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Gallium is at the core of nuclear safety

Metal Tech News - July 1, 2024

Oak Ridge National Laboratory experiments demonstrate that critical metal can withstand prolonged reactor heat and radiation.

Conventional nuclear reactors and next-generation modular and microreactors rely on thousands of sensors delivering data to sophisticated electronic monitoring devices for safe and efficient operations. Traditional silicon-based electronics, however, do not hold up to the heat and radiation emitted from the core and must be installed at a distance.

New research at Oak Ridge National Laboratory (ORNL) demonstrates that gallium-nitride semiconductors have a much higher resilience to the rigors of a nuclear core than their silicon counterparts.

This means that monitoring electronics with these semiconductors could be positioned closer and gather more precise measurements.

A typical commercial nuclear reactor can have more than 2,500 sensors monitoring for pressure, temperature, neutrons, and other parameters that provide data on the health of the equipment. This can help prevent unscheduled shutdowns that can cost millions of dollars each day in lost generation revenue.

Currently, the complex electronics that process the data delivered by these sensors must be placed away from the reactor core. As a result, the data must travel through lengthy cables that can pick up outside noise and degrade the signal.

To overcome this core data retrieval and processing dilemma, and improve the accuracy and precision of the sensors, ORNL scientists decided to explore gallium nitride as a more resilient substitute for silicon-based transistors.

Gallium nitride outperforms

Gallium nitride is a wide bandgap semiconductor material that allows electronic components to be smaller, faster, more reliable, and more efficient than those made with silicon materials. For this reason, the gallium-based semiconductor is commonly used in high-performance and fast-charging smartphones and is expected to deliver similar advantages to electric vehicles.

This material is also much more resistant to heat and radiation than silicon, which is where its nuclear applications come into play.

To find out just how resilient it is, ORNL researchers tested gallium nitride transistors placed close to a research reactor core at Ohio State University. These transistors withstood high heat and radiation for three consecutive days, including seven hours, with the reactor running at 90% power.

Michael Huson/The Ohio State University

Oak Ridge National Laboratory researcher Kyle Reed led a team testing an ORNL-made transistor in the reactor pool at The Ohio State University Nuclear Reactor laboratory.

The gallium nitride transistors stood up to 100 times higher accumulated dose of radiation than standard silicon devices at a sustained temperature of 125 degrees Celsius (257 degrees Fahrenheit) – far exceeding the team's expectations.

"We fully expected to kill the transistors on the third day, and they survived," said lead researcher Kyle Reed, a member of the Sensors and Electronics group at ORNL.

The research carried out by the national lab scientists indicates that gallium nitride transistors are capable of surviving at least five years in a reactor, the minimum amount of time electronics need to persist to align with maintenance schedules, avoiding unnecessary shutdowns to replace failed components.

"Our work makes measuring the conditions inside an operating nuclear reactor more robust and accurate," Reed added.

The research may also be a key discovery for advanced microreactors, which, due to their compact size, will need sensors capable of withstanding more adverse radiation conditions than conventional reactors in the U.S.

Moving forward

Utilizing the data from the ORNL testing, Ohio State University is now working on computer models to predict how various gallium nitride circuit designs will perform under different levels of radiation and temperature.

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Gallium is a tech metal with a melting point of 85.6 F that is often used in semiconductors.

"Since the ultimate goal is to design circuits with these materials, once we understand the temperature and radiation effects, we can compensate for them in the circuit design," Reed said.

The researchers are optimistic that they could one day be able to completely do away with the wires connecting nuclear reactor sensors to monitoring electronics. Gallium nitride circuits are already used for devices that support radio frequency applications, such as smartphones.

Reed hopes the ORNL research into gallium nitride for nuclear reactor electronics and other applications will create new markets for this wide bandgap semiconductor.

"We're opening up different side avenues for using gallium nitride, so we can start to create a more reasonable market demand for investment, research and workforce development for subclasses of electronics beyond consumer-grade," he said.

In addition to Reed, ORNL researchers and staff that contributed to the gallium nitride studies include Dianne Ezell, Nance Erickson, Brett Witherspoon, Craig Gray, Emma Brown, Kevin Deng, Adam Buchalter, and Caleb Damron.

Author Bio

Shane Lasley, Metal Tech News

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With more than 16 years of covering mining, Shane is renowned for his insights and and in-depth analysis of mining, mineral exploration and technology metals.

 

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