A monitor that frequently checks air ducts for accumulated nuclear material at nuclear fuel cycle facilities has been developed by a team at the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL).

While facilities that manufacture nuclear fuel or that process nuclear waste seal off areas where the material is kept and screen the airflow via high-efficiency particulate air filters, tiny particles can still escape into the facility’s air ducts. Monitoring is occasional and requires one person to extend a radiation counter at the end of a long pole through overhead ventilation ducts.

Source: Carlos Jones/ORNL, U.S. Dept of Energy

Commercial nuclear fuel cycle facilities use strict monitoring and regulatory controls to prevent nuclear material diversion and protect workers, the public and the environment. Monitoring systems are especially important for detecting radiological material buildup in areas such as air ducts, where unshielded radiation can create health hazards and unmonitored nuclear material could pose national security risks.

As such, the ORNL team developed the new monitor, which is designed to check every minute or every second for the accumulation of nuclear material in the air ducts. The new low-cost, 12 in cylindrical detector can be attached to the side of a duct and is either powered with a battery or through Power over Ethernet (PoE). When powered with a battery, the detector can operate for roughly one month at a time, taking samples about once a minute and recording the data. With the Ethernet connection, more data can be saved and transmitted every second.

The detector uses an inexpensive plastic scintillating crystal that emits photons when exposed to radiation. Silicon photomultipliers convert the light into electrical pulses, allowing the system to identify radiation energy signatures associated with uranium and other nuclear materials.

The design replaces traditional vacuum tubes with smaller, lower-cost silicon photomultipliers and combines analog processing with digital microcontrollers. The plastic scintillator costs about $1 to $2, compared with $1,000 to $10,000 for conventional radiation detectors, potentially enabling broader monitoring across nuclear facilities.

The low-cost radiation detector has been successfully demonstrated in battery-powered mode at an ORNL nuclear material processing facility. Data from the tests will help train an AI-enhanced algorithm to automatically alert operators when nuclear material reaches potentially unsafe levels.

For now, the team is testing the electronics for heat resistance before integrating the AI algorithm. The team plans to demonstrate the complete system using PoE at an ORNL building with a molten salt reactor test loop and is working with nuclear fuel and fabrication companies to validate the technology.

The detectors could eventually be used in nuclear safety and security applications, including molten salt reactors, small modular reactors and portal monitors designed to detect unauthorized movement of nuclear materials.