Unique combustion technique could produce safer nuclear fuel

As the world commits to minimising global temperature rises through decarbonisation, many governments are – sometimes reluctantly – embracing nuclear power as a complement to renewable energy generation. Uranium dioxide, a radioactive actinide oxide, is the most widely used nuclear fuel in modern nuclear power plants.

However, Los Alamos researchers have suggested that in the future, nuclear fuels could be produced through a combustion process recently established for lanthanide metals: non-radioactive and positioned one row above actinides on the period table.

“Actinide nitride fuels are potentially a safer and more economical option in current power-generating systems,” said Dr Bi Nguyen, lead author of the Inorganic Chemistry study. “Nitride fuels are also well-suited to future Generation IV nuclear power systems, which focus on safety, and feature a sustainable closed reactor fuel cycle.”

Actinide nitride fuels (which contain nitrogen, while oxides contain oxygen) have a significantly higher energy density than actinide oxide fuels, as well as better thermal conductivity, allowing for lower temperature operations and thus a larger margin to meltdown under abnormal conditions.

Despite these benefits, actinide nitrides are challenging to produce due to the high temperatures and sophisticated equipment required. Scaling up production of high-purity actinide nitrides contains to be a major obstacle to their adoption by the nuclear industry.

Both actinides and lanthanides are found at the bottom of the periodic table, and potential methods to make actinide materials are typically first tested with the lanthanides due to their similar behaviours.

Now, Los Alamos researchers have discovered that LnBTA (lanthanide bistetrazolatoamine) compounds can be burned to produce high-purity lanthanide nitride foams through a unique technique called combustion synthesis. This technique makes use of a laser pulse to initiate dehydrated LnBTA complexes, which then undergo a self-sustained combustion reaction in an inert atmosphere, yielding lanthanide nitride foams.

Los Alamos National Laboratory’s Weapons Modernisation and Chemistry divisions are now collaborating to examine whether combustion synthesis could also be applied to produce actinide nitride fuels.