A direct measurement of the thermal neutron conversion ratio of natural uranium

1969 ◽  
Vol 47 (12) ◽  
pp. 1317-1325 ◽  
Author(s):  
C. B. Bigham ◽  
R. W. Durham ◽  
J. Ungrin
Keyword(s):  
Thermal Neutron ◽  
Cross Section ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Direct Method ◽  
Natural Uranium ◽  
Conversion Ratio ◽  
Absorption Cross ◽  
A Direct Method ◽  
Good Agreement

A direct method for measuring the thermal neutron conversion ratio of natural uranium (capture in 238U)/(destruction of 235U), gives 0.5655 ± 0.0025 (20 °C Maxwellian) in good agreement with 0.565 ± 0.009 from the separately measured cross sections. The corresponding value for the 2200 m/s absorption cross section of 238U is 2.721 ± 0.016 b. The method is based on the use of a sample of 243Am, which α-decays to 239Np, for correlating the efficiencies of the fission counter and γ counter used to measure the number of fissions and the amount of 239Np produced during an irradiation of a natural uranium sample.

The effective absorption cross-section of thermal neutrons in a medium containing strongly or weakly absorbing centres

Open Physics ◽  
2003 ◽  
Vol 1 (2) ◽  
Author(s):  
Krzysztof Drozdowicz ◽  
Barbara Gabańska ◽  
Andrzej Igielski ◽  
Ewa Krynicka ◽  
Urszula Woźnicka
Keyword(s):  
Thermal Neutron ◽  
Cross Section ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Homogeneous Medium ◽  
Coarse Grained ◽  
Thermal Neutrons ◽  
Absorption Cross ◽  
Effective Absorption ◽  
Two Component

AbstractThe structure of a heterogeneous system influences diffusion of thermal neutrons. The thermal-neutron absorption in grained media is considered in the paper. A simple theory is presented for a two-component medium treated as grains embedded in the matrix or as a system built of two types of grains (of strongly differing absorption cross-sections). A grain parameter is defined as the ratio of the effective macroscopic absorption cross-section of the heterogeneous medium to the absorption cross-section of the corresponding homogeneous medium (consisting of the same components in the same proportions). The grain parameter depends on the ratio of the absorption cross-sections and contributions of the components and on the size of grains. The theoretical approach has been verified in experiments on prepared dedicated models which have kept required geometrical and physical conditions (silver grains distributed regularly in Plexiglas). The effective absorption cross-sections have been measured and compared with the results of calculations. A very good agreement has been observed. In certain cases the differences between the absorption in the heterogeneous and homogeneous media are very significant. A validity of an extension of the theoretical model on natural, two-component, heterogeneous mixtures has been tested experimentally. Aqueous solutions of boric acid have been used as the strongly absorbing component. Fine- and coarse-grained pure silicon has been used as the second component with well-defined thermal-neutron parameters. Small and large grains of diabase have been used as the second natural component. The theoretical predictions have been confirmed in these experiments.

scholarly journals Ultraviolet Absorption Cross-Sections of Ammonia at Elevated Temperatures for Nonintrusive Quantitative Detection in Combustion Environments

2021 ◽  
pp. 000370282199044
Author(s):  
Wubin Weng ◽  
Shen Li ◽  
Marcus Aldén ◽  
Zhongshan Li
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Elevated Temperatures ◽  
Uv Absorption ◽  
Energy Utilization ◽  
Quantitative Detection ◽  
Absorption Cross ◽  
Hot Gas

Ammonia (NH3) is regarded as an important nitrogen oxides (NOx) precursor and also as an effective reductant for NOx removal in energy utilization through combustion, and it has recently become an attractive non-carbon alternative fuel. To have a better understanding of thermochemical properties of NH3, accurate in situ detection of NH3 in high temperature environments is desirable. Ultraviolet (UV) absorption spectroscopy is a feasible technique. To achieve quantitative measurements, spectrally resolved UV absorption cross-sections of NH3 in hot gas environments at different temperatures from 295 K to 590 K were experimentally measured for the first time. Based on the experimental results, vibrational constants of NH3 were determined and used for the calculation of the absorption cross-section of NH3 at high temperatures above 590 K using the PGOPHER software. The investigated UV spectra covered the range of wavelengths from 190 nm to 230 nm, where spectral structures of the [Formula: see text] transition of NH3 in the umbrella bending mode, v2, were recognized. The absorption cross-section was found to decrease at higher temperatures. For example, the absorption cross-section peak of the (6, 0) vibrational band of NH3 decreases from ∼2 × 10−17 to ∼0.5 × 10−17 cm2/molecule with the increase of temperature from 295 K to 1570 K. Using the obtained absorption cross-section, in situ nonintrusive quantification of NH3 in different hot gas environments was achieved with a detection limit varying from below 10 parts per million (ppm) to around 200 ppm as temperature increased from 295 K to 1570 K. The quantitative measurement was applied to an experimental investigation of NH3 combustion process. The concentrations of NH3 and nitric oxide (NO) in the post flame zone of NH3–methane (CH4)–air premixed flames at different equivalence ratios were measured.

THERMAL NEUTRON ABSORPTION CROSS SECTION OF Xe135

1959 ◽  
Vol 37 (5) ◽  
pp. 531-536 ◽  
Author(s):  
H. R. Fickel ◽  
R. H. Tomlinson
Keyword(s):  
Thermal Neutron ◽  
Cross Section ◽  
Mass Spectrometer ◽  
Absorption Cross Section ◽  
Yield Ratio ◽  
Neutron Absorption ◽  
Absorption Cross ◽  
Fission Yield ◽  
Effective Neutron ◽  
Neutron Absorption Cross Section

The effective neutron absorption cross section of Xe135 has been measured with a mass spectrometer by observing the variation in the Cs135/Cs137 fission yield ratio obtained at various thermal neutron fluxes. Values of 3.15 ± 0.06 megabarns and 3.27 ± 0.11 megabarns have been determined for neutron temperatures of 120 °C and 137 °C respectively.

scholarly journals Determination of the absorption cross-sections of higher order iodine oxides at 355 nm and 532 nm

2020 ◽  
Author(s):  
Thomas R. Lewis ◽  
Juan Carlos Gómez Martin ◽  
Mark A. Blitz ◽  
Carlos A. Cuevas ◽  
John M. C. Plane ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Atmospheric Chemistry ◽  
Absorption Cross Section ◽  
Absorption Cross ◽  
Time Resolved ◽  
Flight Mass Spectrometry ◽  
Iodine Oxides ◽  
Photo Ionization

Abstract. Iodine oxides (IxOy) play an important role in the atmospheric chemistry of iodine. They are initiators of new particle formation events in the coastal and polar boundary layer and act as iodine reservoirs in tropospheric ozone-depleting chemical cycles. Despite the importance of the aforementioned processes, the photochemistry of these molecules has not been studied in detail previously. Here, we report the first determination of the absorption cross sections of IxOy, x = 2, 3, 5, y = 1–12 at λ = 355 nm by combining pulsed laser photolysis of I2/O3 gas mixtures in air with time-resolved photo-ionization time-of-flight mass spectrometry, using NO2 actinometry for signal calibration. The oxides selected for absorption cross section determinations are those presenting the strongest signals in the mass spectra, where signals containing 4 iodine atoms are absent. The method is validated by measuring the absorption cross section of IO at 355 nm, σ355 nm, IO = (1.2 ± 0.1) ×  10–18 cm2, which is found to be in good agreement with the most recent literature. The results obtained are: σ355 nm, I2O3 

Measurement of the Thermal Neutron Absorption Cross Section of Rock Samples

1983 ◽  
pp. 143-151
Author(s):  
J.A. CZUBEK ◽  
K. DROZDOWICZ ◽  
E. KRYNICKA-DROZDOWICZ ◽  
A. IGIELSKI ◽  
U. WOźNICKA
Keyword(s):  
Thermal Neutron ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Neutron Absorption ◽  
Absorption Cross ◽  
Rock Samples ◽  
Neutron Absorption Cross Section

THE FISSION YIELDS OF THE CESIUM ISOTOPES FORMED IN THE THERMAL NEUTRON FISSION OF U235 AND THE NEUTRON ABSORPTION CROSS SECTION OF Xe135

1955 ◽  
Vol 33 (11) ◽  
pp. 640-649 ◽  
Author(s):  
J. A. Petruska ◽  
E. A. Melaika ◽  
R. H. Tomlinson
Keyword(s):  
Thermal Neutron ◽  
Cross Section ◽  
Isotope Dilution ◽  
Absorption Cross Section ◽  
Neutron Absorption ◽  
Absorption Cross ◽  
Neutron Fission ◽  
Thermal Neutron Fission ◽  
Fission Yields ◽  
Neutron Absorption Cross Section

The absolute fission yields of the cesium isotopes occurring in the thermal neutron fission of U235 have been determined with a mass spectrometer using isotope dilution techniques. Values of 6.59%, 6.41%, and 6.15% have been obtained for the yields of Cs133, Cs135, and Cs137 respectively. The neutron absorption cross section of Xe135 has also been measured to be 866 times greater than that of B10 for a Maxwellian distribution of neutron velocities corresponding to a neutron temperature of 57 °C. This ratio gives a thermal neutron absorption cross section of 3.47 × 106 barns for Xe135 assuming it is a 1/ν detector.

Thermal neutron absorption cross-section for small samples: experiments in spherical geometry

1981 ◽  
Vol 14 (6) ◽  
pp. 977-984 ◽  
Author(s):  
J A Czubek ◽  
K Drozdowicz ◽  
A Igielski ◽  
E Krynicka-Drozdowicz ◽  
Z Sobczynski ◽  
...  
Keyword(s):  
Thermal Neutron ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Spherical Geometry ◽  
Small Samples ◽  
Neutron Absorption ◽  
Absorption Cross ◽  
Neutron Absorption Cross Section
Sign in / Sign up

Export Citation Format

Share Document