ARCHIVED - Detecting illegal nuclear weapons
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September 01, 2011— Ottawa, Ontario
NRC researchers in collaboration with the Canadian Nuclear Safety Commission have developed a hand-held scanner to help the world’s nuclear inspectors identify radioactive materials intended for use in nuclear weapons.
The five-kilogram device was created for the Vienna-based International Atomic Energy Agency (IAEA), which is responsible for safeguarding global supplies of uranium, plutonium and thorium to prevent the spread of nuclear weapons. IAEA inspectors visit nuclear facilities around the world to verify that countries are meeting their obligations under the Nuclear Non-Proliferation Treaty and other international agreements.
When inspectors suspect that illegal nuclear activities may be taking place at facilities that countries claim to be using for non-military purposes, the current procedure involves swiping the building’s walls with a tissue and then sending the samples to Vienna for analysis. While the results are generally reliable, both the time involved and the costs ($500 to 1000 per sample) are significant.
“IAEA needs a technology that can instantly detect what inspectors are looking for: uranium oxide particles,” says Dr. Mohamad Sabsabi of the NRC Industrial Materials Institute in Boucherville, Quebec. These particles indicate that uranium enrichment is taking place.
The NRC device, which is based on a technology called laser-induced breakdown spectroscopy (LIBS), features a finger-sized laser used to scan the surface of walls for uranium oxide.
What is LIBS?
Laser-induced breakdown spectroscopy consists of a laser and a spectrograph — a device that detects and measures various frequencies of light. LIBS works by focusing a laser beam on a target, where it causes a tiny amount of material to heat up and breakdown into a gas-like substance called plasma. The plasma emits light waves — each element emits a unique spectrum — that are detected by the spectrograph and analyzed.
According to Dr. Sabsabi, LIBS is so sensitive that it can detect particles that are under 1 micrometre in size. “Even if a facility’s walls have been freshly painted to cover up illegal activities, LIBS can detect uranium oxide particles under the paint,” he says. What’s more, it can instantly determine where the uranium originated as well as whether the facility is being used for peaceful or military purposes.
“Using our device, you can tell if the uranium oxide came from Russia, Australia, Canada or wherever — in fact, you can trace the material back to a specific mine or enrichment plant,” says Dr. Sabsabi. This means that “if IAEA inspectors discover that a country is secretly developing nuclear weapons, they can also figure out which country sold it the uranium.”
Besides detecting uranium oxide, LIBS can identify which of the two main uranium isotopes are present and therefore the degree of nuclear enrichment occurring at the facility. If the ratio of uranium-235 to uranium-238 exceeds 4.5 percent, this means the facility is likely being used to make nuclear weapons. However, a ratio of 0.7 to 4.5 percent is considered normal for nuclear power generation and other non-military purposes.
The LIBS scanner is currently being evaluated by IAEA inspectors. “We’ve already shown that it works in proof-of-concept testing. They’re now giving us feedback on what could be improved from a technical point of view, so we can introduce a commercial version,” says Dr. Sabsabi.
Besides simplifying inspections of nuclear facilities, LIBS scanners may someday help prevent terrorist activities involving nuclear materials. “Border security agents could use our device to test the contents of shipping containers for uranium oxide,” he explains.
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