Nuclear Hydrogen Production (NHP) is the idea that the heat and/or electricity from a nuclear reactor can be used to electrolyse, thermolyse, or thermochemically analyse water - separating hydrogen and oxygen. The resulting hydrogen is useful for a variety of markets including hydrocarbon upgrading & refining, ammonia production, and transportation. The merit of the nuclear hydrogen production scheme is that it does not produce greenhouse gases. Alternative hydrogen production schemes currently in use invariably generate carbon dioxide at some stage. The most common technique is methane steam reforming - here carbon dioxide first arises from the burning of methane to produce heat to generate steam, then again in the reforming step that separates the carbon from the methane by successive oxidation to generate hydrogen. Even the alternative electrolysis method that is also common generates carbon dioxide when fossil fuels are burned in the generation of the electricity - whether from gas-fired or coal-fired plants.
While nuclear hydrogen production (NHP) schemes thus are carbon-dioxide emission free, they do involve the use of corrosive fluids (such as sulphuric acid) at high temperatures; generation of noxious & poisonous gases (such as sulphur dioxide and hydrochloric acid); and issues from the possible generation of radioactive products such as tritium. As well, heat transfer fluids carrying heat from the reactor to the thermochemical plant may interact with the chemicals in the plant. Or, in the current conceptual version of the Very High Temperature Reactor, the coolant might be helium, as might also be the heat transfer fluid. Some contamination of tritium in helium is possible and more might arise from transmutation of helium isotopes. In addition, the very idea of having a thermochemical plant located close to a nuclear reactor is unprecedented. Both the hydrogen and the oxygen produced in the thermochemical scheme will need to be safely stored, to prevent the possibility of leakage, deflagration or detonation.
Such considerations impose a number of requirements on the layout of nuclear plants and thermochemical plants, they impose requirements on the amount and quantity hydrogen and oxygen that may be created and stored on site, and on the location of the control room in a nuclear power plant. They also have implications for probabilistic safety analyses (PSA) for combined nuclear-and-thermochemical plants.
The idea of nuclear hydrogen production is especially attractive also in the context of extraction and processing of crude oil from the Alberta Tar Sands. Several reactor-hydrogen production configuration schemes are currently being examined and considered for this project at the present time. Nuclear steam methane reforming (which generates steam from nuclear heat, and uses nuclear heat in the reaction), for example, is a possible transitional technology that decreases the overall carbon footprint of the process (it does not completely eliminate the carbon dioxide production, since it retains the reforming step). For all of these considerations, it is possible that the Tar Sands may emerge as the locus of the first commercial nuclear hydrogen production project anywhere.
I discussed issues surrounding this in my paper Safety Issues in Nuclear Hydrogen Production with the Very High Temperature Reactor (VHTR) presented at the Canadian Nuclear Society Annual Conference 2008, Toronto.
