Most efforts to deal with spent nuclear fuel involve getting rid of it permanently. The most popular method is deep burial in geological repositories. However, there are also efforts to find a commercial use for it.
     Scientists in Slovenia at the Jožef Stefan Institute (JSI) and the U.K.’s Lancaster University and Aston University have shown that spent nuclear fuel could be utilized to produce a valuable fuel additive required for renewable biodiesel. Their paper titled Nuclear-driven production of renewable fuel additives from waste organics was published in the journal Nature Communications Chemistry last week. The article said that there are “unexplored renewable processes that can be realized using ionizing radiation – especially considering used fuel pools as a source of catalytic energy.”
     The new research report explains that the process of manufacturing biodiesel also produces glycerol as a by-product. With the increase in the use of biodiesel around the globe, low grades of glycerol are currently being disposed of which adds cost to the renewable sector.
     The researchers placed samples of glycerol insider the research reactor at the JSI. They found that irradiation of the glycerol by neutrons and gamma rays in the reactor can catalyze glycerol to create a very valuable fuel additive known as solketal. This chemical is currently used to make biodiesel as well as other liquid fuels.
     After they had confirmed the radiocatalytic effect, the researchers considered two potential ways in which the nuclear industry could create solketal alongside normal power plant operations.
     One method called for arranging the tubes of glycerol in the space between a light water reactor pressure vessel and its concrete biological shield. Some solketal could be produced in this way but it might come with potential problems for power plant operation and neutron radiation could cause materials in the system to become radioactive.
     A better method for solketal production would be to run tubes of glycerol through spent nuclear fuel cooling pools where highly radioactive spent nuclear fuel is stored for preliminary cooling. This method would result in a greater surface are of glycerol for irradiation. This arrangement would also limit radiation to gamma rays and avoid the complications of neutron activation. A practical arrangement could see the chemical processing taking place in other buildings. This would minimize disruption to power plant operation.
     The research paper suggests that the fuel pool production method has the potential to scale up to produce about fifty-seven tons of solketal per year for a typical spent nuclear fuel pool. Further expansion could reach as many as one hundred and eighty spent nuclear fuel storage sites inside the European Union. This could result in a maximum estimated capacity of about ten thousand tons of solketal per year. Solketal has a market price of about three thousand dollars per ton.
     Representative of the JSI said, “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.”