Travellers entering Singapore through the Causeway have been experiencing delays as the Singapore authorities hunt for clues of a 23kg radioactive dispersal device (RDD) that went missing on Aug 10 in Selangor, Malaysia.
Personnel with the Immigration and Checkpoints Authority (ICA) are screening for radiation levels on cargo, vehicles and travellers entering Singapore, including at airports.
The device reportedly consists of a large metal tube with a handle on top, and is said to contain the radioactive isotope iridium-192, which emits beta and gamma radiation and has an estimated half-life of 73 days.
It went missing while it was being transported from Seremban to Shah Alam by two technicians of a company that offers testing, calibration and inspection services to heavy industries.
Malaysian newspaper The Star reported that the increased security checks have resulted in noticeably longer waiting times for motorists heading into Singapore via the Causeway.
According to Professor Tim White, President's Office research director for engineering and physical sciences at the Nanyang Technological University, the iridium isotope emits high-energy gamma rays, and is commonly used to assess the quality of welds in thick metal plates.
But close physical exposure to the material can cause serious injury to humans, he said.
"Though non-destructive testing (NDT) using radioactive sources is a common tool for assessing the integrity of metal piping, all companies and engineers using this equipment must be licensed and trained," he said.
"The radioactive sources are also required to be securely stored, with audits carried out regularly by government agencies."
Prof White said there is little danger as long as the NDT device is intact and the radioactive source is in a sealed container.
But if the radioactive disc is removed from its shield and held next to the body for some time, such as in a pocket, it can cause radiation burns.
Bernama reported that the Selangor police and the Atomic Energy Licensing Board have mobilised a task force to locate the device. The authorities are also worried the RDD may cause massive radiation exposure if it is dismantled for scrap metal.
Prof White said the radioactive source is usually a metal disc measuring a few millimetres in diameter and fractions of a millimetre thick, making it difficult to weaponise. The greater risk could be if someone untrained tries to disassemble the NDT device.
