Abstract
In this research, a combined fast-neutron/γ-raybackscatter imaging technique is described. The aim of this work is to understand corrosion defects in pipelines by measuring differences in the scattered radiation flux, generated when different steel thicknesses are irradiated by a neutron and γ-ray focused beam. A californium-252 radiation source is used to produce fast neutron and γ rays, exploiting its spontaneousfission. This mixed radiation field is collimated and directed towards the steel samples. Backscattered neutrons and γ rays aremeasured as a function of the steel thickness using 4 liquid organic scintillation detectors linked to a real-time, pulse-shape discrimination system, which separates and retains the neutron and γ-ray event data. In this paper, we describe how, using asingle radiation source and detection system, it is possible to perform and combine two complementary imaging modalities. This research is validated by an MCNP6 computer simulation study. The backscatter imaging system developed for this research and the experimental results of the measurements carried out using the National Physical Laboratory neutron low-scatter facility are also presented in this paper.
Highlights
BACKSCATTER radiography and backscatter computer tomography (BCT) are non-destructive testing (NDT) techniques that exploit the scattered radiation in contrast to that which is transmitted
X-ray backscatter imaging has been studied for the last three decades and utilizes the scattered radiation arising by virtue of the Compton Effect, the extent of which depends on the electron density in the scatterer rendering this technique effective for heavy metals
There are few if any papers in the literature reporting the use of fast neutrons in place of X-ray as the probing radiation for backscatter radiography
Summary
BACKSCATTER radiography and backscatter computer tomography (BCT) are non-destructive testing (NDT) techniques that exploit the scattered radiation in contrast to that which is transmitted. The latter is used in the more common and well-known computerized axial tomography (CT). X-ray BCT has applications in non-destructive testing for quality control and for security inspection, such as the detection of dangerous materials, border inspections, biomedical science, several engineering fields, above all, oil and gas sector and aerospace. Fast neutrons interact differently compared to X- and rays and, in particular, elastic nuclear scattering of neutrons and the corresponding cross section can be exploited, as neutrons have high penetration capabilities, which allow high-density materials to be investigated
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