bluuebunny/crossref_metadata_2025 huggingface dataset:
Research on the Source Convergence Diagnose Method of Monte Carlo Critical Calculation for Loosely Coupled System
Authors: Cheng Yuting , Zhou Qi , Zhu Qingfu , Xia Zhaodong , Ning Tong , Zhang Zhengyang
Published: October 2024

In order to improve the reliability and accuracy of Monte Carlo program in the critical safety calculation of loosely coupled systems, an improved Shannon entropy diagnose method considering the distribution of fission sources and the statistical bias is proposed in this paper. The relative deviation of the distribution of fission sources between adjacent generations and the standard deviation of fission source is proposed. The standard deviation of fission source distribution during source iteration are used as the weight of fission source distribution. Finally, an improved Shannon entropy diagnose method considering the distribution of fission sources and the statistical bias is proposed. This improved Shannon entropy convergence index makes up for the shortcomings of traditional Shannon entropy for lacking the details of local fission source. The improved Shannon entropy convergence index is applied to the benchmark problem: loosely coupled solution Slabs. The results show that compared with the traditional Shannon entropy index, this improved Shannon entropy is more sensitive to the iterative convergence process and can more intuitively and accurately determine the convergence of fission source distribution accompanied by source iteration.
Neutronics and thermal hydraulics analysis on a Lead-bismuth-cooled fast reactor
Authors: Liu Chunyuan , Chen Xiaosong , Yeoh Eing Yee , Li Linsen , Xiao Yueting
Published: October 2024

Breeding Lead-base Economical Safe System-Demonstration BLESS-D is a lead-bismuth-cooled fast reactor proposed by China State Power Investment Corporation Research Institute. It features a pool-type configuration of pressure vessel with a thermal/electric power of 300/100 MW. Neutronics and thermal hydraulics analysis are performed, mainly including a sensitivity study of the fuel components, fuel enrichment, and control-assembly arrangement on the lifetime, and the temperature filed for the fuel assembly with the largest thermal power. The results show that compared with PWR, the 239Pu production for BLESS-D is significantly higher, and the quantity of MAs is also reduced, while the productions of LLFPs are at the same scale. It has also been found that under steady state conditions, the largest temperatures of the fuel pellet, cladding and coolant are all below relevant criteria, showing a good performance in the thermal hydraulics for the design. Optimizing the fuel loading scheme for achieving a safer performance would be a part of the future’s work.
salome_cfd: An HPC framework for thermalhydraulics and multiphysics powered by the open-source Computational Fluid Dynamics Toolbox code_saturne
Authors: Koren Chaï
Published: October 2024

EDF R&D lab Chatou, Fluid Mechanics Energy and Environment department (MFEE), has been developping an HPC oriented Computational Fluid Dynamics toolbox since the late 1990s. This toolbox is based on the open-source Computational Fluid Dynamics (CFD) and multiphysics solver code_saturne. It has a proprietary extension, neptune_cfd, which is a Computational Multiphase Fluid Dynamics solver dealing with multi-phase flows. After a brief overview of code_saturne and neptune_cfd architecture and HPC capabilites, the present paper will focus on the effort made at EDF R&D to harness HPC clusters for thermalhydraulics at an industrial scale. This is made available by codes built from the start with massively-parallel architectures in mind, thus leading to highly scalable solvers which are able to handle tens of billions of cells. User-friendly access and interoperability are pivotal for engineers to take advantage of these HPC capabilities. Among common applications requiring HPC resources, a focus is first made on frontier scale simulations, then on parametric studies and uncertainty quantifications experiments, where a twolevel parallelism is needed : a parallel Design of Experiment evaluation drives computations themselves (massively) parallel.
Data transfers for full core heterogeneous reactor high-fidelity multiphysics studies
Authors: Giudicelli Guillaume , Kong Fande , Stogner Roy , Harbour Logan , Gaston Derek , Terlizzi Stefano , Prince Zachary
Published: October 2024

Multiphysics simulations for nuclear reactor analysis are usually performed by resorting to operator splitting and fixed point iterations between single-physics solvers. This enables the separate solution of each physics, such as neutronics, fuel performance, and thermal hydraulics, on meshes tailored to the requirements of the respective numerical discretizations of the equations. As the equations are coupled, several fields must be transferred between singlephysics solves. Projecting fields between meshes while preserving order of accuracy, conservation properties, and mapping non-overlapping geometries is a complex endeavour. This conference paper will present the transfers as implemented in MOOSE, which can handle arbitrary meshes, arbitrary mappings, conservation of integral quantities, and are made to scale with distributed simulations on both ends of the transfers. Their adequacy for advanced nuclear reactor multiphysics coupling is shown through examples and numerical studies.
Cross section modeling using Monte Carlo tally derivatives for transient multiphysics prediction
Authors: Kreher Miriam , Forget Benoit
Published: October 2024

Monte Carlo neutron transport is often seen as the standard for accurate neutronics simulation of nuclear reactors in steady-state. However, the time dependent equation includes time derivatives of flux and delayed neutron precursors which are difficult to model and tally. In this work, a high-order/low-order approach is adopted that uses the omega method to approximate the time derivatives as frequencies. While this scheme has been previously applied to prescribed transients, thermal feedback is now incorporated to provide a fully self-propagating Monte Carlo transient multiphysics solver which can be applied to transients of several seconds long. Such multiphysics problems are less straight-forward than prescribed transients that can be forced to be axially symmetric or otherwise artificially constrained. This work leverages tally derivatives, which are a Monte Carlo perturbation technique that can identify how a tally will change with respect to a small change in the system, to successfully predict thermal feedback and greatly improve accuracy in an axially non-symmetric, flow-initiated transient. Results show good agreement with a reference solution where very fine outer time steps are used for Monte Carlo calculations.
Neutron resonance cross sections evaluation based on the phase shift deep neural network
Authors: Hu Zehua
Published: October 2024

Neutron resonance cross sections are essential in many nuclear science and application fields. Evaluated nuclear libraries usually derive neutron resonance parameters using R-matrix theory. However, determining these parameters and reconstructing the pointwise cross sections required for transport calculations is a time-consuming process. This paper presents a new method for fitting neutron resonance cross sections by using a phase shift deep neural network (PhaseDNN). The network presents resonance cross sections based on its network parameters. This approach allows for the quick calculation of cross section values from the given network parameters. Additionally, PhaseDNN can fit network parameters to experimental data to obtain a smooth resonance cross section curve. Therefore, it has the potential to be an alternative to R-matrix theory.
NEA GitLab: A centralised platform for development and deployment of nuclear codes and data
Authors: Stainer Thomas , Fleming Michael , Holcomb Andrew , Ogawa Tatsuhiko , Valtavirta Ville , Foster David , Bailey Greg , Gilbert Mark
Published: October 2024

The NEA Data Bank is an international reference centre for computer codes, nuclear and thermochemical data which has traditionally used simple file servers, and even DVDs, to deliver valuable content to end users across the globe. With the recent implementation of a self hosted GitLab system at the NEA it has enabled the Data Bank to streamline delivery, automate processes and testing, while empowering code owners and developers with a secure platform to collaborate and develop codes. In this paper we present the NEA Git- Lab system with some concrete examples of codes such as Kraken, PHITS and FISPACT-II taking advantage of many of the services and functionalities provided by GitLab. We illustrate methodologies on how to work effectively with third party software in a position of being a custodian of code, rather that a code owner, providing DevSecOps as a service.
Compendium on Monte Carlo simulation of photoneutrons in the Giant Dipole Resonance energy range: The first five elements
Authors: Garnaud Louis , Sobczak Luna , Piekar Johann , Sari Adrien , Jinaphanh Alexis , Nasri Amine , Jouanne Cédric , Ogawa Tatsuhiko , Zoia Andrea
Published: October 2024

Neutrons generated by photonuclear reactions, “photoneutrons”, are encountered in various applications involving high-energy gamma sources, electron accelerators or nuclear reactors. Monte Carlo particle-transport codes are generally used to simulate the emission of photoneutrons, characterize their field or assess their impact on nuclear systems. The aim of this work is to create a compendium on the simulation of photoneutrons using several Monte Carlo codes, i.e., MCNP6, PHITS and TRIPOLI-4, each code being run successively with ENDF/B-VIII.0 and JENDL-5 nuclear data libraries. We study the photoneutron fields produced by 50 elements with their natural isotopic composition from the reaction energy threshold up to 30 MeV, i.e., in the regime of the Giant Dipole Resonance (GDR). The photoneutron fields are characterized according to three observables, i.e., photoneutron current, energy spectrum and angular distribution. This paper presents the results obtained for the first five elements in order of increasing atomic number, i.e., deuterium, beryllium, carbon, nitrogen and oxygen. The compendium could serve as a handbook for users to master the current strengths and limitations of the codes, for code developers to make progress in the sampling of neutron-emitting photonuclear reactions, and more broadly for all researchers working on photoneutrons, whether they are evaluators of nuclear data libraries or experimental nuclear physicists.
Discrepancy across various OpenMC versions due to thermal neutron scattering law
Authors: Wang Tianxiang , Chen Shengli , Xu Shuqi , Li Zhuo
Published: October 2024

The performance of neutron transport calculations is heavily reliant on the fidelity of nuclear data. The Free Gas Model (FGM) is no longer applicable at low neutron energy range due to nucleus binding effects, necessitating the implementation of the Thermal Scattering Law (TSL). The present study systematically reports the unexpected discrepancies in keff calculations with TSL across different versions of OpenMC, an open-source Monte Carlo code developed by MIT. Based on four representative benchmark series (HMT-026, HMT-027, BEAVRS, and TRIGA fuel rod), the analysis reveals that updates in OpenMC v0.13.0 significantly contribute to these discrepancies, sometimes up to ~1000 pcm. After further review, a modification in the source code for coherent elastic scattering (suggestion #1949) may affect the sampling of the cosine of the coherent scattering angle. Additionally, recompilation of OpenMC v13.2 using the older segment code aligns reactivity calculations closely with version 0.12.2 and thus confirms the above conclusion. Nevertheless, both the developers and we are still uncertain whether this update is correct until now. A systematic examination of the source code is necessary in the near future. Another direct conclusion from the present study is the importance of including diverse benchmarks for code verification and validation.
Highlighting cross section library effects on absorption rates and flux for natural elements in a thermal spectrum using TRIPOLI-5
Authors: Fröhlicher Kévin , Dechenaux Benjamin , Mancusi Davide , Ichou Raphaëlle , Malvagi Fausto
Published: October 2024

This work presents an investigation of cross section library effects with the new TRIPOLI-5 Monte Carlo code, a joint project between CEA, IRSN and EDF in France. Cross section library effects on the absorption rate and the flux spectrum were highlighted for natural elements subjected to a thermal neutron flux. The numerical benchmark that is presented here is a sphere with a radius of 30 cm filled with 10−2 atoms·(barn·cm)−1 of a single element according to its natural isotopic abundances. For the thermal flux case, a smaller sphere with a radius of 1 cm is placed at the center of the main sphere to obtain a thermal-like flux from a pointwise Maxwellian source using a mixture of hydrogen and boron-10. A total of 12 cross sections libraries have been compared.
Use of correlations for neutron induced fission yields in DARWIN/PEPIN2 Uncertainty Quantification
Authors: Huynh Tan-Dat , Lahaye Sébastien , Tsilanizara Aimé
Published: October 2024

Uncertainty quantification on Decay Heat is of utmost importance for the safety evaluations linked to nuclear waste management. International nuclear data libraries like JEFF, ENDF/B or JENDL provide evaluations on independent fission yields, but generally no correlations between those fission yields. With those data, independent fission yields can be considered as the most important contributor to the Decay Heat uncertainty. Nevertheless, other data are available, like correlation matrices for some fissile systems, or the use of fission yields by mass. Complete correlation matrices appear in nuclear data libraries, like JEFF-4, but are still very scares as only the most prominent fissile systems for nuclear reactor applications have been added. Another approach is to consider the use of the fission yields by mass, which uncertainty is smaller than those of independent fission yields, and adding a constraint when propagating uncertainties. In the work, we show the impact of considering the fission yields by mass, as it was implemented in DARWIN/PEPIN2.4.8. We compare DARWIN/PEPIN2.4.8 results, obtained on a first order direct perturbation approach, with a random sampling method through the use of an URANIE/MENDEL scheme.
Design of a new physics database for FLUKA’s next generation
Authors: Schoofs P.
Published: October 2024

The physics database used by FLUKA dates back more than thirty years. It relies on legacy data structures that, although efficient, are increasingly complicated to maintain. The inception of a new generation of FLUKA code represents a great opportunity to modernize this database. This major upgrade implements a modularization of the data structures and a simplification of the formats. It comes along with the development of auxiliary scripts permitting extensive data testing and regular updating. Interfaces of the new database with both the existing generation of FLUKA as well as the new one are described, including the hierarchical object-oriented paradigm chosen to access data elements in the modernized codebase. Finally, perspectives are given to the extension of this work in terms of contents and features.
Using OpenMC in simulations of a low dimensional cold neutron moderator for the ICONE project
Authors: Wagner Richard , Ott Frédéric , Darpentigny Jacques
Published: October 2024

In this contribution we showcase the use of OpenMC for the validation and optimization of a low dimensional cold neutron moderator for the ICONE project. An overview of our simulation strategy is given and initial results for an optimized layout of a low-dimensional cold neutron moderator are presented. The increase in neutron emission brightness when using a low-dimensional geometry is verified.
A Compact Model for Unresolved Resonance Region Cross Sections
Authors: Ridley Gavin , Burke Timothy , Forget Benoit
Published: October 2024

For decades, the probability table technique has been used to model the behavior of neutron cross sections in the unresolved resonance region with a stochastic approach. Early work from Hwang hinted at the possibility of a universal probability distribution to fit the URR cross section distribution. In this work we present a solution to Hwang’s problem: the normal inverse Gaussian distribution fits the probabilistic behavior of the total cross section almost perfectly for the most important nuclides, both in asymptotic behavior and around the more probable regions.
Evaluation of memory-preserving models for particle transport in random media
Authors: Samba Gerald , Charpentier Nicolas , Stepanovic Bogdan , Soulard Olivier , Laguzet Laetitia
Published: October 2024

A shortcoming of the Levermore-Pomraning (LP) model is its inaccuracy to treat the transport of particles in a diffusive material alternating with a transparent one. Enhanced-memory LP models have been proposed by Zimermann et al. (1991) and Larmier (2018) to circumvent this issue. The main purpose of this paper is to evaluate the PBS2 model also known as Algorithm C in these geometries. A second objective is to generalize it to an arbitrary number of interfaces allowing the same code to give either an approximation of the solution with a few interfaces or a reference result by increasing their number. A third one is to give a mathematical formulation of these models.
Optimal Monte Carlo particle splitting for neutron transport equation
Authors: ShangGuan DanHua , Fu YuanGuang , Ying YangJun , Wang Wei , Xu HaiYan
Published: October 2024

Global tallying problem is hard to be solved efficiently when using Monte carlo method to simulate neutron transport equation, especially for sys- tem with big scale and/or strong imbalanced characteristics. Among numerous global variance reduction methods, particle splitting is an easy-to-implement method, but the efficiency is hard to be satisfying for practical problems. The essential challenge lies in the fact there are too many parameters to be opti- mized. In this paper, a systematic approach for setting all splitting parameters is proposed based on maximization of some global efficiency indicator. Results of two models show this approach can increase the global efficiency indicator up to two orders of magnitude while keeping the results unbiased.
Branchless Collisions for Reducing Spatial Correlations in Continuous Energy Monte Carlo Power Iteration
Authors: Bonnet T. , Belanger H.
Published: October 2024

Branchless collisions are customarily used in time-dependent Monte Carlo simulations and have been recently introduced in Monte Carlo power iteration. Previous works have shown that branchless collisions are very efficient in quenching spatial correlations in a multi-group framework, and a preliminary work was previously conducted in order to extend the use of branchless collisions to continuous energy. In that work, two variants of branchless collisions were introduced: branchless on the material, and branchless on the isotope. In this work, we analyse in depth the effect of using branchless collisions in realistic systems on spatial correlations, and we show that performing branchless collisions on the material consistently results in a smaller effect of spatial correlations than when using a standard branching collision algorithm.
Distributed Memory Algorithms for Weight Cancellation in Monte Carlo Particle Transport Simulations
Authors: Grablevsky Nicholas , Belanger Hunter
Published: October 2024

Recent literature has demonstrated use cases for Monte Carlo transport simulations where particles can have statistical weights that are positive or negative. There are even examples which require particles to have complex statistical weights, and the real and imaginary components can be positive or negative. In such cases, weight cancellation algorithms can be very efficient at reducing the variance, or might even be required for a simulation to converge. Previous works that have employed weight cancellation in distributed memory simulations required that all fission particles be sent to a single node for the cancellation operation. This work examines possible implementations of distributed memory weight cancellation algorithms that do not require the transfer of the fission source to a single node.
Robustness of zero-variance Monte Carlo games
Authors: Ferreira Thayz Gomes , Jinaphanh Alexis , Mancusi Davide , Zoia Andrea
Published: October 2024

Zero-variance Monte Carlo games are ideal sampling strategies that provide the theoretical foundations upon which very successful variancereduction schemes are built. In this work, we explore the robustness of zerovariance games and assess in particular the impact of two common simplifications used in production Monte Carlo codes. First, using a discretized adjoint function to bias the kernels that define the stochastic process. Second, replacing the exact sampling of the flight kernel by approximate sampling strategies that are more amenable to be implemented in production Monte Carlo codes. The resulting effects on the variance and on the Figure of Merit (FoM) will be probed in the framework of a benchmark configuration based on the singlespeed two-direction transport model.
A variance-reduction strategy for the sensitivity of βeff
Authors: Jinaphanh Alexis , Zoia Andrea
Published: October 2024

The Monte Carlo computation of the GPT-based sensitivity of the effective delayed neutron fraction βeff to nuclear data proves to be quite difficult to converge due to the small amount of delayed neutrons that are sampled in k-eigenvalue calculations. This paper describes a variance-reduction method aimed at efficiently computing the sensitivity coefficients of βeff, reducing the associated Monte Carlo uncertainty and increasing the Figure Of Merit. This variance-reduction technique allows also computing the sensitivities of βj eff for a specific precursor family j. Verification and performance evaluation are achieved using simple configurations admitting analytical solutions and several continuousenergy benchmarks.
LAST – a Library And Stochastic Transport tool
Authors: Tamagno Pierre , Vandermeersch Elias
Published: October 2024

A new stochastic particle transport tool named LAST has been developed to allow seamless integral data assimilation on nuclear reaction model parameters during the evaluation process of nuclear data. The present work demonstrates its capability to perform actuate once-through information propagation from pre-processed application library to integral multiplication factor. Exact perturbation on reactivity is the starting point of the integral feedback on nuclear reaction model parameters. Its implementation in LAST is also shown.
Extension of particle-based in-situ visualization for multipoint VR visualization
Authors: Kawamura Takuma , Shimomura Kazuya , Osaki Tsukasa , Idomura Yasuhiro
Published: October 2024

In the field of nuclear engineering, complex simulations on exascale supercomputers generate large-scale data. To facilitate efficient analysis of such simulation data, one needs to share them among scientists at remote locations. However, data I/O and data transfer for such large-scale data are quite costly. To resolve these issues, we developed a remote in-situ visualization system IS-PBVR based on the particle-based volume rendering (PBVR), which is suitable for parallel processing on modern supercomputers. In this study, we extend IS-PBVR for VR visualization on multiple client PCs, thus developing a multi-point remote VR visualization. We apply this technique to fluid simulations on GPU-based supercomputers and verify its utility by sharing in-situ VR visualization between multiple client PCs.
Orano gamma and neutron DER calculation tool for realistic geometry using MCNP6.2
Authors: Blanc Antoine , Herbreteau Jérémie
Published: October 2024

SCAR, a tool developed by Orano, computes both gamma and neutron DER calculation with MCNP6.2 for realistic geometries, representatives of the fuel cycle radioactive sources, with high-level of confidence and in a short computer time. Obtaining DER values with relative error inferior to 5 %, for a common waste canister, for forty shielding thickness and several distances from the source is about 1 minute of engineer time and 10 min of computer time (8 CPU @ 3GHz). The use of SCAR in industrial projects at Orano has already presented benefits in term of shielding thickness and therefore in global cost of a project. The future objective of SCAR is to create a large DER data set in order to train an AI which will be implemented into civil engineering software to automatically size the thickness of the facilities walls. The tool is not intended to be distributed outside of Orano.
Time discretization sensitivity analysis for a rod ejection transient scenario in a generic SMR concept using Serpent/SUBCHANFLOW
Authors: Huaccho Gianfranco , Sánchez-Espinoza Victor Hugo , Mercatali Luigi
Published: October 2024

This paper analyses a control rod ejection transient scenario in a generic SMR concept using the multi-physics coupling tool which includes the Monte Carlo Serpent code (developed at VTT, Finland) and the subchannel thermal-hydraulic code SUBCHANFLOW (developed at KIT, Germany). A Hot Zero Power state (HZP at 330 W) is considered for the initial condition. A control rod assembly located in the peripheral part of the core is ejected in 0.05 s, inserting a reactivity of ~1.4$ into the system and producing a fast excursion of the power in an asymmetric shape, achieving a peak power ~107 times bigger than the initial state. The thermal-hydraulic feedback then controls the prompt-critical condition, achieving a subcritical state. The analysis is restricted to one second time evolution, and a sensitivity analysis on the time discretization using different time bins is performed. The results show how the use of different time discretizations impact the prediction of the main safety parameters’ evolution, with differences up to ~50% in peak power, ~100 °C in fuel temperature, ~20 °C in cladding temperature, and ~40% in DNB ratio. For this particular problem, it is concluded that shorter time bins are needed; minimum differences in terms of temperatures were observed when using 1 ms and 0.5 ms bins, suggesting that time bins of these orders are appropriate for the type of scenario analyzed in this work.
Investigation of Transients with Serpent using the OECD/NEA C5G7-TD Benchmark
Authors: Antunes Acosta Fernandes Ana Carolina , Rouxelin Pascal , Ivanov Kostadin , Avramova Maria
Published: October 2024

This paper shows models developed and results obtained for neutronics simulations of the 3D core of C5G7-TD Benchmark using the Serpent code, and an approach for multi-physics coupling for Serpent/CTF codes was presented. Neutronic simulations included control rod movements and moderator density changes, showing good Serpent results when compared to other codes. Future efforts will include the multi-physics simulation of the transients included in Phase II of the Benchmark.
Preliminary analysis of TREAT free-field experiments using OpenMC
Authors: Ferney Paul , Holschuh Tommy , Chipman Andrew , Jensen Colby
Published: October 2024

This work analyses activation calculations for dosimetry materials during a steady-state irradiation in the Transient Reactor Test (TREAT) reactor core. Hence, we developed a workflow based on the Monte Carlo code OpenMC alongside a custom depletion solver. The irradiation-induced activity as a function of time is computed, and several sensitivity studies are performed to evaluate uncertainty. This study has shown activity computations are sensitive to flux amplitude, irradiation time, atoms quantity and microscopic cross sections. Stochastic uncertainties have been propagated to evaluate the activity uncertainty for each dosimetry material. Most uncertainties are below our target of 3%, which demonstrates OpenMC as a powerful predictive and analysis tool. The precise results obtained through this newly developed computation scheme will be used in future experiments to characterize quantities of interest when operating the TREAT reactor in new configurations.
A Novel Fission-Matrix Based Radial Boundary Correction Methodology and its Implementation into the RAPID Code System
Authors: Al Hajj Walid , Haghighat Alireza
Published: October 2024

The RAPID code system utilizes a novel combined fission matrix methodology to rapidly solve the whole-core eigenvalue problem. To represent axial and radial reflector regions, the fission density distribution in the boundary assemblies, a fission density correction factor methodology was devised and demonstrated. Although, accurate results were achieved, because of the need for a full core Monte Carlo calculation, this technique requires significant computing resources. To address this issue, this paper introduces a novel FM based methodology, which achieves accurate results, however at very small computing expense. The methodology has been implemented into the RAPID code system, and successfully demonstrated for the Watts Bar whole core OECD/NEA
SiC Detector Thickness Optimization for Enhanced Response Variability
Authors: Belfiore Enrica , Antoni Rodolphe , Ben Mosbah Mehdi , Allinei Pierre-Guy , Potiron Quentin
Published: October 2024

Neutron spectroscopy is a crucial point in several nuclear applications. Accurately measuring fast neutron energy distributions in high-flux conditions reveals a significant technology gap, hindering the acquisition of precise energy fluence distributions. This project investigates the potential of machine learning to bridge this gap, focusing on neutron energies from 100 keV to 20 MeV and fluence rates from 1010 n/cm2s to 1012 n/cm2s using solid detectors such as Silicon Carbide (SiC) and Chemical Vapor Deposition (CVD) diamonds. This paper details the simulation design phase of our project, emphasizing the exploration of optimal SiC solid detector thickness to introduce crucial variability for machine learning training.
Radiation shielding analysis and criticality safety calculation for spent fuel transportation cask
Authors: Chen Xiaosong , Yeoh Eing Yee , Zhen Gang , Luo Zhen
Published: October 2024

China anticipates a shortage in storage capacity for spent fuels at reactor sites for the AP1000 NPPs within the next 10 to 20 years. We proposed a conceptual design for a transportation cask capable of loading 21 spent fuel assemblies in AP1000 reactors and studied its criticality safety and radiation safety characteristics. Throughout these operations, three key concepts were taken into account: source term, radiation shielding, and criticality calculations. The sources of the 4.95% enriched spent assemblies following a cooling period of 21 years were calculated by the cosNAB code. The results of the source term computation were utilized as input data for the Monte Carlo code cosRMC, which was employed for shielding calculation and criticality safety analysis. The calculation results have verified the feasibility of the design, which can provide a reference for the development of spent fuel transportation casks for the AP1000 reactor.
A weight window approach for dose rate calculations in Lead-cooled Fast Reactors with OpenMC
Authors: Zammataro Matteo , Falabino Matteo , Abrate Nicolò , Carta Mario , Tomatis Daniele
Published: October 2024

This paper presents the application of a variance reduction technique for radiation shielding calculations in Lead-cooled Fast Reactors (LFRs) using the OpenMC Monte Carlo code. The study focuses on assessing the computational efficiency of the Method of Automatic Generation of Importances by Calculation (MAGIC). This technique is employed to generate weight windows for Monte Carlo simulations, aiming at enhancing the efficiency of dose rate estimations for LFRs. Through a detailed study of a LFR mock-up model, the performance differences between a MAGIC-accelerated and a non-accelerated simulation are investigated in terms of both accuracy and computational cost. The results demonstrate the benefits of the variance reduction method, showing its effectiveness in spreading particles throughout the model while improving the accuracy of Monte Carlo estimates far from the core. In addition, this work demonstrates the performances of the MAGIC method in eigenvalue calculations. This work shows an interesting optimisation of Monte Carlo simulations for LFRs and can be considered as a first milestone for newcleo’s radiation shielding studies.
Multi-material topology optimization of nuclear devices – principle and application
Authors: Chabod Sébastien , Santos Daniel , Sauzet Nadine
Published: October 2024

In this paper, we present a multi-material topology optimization procedure, capable of generating the best possible structure of a nuclear device from a list of design objectives and constraints. We propose an example of applying this new tool to calculate the structure of a neutron moderator, which will be used to generate an epithermal field for metrological applications at a facility of the Institute for Radiation Protection and Nuclear Safety (IRSN, France).
Monte Carlo Simulation of Prompt Dose in the National Ignition Facility
Authors: Khater Hesham
Published: October 2024

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is the world’s largest and most powerful laser system for inertial confinement fusion. The NIF is a 192-laser beam facility that produces more than 2 MJ and 500 TW of ultraviolet light. The facility is expected to generate shots with varying fusion yield (up to 20 MJ or 7.1x1018 neutrons per shot) and a maximum annual yield of 1200 MJ. Monte Carlo simulations have been performed to estimate prompt dose values (neutrons and photons) inside the facility as well as at different locations outside the facility shield walls. The Target Chamber shielding, along with Target Bay and Switchyard walls, roofs, and doors will reduce exposures in occupied areas to acceptable levels. The thicknesses of the different shield doors in the facility were optimized such that prompt dose in occupied areas is limited to < 50 μSv per 20 MJ shot and < 1 mSv for 1200 MJ of annual fusion yield. Most of the normally occupied areas experience limited prompt dose values of < 50 μSv per shot. Low dose values are also expected outside the NIF facility. The maximum annual off-site dose to a maximally exposed individual is small and estimated at 24 μSv for 1200 MJ of fusion yield.
GATE Monte Carlo simulation toolkit for medical physics
Authors: Kochebina Olga , Sarrut David , Arbor Nicolas , Baudier Thomas , Borys Damian , Favaretto Martina , Etxebeste Ane , Fuchs Hermann , Gajewski Jan , Grevillot Loïc , Jacquet Maxime , Jan Sébastien , Kagadis George C. , Kang Han Gyu , Kirov Assen , Krah Nils , Krzemien Wojciech , Lomax Antony , Papadimitroulas Panagiotis , Pereda Alexis , Pommranz Christian , Resch Andreas , Roncali Emilie , Rucinski Antoni , Winterhalter Carla , Maigne Lydia
Published: October 2024

The GATE toolkit (GEANT4 Application for Tomographic Emission) is a GEANT4-based (GEometry ANd Tracking) platform for Monte Carlo simulations in medical physics. GATE applications can be divided into two main axes: radiation-based medical imaging and radiotherapy/dosimetry. The accurate modeling of the first one is crucial for system design and optimization as well as for development and refinement of image analysis algorithms. The importance of the precise simulation of the second is essential for characterisation of external beam radiotherapy (proton therapy and carbon ion therapy) and absorbed dose assessment. Within this paper, we discuss the main features of GATE and give a general view on applications, followed by insights into future development perspectives.
Monte Carlo simulation of Mo-99 isotope production with increased specific activity in WWR-K reactor
Authors: Sairanbayev D. , Gizatulin Sh. , Gurin A. , Aitkulov M. , Kisselyov K. , Nessipbay A. , Ashibayev A. , Kulakov A. , Shaimerdenov A.
Published: October 2024

The activation method used for the production of molybdenum-99 in the WWR-K reactor currently allows the maximum production of the specific activity of molybdenum-99 equal to (85 ± 11) GBq/g Mo as a result of seven-day neutron irradiation of natural molybdenum (VI) oxide. It is known that the reaction 98Mo(n,γ)99Mo is induced in the thermal region, and there are also large resonances in the energy region of about 12 eV and in the range of 0.4–10 keV, and these resonances do not compete with the radiative absorption reactions of other molybdenum isotopes in this area. Thus, an increase in the proportion of epithermal and thermal neutrons will lead to an increase in the production of molybdenum-99. The purpose of this work is to develop the design of an irradiation capsule that creates specified irradiation conditions. For this purpose, various designs of irradiation capsules with different materials that moderate neutrons were considered by calculation. Based on the results of Monte Carlo simulation, the optimal design of the irradiation capsule was selected, which makes it possible to increase the production of specific activity of molybdenum-99. Irradiating trioxide molybdenum with natural composition allows to increase the specific activity by 26%, while using trioxide molybdenum with a 98.7% enrichment molybdenum-98 – by 25%. The paper provides a description of the capsule designs considered and the results of computational modeling with MCNP code for molybdenum of different enrichments.
Prediction of Fuel Debris Location in Fukushima Nuclear Power Plant using Machine Learning
Authors: Alrawash Saed , Hale Matthew F. , Lennox Barry , Joyce Malcolm J. , West Andrew , Watanabe Minoru , Zhang Zhongming , Aspinall Michael D.
Published: October 2024

Accurate fuel debris location is crucial part of the decommissioning of the Fukushima Nuclear Power plants. Conventional methods face challenges due to extreme radiation and complex structure of the materials involved. In this study, we propose a novel approach utilising neutron detection and machine learning to estimate fuel material location. Geant4 simulations and pythonTM scripts have been used to generate a comprehensive dataset to train a machine learning model using MATLAB’s regression learner. A Gaussian Process Regression model was chosen for training and prediction. The results show excellent prediction performance to estimate the corium thickness effectively and to locate the nuclear fuel material with a mean square error (MSE) of 0.01. By combining the machine learning with nuclear simulation codes, this promises to enhance the nuclear decommissioning efforts to retrieve nuclear fuel debris.
CurieLM: Enhancing Large Language Models for Nuclear Domain Applications
Authors: Bouhoun Zakaria , Allali Ahmed , Cocci Riccardo , Assaad Mohamad Ali , Plancon Alexandra , Godest Frederic , Kondratenko Kirill , Rodriguez Julien , Vitillo Francesco , Malhomme Olivier , Bechet Lies Benmiloud , Plana Robert
Published: October 2024

Large Language Models (LLMs), such as the Mistral model, have exhibited remarkable performance across diverse tasks. However, their efficacy in nuclear applications remains constrained by a lack of domain-specific knowledge and an inability to effectively leverage that knowledge. Nuclear-related tasks, including safety assessments and requirement analyses, pose unique challenges due to the intricate domain expertise and diverse constraints involved. To address these limitations, we introduce CurieLM, an LLM specifically tailored for the nuclear domain. CurieLM builds upon the Mistral model, enhancing its capabilities through domain-specific fine-tuning. Our team of nuclear engineers overcame the initial hurdle of accessing high-quality nuclear data, enabling CurieLM to comprehend and accurately respond to nuclear-specific instructions. This manuscript outlines the development and optimization process of CurieLM, marking a significant step toward enhancing nuclear-related natural language processing tasks. Experimental results demonstrate a 13% performance improvement over base LLMs, underscoring the effectiveness of our approach. Domain-specific LLMs like CurieLM hold a great potential across various applications, and this study sets the stage for further exploration in this emerging field.
Enzymatic Plasmonic Optical Fiber Biosensor for Uric Acid Detection
Authors: Assunção Ana Sofia , Sebastião Mariana , Fernandes António J.S. , Teixeira António J.S. , Costa Florinda M. , Leitão Cátia , Pereira Sónia O.
Published: October 2024

Uric acid plays important roles in the body, acting as an antioxidant, contributing to the elimination of metabolic waste, and helping to combat some infections. Alterations in uric acid concentration can be important indicators of disease and their real-time and point-of-care monitoring is of extreme importance, for instance in primary care facilities. Optical fibre biosensors are a promising option, allowing real-time detection, quantification, and monitoring of uric acid concentrations in blood plasma or urine. In this work, enzymatic plasmonic sensors were developed for the detection of uric acid using multimode optical fibres composed of a 400 µm silica core and a polymer cladding. To prepare the sensors, the coating and cladding were removed from a section at the fibre tip, and nano film of gold was deposited on their surface, obtaining gold-coated sensors at the fibre tips (Au-tips). Initially, the sensor was characterized to bulk refractive index, exhibiting a sensitivity of 1420.7 ± 59.8 nm/RIU. The Au-tip was biofunctionalized with the enzyme uricase and detection tests were carried out. Uric acid detection tests revealed a response consistent with the Michaelis-Menten function, which was employed to assess the enzymatic kinetics of uricase immobilized on the Au-tips.
Design and Development of a Color Picker System to Integrate in POC Device Systems
Authors: Serafinelli Caterina , Fantoni Alessandro , Fernandes Miguel Tavares , Alegria Elisabete C.B.A. , Vieira Manuela
Published: October 2024

Nowadays is increasing the demand for miniaturized, user-friendly, automated, and portable sensing systems able to provide a fast and reliable response. In this context, colorimetric detection has emerged for its intrinsic advantages, such as simplicity and rapidity, but also for the outstanding development of novel materials, such as plasmonic nanoparticles, and new technologies. Here, the Color Picker system, a system reproducing in the ba has been developed and tested on a plasmonic paper. The aim is to provide a tool for a colorimetric detection that can be successively integrated in next generation diagnostic devices for real world applications.
WDM C-band four channel demultiplexer using cascaded multimode interference on SiN strip waveguide structure
Authors: Malka Dror
Published: October 2024

Back reflection challenges significantly constrain the efficiency of optical communication networks employing dense wavelength division multiplexing (DWDM) technology, particularly those based on Silicon (Si) Multimode Interference (MMI) waveguides. To mitigate this limitation, we present a novel 1×4 optical demultiplexer design using MMI within a Silicon-Nitride (SiN) strip waveguide configuration, operating within the C-band spectrum. Our design was optimized using AI-enhanced RSoft-CAD simulations that combined the Beam Propagation Method (BPM) and Finite-Difference Time-Domain (FDTD) techniques, integrated with convolutional neural network (CNN) machine learning algorithms. The simulation results demonstrate that the proposed device efficiently transmits four channels with 10 nm spacing in the C-band, showing low power loss ranging from 1.98-2.35 dB, a broad bandwidth of 7.68-8.08 nm, and excellent crosstalk suppression between 20.8-23.4 dB. Leveraging the low refractive index of SiN, we achieve ultra-low back reflection of 40.58 dB without requiring specialized angled MMI designs, which are often necessary in Si-based MMI technology. Consequently, this SiN-based MMI demultiplexer provides an effective solution for DWDM systems, enabling high data transmission rates with minimal back reflection in optical communication networks.
Mobile system to detect plastic particles in critical scenarios: Potential approach for attachment in UAVs
Authors: Pereira Guilherme , Marques Carlos
Published: October 2024

This study aims to develop an efficient and cost-effective system for detecting small particles, with the potential for integration with unmanned aerial vehicles (UAVs). The research is divided into two main components: simulation and practical experimentation. The findings demonstrate that the system is capable of detecting particles with widths up to 400 µm. Additionally, it was established that the signal response could be modulated following a sigmoid function. These results confirm the functionality of the system; however, the simulation component indicates potential areas for improvement. Moreover, there is significant potential for the system to be adapted for UAV attachment.
Efficient generation of two coherent spectral lines using two mutually injection locked DFB lasers
Authors: Rama Leonardo , Violas Manuel , Drummond Miguel
Published: October 2024

This work proposes a new energy efficient method for generating two mutually coherent laser lines. This method combines mutual optical injection locking with external modulation, which can be implemented with an electro-absorption modulator (EAM). Numerical simulations demonstrate that the proposed method is feasible within a narrow locking range. In addition, it is demonstrated that suppressing the optical carrier of the modulated signal extends the locking range by a factor of 3.
A Comparative Study of Surface Plasmon and Tamm Plasmon Polaritons for Hydrogen Sensing
Authors: Almeida Miguel A.S. , Carvalho João P.M. , Pastoriza-Santos Isabel , Almeida José M.M.M. , Coelho Luís C.C.
Published: October 2024

Due to the exponential increase in energy consumption and CO2 emissions, new sustainable energy sources have emerged, and hydrogen (H2) is one of them. Despite all the advantages, H2 has high flammability, so constant monitoring is essential. Two optical techniques were numerically studied and compared with the goal of H2 sensing: surface plasmon polaritons (SPP) and Tamm plasmon polaritons (TPP). The H2-sensitive material used was palladium (Pd) in both techniques. The SPP structure was found to have more sensitivity to H2 than TPP, 23 and 5nm/4vol% H2, respectively. However, the latter has lower FWHM, with the minimum of the band showing reflectivity near 0%. In addition, TPP also uses more costeffective materials and can be interrogated at normal incidence with depolarized light. The potential of using each of these optical techniques for H2 sensing was demonstrated.