Monte Carlo Code Research Articles

Tuning the range-energy relationship parameter for Monte Carlo-based proton Bragg curve spreading in muscle, bone, and polymethylmethacrylate.

Determination of spread-out Bragg peak (SOBP) inside media other than water is important for research or clinical purposes. Current study aims to characterize the optimal "p" values needed for the simulation of proton SOBP inside some dosimetry media using MCNPX Monte Carlo code. Following the provided data by ICRU-49 and applying the Bortfeld and Jette recommendations, the "p" values were determined for muscle, compact bone, and PMMA. Then, "p" values were optimized to reach accurate weight fractions for the Monte Carlo simulation of SOBP curves. Obtained optimal "p" values can produce accurate proton weight fractions for flat SOBP simulation. The slope of the SOBP region was highly dependent on the "p" value, so small changes in this parameter can largely tilt up or down the SOBP. The tabulated optimal "p" values can be reliably used for proton weight fraction determination during the Monte Carlo simulation of the proton beam SOBP curve inside the investigated media.

Design and implementation of the first proton beam transport line in VEGA-3 Petawatt laser system

Laser–Plasma ion acceleration is acquiring importance on a daily basis due to incipient applicability in certain research fields. However, the energy and divergence control of these brilliant sources can be considered a bottleneck in the development of some applications. In this work, we present the commissioning of a compact proton beamline based on a triplet of quadrupoles dedicated to focus and collect short and energetic pulses, open to the user community. The focused proton beam characterization has been carried out by imaging of scintillation detectors with different particle filters. Experimental results have been compared with numerical simulations performed with Monte Carlo code (MCNP6) and TSTEP that have been used to retrieve the deposited energy, the particle tracking, and the particle distribution in different focal configurations, respectively. Charges of nC ( protons with energies up to 17.25 MeV) have been measured at the focal planes reducing the beam to spot sizes of a few millimetres in RMS (root mean square). The percentage fluctuation of the transported charges values has been studied. Finally, the beam rigidity has been measured by transverse moving of the quadrupoles and subsequent beam centroid shift, allowing to cross correlate the deflected energy with the energy ranges resulting from the filtering process.

Effect of Ti, Bi, W, Zn, and Pb nanoparticles on the radiation shielding properties in transparent medium: a Monte Carlo study

Recently, researchers have tried to examine novel materials to enhance radiation shielding in hospitals and medical centers as a replacement for regular shielding materials such as lead and concrete. To assess the impact of new radiation shield materials, this study is devoted to the examining the silicon shields as well as silica and tellurium glasses containing nanoparticles and micro-particles. For this purpose, using Monte Carlo code MCNPX, the role of Ti, Bi, W, Zn, and Pb particles in silicon shields, also tellurium and silica glasses incorporating Bi2O3, ZnO, TiO2, WO3, and PbO particles in nanometer and micrometer scales with proportions of 10%, 15%, 20%, 25%, 30%, 35%, 40%, and 45% are examined. The MCNP results demonstrate a strong agreement with the XCOM data, with a relative difference less than 2.11% across all samples. The Kolmogorov-Smirnov (K-S) test has been conducted to evaluate the consistency between the simulated data and the XCOM data, with the maximum vertical deviation (Dmax) less than 0.01%. The results show the improvement of radiation protection characteristics following the particle size reduction from micrometers to nanometers in all shields. Moreover, it was observed that increasing the proportion of nanoparticles in the shields enhances the protective properties. As a result, the shields containing the smallest size and accommodating the highest number of particles exhibit the best radiation shielding properties. Finally, the tellurium glasses doped with 45% nanoparticles of WO3 demonstrated the best shielding properties.

Spectroscopic, calorimetric, and radiation shielding analysis of lead-free transparent dysprosium-doped phosphate glasses

Eco-friendly phosphate glasses with 50P2O5-(50 – x)BaO-xDy2O3 (x = 0, 0.5, 1.0, 2.0, 3.0, 4.0 mol %) compositions were prepared and studied focusing on their potential for radiation attenuation and shielding applications. The glasses were synthesized by melting and subsequently characterized by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, densitometry, refractive index, optical absorption, and differential scanning calorimetry (DSC). XRD confirmed the amorphous nature of the glasses, while FT-IR spectra indicated that the glass structure was preserved upon Dy2O3 inclusion. It was observed that both the density and refractive index generally increased with higher Dy2O3 content. Optical absorption data showed a linear increase in Dy3+ ion absorption with Dy2O3 concentration, confirming the effective incorporation of Dy3+ ions. Tauc and Urbach plots were also employed to analyze the absorption edges of the glasses. DSC thermograms revealed that the glass transition temperatures increased while glass stability improved with higher Dy2O3 content. The radiation shielding properties were assessed by evaluating parameters such as mass attenuation coefficients, linear attenuation coefficients, tenth value layer, mean free path, effective conductivity, and effective electron density against gamma-ray photons. Dysprosium doping was found to enhance gamma-ray shielding (from 1 keV to 100 GeV) based on theoretical methods. Additionally, the 3 mol % Dy2O3 doped sample exhibited greater fast neutron removal cross-sections. However, the undoped barium phosphate host demonstrated better stopping potential and lower projected ranges against ions (protons and carbon). Photon trajectories and dose attenuation properties were also investigated using the Particle and Heavy Ions Transport System (PHITS) Monte Carlo code, indicating that the Dy3+ doped lead-free transparent glass protects against ionizing radiation. Hence, the barium phosphate host and Dy3+-doped counterparts are attractive for use in ionizing radiation and nuclear facilities, such as hospitals, research centers, and industries.

Beam quality correction factors for dose measurements around 192Ir brachytherapy sources.

To provide beam quality correction factors ( ) for detectors used in 192Ir brachytherapy dosimetry measurements. Ten detectors were studied, including the PTW 30013 and Exrading12 Farmer large cavity chambers, seven medium (0.1-0.3cm3) and small(<0.1cm3) cavity chambers, and a synthetic microdiamond detector. The kQ,Qo correction factors were calculated at distances from 1 to 10cm away from an 192Ir source, using the EGSnrc Monte Carlo (MC) code. All detectors were calibrated in a 60Co 10×10cm2 reference field provided by standard calibration laboratories. The impact of the central electrode, stem and wall on the detectors' responses in 192Ir photon energies was investigated. An experimental procedure was additionally applied for dose measurements around a microSelectron-v2 192Ir high dose rate (HDR) brachytherapy source using a motorized water phantom. Farmer chambers underestimated the dose near the source due to signal volume averaging effects, resulting in kQ,Qo values ranging from 1.177 and 1.317 at 1cm, decreasing with distance to between 0.980 and 1.005 at 10cm. Small cavity volume detectors should be used close to the source. The kQ,Qo for the studied small and medium cavity volume detectors were found to be close to unity (within 1.3%), showing also a small dependence on source-to-detector distance, except for ion chambers containing high-Z materials in their construction. The presence of high-Z materials caused an overresponse in these detectors, resulting in kQ,Qo values ranging from 0.950 at 1cm to 0.729 at 10cm away from the source. A dose rate constant of (1.114±0.023)cGyh-1U-1 was found in agreement with the literature (within 0.5%). kQ,Qo values were calculated for dose measurements around 192Ir brachytherapy sources. Farmer chambers should be preferred for measurements at increased distances, whereas small or medium cavity volume detectors, not containing high-Z materials, should be used close to the source.

Feasibility verification of deep-learning based collimator-less imaging system using a voxelated GAGG(Ce) single volume detector: A Monte Carlo simulation

A 4π-field of view deep-learning-based collimator-less imaging system was designed with the Monte Carlo method and performance of the system was studied to verify the feasibility of system. A 4 × 4 × 4 voxelated single-volume GAGG(Ce) system and 57Co, 133Ba, 22Na, and 137Cs point sources at 2000 positions were modeled using Monte-Carlo N-particle transport code version 6 (MCNP6). Two types of the localized energy deposition acquired with a voxelated detector system with and without energy bins, were calculated. The F6 tally was used to provide the entire energy deposited in each voxel and the F8 tally to provide energy spectrum data for each voxel. This system utilized these energy deposition patterns depending on the source type and position to reconstruct the source distribution image. A fully convolutional network which is advantageous for the prediction of image outputs was used to estimate source distribution. The models utilizing energy deposition patterns generated on total energy deposition and energy spectrum data were trained with labels from 30° to 10 degree of full-width half-maximum (FWHM). As a result of training with single and multiple source data, types of isotopes and source locations were discriminated up to 5 sources when using energy spectral data, and the average image similarity between ground truth images and predicted ones were 0.9936 for total energy deposition model and 0.9966 for divided energy bin model. These results showed the feasibility of a collimator-less imaging system based on deep learning method that requires no filtration of any type of interaction.

The effectiveness of combining gadolinium and boron neutron capture therapy at the cellular level

ABSTRACT The present study developed a program to investigate the effectiveness of combining gadolinium and boron neutron capture therapy at the cellular level. The program can automatically generate a 3D random cell array for the Monte Carlo code PHITS. It can create a cell array with random cell shape, size, structure distribution, and cell rotation to build as realistic human cell models as possible. The cell array is utilized to calculate the distribution of 157Gd or/and 10B in different cell structures. It also examines the scenario of two separate drug injections: first, administering BPA for irradiation, followed by the injection of 157Gd for subsequent irradiation. In both cases, the distribution of drugs within the cell structures is assumed to be random. The results showed that 1000 ppm of the 157Gd uniformly filling the whole-cell array and 65 ppm of BPA exhibited a comparable biologically equivalent dose at the cellular level. The biological equivalent dose significantly increases when gadolinium drugs enter the nucleus. Incorporating 157Gd into the nucleus can provide a sufficient therapeutic effect, making the combination of gadolinium and boron neutron capture therapy a promising approach for neutron capture therapy.

Fast and precise dose estimation for very high energy electron radiotherapy with graph neural networks

IntroductionExternal beam radiotherapy (RT) is one of the most common treatments against cancer, with photon-based RT and particle therapy being commonly employed modalities. Very high energy electrons (VHEE) have emerged as promising candidates for novel treatments, particularly in exploiting the FLASH effect, offering potential advantages over traditional modalities.MethodsThis paper introduces a Deep Learning model based on graph convolutional networks to determine dose distributions of therapeutic VHEE beams in patient tissues. The model emulates Monte Carlo (MC) simulated doses within a cylindrical volume around the beam, enabling high spatial resolution dose calculation along the beamline while managing memory constraints.ResultsTrained on diverse beam orientations and energies, the model exhibits strong generalization to unseen configurations, achieving high accuracy metrics, including a δ-index 3% passing rate of 99.8% and average relative error &lt;1% in integrated dose profiles compared to MC simulations.DiscussionNotably, the model offers three to six orders of magnitude increased speed over full MC simulations and fast MC codes, generating dose distributions in milliseconds on a single GPU. This speed could enable direct integration into treatment planning optimization algorithms and leverage the model’s differentiability for exact gradient computation.

Simulation studies for methodological research in psychology: A standardized template for planning, preregistration, and reporting.

Simulation studies are widely used for evaluating the performance of statistical methods in psychology. However, the quality of simulation studies can vary widely in terms of their design, execution, and reporting. In order to assess the quality of typical simulation studies in psychology, we reviewed 321 articles published in Psychological Methods, Behavior Research Methods, and Multivariate Behavioral Research in 2021 and 2022, among which 100/321 = 31.2% report a simulation study. We find that many articles do not provide complete and transparent information about key aspects of the study, such as justifications for the number of simulation repetitions, Monte Carlo uncertainty estimates, or code and data to reproduce the simulation studies. To address this problem, we provide a summary of the ADEMP (aims, data-generating mechanism, estimands and other targets, methods, performance measures) design and reporting framework from Morris et al. (2019) adapted to simulation studies in psychology. Based on this framework, we provide ADEMP-PreReg, a step-by-step template for researchers to use when designing, potentially preregistering, and reporting their simulation studies. We give formulae for estimating common performance measures, their Monte Carlo standard errors, and for calculating the number of simulation repetitions to achieve a desired Monte Carlo standard error. Finally, we give a detailed tutorial on how to apply the ADEMP framework in practice using an example simulation study on the evaluation of methods for the analysis of pre-post measurement experiments. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Construction of a realistic voxel phantom of the Japanese red fox (Vulpes vulpes japonica) based on MRI imaging and estimation of its background external radiation dose rate from environmental radionuclides.

In this study, we selected the Japanese red fox (Vulpes vulpes japonica) as a representative mid-size mammal from the forests near the spent nuclear fuel reprocessing plant at Rokkasho. A fox voxel phantom was constructed based on magnetic resonance imaging of a female red fox caught in Rokkasho. This phantom consisted of 264×321×383 voxels (each voxel size: 0.78×0.78×2mm) with internal organs. The external radiation dose rate to the voxel phantom by beta and gamma rays from environmental radionuclides was estimated using a Monte Carlo code (EGS4 and UCPIXEL). We estimated the dose rates to the phantom on the ground and in an average fox burrow in the Rokkasho forest, which were 11 and 27 nGy h-1, respectively. Assuming that the animal on the ground was irradiated by cosmic rays of 27 nGy h-1, the total external dose rate was evaluated to be 38 nGy h-1. Based on the assumption that the fox lives on the ground for 12h and in the burrow for 12h, the dose rate was estimated to be 33 nGy h-1.

Partial volume correction for Lu-177-PSMA SPECT

BackgroundThe limited spatial resolution in SPECT images leads to partial volume effect (PVE), degrading the subsequent dosimetric accuracy. We aim to quantitatively evaluate PVE and partial volume corrections (PVC), i.e., recovery coefficient (RC)-PVC (RC-PVC), reblurred Van-Cittert (RVC) and iterative Yang (IY), in 177Lu-PSMA-617 SPECT images.MethodsWe employed a geometrical cylindrical phantom containing five spheres (diameters ranging from 20 to 40 mm) and 40 XCAT phantoms with various anatomical variations and activity distributions. SIMIND Monte Carlo code was used to generate realistic noisy projections. In the clinical study, sequential quantitative SPECT/CT imaging at 4 time-points post 177Lu-PSMA-617 injections were analyzed for 10 patients. Iterative statistical reconstruction methods were used for reconstruction with attenuation, scatter and geometrical collimator detector response corrections, followed by post-filters. The RC-curves were fit based on the geometrical phantom study and applied for XCAT phantom and clinical study in RC-PVC. Matched and 0.5-2.0 voxels (2.54–10.16 mm) mismatched sphere masks were deployed in IY. The coefficient of variation (CoV) was measured on a uniform background on the geometrical phantom. RCs of spheres and mean absolute activity error (MAE) of kidneys and tumors were evaluated in simulation data, while the activity difference was evaluated in clinical data before and after PVC.ResultsIn the simulation study, the spheres experienced significant PVE, i.e., 0.26 RC and 0.70 RC for the 20 mm and 40 mm spheres, respectively. RVC and IY improved the RC of the 20 mm sphere to 0.37 and 0.75 and RC of the 40 mm sphere to 0.96 and 1.04. Mismatch in mask increased the activity error for all spheres in IY. RVC increased noise and caused Gibbs ringing artifacts. For XCAT phantoms, both RVC and IY performed comparably and were superior to RC-PVC in reducing the MAE of the kidneys. However, IY and RC-PVC outperformed RVC for tumors. The XCAT phantom study and clinical study showed a similar trend in the kidney and tumor activity differences between non-PVC and PVC.ConclusionsPVE greatly impacts activity quantification, especially for small objects. All PVC methods improve the quantification accuracy in 177Lu-PSMA SPECT.

Study of CdTe detector response functions using different MCNPX computational modeling detailing

The spectra measured with cadmium telluride (CdTe) detectors show high spectral distortions that must be corrected by applying a mathematical algorithm along with the detector's response functions. Simplified computational modeling of the CdTe detector is generally used to obtain its response functions. In this work, the Monte Carlo code MCNPX was used to study the response functions of a CdTe detector using more complex detector modeling and compared it with those obtained by simplified modeling. Raw spectra were corrected using the response matrices obtained for the simplified and detailed modeling of the CdTe and compared with those obtained with reference-validated software.

In silico dosimetry for a prostate cancer treatment using 198Au nanoparticles

Objective. To estimate dose rates delivered by using radioactive198Au nanoparticles for prostate cancer nanobrachytherapy, identifying contribution by photons and electrons emmited from the source.Approach. Utilizingin silicomodels, two different anatomical representations were compared: a mathematical model and a unstructured mesh model based on the International Commission on Radiological Protection (ICRP) Publication 145 phantom. Dose rates by activity were calculated to the tumor and nearby healthy tissues, including healthy prostate tissue, urinary bladder wall and rectum, using Monte Carlo code MCNP6.2.Main results. Results indicate that both models provide dose rate estimates within the same order of magnitude, with the mathematical model overestimating doses to the prostate and bladder by approximately 20% compared to the unstructured mesh model. The discrepancies for the tumor and rectum were below 4%. Photons emmited from the source were defined as the primary contributors to dose to other organs, while 97.9% of the dose to the tumor was due to electrons emmited from the source.Significance. Our findings emphasize the importance of model selection in dosimetry, particularly the advantages of using realistic anatomical phantoms for accurate dose calculations. The study demonstrates the feasibility and effectiveness of198Au nanoparticles in achieving high dose concentrations in tumor regions while minimizing exposure to surrounding healthy tissues. Beta emissions were found to be predominantly responsible for tumor dose delivery, reinforcing the potential of198Au nanoparticles in localized radiation therapy. We advocate for using realistic body phantoms in further research to enhance reliability in dosimetry for nanobrachytherapy, as the field still lacks dedicated protocols.

Advanced Monte Carlo simulations and benchmark of residual dose rate assessments in the ATLAS detector at CERN LHC

Background The European Organization for Nuclear Research (CERN) pushes the frontiers of physics through the Large Hadron Collider (LHC), a 27-kilometre hadron accelerator capable of producing proton-proton collisions at a center-of-mass energy of up to 13.6 TeV. Its four main detectors (ALICE, ATLAS, CMS, LHCb) are unique examples of advanced particle detection technology and complexity. Ensuring radiological safety throughout the LHC’s environments and lifecycle is a critical task managed by the CERN Radiation Protection group. In this context, assessing residual dose rates is crucial for planning exposure situations, such as maintenance and upgrade projects during LHC shutdowns. Methods This work presents advanced Monte Carlo techniques developed at CERN to predict residual dose rates in the LHC experimental caverns, focusing on the ATLAS detector. Predictions are made using the FLUKA Monte Carlo code and the SESAME toolkit for two-step simulations. The simulation results are benchmarked against experimental residual dose rate measurements collected during LHC Long Shutdown 2 at ATLAS. Additionally, forecasts for Long Shutdown 3 are also presented. Results The FLUKA benchmark for the ATLAS detector demonstrates a general agreement within a factor of 1.5. This consistency validates both the FLUKA geometry model of the ATLAS detector and the reliability of the Monte Carlo techniques used to predict residual dose rates in such complex environments. Conclusions The study highlights the predictive capabilities of the FLUKA and SESAME coupling for simulating residual dose rates in large LHC experiments. This method plays a crucial role in ensuring radiological safety, primarily for dose prediction and optimization. The reliability of this approach is significantly supported by the benchmark results obtained at ATLAS and presented in this paper.

Evaluation of dynamical behavior of Thorium fueled SMART reactor using lumped parameter dynamic model

The point reactor dynamic model is based on the lumped parameter model and, unlike the traditional reactor kinetics model, takes into account the effects of the fuel and moderator temperature on the system reactivity. This model is a system of nonlinear and nonhomogeneous differential equations and is used in the transient analysis of an initially critical system subjected to any perturbation. In this study, transient analysis of the Th-fueled SMART reactor is performed by the point dynamics model. Initially, the reactor is kept critical using the reactivity control mechanisms such as control rods insertioın and soluble boron addition to the moderator. The required neutronic parameters such as precursors’ parameters, neutron generation time, and reactivity coefficients are calculated using the Serpent 2 Monte Carlo code. The moderator average temperature and system pressure are used as two distinct thermodynamic properties to determine thermal-hydraulic parameters such as heat capacity, conductivity coefficient, convection coefficient, and fuel thermal resistance. For different reactivity insertion scenarios, MATLAB ODE45 suite is used to solve the point dynamic equations. The validity of the provided code is also verified either through comparison with the analytically solvable form of the point dynamic model or by analyzing the asymptotic equilibrium values of the considered parameters. Finally, it is seen that when an initially critical reactor operating at a certain power level undergoes a perturbation, after a short time the system becomes again critical and operates at an almost stable power level different from the pre-perturbation power level. This, in turn, implies that the calculated neutronic and thermal-hydraulic parameters are physically meaningful.

Single- and Multinozzle Plume Impingement to Detumble Space Debris

The management of space debris is increasingly crucial for ensuring the safety of space missions by mitigating collision risks. Most proposed debris management systems involve the capture and deorbiting of debris. However, it is also essential to eliminate any residual rotation and nutation of the debris to perform capture without accidents. The current work examines the effectiveness of thruster plume impingement for despinning space debris. A proof-of-concept study of plume impingement dynamics is conducted on a rectangular prism target using single- and multiple-nozzle arrangements for different target offsets and orientations. The three-dimensional simulation is carried out using the open-source Direct Simulation Monte Carlo code SPARTA. Staging and dynamic grid adaptation techniques are incorporated to obtain high-resolution results for the multiscale problem. It is observed that the plume–plume interaction in the multinozzle configuration leads to the beneficial formation of a relatively narrow beam of flow interacting with the target; that is, a multinozzle plume exerts a more concentrated directed force, which imparts greater countertorque across a broader spectrum of target orientations than a single-nozzle plume.

THOR: inclusion of charge carriers’ creation and transport in semiconductor detectors in the PENELOPE Monte Carlo simulation code

This study introduces the simulation framework THOR, which was designed to include the creation and transport of electrons and holes in pixelated semiconductors detectors used for x-ray imaging in the PENELOPE v. 2014 Monte Carlo code and its penEasy v.2015 extension. Following the simulation of radiation transport and energy deposition in the detector, the THOR code breaks down into electron-hole pair (EHP) creation, transport, trapping, and modes of detection, including simulations of energy integrating and photon counting detectors. Validation of the THOR code was conducted using the ARTEMIS code. This study shows the impact of the simulation parameters (detector geometry, photon energy, charge carrier dispersion, etc.) on the detector performance metrics. Notably, the energy cut-off for electrons and photons were found to significantly influence accuracy and computational speed, with the identification of the optimal value as 250 eV for improved computational performance without sacrificing accuracy. The ability to adjust the energy necessary to create an EHP specifically for a-Se sensors introduce a novel approach to balancing speed and accuracy effectively. Moreover, the THOR code allows the user to choose the bias direction and which charge is collected, showing the code’s adaptability across various operational scenarios and materials. For instance, the results showed that using a negative bias and collecting holes results in less spatial resolution because the charge would have to travel a longer distance to be collected. Moreover, the trapping is also a factor, since the and the probability of trapping increases with the distance traveled by the charge carrier. The inclusion or exclusion of charge trapping in simulations can significantly influence the detector efficiency, with differences up to 60%. Analysis of physical parameters such as photon energy, detector thickness, composition, and applied electric field provides insights into their effects on detector performance metrics. Understanding these effects is essential for optimizing imaging systems for specific applications, thereby advancing diagnostic capabilities and patient care in medical imaging. In summary, this study offers a comprehensive understanding of detector behavior and simulation optimization, aiming to enhance imaging techniques.

Design and implementation of HDF5-format neutron nuclear database in RMC code

This study developed a new structured nuclear database to improve the readability and extensibility of the ACE (A Compact ENDF) nuclear database, save disk space, reduce memory usage, and enhance the computational efficiency of the Reactor Monte Carlo (RMC) code. A Python package was developed to store nuclear data in HDF5 format. Compared to the ACE database, the HDF5-format database shows significant improvements: an 80% reduction in disk space for continuous energy neutron data and a 60% reduction for neutron thermal scattering data. The HDF5-format database was implemented in RMC’s criticality calculation mode and validated through VERA benchmark problem 2B, demonstrating perfect agreement with the ACE results in keff and neutron flux counts. The Computational results indicate a 7.7% reduction in memory usage and a 20.1% improvement in computational efficiency with the HDF5-format database. Additional tests show that using the database at a single temperature point reduces memory usage by 5.4% and running time by 13.2%. At two temperature points, memory usage decreases by 35.2% and running time by 18.0%. The new data structure reduces temperature-independent redundant data and improves indexing efficiency, leading to greater savings with more temperature points. This development enhances performance of criticality calculation of RMC and addresses ACE database limitations.

Preliminary neutronic analyses for annular VHTR with different coated fuel particle designs

Abstract The purpose of the present work is to determine the neutronic characteristics of annular cylindrical prismatic Very High Temperature Gas-cooled Reactor (VHTR) with different advanced fuel designs. The study includes detailed neutronic investigations of the eight types of TRISO (containing SiC layer) and TRIZO (containing ZrC layer) fuel particles for annular VHTR core. All calculations were performed using continuous energy Monte Carlo code MVP2.0 and MVPBURN with JENDL4.0 nuclear data library. The obtained results indicated that SiC + PyC and PyC layers in TRISO fuel appeared to be not excellent choice for the annular VHTR core due to its shorter operation year and, lower fuel burnup. The annular cylindrical prismatic core fueled with TRIZO fuel particle shows good neutronic characteristics compared to those designed with other TRISO fuel particles.

Benchmark verification of PIC-DSMC programs

We examine a number of common verification and benchmark problems for Particle-in-Cell and Direct Simulation Monte Carlo codes. Since results, including convergence rates, comparison to analytic solutions, and code-to-code comparisons, for these problems are often used as evidence of correctness for simulation codes, it is necessary to understand what successful verification using one or more of these problems implies about the correctness of the simulation code. To that end, a series of benchmark problems is performed in Aleph, a PIC-DSMC code developed at Sandia National Laboratories, including both at the canonical numerical parameters and others where verification should fail. The results presented suggest that improvements and extensions to current benchmark problems and additional problem specifications would benefit existing and future codes thereby providing greater confidence in predictive results.