Neutron attenuation

Neutron attenuation Emits high-energy neutrons into the soil that collide with hydrogen atoms associated with soil water and counts the number of pulses, which is correlated to moisture content Consists of a probe inserted into access boreholes with aluminum or polyvinyl chloride casing... 

There are a number of papers in the open literature explicitly reporting on the properties of boron cluster compounds for potential neutron capture applications.1 Such applications make full use of the 10B isotope and its relatively high thermal neutron capture cross section of 3.840 X 10 28 m2 (barns). Composites of natural rubber incorporating 10B-enriched boron carbide filler have been investigated by Gwaily et al. as thermal neutron radiation shields.29 Their studies show that thermal neutron attenuation properties increased with boron carbide content to a critical concentration, after which there was no further change. 

A neutron will move through material along a straight line with a constant energy until it encounters a nucleus and induces a nuclear reaction. Thus, neutron attenuation follows an exponential law similar to that for photons. Written in terms of an energy-dependent attenuation length, p, we have... 

The density and thermal neutron cross-section values in Table 6 pertain to the thermal neutron attenuation gauging process. In this method, advantage is taken of the large thermal neutron scattering cross-section of hydrogen as compared to most other elements. In its simplest form, when a beam of thermal neutrons of intensity IQ traverses a sample of thickness x, the intensity 1 of neutrons measured by a thermal neutron detector will be... 

The method of neutron radiography is simple to implement. Since water has a large neutron attenuation coefficient, the technique of radiography has a high sensitivity for small water mass changes... 

R.J. Rasmussen, W.S. Fanselow, H.W. Lefevre, M.S. Chmelik, J.C. Overley, A.P. Brown, G.E. Sieger and R.M.S. Schofield, Average atomic number of heterogeneous mixtures from the ratio of gamma to fast-neutron attenuation, Nucl. Instrum. Methods Phys. Res. Sec. A, 124(4) (1997) 611-614. 

Naoumov V.A., Rubin I.E., Dneprovskaya N.M. et al. (1996) Description of neutron attenuation in the biological shield using the nethod of probabilities of penetrations Preprint IPE-17, Institute of problems of energetics of AS of Beloruss, Minsk (in Russian). 

The determination of ash in coal slurries uses the basic principle of measurement of those for solid coal. The extra problem is that the entrained air could seriously affect the accuracy of these devices. Various methods are used to compensate for this, such as pressurizing the system to collapse the air bubbles (ASHSCAN) or using a neutron attenuation measurement to correct for possible air entrainment (AMDEL). 

In the absence of wore experiaental results it was necessary to estiaate the attenuation characteristics of barytes concrete. The procedure used for estiaating the neutron relaxation length aaounts to an extrapolation of the observations on neutron attenuation in ordinary concrete. 

In the recipe adopted for treatment of the fast-neutron attenuation, it is assumed that all fast neutrons entering the concrete are captured after penetrating the concrete by a distance equal to the "age displacement." IHie secondary y rays so formed are then postulated to all flow outward with the estimated 10 cm relaxation length. The required shielding is calculated on the basis that these y rays and the neutrons are to be attenuated to tolerance. It can be shown that this- is a more conservative- procedure than that of considering an exponentially distributed source of capture y rays from the absorption - of the neutrons in the- shield. ... 

The neutron attenuation by the 9 in. of steel, whose effective relaxation length is 4.9 cm, is... 

In the second series the northwest thimble hole was closed, as described later, and additional foil exposures were made at many of the locations mentioned above. Neutron attenuations in the water above the lattice up to the elevation of the shim-rod electromagnets were measured also. 

Increasing the amount of hydrogen In concrete Improves Its neutron attenuating properties, as demonstrated by Dyson and Harrison. iVo possible methods of Increasing the proportion of hydrogen In hardened concrete are to Increase the amount of free and chemically bound water In the hardened cement paste or to use hydrous aggregates. 

DYSON, J.A. and HARRISON, J.R. The Dependence of Fast Neutron Attenuation In Portland Cement on Its drogen Content. AERE, R/R 1942. April 1956. 

Before fire testing, the Fire Science Group tested lined containers for their neutron-absorption properties. After exposing each container to flames for 10 to 20 min, they reevaluated its neutron attenuation. For a Cf fission spectrum moderated by 25 cm of DjO, the liner reduced the low-energy neutron flux by an average factor of about SO before and after fire testing. These tests also showed the neutron-absorption properties of the liner were not greatly affected despite the partial collapse and loss (as much as 8%) of absorber in the form of steam. 

Zeidler A (2012) X-ray and neutron attenuation correction factors for spherical samples. J Appl Crysttillogr 45(1) 122-123... 

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