bluuebunny/crossref_metadata_2025 huggingface dataset:
An Eye Model for Computational Dosimetry Using A Multi-Scale Voxel Phantom
Authors: Caracappa Peter F. , Rhodes Ashley , Fiedler Derek
Published: June 2014

The lens of the eye is a radiosensitive tissue with cataract formation being the major concern. Recently reduced recommended dose limits to the lens of the eye have made understanding the dose to this tissue of increased importance. Due to memory limitations, the voxel resolution of computational phantoms used for radiation dose calculations is too large to accurately represent the dimensions of the eye. A revised eye model is constructed using physiological data for the dimensions of radiosensitive tissues, and is then transformed into a high-resolution voxel model. This eye model is combined with an existing set of whole body models to form a multi-scale voxel phantom, which is used with the MCNPX code to calculate radiation dose from various exposure types. This phantom provides an accurate representation of the radiation transport through the structures of the eye. Two alternate methods of including a high-resolution eye model within an existing whole body model are developed. The accuracy and performance of each method is compared against existing computational phantoms.
Geometric Templates for Improved Tracking Performance in Monte Carlo Codes
Authors: Nease Brian R. , Millman David L. , Griesheimer David P. , Gill Daniel F.
Published: June 2014

One of the most fundamental parts of a Monte Carlo code is its geometry kernel. This kernel not only affects particle tracking (i.e., run-time performance), but also shapes how users will input models and collect results for later analyses. A new framework based on geometric templates is proposed that optimizes performance (in terms of tracking speed and memory usage) and simplifies user input for large scale models. While some aspects of this approach currently exist in different Monte Carlo codes, the optimization aspect has not been investigated or applied. If Monte Carlo codes are to be realistically used for full core analysis and design, this type of optimization will be necessary. This paper describes the new approach and the implementation of two template types in MC21: a repeated ellipse template and a box template. Several different models are tested to highlight the performance gains that can be achieved using these templates. Though the exact gains are naturally problem dependent, results show that runtime and memory usage can be significantly reduced when using templates, even as problems reach realistic model sizes.
Prompt alpha eigenvalue calculations with TRIPOLI-4
Authors: Zoia Andrea , Brun Emeric , Malvagi Fausto
Published: June 2014

Monte Carlo criticality analyses aimed at determining reactor parameters have been historically based on iterative algorithms whose outcome is the effective multiplication coefficient (keff), i.e., the fundamental eigenvalue of the transport equation. Less attention has been comparatively paid to Monte Carlo algorithms for the estimation of the so-called (prompt)αeigenvalues, which provide information about the (prompt) time evolution of the system. In recent years, this issue has witnessed a renewed interest, mostly due to increased computer power, allowing for reliable and stable search strategies for assessing the fundamental α eigenvalue. In this work, we revisit the theory behind α eigenvalues and propose a Monte Carlo iterative algorithm for the development version of Tripoli-4. In order toillustrate the algorithm, some significant examples are finally discussed.
Modeling and Estimating Small Unreliabilities for Static Networks with Dependent Components
Authors: Botev Zdravko I. , L’Ecuyer Pierre , Tuffin Bruno
Published: June 2014

We study static network reliability models in which the component failures are not independent. To model the dependence and also to develop effiective simulation methods that estimate the system unreliability, we extend the static model into an auxiliary dynamic model where the components fail at random time, according to a Marshall-Olkin multivariate exponential distribution. We examine and compare diffierent versions of this model and develop efficient unreliability estimation methods based on conditional Monte Carlo and on a generalized splitting methodology.
Anomalous Behavior of Monte Carlo Uncertainties near Reflecting Boundaries
Authors: Sutton Thomas M.
Published: June 2014

It has been observed that statistical uncertainties on tallies in Monte Carlo iterated-fission-source calculations tend to be larger for tally regions near reflective boundaries than for similar tally regions far from such boundaries. Using a theoretical methodology developed by Brissenden and Garlick, the cause of this behavior was found to be a greater correlation between fission generations in the regions near the reflective boundaries. The theory was found to be in qualitative agreement with Monte Carlo results for a simple test problem. It is also shown that applying the coarse mesh finite difference method eliminates the anomalous behavior.
Probabilistic margin evaluation on accidental transients for the ASTRID reactor project
Authors: Marquès Michel
Published: June 2014

ASTRID is a technological demonstrator of Sodium cooled Fast Reactor (SFR) under development. The conceptual design studies are being conducted in accordance with the Generation IV reactor objectives, particularly in terms of improving safety. For the hypothetical events, belonging to the accidental category “severe accident prevention situations” having a very low frequency of occurrence, the safety demonstration is no more based on a deterministic demonstration with conservative assumptions on models and parameters but on a “Best-Estimate Plus Uncertainty” (BEPU) approach. This BEPU approach ispresented in this paper for an Unprotected Loss-of-Flow (ULOF) event. The Best-Estimate (BE) analysis of this ULOFt ransient is performed with the CATHARE2 code, which is the French reference system code for SFR applications. The objective of the BEPU analysis is twofold: first evaluate the safety margin to sodium boiling in taking into account the uncertainties on the input parameters of the CATHARE2 code (twenty-two uncertain input parameters have been identified, which can be classified into five groups: reactor power, accident management, pumps characteristics, reactivity coefficients, thermal parameters and head losses); secondly quantify the contribution of each input uncertainty to the overall uncertainty of the safety margins, in order to refocusing R&D efforts on the most influential factors. This paper focuses on the methodological aspects of the evaluation of the safety margin. At least for the preliminary phase of the project (conceptual design), a probabilistic criterion has been fixed in the context of this BEPU analysis; this criterion is the value of the margin to sodium boiling, which has a probability 95% to be exceeded, obtained with a confidence level of 95% (i.e. the M5,95percentile of the margin distribution). This paper presents two methods used to assess this percentile: the Wilks method and the Bootstrap method ; the effectiveness of the two methods is compared on the basis of 500 simulations performed with theCATHARE2 code. We conclude that, with only 100 simulations performed with the CATHARE2 code, which is a number of simulations workable in the conceptual design phase of the ASTRID project where the models and the hypothesis are often modified, it is best in order to evaluate the percentile M5,95 of the margin to sodium boiling to use the bootstrap method, which will provide a slightly conservative result. On the other hand, in order to obtain an accurate estimation of the percentileM5,95, for the safety report for example, it will be necessary to perform at least 300 simulations with the CATHARE2 code. In this case, both methods (Wilks and Bootstrap) would give equivalent results.
Visualization tools for uncertainty and sensitivity analyses on thermal-hydraulic transients
Authors: Popelin Anne-Laure , Iooss Bertrand
Published: June 2014

In nuclear engineering studies, uncertainty and sensitivity analyses of simulation computer codes can be faced to the complexity of the input and/or the output variables. If these variables represent a transient or a spatial phenomenon, the difficulty is to provide tool adapted to their functional nature. In this paper, we describe useful visualization tools in the context of uncertainty analysis of model transient outputs. Our application involves thermal-hydraulic computations for safety studies of nuclear pressurized water reactors.
Stochastic Perturbation Algorithms for Kinetic Monte Carlo Simulations
Authors: Jin Shim Hyung
Published: June 2014

The accuracy of the kinetic Monte Carlo (KMC) simulations depends on the reliability of transition data used in the calculations. The sensitivity analyses may be useful to quantify the uncertainty of the KMC output and enhance the accuracy by ordering the transition data by importance. I derive a formulation of the differential operator sampling method for the KMC perturbation analysis from the Neumann series solution to the KMC master equation. The effectiveness of the KMC perturbation method is demonstrated in a simplified radioactive decay problem and the Langmuirian adsorption dynamics problem.
Fission Matrix Capability for MCNP Monte Carlo
Authors: Brown Forrest , Carney Sean , Kiedrowski Brian , Martin William
Published: June 2014

We describe recent experience and results from implementing a fission matrix capability into the MCNP Monte Carlo code. The fission matrix can be used to provide estimates of the fundamental mode fission distribution, the dominance ratio, the eigenvalue spectrum, and higher mode forward and adjoint eigenfunctions of the fission neutron source distribution. It can also be used to accelerate the convergence of the power method iterations and to provide basis functions for higher-order perturbation theory. The higher-mode fission sources can be used in MCNP to determine higher-mode forward fluxes and tallies, and work is underway to provide higher-mode adjoint-weighted fluxes and tallies. Past difficulties and limitations of the fission matrix approach are overcome with a new sparse representation of the matrix, permitting much larger and more accurate fission matrix representations. The new fission matrix capabilities provide a significant advance in the state-of-the-art for Monte Carlo criticality calculations.
Extensions of the MCNP5 and TRIPOLI4 Monte Carlo Codes for Transient Reactor Analysis
Authors: Eduard Hoogenboom J. , Sjenitzer Bart L.
Published: June 2014

To simulate reactor transients for safety analysis with the Monte Carlo method the generation and decay of delayed neutron precursors is implemented in the MCNP5 and TRIPOLI4 general purpose Monte Carlo codes. Important new variance reduction techniques like forced decay of precursors in each time interval and the branchless collision method are included to obtain reasonable statistics for the power production per time interval.

For simulation of practical reactor transients also the feedback effect from the thermal-hydraulics must be included. This requires coupling of the Monte Carlo code with a thermal-hydraulics (TH) code, providing the temperature distribution in the reactor, which affects the neutron transport via the cross section data. The TH code also provides the coolant density distribution in the reactor, directly influencing the neutron transport. Different techniques for this coupling are discussed.

As a demonstration a 3x3 mini fuel assembly with a moving control rod is considered for MCNP5 and a mini core existing of 3x3 PWR fuel assemblies with control rods and burnable poisons for TRIPOLI4. Results are shown for reactor transients due to control rod movement or withdrawal. The TRIPOLI4 transient calculation is started at low power and includes thermal-hydraulic feedback. The power rises about 10 decades and finally stabilises the reactor power at a much higher level than initial. The examples demonstrate that the modified Monte Carlo codes are capable of performing correct transient calculations, taking into account all geometrical and cross section detail.
Use of the ETA-1 reactor for the validation of the multi-group APOLLO2-MORET 5 code and the Monte Carlo continuous energy MORET 5 code
Authors: Leclaire N. , Cochet B. , Le Dauphin F.X. , Haeck W. , Jacquet O.
Published: June 2014

The present paper aims at providing experimental validation for the use of the MORET 5 code for advanced concepts of reactor involving thorium and heavy water. It therefore constitutes an opportunity to test and improve the thermal-scattering data of heavy water and also to test the recent implementation of probability tables in the MORET 5 code.
Present Status and Extensions of the Monte Carlo Performance Benchmark
Authors: Eduard Hoogenboom J. , Petrovic Bojan , Martin William R.
Published: June 2014

The NEA Monte Carlo Performance benchmark started in 2011 aiming to monitor over the years the abilities to perform a full-size Monte Carlo reactor core calculation with a detailed power production for each fuel pin with axial distribution. This paper gives an overview of the contributed results thus far. It shows that reaching a statistical accuracy of 1 % for most of the small fuel zones requires about 100 billion neutron histories. The efficiency of parallel execution of Monte Carlo codes on a large number of processor cores shows clear limitations for computer clusters with common type computer nodes. However, using true supercomputers the speedup of parallel calculations is increasing up to large numbers of processor cores. More experience is needed from calculations on true supercomputers using large numbers of processors in order to predict if the requested calculations can be done in a short time.

As the specifications of the reactor geometry for this benchmark test are well suited for further investigations of full-core Monte Carlo calculations and a need is felt for testing other issues than its computational performance, proposals are presented for extending the benchmark to a suite of benchmark problems for evaluating fission source convergence for a system with a high dominance ratio, for coupling with thermal-hydraulics calculations to evaluate the use of different temperatures and coolant densities and to study the correctness and effectiveness of burnup calculations. Moreover, other contemporary proposals for a full-core calculation with realistic geometry and material composition will be discussed.
Domain Decomposition PN Solutions to the 3D Transport Benchmark over a Range in Parameter Space
Authors: Van Criekingen S.
Published: June 2014

The objectives of this contribution are twofold. First, the Domain Decomposition (DD) method used in the parafish parallel transport solver is re-interpreted as a Generalized Schwarz Splitting as defined by Tang [SIAM J Sci Stat Comput, vol.13 (2), pp. 573–595, 1992]. Second, parafish provides spherical harmonic (i.e., PN) solutions to the NEA benchmark suite for 3D transport methods and codes over a range in parameter space. To the best of the author’s knowledge, these are the first spherical harmonic solutions provided for this demanding benchmark suite. They have been obtained using 512 CPU cores of the JuRoPa machine installed at the Jülich Computing Center (Germany).
Efficient and Portable Krylov Eigensolver on Many Core Architectures
Authors: Calvin C. , Petiton S. , Ye F. , Boillod-Cerneux F.
Published: June 2014

We present in this article a highly parallel Krylov solver for large eigenvalue problems, The Explicit Restarted Arnoldi Method (ERAM). Our ERAM implementation may be executed on many core configurations, both homogeneous and heterogeneous ones, in order to take advantage of most of present and future supercomputers. From these experiments, we propose our approach for designing efficient and portable algorithms on multi-core architectures. It is based on the design of generic algorithms using TRILINOS approach and specialized implementation of elementary operations (matrix-matrix, matrix-vector, scalar product ...) on accelerators mentioned above. Some results on large sparse and dense matrices on petascale class machines using CPU and GPUs, and some first results obtained on Intel MIC processor are presented and analysed.
Hybrid parallel strategy for the simulation of fast transient accidental situations at reactor scale
Authors: Faucher V. , Galon P. , Beccantini A. , Crouzet F. , Debaud F. , Gautier T.
Published: June 2014

This contribution is dedicated to the latest methodological developments implemented in the fast transient dynamics software EUROPLEXUS (EPX) to simulate the mechanical response of fully coupled fluid-structure systems to accidental situations to be considered at reactor scale, among which the Loss of Coolant Accident, the Core Disruptive Accident and the Hydrogen Explosion.

Time integration is explicit and the search for reference solutions within the safety framework prevents any simplification and approximations in the coupled algorithm: for instance, all kinematic constraints are dealt with using Lagrange Multipliers, yielding a complex flow chart when non-permanent constraints such as unilateral contact or immersed fluid-structure boundaries are considered. The parallel acceleration of the solution process is then achieved through a hybrid approach, based on a weighted domain decomposition for distributed memory computing and the use of the KAAPI library for self-balanced shared memory processing inside subdomains.
Multi level programming Paradigm for Extreme Computing
Authors: Petiton S. , Sato M. , Emad N. , Calvin C. , Tsuji M. , Dandouna M.
Published: June 2014

Abstract: In order to propose a framework and programming paradigms for post-petascale computing, on the road to exascale computing and beyond, we introduced new languages, associated with a hierarchical multi-level programming paradigm, allowing scientific end-users and developers to program highly hierarchical architectures designed for extreme computing. In this paper, we explain the interest of such hierarchical multi-level programming paradigm for extreme computing and its well adaptation to several large computational science applications, such as for linear algebra solvers used for reactor core physic. We describe the YML language and framework allowing describing graphs of parallel components, which may be developed using PGAS-like language such as XMP, scheduled and computed on supercomputers. Then, we propose experimentations on supercomputers (such as the “K” and “Hooper” ones) of the hybrid method MERAM (Multiple Explicitly Restarted Arnoldi Method) as a case study for iterative methods manipulating sparse matrices, and the block Gauss-Jordan method as a case study for direct method manipulating dense matrices. We conclude proposing evolutions for this programming paradigm.
Utilization of Minor Actinides (Np, Am, Cm) in Nuclear Power Reactor
Authors: Gerasimov A. , Bergelson B. , Tikhomirov G.
Published: June 2014

Calculation research of the utilization process of minor actinides (transmutation with use of power released) is performed for specialized power reactor of the VVER type operating on the level of electric power of 1000 MW. Five subsequent cycles are considered for the reactor with fuel elements containing minor actinides along with enriched uranium. It was shown that one specialized reactor for the one cycle (900 days) can utilize minor actinides from several VVER-1000 reactors without any technological and structural modifications. Power released because of minor actinide fission is about 4% with respect to the total power
A Large Scale Three-Dimensional Simulation on Thermal-Hydraulics of Supercritical Pressure Water in a Fuel Bundle for SCWR
Authors: Takase Kazuyuki , Misawa Takeharu , Yoshida Hiroyuki , Ose Yasuo
Published: June 2014

Development of a numerical analysis method was performed to clarify thermal-hydraulic characteristics in supercritical water reactors. Because the thermo-physical property of fluids at the supercritical pressure condition is different from that at the subcritical condition and has a special feature, current numerical analysis codes cannot be applied. Then, Japan Atomic Energy Agency is developing a numerical analysis code which can calculate the thermo-fluid properties of the supercritical fluids correctly. This paper describes the predicted results of a newly developed analysis code and the comparison results with the experimental results.
PTRAC File Utilization for Calculation of Free-Air Ionization Chamber Correction Factors by MCNPX
Authors: Šolc Jaroslav , Sochor Vladimír
Published: June 2014

A free-air ionization chamber is used as a standard of photon air-kerma. Several correction factors are applied to the air-kerma value. Correction factors for electron loss (kloss) and for additional ionization current caused by photon scatter (ksc), photon fluorescence (kfl), photon transmission through diaphragm edge (kdtr), and photon scatter from the surface of the diaphragm aperture (kdsc) were determined by the MCNPX code utilizing information stored in Particle Track (PTRAC) output files. Individual steps of the procedure are described and the calculated values of the correction factors are presented. The values are in agreement with the correction factors published in a literature for similar free-air chambers.
CABRI Reactor: The fast neutron Hodoscope Calibration curves calculation with MORET
Authors: Bernard Franck , Chevalier Vincent , Venanzi Damiano
Published: June 2014

This poster presents the Hodoscope calibration curves calculation with 3D Monte Carlo code MORET. The fast neutron hodoscope is a facility of the CABRI research reactor at Cadarache (FRANCE). This hodoscope is designed to measure the fuel motion during a RIA in a pressurized water reactor. The fuel motion is measured by counting fast fission neutrons emerging from the test fuel placed in an experimental loop functioning like a Pressurized Water Reactor (T=300°C and P=155 bar), at the center of the CABRI core. The detection system of the hodoscope measures a signal which is a function of the fuel motion. The calibration curves allow then to convert the signal in a fuel mass. In order to calculate these curves, we have developed a method based on a Monte Carlo calculation code.
Image based Monte Carlo Modeling for Computational Phantom
Authors: Cheng Mengyun , Wang Wen , Zhao Kai , Fan Yanchang , Long Pengcheng , Wu Yican ,   FDS Team
Published: June 2014

The evaluation on the effects of ionizing radiation and the risk of radiation exposure on human body has been becoming one of the most important issues for radiation protection and radiotherapy fields, which is helpful to avoid unnecessary radiation and decrease harm to human body. In order to accurately evaluate the dose on human body, it is necessary to construct more realistic computational phantom. However, manual description and verfication of the models for Monte carlo(MC)simulation are very tedious, error-prone and time-consuming. In addiation, it is difficult to locate and fix the geometry error, and difficult to describe material information and assign it to cells.

MCAM (CAD/Image-based Automatic Modeling Program for Neutronics and Radiation Transport Simulation) was developed as an interface program to achieve both CAD- and image-based automatic modeling by FDS Team (Advanced Nuclear Energy Research Team, http://www.fds.org.cn). The advanced version (Version 6) of MCAM can achieve automatic conversion from CT/segmented sectioned images to computational phantoms such as MCNP models.

Imaged-based automatic modeling program(MCAM6.0) has been tested by several medical images and sectioned images. And it has been applied in the construction of Rad-HUMAN. Following manual segmentation and 3D reconstruction, a whole-body computational phantom of Chinese adult female called Rad-HUMAN was created by using MCAM6.0 from sectioned images of a Chinese visible human dataset. Rad-HUMAN contains 46 organs/tissues, which faithfully represented the average anatomical characteristics of the Chinese female. The dose conversion coefficients(Dt/Ka) from kerma free-in-air to absorbed dose of Rad-HUMAN were calculated. Rad-HUMAN can be applied to predict and evaluate dose distributions in the Treatment Plan System (TPS), as well as radiation exposure for human body in radiation protection.
Development of Visualization Software for McCARD Code
Authors: Je Park Chang , Lee Byungchul , Jin Shim Hyung , Yoeng Choi Kwang , Hyun Roh Chang
Published: June 2014

In order to confirm geometrical modeling of input file of the McCARD (Monte Carlo Code for Advanced Reactor Design and analysis) code, a 2D visualization program with a 3D modeling has been developed. It requires lots of mathematical operations and advanced technologies for design graphical program of complicated geometries. The software is coded with the visual C++ language and run under the Windows PC environment.
Taylor series development in the Monte Carlo code Tripoli-4
Authors: Mazzolo Alain , Zoia Andrea , Martin Brunella
Published: June 2014

Perturbation methods for one or several variables based on the Taylor series development up to the second order is presented for the collision estimator in the framework of the Monte Carlo code Tripoli-4. Comparisons with the correlated sampling method implemented in Tripoli-4 demonstrate the need of including the cross derivatives in the development.
DBRC and WCM scattering kernels for TRIPOLI-4, version 9
Authors: Zoia Andrea , Brun Emeric , Jouanne Cédric , Malvagi Fausto
Published: June 2014

Recent works have pointed out some relevant shortcomings of the so called ‘Sampling of the Velocity of the Target nucleus’ (SVT) algorithm, which is currently used in most Monte Carlo codes for the Doppler broadening of the elastic scattering kernel. To overcome these limitations, which affect resonant nuclei such as 238U, and whose consequences in pincell criticality calculations can amount to a drop of a few hundred pcm, the Doppler Broadening Rejection Correction (DBRC) and the Weight Correction Method (WCM) have been proposed. In this work, we illustrate the implementation of DBRC and WCM in the TRIPOLI-4 Monte Carlo code. Several validation tests are discussed, and the impact of using DBRC or WCM to replace SVT is analyzed in detail in static as well as burnup calculations for UOX and MOX pincells, and in a PWR full-core simulation.
RayXpert V1: 3D software for the gamma dose rate calculation by Monte Carlo
Authors: Peyrard P. F. , Pourrouquet P. , Dossat C. , Thomas J. C. , Chatry N. , Lavielle D. , Chatry C.
Published: June 2014

RayXpert has been developed to ease the access to the power and accuracy of the 3D Monte Carlo method in the field of gamma dose rate estimate. Optimization methods have been implemented to address dose calculation behind thick 3D structures. At the same time, the engineering interface makes all the preprocessing tasks (modeling, material settings,…) faster using predefined tables and push button features.
A Parallel Full Core Transport Calculation Based On Domain Decomposition Method
Authors: Lenain Roland , Masiello Emiliano , Sanchez Richard , Damian Frederic
Published: June 2014

A new interactive homogenization procedure for reactor core or colorset calculations is proposed that requires iterative transport assembly and diffusion core calculations. At each iteration the transport solution of every assembly is used to produce homogenized cross sections for the core calculation. The converged solution gives assembly fine multigroup transport fluxes that preserve macrogroup assembly exchanges in the core. This homogenization avoids the periodic lattice - leakage model approximation and gives detailed assembly transport fluxes without need for an approximated flux reconstruction. In this paper we combined the benefit of a Domain Decomposition Method, that split the original transport problem in several multigroup fixed-source problems, with the effective solution of the Coarse-Mesh Finite-Differences operator that provides the whole-core eigenvalue and the neutron exchange between assemblies.
Monte Carlo Capabilities of the SCALE Code System
Authors: Rearden B. T. , Petrie L. M. , Peplow D. E. , Bekar K. B. , Wiarda D. , Celik C. , Perfetti C. M. , Ibrahim A. M. , Hart S. W. D. , Dunn M. E.
Published: June 2014

SCALE is a widely used suite of tools for nuclear systems modeling and simulation that provides comprehensive, verified and validated, user-friendly capabilities for criticality safety, reactor physics, radiation shielding, and sensitivity and uncertainty analysis. For more than 30 years, regulators, licensees, and research institutions around the world have used SCALE for nuclear safety analysis and design. SCALE provides a “plug-and-play” framework that includes three deterministic and three Monte Carlo radiation transport solvers that can be selected based on the desired solution, including hybrid deterministic/Monte Carlo simulations. SCALE includes the latest nuclear data libraries for continuous-energy and multigroup radiation transport as well as activation, depletion, and decay calculations. SCALE’s graphical user interfaces assist with accurate system modeling, visualization, and convenient access to desired results. SCALE 6.2, to be released in 2014, will provide several new capabilities and significant improvements in many existing features, especially with expanded continuous-energy Monte Carlo capabilities for criticality safety, shielding, depletion, and sensitivity and uncertainty analysis. An overview of the Monte Carlo capabilities of SCALE is provided here, with emphasis on new features for SCALE 6.2.
McCARD for Neutronics Design and Analysis of Research Reactor Cores
Authors: Jin Shim Hyung , Jin Park Ho , Kwon Soonwoo , Ho Seo Geon , Hyo Kim Chang
Published: June 2014

McCARD is a Monte Carlo (MC) neutron-photon transport simulation code developed exclusively for the neutronics design and analysis of nuclear reactor cores. McCARD is equipped with the hierarchical modeling and scripting functions, the CAD-based geometry processing module, the adjoint-weighted kinetics parameter and source multiplication factor estimation modules as well as the burnup analysis capability for the neutronics design and analysis of both research and power reactor cores. This paper highlights applicability of McCARD for the research reactor core neutronics analysis, as demonstrated for Kyoto University Critical Assembly, HANARO, and YALINA.
MONK and MCBEND: Current Status and Recent Developments
Authors: Richards Simon D. , Baker Chris M. J. , Bird Adam J. , Cowan Pat , Davies Nigel , Dobson Geoff P. , Fry Tim C. , Kyrieleis Albrecht , Smith Paul N.
Published: June 2014

MONK® and MCBEND are Monte Carlo software packages for: nuclear criticality and reactor physics; and radiation shielding and dosimetry applications, respectively. The codes are actively developed, maintained and supported by AMEC’s ANSWERS® Software Service in line with the ANSWERS vision of providing easy-to-use software that meets the current and emerging needs of the user community. This paper summarises the current status of MONK and MCBEND and the recent developments which have been carried out to the codes, and their supporting nuclear data libraries and visualisation package.
OpenMC: A State-of-the-Art Monte Carlo Code for Research and Development
Authors: Romano Paul K. , Horelik Nicholas E. , Herman Bryan R. , Nelson Adam G. , Forget Benoit , Smith Kord
Published: June 2014

This paper gives an overview of OpenMC, an open source Monte Carlo particle transport code recently developed at the Massachusetts Institute of Technology. OpenMC uses continuous-energy cross sections and a constructive solid geometry representation, enabling high-fidelity modeling of nuclear reactors and other systems. Modern, portable input/output file formats are used in OpenMC: XML for input, and HDF5 for output. High performance parallel algorithms in OpenMC have demonstrated near-linear scaling to over 100,000 processors on modern supercomputers. Other topics discussed in this paper include plotting, CMFD acceleration, variance reduction, eigenvalue calculations, and software development processes.
The PENELOPE code system. Specific features and recent improvements
Authors: Salvat Francesc
Published: June 2014

Since its first release, back in 1996, the Monte Carlo code system penelope has evolved into a flexible and reliable tool for describing coupled electron-photon transport in complex material structures. The present article contains an overview of the physical interaction models, particle tracking methods, geometry tools, and variance-reduction techniques implemented in penelope. Recent refinements aimed at improving the accuracy of the code, and its stability under variations of user-defined simulation parameters, are also described. These include the use of reliable cross sections for the ionization of inner atomic electron shells by electron/positron impact, a reformulation of the random-hinge method, and the use of fuzzy quadric surfaces in the description of the geometry.
RMC - A Monte Carlo Code for Reactor Core Analysis
Authors: Wang Kan , Li Zeguang , She Ding , Liang Jin’gang , Xu Qi , Qiu Yishu , Yu Jiankai , Sun Jialong , Fan Xiao , Yu Ganglin
Published: June 2014

A new Monte Carlo transport code RMC has been being developed by Department of Engineering Physics, Tsinghua University, Beijing as a tool for reactor core analysis on high-performance computing platforms. To meet the requirements of reactor analysis, RMC now has such functions as criticality calculation, fixed-source calculation, burnup calculation and kinetics simulations. Some techniques for geometry treatment, new burnup algorithm, source convergence acceleration, massive tally and parallel calculation, and temperature dependent cross sections processing are researched and implemented in RMC to improve the effciency. Validation results of criticality calculation, burnup calculation, source convergence acceleration, tallies performance and parallel performance shown in this paper prove the capabilities of RMC in dealing with reactor analysis problems with good performances.
Enhanced performance of ferroelectric-based all organic capacitors and transistors through choice of solvent
Authors: Knotts G. , Bhaumik A. , Ghosh K. , Guha S.
Published: June 2014

We examine the role of solvents in the performance of pentacene devices using the ferroelectric copolymer poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFe) as a gate insulating layer. High dipole moment solvents, such as dimethyl sulfoxide (DMSO), used to dissolve the copolymer for spincasting, increase the charge carrier mobility in field-effect transistors by nearly an order of magnitude as compared to lower dipole moment solvents. The polarization in Al/PVDF-TrFe/Au metal-ferroelectric-metal devices is also investigated. An increase in remnant polarization of ∼20% is observed in the sample using DMSO as the ferroelectric solvent. The DMSO based sample shows a hysteresis in its displacement curve even at the lowest measured voltage, indicating that the dipoles in the copolymer are more ordered initially.
Inequalities for quantum marginal problems with continuous variables
Authors: Krbek Michael , Tyc Tomáš , Vlach Jan
Published: June 2014

We consider a mixed continuous-variable bosonic quantum system and present inequalities which must be satisfied between principal values of the covariances of a complete set of observables of the whole system and the principal values of the covariances of a complete set of observables of a subsystem. We use several classical results for the proof: the Courant-Fischer-Weyl min-max theorem for Hermitian operators and its consequence, the Cauchy interlacing theorem, and prove their analogues in the symplectic setting. For the case of passive transformations of Gaussian mixed states we also prove that the obtained inequalities are, in a sense, the best possible. The obtained mathematical results are applied to the system of n uncorrelated thermal modes of the electromagnetic field. Finally, we present the results of numerical simulations of the problem, suggesting avenues of further research.
An ultrasensitive quartz crystal microbalance-micropillars based sensor for humidity detection
Authors: Wang Pengtao , Su Junwei , Su Che-Fu , Dai Wen , Cernigliaro George , Sun Hongwei
Published: June 2014

A unique sensing device, which couples microscale pillars with quartz crystal microbalance (QCM) substrate to form a resonant system, is developed to achieve several orders of magnitude enhancement in sensitivity compared to conventional QCM sensors. In this research, Polymethyl Methacrylate (PMMA) micropillars are fabricated on a QCM substrate using nanoimprinting lithography. The effects of pillar geometry and physical properties, tuned by molecular weight (MW) of PMMA, on the resonant characteristics of QCM-micropillars device are systematically investigated. It is found that the resonant frequency shift increases with increasing MW. The coupled QCM-micropillars device displays nonlinear frequency response, which is opposite to the linear response of conventional QCM devices. In addition, a positive resonant frequency shift is captured near the resonant point of the coupled QCM-micropillars system. Humidity detection experiments show that compared to current nanoscale feature based QCM sensors, QCM-micropillars devices offer higher sensitivity and moderate response time. This research points to a novel way of improving sensitivity of acoustic wave sensors without the need for fabricating surface nanostructures.
Rotational excitation of HCN by para- and ortho-H2
Authors: Vera Mario Hernández , Kalugina Yulia , Denis-Alpizar Otoniel , Stoecklin Thierry , Lique François
Published: June 2014

Rotational excitation of the hydrogen cyanide (HCN) molecule by collisions with para-H2( j = 0, 2) and ortho-H2( j = 1) is investigated at low temperatures using a quantum time independent approach. Both molecules are treated as rigid rotors. The scattering calculations are based on a highly correlated ab initio 4-dimensional (4D) potential energy surface recently published. Rotationally inelastic cross sections among the 13 first rotational levels of HCN were obtained using a pure quantum close coupling approach for total energies up to 1200 cm−1. The corresponding thermal rate coefficients were computed for temperatures ranging from 5 to 100 K. The HCN rate coefficients are strongly dependent on the rotational level of the H2 molecule. In particular, the rate coefficients for collisions with para-H2( j = 0) are significantly lower than those for collisions with ortho-H2( j = 1) and para-H2( j = 2). Propensity rules in favor of even Δj transitions were found for HCN in collisions with para-H2( j = 0) whereas propensity rules in favor of odd Δj transitions were found for HCN in collisions with H2( j ⩾ 1). The new rate coefficients were compared with previously published HCN-para-H2( j = 0) rate coefficients. Significant differences were found due the inclusion of the H2 rotational structure in the scattering calculations. These new rate coefficients will be crucial to improve the estimation of the HCN abundance in the interstellar medium.
Block diagonalization of the equation-of-motion coupled cluster effective Hamiltonian: Treatment of diabatic potential constants and triple excitations
Authors: Cave Robert J. , Stanton John F.
Published: June 2014

We present a diabatization method applicable to spectroscopic studies based on Equation-of-Motion Coupled Cluster (EOM-CC) energies and biorthogonal wavefunctions that uses the Block Diagonalization (BD) approaches of Cederbaum et al. [L. S. Cederbaum, J. Schirmer, and H. D. Meyer, J. Phys. A: Math. Gen. 22, 2427 (1989)] and Domcke et al. [W. Domcke and C. Woywod, Chem. Phys. Lett. 216, 362 (1993); W. Domcke, C. Woywod, and M. Stengle, Chem. Phys. Lett. 226, 257 (1994)]. The method gives excellent agreement with coupling constants calculated using the analytic gradient approach of Ichino et al. [T. Ichino, J. Gauss, and J. F. Stanton, J. Chem. Phys. 130, 174105 (2009)]. While the BD method is a finite difference approach, it can be applied at any geometry, can generate (pointwise) diabatic potential energy surfaces, and can be used with EOM wavefunctions that include triple (or higher) excitations. The method is applied to several model systems and its sensitivity to orbital choice, excitation space, and projection space is explored.
Dynamical thermoelectric coefficients of bulk semiconductor crystals: Towards high thermoelectric efficiency at high frequencies
Authors: Ezzahri Younès , Joulain Karl
Published: June 2014

We investigate in this work the fundamental behavior of the dynamical thermoelectric coefficients of a bulk cubic semiconductor (SC) crystal. The treatment is based on solving Boltzmann electron transport equation in the frequency domain after simultaneous excitations by dynamical temperature and electric potential gradients, within the framework of the single relaxation time approximation. The SC crystal is assumed to be a linear, elastic homogenous, and isotropic medium having a parabolic energy band structure. We further assume to deal with one type of carriers (electrons or holes) that reside in a single energy band, and we neglect any phonon drag effect. Our approach allows us to obtain very compact expressions for the different dynamical thermoelectric coefficients that nicely capture the essential features of the dynamics of electron transport. We emphasize our study about the dynamical behavior of the thermoelectric figure of merit ZT(Ω) of the SC crystal by considering the coupled electron-phonon transport. Our study revealed a very interesting and compelling result in which ZT increases in the high frequency regime with respect to its steady-state value. The fundamental reason of this enhancement is due to the intrinsic uncoupling in the dynamics of electrons and phonons in the high frequency regime.
Absolute fragmentation cross sections in atom-molecule collisions: Scaling laws for non-statistical fragmentation of polycyclic aromatic hydrocarbon molecules
Authors: Chen T. , Gatchell M. , Stockett M. H. , Alexander J. D. , Zhang Y. , Rousseau P. , Domaracka A. , Maclot S. , Delaunay R. , Adoui L. , Huber B. A. , Schlathölter T. , Schmidt H. T. , Cederquist H. , Zettergren H.
Published: June 2014

We present scaling laws for absolute cross sections for non-statistical fragmentation in collisions between Polycyclic Aromatic Hydrocarbons (PAH/PAH+) and hydrogen or helium atoms with kinetic energies ranging from 50 eV to 10 keV. Further, we calculate the total fragmentation cross sections (including statistical fragmentation) for 110 eV PAH/PAH+ + He collisions, and show that they compare well with experimental results. We demonstrate that non-statistical fragmentation becomes dominant for large PAHs and that it yields highly reactive fragments forming strong covalent bonds with atoms (H and N) and molecules (C6H5). Thus nonstatistical fragmentation may be an effective initial step in the formation of, e.g., Polycyclic Aromatic Nitrogen Heterocycles (PANHs). This relates to recent discussions on the evolution of PAHNs in space and the reactivities of defect graphene structures.
Fabrication of sub-12 nm thick silicon nanowires by processing scanning probe lithography masks
Authors: Kyoung Ryu Yu , Aitor Postigo Pablo , Garcia Fernando , Garcia Ricardo
Published: June 2014

Silicon nanowires are key elements to fabricate very sensitive mechanical and electronic devices. We provide a method to fabricate sub-12 nm silicon nanowires in thickness by combining oxidation scanning probe lithography and anisotropic dry etching. Extremely thin oxide masks (0.3–1.1 nm) are transferred into nanowires of 2–12 nm in thickness. The width ratio between the mask and the silicon nanowire is close to one which implies that the nanowire width is controlled by the feature size of the nanolithography. This method enables the fabrication of very small single silicon nanowires with cross-sections below 100 nm2. Those values are the smallest obtained with a top-down lithography method.
Bandgap properties of diamond structure photonic crystal heterostructures with inclined and curved interfaces
Authors: Lei Haitao , Li Yong , Wang Hong
Published: June 2014

The 3D (dimensional) diamond structure photonic crystal heterostructures with different lattice constants were prepared using rapid prototyping and gel casting with alumina. In this paper, heterostructures with inclined and curved interfaces were designed and its bandgap properties were studied. The normalized resonant intensity of electromagnetic wave in heterostructure with inclined and curved interface is stronger than that in the ordinary heterostructure without modified interface. The influence of curved interface on transmission properties of electromagnetic wave was investigated with the radius of curvature ranging from 17 mm to 37 mm at 5 mm interval. The results show that two resonant modes appear in the photonic band gap, being similar to the band gap characteristics of the photonic crystals with two defects inside. With the increasing of the radius of curvature, the resonant mode shift to higher frequency. In the structure with a radius of curvature of 32 mm, a guiding band appears in the photonic band gap. Further increase in the radius of curvature, the guiding band will split into two resonant modes again and the two resonant modes shift to lower frequencies.
Tuning the work function of graphene by nitrogen plasma treatment with different radio-frequency powers
Authors: Zeng Jian-Jhou , Lin Yow-Jon
Published: June 2014

Graphene prepared by the chemical vapor deposition method was treated with nitrogen plasma under different radio-frequency (rf) power conditions in order to experimentally study the change in the work function. Control of the rf power could change the work function of graphene from 4.91 eV to 4.37 eV. It is shown that the increased rf power may lead to the increased number of graphitic nitrogen, increasing the electron concentration, and shifting the Fermi level to higher energy. The ability to controllably tune the work function of graphene is essential for optimizing the efficiency of optoelectronic and electronic devices.
Suppression of tin precipitation in SiSn alloy layers by implanted carbon
Authors: Gaiduk P. I. , Lundsgaard Hansen J. , Nylandsted Larsen A. , Bregolin F. L. , Skorupa W.
Published: June 2014

By combining transmission electron microscopy and Rutherford backscattering spectrometry, we have identified carbon related suppression of dislocations and tin precipitation in supersaturated molecular-beam epitaxial grown SiSn alloy layers. Secondary ion mass spectrometry has exposed the accumulation of carbon in the SiSn layers after high temperature carbon implantation and high temperature thermal treatment. Strain-enhanced separation of point defects and formation of dopant-defect complexes are suggested to be responsible for the effects. The possibility for carbon assisted segregation-free high temperature growth of heteroepitaxial SiSn/Si and GeSn/Si structures is argued.