Enhancing neutron radiography radiographs for non destructive testing
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Neutron Radiography is utilized by industry as a non destructive investigation technique. It is simalar to X-ray radiography except that neutrons, either from a nuclear research reactor, isotope or neutron generator is used as source. The images (radiographs) obtained from neutrons differ from these taken by X-rays because the interaction properties of a certain type of material are different for X-rays and for neutrons.
To obtain neutron radiographs, either film or low light level CCD cameras with a frame grabber is utilized. The radiographs from our CCD camera are full of noise and sometimes don't have the dynamic range that we need. Sometimes part of the image is important to us and then only that part is enhanced. Image-Pro Plus helps in all these circumstances to enhance our images so that the information we need is made visible. Spatial calibration is also used to do some length measurements inside samples. The pixel grey scale index is also utilzed to calculate the neutron absobtion of a certain type of material.
On the right and below are four example radiographs.
Above: This is comparison of X-rays and neutrons with a .38 Special bullet sample. You can see that the soft lead nose can't be penetrated by X-rays (X), as expected, but in the (N) neutron radiograph, a void is seen at the bottom. Also revealed with neutrons is the powder level. With X-rays no powder can be detected. (Neutrons tend to be absorbed by hydrogen enriched materials, therefore this difference). I enhanced both images with Image-Pro Plus to obtain these nice images.
Above: This is a neutron radiograph as we get it from our CCD camera, without any image enhancement. It is a radiograph of aluminium corrosion products on a sample from an airplane.
Above: This is the same aluminium corrosion sample after some Image-Pro Plus image enhancement tools have been utilized. The dynamic range was stretched to the full for the area that we need and the pop rivets (white spots) and the corrosion products (black areas) are now clearly visible.
Above: This is a radiograph containing 2 images, being put together with the aid of Image-Pro Plus to show the effect of image enhancement in a neutron radiography environment. The sample is a motorbike rim made from lightweight carbon fibre. Neutron penetration through the material is good. The radiograph on the right reveals a faint defect at the bottom but to the eye it seems not such a big problem. With image enhancement from Image-Pro Plus the radiograph on the left clearly show that there is a lack of material in that area - a great problem during high speeds.
Frikkie de Beer
Head Technician: Neutron Radiography
Atominc Energy Corporation of South Africa (AEC)
Pretoria, South Africa
Email: nbeams@aec.co.za
AEC web site: http://www.aec.co.za
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