Amid the global requirement in setting stringent targets to achieve carbon neutrality, the energy sector will need to put in tremendous efforts in achieving decarbonization and reducing pollution in its third energy revolution. The development and utilisation of hydrogen is a promising option in world energy technological revolution. Hydrogen not only is clean during its consumption, it will also be properly qualified as clean by adopting an efficient and environmentally-friendly production technology. Being readily scalable, hydrogen production by nuclear power offers the opportunity to make a significant contribution to the hydrogen economy in the coming decades.
In the latest research of Generation IV reactor technologies such as High Temperature Gas-Cooled Reactor (HTGR) or Molten Salt Reactor, one of their key attributes is the quality of heat that these high temperature reactors can produce, with their reactor outlet coolant temperature exceeding 700°C. This high temperature leads to a high plant efficiency, but more importantly, it provides the thermal condition for hydrogen production. Several production methods are currently being developed, including the electrolysis of steam at above 550°C, known as High Temperature Steam Electrolysis (HTSE) and chemical reactions with sulphuric acid and iodine as intermediate reaction agents at above 800°C, or High Temperature Thermochemical Production (HTTP). It is envisaged that these two processes will attain an efficiency at 45-50%, offering a significant improvement over conventional electrolysis supported by the current Pressured Water Reactor (PWR) that delivers a 25% efficiency. The hydrogen produced can be delivered immediately to a nearby industrial user or transported for remote use, and oxygen is a useful by-product.
Successful technology advancement requires production efficiency, operational reliability and competitive cost. From a study conducted by the International Atomic Energy Agency on the cost of hydrogen production by nuclear power, HTGR matched with technologies like HTSE and HTTP has a cost at around US$2.45-4.34/kg, offering better cost competitiveness than using conventional electrolysis supported by a PWR which costs round US$2.94-4.40/kg. These costs are competitive to the cost of hydrogen produced by renewable energy sources that ranges between US$2.5-6.8/kg in 2020.
This article is contributed by Ir Prof Ken C N Cheung with the coordination of the Nuclear Division.