Nuclear power stations are an important part of low-carbon electricity generation in many countries. In the UK, roughly 20% of all electricity is generated using nuclear energy. The Hinkley Point C power station contributes to the renewal of the UK’s national infrastructure. Together with renewables, and possibly natural gas fired stations linked to carbon capture and storage, the UK electricity system will be decarbonised in the coming years. Electricity, however, currently plays a role in only 1/5th of the energy used in the UK. Noting the benefits arising from the coming decarbonisation of electricity, the role played by electricity will surely grow as the UK and other countries try to achieve Net-Zero emissions by 2050. However, electricity alone won’t be able to do everything. Even with substantial growth in electricity use, and even with large improvements in energy efficiency, there will still be a need for action in other important sectors, some of which are hard to decarbonise. It is here that nuclear technology has the potential to play an exciting role.
The list of hard to decarbonise sectors is varied and broad. It includes maritime shipping, aviation, steel making, glass and cement making, domestic heating and many more. The idea of using nuclear energy to address these challenges is not new and, indeed, it long predates concern for global climate change. For example, in the period of early enthusiasm for civil nuclear technology in the 1960s various countries produced nuclear powered ships for non-military purposes. One such example was the American NS Savannah shown below. Fifty years ago, the conventional use of heavy fuel oil was too economically attractive and the nuclear technologies somewhat too cumbersome. Consequently, the idea of nuclear merchant ships faded away. However, our concerns are different now and given that maritime shipping represents about 2.5% of global greenhouse gas emissions, the NS Savannah concept might be a good example of a much needed Back to the Future technology.
In October 2020, a Royal Society Policy Brief was published following a knowledge gathering process led by Professor Robin Grimes of Imperial College London. The briefing stresses that the electricity system of the future will, given a growing reliance on renewables, face more variation. One way to make up that shortfall would be to develop new nuclear power stations. In the situation that the weather and time of day favours renewable generation the new nuclear energy sources are best not turned off, but rather redirected to other beneficial uses such as supplying low-carbon industrial process heat or district heating. This variable mix of electricity generation and heat supply is termed ‘co-generation’. In the spirit of addressing the deep decarbonisation challenges listed earlier, one can further imagine nuclear reactors not tasked with generating electricity at all.
One particularly attractive path for nuclear energy utilisation would be for it to facilitate low-carbon hydrogen production. This could be achieved using nuclear cogeneration for high-temperature steam electrolysis. For high levels of efficiency, temperatures far above those currently available from today’s nuclear power plants would be needed. One solution would be for a gas-cooled very high temperature reactor not too dissimilar from the UK’s unique Advanced Gas Cooled reactor concept from 40 years ago. Future Very High Temperature Reactors could also drive catalytic thermochemical splitting of water. One more easily achieved route to low-carbon hydrogen production would be for nuclear energy to provide a heat input into the steam reformation of natural gas (methane) coupled with carbon capture and storage. This could be a very attractive option in the medium term. Low-carbon hydrogen production could greatly assist with a range of hard decarbonisation challenges. Hydrogen could cleanly fuel ships, trains, trucks and aeroplanes. Hydrogen can also be used as a reducing agent in iron and steel manufacture (replacing coking coal) and hydrogen can provide a useful storage buffer for volatile electricity systems. Either directly, or via hydrogen, nuclear energy has much to contribute to meeting the difficult challenge of reaching Net Zero emissions by 2050. There is a new golden age of socially beneficial nuclear engineering ahead.