Researchers at the Department of Energy’s Oak Ridge National Laboratory (ORNL) have developed a compact radiation monitor that continuously checks air ducts in nuclear fuel cycle facilities for traces of nuclear material.
Continuous, low-cost monitoring
Today, many facilities still rely on sporadic manual checks with handheld probes on poles inside overhead ventilation ducts. ORNL’s new device replaces this with automated, continuous monitoring.
The detector is a 30 cm (12 inch) cylindrical unit that bolts onto the side of a duct and operates in two modes:
- Battery-powered: runs for about a month, sampling roughly once per minute and logging data locally
- Power over Ethernet (PoE): enables higher data rates, with measurements every second and live data transmission
This allows facilities that handle nuclear fuel or waste to detect build-up of radioactive particles that pass through HEPA filters and accumulate in ductwork, improving worker safety and material accountancy.
Plastic scintillator + SiPM + secure microcontroller
The monitor uses an inexpensive plastic scintillating crystal. When struck by radiation, it emits light, which is converted into electrical pulses by a silicon photomultiplier (SiPM). Because uranium and other nuclear materials have distinct energy signatures, the electronics are tuned to count pulses corresponding to unsafe levels for specific materials.
“We’re really combining the old and the new—the best of historical analog processing, which needs less power, combined with the latest digital microcontrollers incorporating advanced security features,” said Brett Witherspoon, technical lead for the project.
By replacing vacuum tubes with SiPM arrays, the system becomes smaller, cheaper and more tolerant to temperature swings. The plastic crystal costs 1–2 USD, compared with 1,000–10,000 USD for inorganic scintillators or semiconductor detectors.
Project lead Callie Goetz is developing an AI-enhanced algorithm that will run on the device and automatically alert operators when nuclear material accumulation reaches a concern threshold.
Beyond fuel cycle ducts
The team is now qualifying the electronics at high temperatures and plans a PoE demonstration in an ORNL building with a molten salt reactor test loop. They are also partnering with enrichment and fuel fabrication companies to validate the monitors in real facilities.
With further improvements in heat tolerance and data acquisition, these detectors could serve in molten salt loops, small modular reactors, and portal monitors outside nuclear sites—even in harsh environments—to help prevent theft and diversion of nuclear material.
Source: Phys.org
