Making nuclear reactors stronger and safer

An international team of researchers has developed a new type of metal alloy that could make nuclear reactors safer and more stable in the long term. The new material is said to be stronger and lasts longer than steel - the metal of choice for current nuclear reactors. Nuclear power currently provides 11% of the world's electricity.

Nuclear reactors typically last for 40 years, because steel can become weaker or even defective over time. Modern-day reactors run at higher temperatures than ever before making the search for a new material even more urgent. If the steel exterior of the reactor becomes defective, it needs to be replaced, costing a huge amount of time and money.

According to researchers from the Oak Ridge National Laboratory in Tennessee and the University of Finland, high-entropy alloys, which use several elements in equal percentages, could be the solution.

To test their hypothesis, they bombarded two such alloys with nickel and gold ions - a simulation of what happens to the metal casing inside a nuclear reactor. In each case, the alloys came out with two or three times fewer defects than steel.

As atoms are split inside a nuclear reactor, intense levels of heat are produced - to power the turbines and generate electricity - as well as more and more neutrons. Most of these neutrons get trapped by the heavy water that fills the reactor, but some make it to the metal exterior that holds everything together, and that can cause defects as they dislodge the atoms forming the metal's crystalline structure.

Because high-entropy alloys use equal mixes of metals spread out evenly, each type of atom is nearly equally exposed to the incoming particles, levelling out the chances of dislodging slightly different-sized atoms and reducing the risk of defects.

While high-entropy metals aren't new, it's only in recent years that scientists have managed to create them to a high enough quality to use for practical applications, and while cost remains a problem, the scientists say this should start to come down in the years ahead.

The team says these alloys won't be ready to use for a long time, but full-scale tests are planned, and there are many different metal alloy mixes that can be tested.

Author
Tom Austin-Morgan

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