse particle-size distribution showed the highest multiplication factor during sedimentation, the trend of which differed from the others in the fuel debris particles dispersing and piled-up phases in the water.

A Novel Coupled Code Shifted M-ary Differential Chaos Shift Keying Modulation

In this paper, a novel coupled code shifted M-ary differential chaos shift keying modulation scheme is proposed as a simple and low-cost solution to reference removal. In this scheme, only two information-bearing signals are transmitted. Both signals are modulated by selected Walsh code sequences with specific indices determined by the index bits, and one of them also carries an additional M-ary information symbol. Since these two information-bearing signals are coupled by the same chaotic message bearer, data bits can be easily recovered according to the correlation between these two signals so that the transmission of reference signals can be completely avoided. Theoretical Bit Error Rate (BER) expressions are derived over the additive white Gaussian noise and multipath Rayleigh fading channels. Furthermore, simulations and comparisons indicate that the proposed system can achieve better BER performance with lower complexity.

Numerical simulation study on pore clogging of pervious concrete pavement based on different aggregate gradation

Pervious concrete (PC) pavements can effectively reduce surface runoff, but it will be clogged with time and its service life will be affected. In this study, based on three groups of PC specimens with different aggregate gradations optimized by previous experiments, the pavement-clogging simulation test is carried out using the two-way coupling of the particle flow code with computational fluid dynamics (PFC-CFD). The results show that when the gradation of aggregates in the pervious pavement is different, the volume fraction of clogging material in the pavement and the time when the volume fraction of the clogging material reaches the maximum are also different. It is related to the zigzag degree and size of the pore in the pervious pavement. The smaller the particle size of coarse aggregate in the pervious pavement, the easier it is to be clogged, and the discontinuous graded coarse aggregate has a good shielding effect on the clogging material. Different clogging material gradations have different effects on the clogging of pervious pavements. According to the aforementioned research results, researchers can select different mix ratios of anti-clogging PC according to different areas of use. The law obtained from the experiment can provide a reference for further study of the double-layer pervious pavement structure design.

The effects of time-variable absorption due to gamma-ray bursts in active galactic nucleus accretion discs

ABSTRACT Both long and short gamma-ray bursts (GRBs) are expected to occur in the dense environments of active galactic nucleus (AGN) accretion discs. As these bursts propagate through the discs they live in, they photoionize the medium causing time-dependent opacity that results in transients with unique spectral evolution. In this paper, we use a line-of-sight radiation transfer code coupling metal and dust evolution to simulate the time-dependent absorption that occurs in the case of both long and short GRBs. Through these simulations, we investigate the parameter space in which dense environments leave a potentially observable imprint on the bursts. Our numerical investigation reveals that time-dependent spectral evolution is expected for central supermassive black hole masses between 105 and 5 × 107 solar masses in the case of long GRBs, and between 104 and 107 solar masses in the case of short GRBs. Our findings can lead to the identification of bursts exploding in AGN disc environments through their unique spectral evolution coupled with a central location. In addition, the study of the time-dependent evolution would allow for studying the disc structure, once the identification with an AGN has been established. Finally, our findings lead to insight into whether GRBs contribute to the AGN emission, and which kind, thus helping to answer the question of whether GRBs can be the cause of some of the as-of-yet unexplained AGN time variability.

FERMI: Fusion Energy Reactor Models Integrator

The Fusion Energy Reactor Models Integrator (FERMI) is an integrated simulation environment under development for the coupled simulation of the plasma, first wall, and blanket of fusion reactor designs. The FERMI goals are to shorten the overall design cycle while guaranteeing unprecedented accuracy, thus integrating fusion design activities, facilitating an optimal reactor design, and reducing development risks. These goals are achieved by coupling single-physics solvers into a multiphysics simulation environment (FERMI). The Integrated Plasma Simulator (IPS)–FASt TRANsport (IPS-FASTRAN) simulation framework is used for the following: plasma physics, MCNP/Shift codes for neutron and photon transport, OpenFoam for computational fluid dynamics and magnetohydrodynamics (MHD), HyPerComp Incompressible MHD solver for Arbitrary Geometry (HIMAG) for dual-coolant lead-lithium (DCLL) blankets, and DIABLO for structural mechanics simulations. These codes are coupled using the open-source library named precise Code Interaction Coupling Environment (preCICE). FERMI’s features are tested with the analysis of the liquid immersion blanket (LIB) [proposed in the Affordable Robust Compact (ARC)–class tokamak design], the DCLL blanket [proposed in the Fusion Pilot Plant (FPP) design], and other benchmark cases. The calculated figures of merit are the tritium breeding ratio, material activation, displacements per atom, shutdown dose rate, heat deposited in the vacuum vessel and blanket, temperature hot spots, and displacements caused by swelling and creep. A critical technical problem is multiphysics code coupling, which is tackled here, and the first three-dimensional (3D) simulations of the DCLL-FPP and LIB-ARC blankets are presented. To the authors’ knowledge, FERMI represents the first effort to perform 3D simulations of nuclear fusion first wall and blankets in a fully coupled multiphysics manner.

Experiment/simulation correlation-based methodology for metallic ballistic protection solutions

A methodology is developed based on the coupling of a finite element code with an optimisation module for the design of land vehicle armouring composed of lightweight aluminium alloy and high strength steel plate. Following an experiment/simulation correlation, a numerical model has been built and calibrated considering monolithic plates and then verified considering a bi-metal protection against tungsten carbide projectile mimicking the core of a 7.62×51 AP8 ammunition. In addition, a method is proposed to obtain the vres−vi curve for the full 7.62×51 AP8 bullet from the vres−vi curve obtained from the core only.

Numerical Modeling of Kinetic Features and Stability Analysis of Jinpingzi Landslide

The kinetic features of a slow-moving landslide situated above the Wudongde hydropower station were analyzed using particle flow code 3D (PFC3D) software. This research was based on geological investigations, remote sensing interpretation, and digital elevation models to build the structure of the Jinpingzi landslide. Finite element analysis (FEM) was used to determine the sliding surface. Strength reduction theory (SRT) and particle flow code coupling were used to invert the macro-strength parameters into micro-strength parameters. Finally, the slope failure process was simulated. Meanwhile, the displacement vector angle (DVA) and velocity were used for stability analysis. The simulation results of the kinetic features of slow-moving landslides show that the initial stage begins with accelerated movement, followed by constant-velocity movement and instability failure. The larger the reduction coefficient is, the shorter the duration of each stage is. A two-parameter instability criterion is proposed based on velocity, DVA, and reduction coefficient. Using this criterion, the critical velocity was 200 mm/s, and the critical DVA was 28.15°. The analysis results agree with the actual field monitoring results and motion process. This work confirms that the PFC3D modeling method is suitable for simulating the motion features of landslides.

Heat loads on the accelerator grids of the ITER HNB prototype

Among the heating and current drive system which are being developed for the ITER experimental reactor, 2 neutral beam injectors with a power of 16.5 MW each will be based on the acceleration of H−/D− ions up to the energy of 870 keV / 1 MeV. Dealing with an accelerated beam power up to 40 MW, beam divergence, aiming and homogeneity have to be optimized to avoid damaging the beamline components or the grids of the accelerator. The design of the ITER HNB prototype, MITICA, was based on the coupling of several codes starting from experimental inputs available at that time. Heat loads, in particular, were estimated by the 2D version of the code Monte Carlo particle tracing code EAMCC. In the last years, a 3D version of the same code was developed and the operation of negative ion sources for fusion increased the knowledge concerning those parameters which are fundamental to estimate the expected heat loads. In this work, calculations are performed by EAMCC3D and the role of different source and accelerator parameters, such as the negative ion temperature and the beam halo, is highlighted.

Free-Ride Coding for Constructions of Coupled LDPC Codes

Free-ride coding, as an approach that admits transmission of a few extra bits over a low-density parity-check (LDPC) coded link without bandwidth expansion, is applied in this paper to construct coupled LDPC codes. Firstly, we present a syndrome channel model and derive the lower and upper bounds on its capacity (referred to as accessible capacity), indicating the feasibility of the reliable transmission of extra bits. Secondly, we present the performance evaluation on both the word error rate (WER) and the bit error rate (BER) for the free-ride codes with simple lower and upper bounds. Then we propose three applications of free-ride coding to construct coupled LDPC codes, including implicit globally-coupled LDPC (GC-LDPC) codes, partial product-LDPC codes, and terminated spatially-coupled LDPC (SC-LDPC) codes, all of which have the figure of merits that they share the same code rates with the basic component LDPC codes. Simulation results show that: 1) the proposed GC-LDPC codes can outperform the component LDPC codes, yielding a coding gain of up to 0.8 dB; 2) the proposed product codes with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(3,6)$ </tex-math></inline-formula> -regular LDPC component codes of length 1024 can lower the WER from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-2}$ </tex-math></inline-formula> down to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-6}$ </tex-math></inline-formula> at the SNR around 2 dB; 3) the proposed terminated SC-LDPC codes can perform as well as the conventional terminated SC-LDPC codes but without any rate loss.

Interphase characterization of glass/epoxy composite using peridynamic method and micro tensile test

ABSTRACT In this paper, a novel procedure is developed to characterize the interphase region using the nonlocal peridynamic method and micro tensile tests of glass/epoxy specimens with a single fiber of glass. For this purpose, micro tensile tests are performed by an accurate tensile test device and high-quality camera imaging for data sampling. The obtained displacements are analysed by the image processing method and used as target values in the peridynamic analyses. Multiscale mass points from macro to micro scale are generated to model the interphase region in single fiber specimens using the state-based peridynamic method. With the coupling of peridynamic and multivariate optimization codes, the program is automatically executed by the prediction of thickness and elastic modulus of interphase to achieve the desired displacements similar to micro tensile test results. In this innovative method, unlike nanoindentation tests, where the results are limited to a specific section or point, the interphase characterization gives an overall elastic modulus value along the examined length of the sample. The obtained results from the presented procedure show that the interphase elastic modulus is between 20.8 and 28.86 GPa and the interphase thickness is between 1.149 and 1.986 microns. The obtained results are in the range of nanoindentation tests results presented in the literature, and the difference could be due to the manufacturing conditions, epoxy properties, and quality of the fiber silane coatings.

KIT Multi-scale thermal–hydraulic coupling methods for improved simulation of nuclear power plants

In a Nuclear Power Plant (NPP), the Thermal-Hydraulic (TH) phenomena take place at different scales in the core and the primary and secondary circuits. Thus different TH codes have been developed to describe the phenomena at the macro- and meso- scale (system, sub-channel, porous media codes). Besides, the use of general-purpose CFD codes for the analysis of specific local problems is rapidly increasing. To take full advantage of the code's strength, the multi-scale TH approach which couple those codes together is becoming a trend in recent years. At Karlsruhe Institute of Technology (KIT), those multi-scale TH approaches involve the system, sub-channel, and CFD codes: 1) the system code TRACE and the sub-channel code SubChanFlow (SCF) were coupled to improve the prediction of the core thermal hydraulics; 2) the system code TRACE and the open-source CFD code TrioCFD were also coupled to improve the prediction of the TH phenomena inside the Reactor Pressure Vessel (RPV). Those works are based on an Interface for Code Coupling (ICoCo) either with or without the SALOME platform. The current investigations demonstrate the potential of multi-scale TH coupling approaches for improved safety-related analysis of the NPP behavior under accidental conditions. In the future, the focus of KIT work is on multiscale coupling based on domain decomposition using both ICoCo and user define functions of commercial CFD codes.

Using Augmented Reality for Visualizing Architectures of Software Modules

Nowadays the technology of augmented reality has become available for a wide audience of users because of a big number of software and hardware enhancements and optimizations done in the last years. The fact that the smartphone is a suitable and relatively cheap device having all the hardware required makes the technology even more accessible and thus widespread. Furthermore, the interaction with three-dimensional objects in space may have positive impact on user’s perception of information. These both facts make the technology of augmented reality a good choice for displaying complex data.The analysis of software plays a significant role in development as it is vital to keep the code clean and sustained all the time. Poor quality code may be unsustainable to the extent it must be fully replaced which results in big losses of resources. In terms of quality checks the analysis must be informative and consume as few resources as possible to be executed so that it is appropriate to perform it regularly. That is the reason for this process to be automated and made convenient to execute and percept.The new system for automatic software analysis is described in this article. ADAR (Architecture Displayer in Augmented Reality) software is best suitable for code coupling and cohesion analysis as it uses three-dimensional graph to display connectivity between parts of software module. High coupling and low cohesion might inform the developers of severe architectural mistakes that may lead to high code fragility. With the use of AR technology the result of high coupling detection analysis in the form of graph is presented in augmented reality to provide user the information in a highly intuitive way.This article also covers different approaches to graph visualization in three-dimensional space. The criteria that allow to achieve high level of aesthetics relative to this problem are stated in paper. The problem of using the force-directed algorithms in terms of high-aesthetic graph visualization is described in details and some arguments pro their usage are given.

Development and verification of the coupling code of discrete ordinates and Monte Carlo methods

This paper studies the discrete ordinates (SN) and Monte Carlo (MC) coupling method, which aims to combine the advantages of the high computational efficiency of SN method and the good geometric modeling ability of MC method. Base on the SN code NECP-Hydra and the MC code NECP-MCX, this paper develops a coupling code NECP-Alter, which converts the angular flux file generated by the SN code into the surface source file for the MC code. Thus, for a shielding problem, the SN calculation is first carried out and the angular flux file of the coupling interfaces is generated. Second, NECP-Alter is adopted to convert the angular flux file to surface source file which can be read by the MC code. Last, the MC calculation is carried out. The numerical results show that the SN-MC coupling method can improve the comprehensive performance of computational accuracy and efficiency in the large-scale PWR shielding problem.