Small Controlled Area Radiography (SCAR) Technique
SCAR, Small Controlled Area Radiography, is a (conventional) radiographic tool utilising collimated either 500 Gbq, Iridium 192 or a Selenium 75 isotope.
The radiation beam is reduced to an area needed to still produce a useful radiograph. Depleted Uranium encased by a steel container holds the source and shields it from its environment; it also acts as a collimator when the source is in the exposed position. This is permitting the use of a very small exclusion zone of only 2-5 metres around the isotope and reduces dose rates for the inspection personel.
SCAR system
General inspection capabilities
The small exclusion zone is significantly less than for traditional radiography systems and considerably lowers the H&S risks that are associated with using radiography. When the source is in the exposed position will the radiation be collimated through a cylinder ending in a pyramidial porthole, allowing the nescessary amount of radiation egress. The escaping beam is therefore heavily directed with litle spread and is relatively easy to attenuate.
Conventional radiography can command exclusion zones of over 100m whilst the SCAR system can work in exclusion zones of as low as 3 meters.
The isotope never leaves the container and is hence designed to be completely fail-safe. The source is ejected from the stored position into the collimator using pneumatics pressing against a return spring. In the event of failure of the pneumatics the source will be reutrned automatically to the stored position by he retun spring. The system is also intrinsically safe.
Clamps and asscesories have been constructed for SCAR to fit pipe diameters between 10-2000mm The method itself is not rapid but vast overall time savings can be achieved through the significantly reduced exclusion zone.
Inspection limitations
- Normally slower to deploy than conventional radiography
- Clearance around pipe for mounting film / digital system.
- Set up time.
