Process heat production from Small Modular Reactors

John Earp looks at the importance of heat as an energy vector alongside electricity and how it has been recognised in the current increased interest in the development of Small Modular Reactors.

Although the concept of small modular reactors has been around in the nuclear sector for several years their profile internationally has been raised by two specific events, firstly their formal definition as less than 300MW(e) as set out by the IAEA[1] and secondly the decision by the US Department of Energy to make a site available at Savanah River for the construction of pilot projects[2].  This latter action followed analysis that said that such reactors might have significant international market potential and it was a factor in the formulation of the IMechE policy statement[3] which recommended that the UK nuclear site at Trawsfynydd would be ideal for a demonstration plant in the UK with the potential for engaging UK companies in the development.

These events among others have contributed to more recent developments of reactors which fall into this category and in particular for the gas cooled variants to be considered not only for electricity generation but also for process heat production.  (Note it would be entirely practical for all of the SMR designs to be used for process heat in the form of steam but the gas cooled variants have had the lead in this area.)

Three high temperature gas cooled reactors, specifically the Pebble Bed Modular Reactor (PBMR)[4], General Atomics GT-MHR[5] and AREVA Antares[6]  can all directly drive a gas turbine for electricity and have the potential for process heat production specifically in their description.  All use helium as the primary coolant and operate at high temperatures (up to 850 Degrees C) which means the process heat is at high temperature compared to other SMR variants utilising water /steam although there are real opportunities for these supporting lower temperature processes. 

At this very early stage of their development there are no specific examples of their deployment or even detailed studies of their utilisation in this mode of operation. However, outline studies have been carried out for their use supporting several significant industries such as providing the heat necessary in petrochemical facilities, the heat for hydrogen production or heat for water desalination and in water purification[7][8].  A specific academic case study was undertaken by the Massachusetts Institute of Technology (MIT)[9][10] for the Athabasca Tar Sands development in Canada where SMR’s were deemed to be viable for providing process heat for steam to extract the oil. Specifically they were found to be more economic than the natural gas alternative, less volatile in terms of price hence more economic and less damaging to the environment (significantly lower CO2 emissions).

Similar academic research is underway in other parts of the world for example in Russia[11] where SMR’s are being seriously considered to support remote northern mineral extraction sites where they operate in a co-generation mode providing both electricity and district heating to combat the extreme prevailing winter conditions.

In conclusion the importance of “heat” as an energy vector alongside electricity has been recognised in the current increased interest in the development of Small Modular Reactors around the world.  The potential of several SMR designs to provide process heat either alongside electricity generation (co-generation) or solely as a provider of heat has been identified and features as part of their “offering”.  Although at this early stage of development there are no direct applications, a number of acclaimed research institutes have considered this potential application of SMRs concluding it to be viable economically and environmentally better than alternatives such as natural gas.