A team of scientists at the US Department of Energy’s Idaho National Engineering and Environmental Laboratory (INEEL) is producing positrons with electron linear accelerators and using them to detect and measure subatomic structural defects.
According to INEEL, the process may save money and extend uninterrupted operation for critical components such as those used in aeroplanes, bridges and utilities.
Material fatigue causes failures in everything from buildings to computer chips and studies indicate that fatigue failures in the United States alone costs $119 billion every year.
Methods for testing also form a lucrative market. In 2000, the market for non-destructive testing equipment was estimated at $827 million while consulting and services were estimated to reach over $900 million.
This technology is reportedly a breakthrough from current methods of using X-rays to detect cracks in materials, as it provides a method for determining fatigue long before a crack ever appears.
The patented system combines accelerators with an in-situ positron measurement process as the basis for a new core technology that can be used in developing new alloys and more durable components while accurately determining the remaining life of components currently in use.
Technicians point a portable linear accelerator – similar to those systems used in cancer therapies – at a steel bridge support, an aeroplane wing spar or at a plastic valve used in a human heart. They then shoot a beam of photons at the material.
This produces short-lived radiation in the material and gives off positrons, which are electrons with a positive charge. Positrons are attracted to the nano-sized defects of the material. As they decay, positrons release their energy as gamma rays. The energy spectrum of the gamma rays creates a distinct and readable signature of the size, quantity and type of the defect.
Using this process, engineers could determine how long aircraft wings can be used or bridge supports will stand. Medical manufacturers could confirm the quality of valves before doctors implant them into patients.
INEEL researchers tested the process – originally developed for aircraft and nuclear reactor components – on a variety of materials including steels, plastics and aluminium.
‘We ran tests on blind samples, sometimes on chunks of unmarked aluminium,’ said physicist Doug Akers. ‘Our results showed exactly where the test specimens were in their life cycle with less than 1 percent uncertainty.’
Not only can this process predict failure in everything from huge and costly superstructures like bridges and nuclear reactors to every day items like microchips and human implants, said the researchers, but positron annihilation can help create new, stronger materials.
Potential commercial applications include measuring fatigue during alloy development and performing quality assurance measurements on components after they have been fabricated.
Earlier this year, Positron Systems Inc. licensed the technology for commercial applications.