scholarly journals Validation of Thermal Neutron Scattering Cross Sections for Heavy Water based on Molecular Dynamics Simulation

2019 ◽  
Vol 211 ◽  
pp. 06001
Author(s):  
Haelee Hyun ◽  
Do Heon Kim ◽  
Young-Ouk Lee
Keyword(s):  
Molecular Dynamics ◽  
Frequency Spectrum ◽  
Heavy Water ◽  
Cross Sections ◽  
Dynamics Simulation ◽  
Water Model ◽  
Water Molecules ◽  
Scattering Cross ◽  
Thermal Scattering ◽  
Scattering Cross Sections

Recently, the thermal scattering libraries of ENDF/B-VIII.0 and JEFF-3.3 for light and heavy water were released with a new water model (CAB model) proposed by Damian. For the CAB model, the molecular dynamics code GROMACS was used to more accurately describe the realistic motions of water molecules. In this paper, to consider the coherent component we also generated the thermal scattering cross section of the deuterium and oxygen bound in the heavy water molecules using the GROMACS code and EPSR code. In addition, the frequency spectrum was also calculated using the GROMACS code. Thermal scattering cross sections based on the newly calculated Sköld correction factor and the frequency spectrum were generated by NJOY2016 code. Finally, the performance of the generated thermal scattering cross sections were validated by performing an ICSBEP benchmark simulation using MCNPX code.

scholarly journals Analysis of the time-of-flight neutron scattering cross-section data for light water measured at the SEQUOIA spectrometer, Spallation Neutron Source (SNS)

2020 ◽  
Vol 239 ◽  
pp. 14007
Author(s):  
Vaibhav Jaiswal ◽  
Luiz Leal ◽  
Alexander I. Kolesnikov
Keyword(s):  
Cross Section ◽  
High Temperatures ◽  
Cross Sections ◽  
Scattering Cross Section ◽  
Spallation Neutron Source ◽  
Light Water ◽  
Section Data ◽  
Scattering Cross ◽  
Thermal Scattering ◽  
Scattering Cross Sections

Thermal neutron scattering cross-section data for light water available in the major nuclear data libraries observes significant differences especially at reactor operating temperatures. During the past few years there has been a renewed interest in reviewing the existing thermal scattering models and generating more accurate and reliable thermal scattering cross sections using existing experimental data and in some cases based on Molecular Dynamics (MD) simulations. There is a need for performing new time-of-flight experiments at high temperatures and pressures, to have a better understanding of the physics involved in the scattering process that could help improve the existing TSL data. Lack of experimental thermal scattering data for light water at high temperatures led to a new measurement campaign within the INSIDER project at the Institut de radioprotection et de sûreté nucléaire (IRSN). Double differential scattering cross section for light water have been measured at the SEQUOIA spectrometer based at the Spallation Neutron Source (SNS), Oak Ridge National Laboratory, United States. Several measurements have been carried out at different temperatures and pressures corresponding to liquid light water. Measurements at five different incident neutron energies Ei (8, 60, 160, 280 and 800 meV) have been carried out to help exploring different regions of the frequency spectrum. This paper presents the analysis of the dynamic structure factor and the derived frequency spectrum of light water. The analysis of the experimental data would provide one with better confidence, the behavior of thermal scattering cross sections for light water at high temperatures, knowledge of which is very important for the design of novel reactors as well as existing pressurized water reactors.

A Molecular Dynamics Study of the Structure of an Aqueous CsF Solution

1983 ◽  
Vol 38 (2) ◽  
pp. 214-224 ◽  
Author(s):  
Gy. I. Szász ◽  
K. Heinzinger
Keyword(s):  
Molecular Dynamics ◽  
Hydration Shell ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Water Model ◽  
Water Molecules ◽  
Heat Of Solution ◽  
Average Temperature ◽  
Experimental Density ◽  
First Hydration Shell

Abstract A molecular dynamics simulation of a 2.2 molal aqueous CsF solution has been performed employing the ST2 water model. The basic periodic cube with a sidelength of 18.50 Å contained 200 water molecules, and 8 ions of each kind, corresponding to an experimental density of 1.26 g/cm3. The simulation extended over 6.5 ps with an average temperature of 307 K. The structure of the solution is discussed by means of radial distribution functions and the orientation of the water molecules. The computed hydration numbers in the first shell of Cs+ and F- are 7.9 and 6.8, respectively; the corresponding first hydration shell radii are 3.22 A and 2.64 A, respectively. Values for the hydration shell energies and the heat of solution have been calculated.

Clustering and condensation effects in the electron scattering cross sections from water molecules

2014 ◽  
Vol 365-366 ◽  
pp. 287-294 ◽  
Author(s):  
F. Blanco ◽  
A. Muñoz ◽  
D. Almeida ◽  
F. Ferreira da Silva ◽  
P. Limão-Vieira ◽  
...  
Keyword(s):  
Electron Scattering ◽  
Cross Sections ◽  
Water Molecules ◽  
Scattering Cross ◽  
Scattering Cross Sections

TREAT Transient Modeling and Impact of Graphite Thermal Scattering

2018 ◽  
Author(s):  
Nina C. Sorrell ◽  
Ayman I. Hawari
Keyword(s):  
Cross Sections ◽  
Test Facility ◽  
Scattering Cross ◽  
Temperature Feedback ◽  
Porous Graphite ◽  
Physics Simulation ◽  
Transient Simulations ◽  
Graphite Structure ◽  
Thermal Scattering ◽  
Scattering Cross Sections

The Transient Reactor Test Facility (TREAT) is a high enriched, graphite moderated, air cooled reactor built for experimental transient fuel testing. Recently, the reactor was returned to operation after having been shut down since 1994. Transients at TREAT are controlled largely by control/transient rod movement and temperature feedback that is attributed to the core’s graphite-fuel matrix. To date, TREAT simulations use the standard ENDF/B-VII.1 graphite thermal neutron scattering cross sections that assume an ideal crystalline form for the core’s graphite. Historically, it has been reported that the use of these cross sections may result in a −2000 pcm discrepancy when attempting to predict TREAT criticality [1]. In this work, a multi-physics simulation of a TREAT transient is performed using the standard ENDF/B-VII.1 graphite thermal scattering cross section libraries and compared with results using graphite libraries that assume a porous graphite structure and a corresponding density consistent with TREAT graphite. The transient simulation methodology couples a full-core transient Monte Carlo calculation in the Serpent code with feedback calculated from temperature estimates derived using the computational fluid dynamics code OpenFOAM. Steady state simulations show that use of the “porous” graphite libraries allows predicting TREAT criticality to within a few hundred pcm. In the current transient simulations, the reactor’s time dependent power behavior is successfully reproduced. With this model, observables such as maximum fuel temperatures and temperature-dependent flux spectra are calculated, using both the traditional ENDF/B-VII.1 and the “porous” graphite thermal scattering libraries.

Perturbation scheme for estimating uncertainties in thermal scattering cross sections of water

2018 ◽  
Vol 121 ◽  
pp. 232-249
Author(s):  
Lance Maul ◽  
José Ignacio Márquez Damián ◽  
George Braoudakis ◽  
Mark Ho ◽  
Guan Heng Yeoh
Keyword(s):  
Cross Sections ◽  
Perturbation Scheme ◽  
Scattering Cross ◽  
Thermal Scattering ◽  
Scattering Cross Sections

Structural Properties of an Aqueous LiI Solution Derived from a Molecular Dynamics Simulation

1981 ◽  
Vol 36 (10) ◽  
pp. 1067-1075 ◽  
Author(s):  
Gy. I. Szasz ◽  
K. Heinzinger ◽  
W. O. Riede
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Water Model ◽  
Water Molecules ◽  
Average Temperature ◽  
Energy Relationships ◽  
Elementary Charge ◽  
Experimental Values

In the molecular dynamics simulation of the aqueous LiI solution the ST2 water model was employed and the ions were described as Lennard-Jones spheres with an elementary charge at the center. The basic periodic cube contained 200 water molecules and 8 ions of each kind equivalent to a 2.2 molal solution. The simulation extended over 10 ps with an average temperature of 305 K. The structure is discussed by means of ion-water, ion-ion and water-water radial pair distribution functions and the orientation of the water molecules. Potential energy relationships are reported and the heat of solution has been calculated and found in agreement with experimental values.

Absolute inner-shell cross section determination for EELS analysis

1988 ◽  
Vol 46 ◽  
pp. 534-535
Author(s):  
P.A. Crozier
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absolute Cross Section ◽  
Specimen Thickness ◽  
Mass Thickness ◽  
Scattering Cross ◽  
Before And After ◽  
Estimated Error ◽  
Scattering Cross Sections ◽  
Electron Microscopist

Absolute inelastic scattering cross sections or mean free paths are often used in EELS analysis for determining elemental concentrations and specimen thickness. In most instances, theoretical values must be used because there have been few attempts to determine experimental scattering cross sections from solids under the conditions of interest to electron microscopist. In addition to providing data for spectral quantitation, absolute cross section measurements yields useful information on many of the approximations which are frequently involved in EELS analysis procedures. In this paper, experimental cross sections are presented for some inner-shell edges of Al, Cu, Ag and Au.Uniform thin films of the previously mentioned materials were prepared by vacuum evaporation onto microscope cover slips. The cover slips were weighed before and after evaporation to determine the mass thickness of the films. The estimated error in this method of determining mass thickness was ±7 x 107g/cm2. The films were floated off in water and mounted on Cu grids.

Sign in / Sign up

Export Citation Format

Share Document