Total cross section for the interaction of cold neutrons with water

Stepanov, S. B.; Zhitarev, V. E.

doi:10.1007/bf01132657

Cited by 8 publications

(4 citation statements)

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“…The measured data and the results of the model are in good agreement. Below 4 Å, where temperature has a smaller effect on the cross section of liquid water, the cross section values measured with WFM choppers are in good agreement with water cross section measured at room temperature and published in literature 43,54,55 . The following important trends can be observed for the measured as well as for the model data:…”

Section: Please Cite This Article As Doi:101063/15110288supporting

confidence: 88%

“…These two elements have similar cross section at short neutron wavelength, but the cross section of lithium increases steeper as a function of wavelength than the cross section of hydrogen. Further, the proton mobility and thus the neutron cross section not only depends on the aggregate state of water or aqueous solutions, but also on temperature 42,43 and acidity. Therefore, HDC-TOF can be used to analyze the temporal and/or spatial evolution of pH or temperature (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Distinction between super-cooled water and ice with high duty cycle time-of-flight neutron imaging

Siegwart

Woracek

Damián

et al. 2019

Review of Scientific Instruments

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We report on measured neutron cross section data for super-cooled water and ice by time-of-flight neutron transmission imaging. In particular we demonstrate the use of high duty cycle time-of-flight (HDC-TOF) measurements to determine the local aggregate state of water with spatial resolution, by exploiting the neutron cross section dependence on the mobility of hydrogen atoms for long neutron wavelengths (> 4 Å). While one can envision many different applications for this method, one example is to provide insights into the freezing mechanism during the start-up of polymer electrolyte fuel cells from below zero degrees. Unlike for other wavelength selective measurements (e.g. Bragg edge imaging), only a limited wavelength resolution is required for this method. With a chopper setup with high duty cycle (30 %), we reached a high contrast-to-noise ratio (CNR) with a contrast between ice and super-cooled water of 8 %. To maximize the CNR, we optimized the duty cycle, pulse period and image processing parameters. Moreover, we present a theoretical framework for performing such optimization calculations, which can be used to maximize CNR for any beam line and any substances.For the optimization procedure presented in this publication, we used cross section values for ice and super-cooled water measured with high wavelength resolution using wavelength frame multiplication choppers. Our results show that the aggregate state of water of a sufficiently thick layer of water (> 0.5 mm) can be reliably determined for a small area (1 mm 2 ) and with a reasonable short acquisition time of 5 minutes.

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Section: Please Cite This Article As Doi:101063/15110288supporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Distinction between super-cooled water and ice with high duty cycle time-of-flight neutron imaging

Siegwart

Woracek

Damián

et al. 2019

Review of Scientific Instruments

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“…To test the behavior of our model with temperature, we compared our calculations with the cold neutron measurements performed by Stepanov and Zhitarev [23,24] at the IRT reactor of the Moscow Engineering Physics Institute. Stepanov published a series of measurements of the total cross section of liquid water at high temperatures for a fixed set of incident energies.…”

Section: Total Cross Sectionmentioning

confidence: 99%

New Thermal Neutron Scattering Kernels for Light and Heavy Water Based on Molecular Dynamics Simulations

2014

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Calculations of moderators require scattering kernels that are accurate in both the energetics and angular distribution of outgoing neutrons. Currently, scattering cross sections available in ENDF format to be used in Monte Carlo and deterministic calculations rely on water models that do not utilize the up-to-date knowledge of its structure and dynamics.In this work we present a new model to compute the scattering kernels for light and heavy water based on molecular dynamics simulations. Using the molecular dynamics program GROMACS and a flexible TIP4P model we obtained the frequency spectra of hydrogen, deuterium and oxygen, bound in light and heavy water. With those spectra we computed the scattering laws using the LEAPR module of NJOY, which uses the incoherent approximation. Scattering laws for D and O in D2O are corrected using the Skld approximation and partial structure factors obtained by Soper.Using those kernels we computed double differential and integral cross sections over a wide range of neutron energies (10 −5 1 eV). These results represent an improvement over existing models when compared with experimental values, especially for low incident neutron energies.

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“…Likewise, experimental thermal scattering data for water at elevated ܶ is very sparse. The little data available is either for cold neutrons (< 1 meV) [12,13,14] of marginal interest in reactor applications or for limited select ܶ [15,16,17]. Not surprisingly, light-water TSL performance has been thoroughly validated at RT, but comprehensive non-proprietary validation across the full range of ܶ of interest in reactor applications is lacking.…”

Section: Introductionmentioning

confidence: 99%

Validation of Thermal Scattering Laws for Light Water at Elevated Temperatures With Diffusion Experiments

2021

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Light water is the most important neutron moderator in many reactor applications. Thermal neutron scattering kernels for H bound in H2O are represented by ENDF-format thermal scattering laws (TSLs) evaluated at discrete temperatures T. Nuclear data evaluations are conventionally validated utilizing a combination of critical benchmarks and experimental cross section data. Existing public critical benchmarks may be inadequate for testing water TSLs over the full range of T of interest in reactor applications, and experimental thermal scattering cross section data for water is sparse at elevated T. In this work, MC21 is used to simulate the decay of the equilibrium thermal neutron flux in light-water spheres of several radii. The fundamental-mode time eigenvalue α is calculated at 22 °C and 227 °C (at saturation pressure) for each sphere using three different H-H2O TSLs. Fitting α to a polynomial function of geometric buckling allows calculation of the thermal neutron diffusion length L. Extrapolation lengths are treated as a function of the transport mean free path and geometry. Experimental L data from 25 publications at 49 temperatures (from 10 °C to 295 °C), computed by several different time-dependent and space-dependent decay methods, is used to develop an empirical fit of L vs. T. The MC21-calculated L for the TSLs tested are within ±1% of the predicted values at 22 °C and 227 °C. This validation approach, which may be repeated at arbitrary T, constitutes an integral benchmark specific to and characterizing the detailed physics of the thermal scattering kernel applied.

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Total cross section for the interaction of cold neutrons with water

Cited by 8 publications

References 0 publications

Distinction between super-cooled water and ice with high duty cycle time-of-flight neutron imaging

Distinction between super-cooled water and ice with high duty cycle time-of-flight neutron imaging

New Thermal Neutron Scattering Kernels for Light and Heavy Water Based on Molecular Dynamics Simulations

Validation of Thermal Scattering Laws for Light Water at Elevated Temperatures With Diffusion Experiments

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