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Renewable fuel additive created in radiation process

Tuesday, 28 September 2021

Radiation from used nuclear fuel could be used to create a valuable fuel additive needed for renewable biodiesel, scientists in Slovenia and the UK have shown. The research highlights that there are "unexplored renewable processes that can be realised using ionising radiation - especially considering used fuel pools as a source of catalytic energy," said the paper, published in Nature Communications Chemistry last week. It was written by scientists from Slovenia's Jožef Stefan Institute and the UK's Lancaster University and Aston University.

Renewable fuel additive created in radiation process — The TRIGA MkII research reactor at the Jožef Stefan Institute (Image: JSI)

The paper, Nuclear-driven production of renewable fuel additives from waste organics, explains that the process of making biodiesel also produces glycerol as a by-product, but with the increase in use of biodiesel globally, low grades of glycerol are currently being disposed of at cost to the renewables sector.

By placing samples of glycerol inside the research reactor at the Jožef Stefan Institute the scientists showed that irradiation by neutrons and gamma rays can catalyse glycerol to create a highly valuable fuel additive known as solketal, which is actually used to make biodiesel as well as other liquid fuels.

After confirming the radiocatalytic effect, the paper considers two potential ways the nuclear industry could create solketal alongside normal power plant operation.

One method was to arrange tubes of glycerol in the space between a light water reactor's pressure vessel and its concrete biological shield. This would be expected to produce some solketal, but might come with potential complications for power plant operation, while neutron radiation could cause materials in the system to become radioactive.

How solketal production could be implemented alongside used nuclear fuel storage

A more promising method would be to run tubes of glycerol through used fuel pools, where highly radioactive used fuel is stored at power plants and interim sites. This method would present a greater surface area of glycerol for irradiation, while the conditions limit radiation to gamma rays, avoiding the complication of neutron activation. A practical arrangement could see the chemical processing taking place in other buildings so as to minimise disruption to power plant operation.

The paper suggests that the fuel pool method has potential to scale up to produce around 57 tons of solketal per year for a typical used fuel pool. Further expansion to a potential 180 used fuel sites within the European Union revealed a maximum production capacity of around 10,000 tons of solketal per year, the paper said. Solketal has a market price of around USD3000 per ton.

"This discovery has opened up entirely new possibilities for the use of radiation from nuclear power plants and spent nuclear fuel storage facilities for the conversion of waste chemicals and is one of the important steps on the path to sustainable development," said the Jožef Stefan Institute.