A nondestructive testing technology that can precisely detect fatigue, embrittlement and other forms of structural damage at the atomic level, before a crack appears, has been developed by the US Department of Energy's Idaho National Engineering and Environmental Laboratory. The process, known as photon induced positron annihilation (PIPA), can also assess the remaining useful life of metallic, composite and polymer materials. This advance in NDT is expected to help prevent component failure due to fatigue cracks and safely extend the service life of expensive and critical parts, for example in boiler piping used in nuclear reactors.
PIPA is claimed to be more precise than any existing nondestructive evaluation technology, including radiography, eddy current, or ultrasonic methods. The process was invented at the Idaho lab but is available through licensee Positron Systems. By 2003 mobile versions should be available.
The PIPA process involves penetrating materials with a photon beam generated by a linear accelerator. This creates positrons, which are attracted to nano-sized defects in the material. Eventually, the positrons collide with electrons and are annihilated, releasing gamma rays whose spectrum creates a distinct signature of the size, quantity and type of defects present.
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