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Nuclear Radiation Sensors

Detection technologies help to limit spread of nuclear weapons

A technician is removing one of the archival bottles used to store xenon samples from the Automated Radioxenon Sampler-Analyzer, an innovative technology developed at PNNL to detect xenon from underground nuclear weapons testing.

Since the earliest nuclear tests in the years following World War II, the world has been living under the threat of nuclear attacks. Two breakthrough technologies developed by researchers at PNNL may significantly lessen that threat.

Known as RASA (Radionuclide Aerosol Sampler/Analyzer) and ARSA (Automated Radioxenon Sampler/Analyzer), these devices can detect radionuclides from nuclear explosions quickly and accurately. "I am particularly proud that my PNNL colleagues took the lead in recognizing that new radionuclide detection systems were needed for nuclear explosion monitoring on a global scale, and for proposing practical, cost-effective designs," says Ray Warner, program manager, National Security Division.

The two technologies, which recently won a coveted Federal Laboratory Consortium award for technology transfer, represent a quantum leap beyond previous monitoring devices; they have greater sensitivity than other systems, are fully autonomous, and give near real-time results. "They also can prove that a nuclear explosion occurred, which other technologies can't do," says RASA developer Harry Miley, also of NSD.

The RASA detects fission products in the form of particulate debris from atmospheric nuclear explosions. The fully automated system draws a huge volume of air daily through a series of filters that remove nearly all of the particles. The filters are sealed, bar coded, and then passed to a radiation detection system within the unit.

The ARSA, on the other hand, analyzes air samples for radioactive xenon that seeps from underground nuclear explosions. "Xenon is a particularly difficult radionuclide to detect, but ARSA can detect it with a sensitivity more than 100 times greater than other systems being used," says NSD's Ted Bowyer, developer of ARSA. The ARSA collects air samples and processes them to trap the radioactive xenon on cryogenic charcoal. The system purifies the xenon and transfers it to a novel, ultra-low background nuclear counting system. Xenon's different isotopes are measured automatically, and the results are passed to a data center.

In addition to their sensitivity, both systems can be monitored completely, controlled and programmed remotely to lower operating costs.

The technologies are being deployed worldwide to verify international compliance with the Comprehensive Nuclear Test Ban Treaty (CTBT). The Treaty, adopted in 1996 by the United Nation's General Assembly and signed by 150 nations, is intended to reduce the threat of nuclear war and monitor weapons testing.

"The treaty requires a network of 80 radio-nuclide monitoring stations covering the globe," Ted says. The RASA and ARSA technologies now are part of that global monitoring network to limit the spread of nuclear weapons. Fifteen monitors already are in place to ensure the treaty's success.

"We're confident that our technologies will play a significant role in bringing the world into compliance with the CTBT within schedule, and permit immediate, highly accurate monitoring for the treaty," Harry says.

By Sue Chin

Sensors & Electronics

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