Poverful gamma sources to inspect goods and vehicles
In customs, seaports, thousands of tonnes of cargo is shipped around the world every day. How do you effectively search millions of containers and vehicles, protecting the security of your borders, without slowing the flow of trade ?
A Shiva bronze statue hidden in a lorry …
A gamma-ray scan revealed a Rijksmuseum’s monumental bronze statue of Shiva cast in solid bronze. Beforehand, the thousand-year-old temple statue was X-rayed, along with the lorry transporting it, in the most powerful X-ray tunnel for containers of the Rotterdam customs authority.
© Rijksmuseum
In recent years, customs stations, police departments, ports and airports are equipped with highly efficient X gamma-rays systems for the inspection of goods. The most powerful inspection portals are able to scan entire trucks or wagons traveling on rails. Particle accelerators associated with gamma rays scan have been implemented in France and other countries to fight fraud and major international trafficking .
These radiographies use radiation generated by small particle accelerators, fixed or onboard inspection vehicles. These radiations are photons produced by bremsstrahlung of accelerated electrons, X-rays or gamma rays. More penetrating than conventional X-rays, they can be classified as gamma rays according to their higher energies.
The gamma energis required for goods inspection is a few MeV. The higher the gamma energy, the more penetratong they are and the image is clear. When high energy penatrating sources are needed, for instance for lorry cargo controls, doors and walls of the installation premises require shielding to meet the radiation protection rules.
Drive through portal cargo inspection systems
With portal systems whole vehicles can be safely inspected. A low energy, low dose X-ray source is used to scan the drivers cabin. Radiation shielding walls (in white) and doors protect the nearby suroundings. Other.systems use a mobile gantry which scan vehicles and containers placed between, the rails;
© DR
In order to identify threats and contraband, the highest quality goods is necessary. The images quality benefits from the use of penetrating gamma through small accelerators and more accurate reconstructions gamma position impacts due to advances in detectors. A whole range of inspection systems are available, ranging from the smallest to the biggest.
The spectrum goes from systems designed for inspecting containers and pallets for air transport, to portals with powerful sources able to scan freight wagons passin on rails. In seaports or border crossings, automated operations controms can scan more than 100 vehicles per hour. Besides customs and port facilities, unoccupied parked trucks and cars can be controlled with a trailer carrying a gamma scanner.
This effective imaging technology, however, should comply with radiation protection rules applicable to workers and to the public, in particular:
-•-The interdiction of activation of building structures, consumer goods and foodstuffs, ensuring that the maximum energy of particles coming out excludes any risk of activation of inspected substances;
-•-The setting up procedures ensuring that checks performed on goods and transport vehicles do not lead to accidental exposure of workers or people. During customs type controls, drivers should be kept away from the truck. Other controls must be in place before irradiation to detect the presence of illegal immigrants in order to avoid their unjustified exposure.