New Fuel Transforms US Nuclear Reactor From Regular To Premium

A U.S. nuclear reactor has taken a major technological step forward by adopting a more advanced type of fuel. Southern Nuclear inserted four Lead Test Assemblies (LTAs) into the Vogtle Unit 2 reactor in Waynesboro, Georgia. These assemblies use uranium enriched above 5% — a first for commercial reactors in the United States.

In general, people often see nuclear fuel as a straightforward concept: the reactor needs fuel, you put it in, and that’s it. But the process is far more complex — especially when compared to burning coal. Nuclear fuel requires not only refining but also enrichment.In other words, we need to increase the proportion of fissile uranium-235 (U-235) relative to uranium-238 (U-238), which isn’t fissile.

Why Enrich Uranium?

Natural uranium contains only about 0.7% U-235, which is too low for most modern reactors. To sustain a chain reaction, we must increase the concentration to around 3% to 5%, producing what’s known as Low-Enriched Uranium (LEU).

High school physics teaches this kind of knowledge.However, not everyone realizes that different reactors require different enrichment levels for different results.

For instance, nuclear submarines run on Highly Enriched Uranium (HEU), which ranges from 20% to 93% U-235 — the upper end of which is classified as weapons-grade. This level of enrichment allows reactors to deliver massive amounts of power.For example, the aircraft carrier USS Enterprise was so powerful that they issued orders never to run it at full throttle.

Another benefit of high enrichment is longevity.Some submarines never require refueling during their entire service life. In fact, modern nuclear submarines don’t design for refueling — doing so would require cutting open the vessel.This type of fuel also allows for compact, efficient reactors that suffer less thermal and radiation damage compared to commercial reactors.

Commercial Reactors Get a Power Boost

Southern Nuclear, working with Westinghouse Electric Company, is not going that far — but they are taking a notable step forward.The aim is to help next-generation designs advance conventional reactors by using HALEU (High-Assay Low-Enriched Uranium), which ranges from 5% to 20% enrichment.

Until recently, researchers had used HALEU only in research reactors or in advanced designs involving technologies like molten salt. Developed under the U.S. Department of Energy’s Accident Tolerant Fuel Program, this commercial test explores the possibility of burning enriched fuel in conventional reactors to boost performance, extend fuel life, and reduce waste.

This is more than just adding more U-235. Higher enrichment requires a new fuel recipe.Manufacturers typically use uranium ceramic pellets for LEU, while they make high-enrichment fuels from uranium-zirconium or uranium-aluminum alloys.

They also include “burnable poisons” — elements like boron-10 and gadolinium-157 — which absorb neutrons and regulate the reaction. Early in the fuel cycle, these poisons suppress the reaction, and over time they burn away, allowing the fuel to maintain a steady output.

ADOPT: The Experimental Fuel

Westinghouse developed the experimental fuel used in this test and named it ADOPT. This enhanced uranium dioxide (UO₂), doped with chromia (Cr₂O₃) and alumina (Al₂O₃), increases uranium density, improves heat transfer, and minimizes the gas release from fission that could damage the fuel. It also reduces the risk of the fuel rods’ metal cladding failing.

According to Westinghouse, a variant known as LEU+ ADOPT can support enrichment levels up to 8%, significantly improving conventional reactor performance and reducing the need for frequent refueling.”Westinghouse’s Springfields facility in the UK manufactured the ADOPT pellets using uranium powder that Idaho National Laboratory supplied. The team then inserted the resulting four fuel assemblies into the Vogtle Unit 2 power plant, where they will now closely monitor them across several reactor cycles.

This achievement is a significant step forward not just for the resilience of the U.S. reactor fleet, but for the future of nuclear energy,” said Pete Sena, Chairman, President, and CEO of Southern Nuclear. “Our goal is to run our reactors longer and more efficiently.Higher-enriched fuel equips us to better meet Georgia’s growing energy needs.

Read the original article on: New Atlas

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