Worldwide, there is significant interest in the development of small and medium modular reactors (SMRs). “At the moment there are 11 countries developing about 50 SMR designs and four units are under construction or have a certified design,” said University of Pretoria Mechanical and Aeronautical Engineering Professor Johan Slabber at the SMR session of the National Nuclear Regulator’s recent 2nd Nuclear Information Conference.
South Africa’s Pebble Bed Modular Reactor (PBMR), which was effectively terminated in 2010 (although the possibility of reactivating the project is being considered), was an SMR. (Slabber noted that the PBMR had started as a small reactor but was then enlarged because of economics.) “Modular reactors are defined as advanced reactors that produce electric power up to 300 MWe,” he explained. “The trend in development has been towards design certification of small modular reactors.”
“The IAEA [International Atomic Energy Agency] has up to now devoted a number of initiatives to support the development and deployment of SMRs,” he pointed out. This category of reactors was regarded as suitable for both established and emerging nuclear countries.
There were a number of driving forces behind these initiatives. They included meeting the need for flexible power generation; replacing ageing fossil fuel power plants; enhancing safety performance through inherent and passive safety mechanisms; and the need for more affordable nuclear plants. The other forces pushing the development of SMRs were their suitability for non-electricity generating or co-generation applications; their ability to provide power options for remote off-grid locations; and the possibility that they could provide synergies with other energy sources.
SMRs could be categorised into a number of generic types, he observed. These were: scaled-down water-cooled reactors; high-temperature reactors (HTRs); liquid metal-cooled fast-neutron reactors; and possibly also transportable reactors.
There were, however, a number of important issues that had to be addressed. It was important for the licensing process that technical issues with innovative designs had to be proved, for example. Then there was the issue of building activities close to an operating reactor; siting difficulties regarding co-generation applications using HTRs; their concept of operations; staffing and security requirements; size of the emergency planning zones for SMRs; the legal and regulatory framework; the licensing process; and capacity building in emerging nuclear countries.
At the same session, North-West University Faculty of Engineering Unit for Energy and Technology Systems Professor Frikkie van Niekerk stressed that SMR technology needed to be accepted by the public. He noted that SMRs were small in terms of their energy output and not necessarily in their physical size. He acknowledged the potential of SMRs – increased safety (with passive safety concepts) and security and flexibility (and some, but not all designs, were nuclear weapons proliferation resistant). They could bring economic benefits such as being easier to finance, permitting modular fabrication, requiring fewer staff, and enabling easier and cheaper decommissioning (one would just remove the entire module).
But there were also challenges and concerns. Could economies of scale be achieved? Was the current licensing regime appropriate for SMRs? What about the nuclear waste they would produce? What about the danger of nuclear proliferation (with the non-proliferation resistant designs)? Would they be affordable? Would the public accept them? There was also the challenge of emergent disruptive new technologies, such as renewable energy and energy storage.
“We have to succeed in this new reactor safety concept …. catastrophe-free nuclear technology,” asserted van Niekerk. “The consequences of an accident have to be restricted to the plant itself.” Among other health and environmental requirements, such catastrophe-free technology would have to ensure, in the event of an accident, that there would be no immediate fatalities outside the nuclear power plants, nor would there be any traceable late fatalities in the population outside the power plant.
Modular reactors are defined as advanced reactors that produce electric power up to 300 MWe
In future, the consequences of a nuclear accident will have to be restricted to the plant itself