Nuclear waste and a hydrogen economy may seem poles apart, but a new study by the University of Sharjah claims that spent fuel from nuclear power plants could be used to increase the efficiency of converting water into hydrogen and oxygen.
At first glance, hydrogen seems like the ideal green energy source. Burn it with oxygen, and its only waste product is water. What’s not to like? The problem is that hydrogen isn’t an energy source. It’s an energy conduit. Calling it an energy source is a bit like thinking that electricity comes from the wall outlet instead of a generator.
This leads us to one of hydrogen’s biggest stumbling blocks from an environmental point of view. Some people would like hydrogen to replace fossil fuels, but the biggest source of hydrogen is fossil fuels. It’s also the most efficient because the fuel also provides the energy needed to change natural gas into hydrogen.
The greener way to make hydrogen is through electrolysis. That is, passing an electric current through water to break down the molecules into hydrogen and oxygen. It’s so simple that it’s a common science experiment for children, but it’s also highly inefficient and requires a dedicated external power source.
University of Sharjah
According to the Sharjah team, one solution to this problem could be to use nuclear waste to boost hydrogen production. From an economic view this is attractive because spent fuel rods taken straight from a reactor are too hot (physically and radioactively) to handle and have to be left in storage pools for years until they can be shifted for reprocessing and disposal, so why not get some good out of them in the meantime?
In addition, spent fuel that isn’t reprocessed is composed almost entirely of uranium, so this can be put to good use as well.
This approach would involve one of several possible methods to improve hydrogen production, primarily by combining conventional electrolysis with exposure to radiation from the nuclear waste. There would be no direct contact between the water and the waste, so there is no danger of contamination.
The first of method is radiolysis, which involves pre-splitting the water molecules by bombarding them with alpha, beta, and gamma particles. This turns the water into hydrogen radicals, hydroxyl radicals, hydrated electrons, molecular hydrogen, and hydrogen peroxide, among others. These are much easier for the electric current to break down into hydrogen, leading to a much greater yield.
The second method uses uranium extracted from the waste to form a catalyst that speeds up the electrochemical reaction without being consumed itself. According to the study, a uranium-based catalyst from waste would be much cheaper than one made from platinum or other precious metals.
The third method doesn’t involve electrolysis at all. Instead, it uses the uranium catalyst to enhance the Steam-Methane Reforming (SMR) reaction, which is the world’s primary industrial hydrogen production process. Such a catalyst would be much less prone than alternatives to carbon buildup and would, therefore, have a longer service life.
The fourth method would use the heat generated by the waste to drive the chemical and electrochemical reactions, making the processes more efficient without the need to invest in a secondary heating system.
“Utilizing nuclear waste is a novel method of producing hydrogen that transforms a persistent environmental issue into a useful resource,” said the team in a statement. “Hydrogen has become a promising energy carrier as the need for sustainable and clean energy sources increases globally.”
Source: University of Sharjah
