Last November, the international nuclear industry was delighted with the news, announced in the Spending Review and [Northern] Autumn Statement by UK Chancellor of the Exchequer (equivalent to Minister of Finance) George Osborne, that the British government was making “a major commitment to small modular nuclear reactors” and was assigning £250-million for nuclear innovation and small modular reactors (SMRs). There will be a competition, which will be launched this year, to select the SMR design that will provide the best value for the UK and lead to the construction of an SMR in the country.
Back in 2012, the US Department of Energy allocated $452-million (over five years) to support the development of US SMR designs based on light water reactor (LWR) technology. (Light water reactors use normal water both to moderate neutron flow and cool the reactor; the most common type of LWR is the pressurised water reactor, or PWR.) But this programme was run on the basis that the companies concerned would provide 50% of the funding for the development of their designs. This put a heavy burden on the enterprises concerned and little progress has taken place, with some companies pulling out. The UK competition looks set to be much wider in technological and geographic scope and likely to be entirely funded by the British taxpayer, which will make it practical for smaller companies to take part.
The US Department of Energy’s Office of Nuclear Energy has defined SMRs as “nuclear power plants that are smaller in size (300 MWe or less) than current generation baseload plants (1 100 MWe or higher) . These smaller, compact designs are factory-fabricated reactors that can be transported by truck or rail to a nuclear power site.” The International Atomic Energy Agency (IAEA) defines a small reactor as having an output of less than 300 MWe. The World Nuclear Association (WNA), basing itself on the US and IAEA definitions, itself defines SMRs as “nuclear reactors generally 300-MWe-equivalent or less, designed with modular technology using module factory fabrication, pursuing economies of series production and short construction times.” There are, of course, some exceptions that do not completely fit these definitions.
SMRs, the IAEA points out, can be water-cooled reactors, liquid-metal-cooled reactors or high-temperature gas-cooled reactors (HTGRs). Some can be employed in multiple module power plants. “Several countries are also pioneering the development and application of transportable nuclear power plants (NPPs), including floating and seabed-based SMRs,” it states on the SMR page of its website.
The IAEA lists the technological advantages of SMRs as being a shorter construction time, because of their modular nature; their improved safety and reliability potential; the simplicity of their designs; their suitability for applications other than electricity generation, such as desalination; and their ability to replace older fossil fuel power plants, thereby reducing greenhouse gas emissions. Their nontechnologi- cal advantages are their suitability for smaller electricity grids; the options they provide for meeting growing electricity demand by incremental increases in generating capacity (by adding more reactor modules); flexibility in siting; the need for smaller emergency planning zones; their greater affordability because of their reduced upfront capital costs; and, consequently, their greater ease of financing.
The potential challenges and concerns regarding SMRs are rooted in the fact that no SMR design is currently in operation. Thus, how easy will it be to license an SMR design? How will they perform in practice? Will the technology used in SMRs prove to be sufficiently mature? What will the operator staffing requirements be for multimodule plants? How economically competitive will they prove to be? How reliable will the cost estimates for the first units prove to be? What about the legal and regulatory systems? The infrastructure requirements? What size will their emergency planning zones need to be? How many security personnel will they need? In addition, some SMR designs will require countries to adopt non-LWR technology. Will SMR designs be available to new nuclear States? And then there are the issues of meeting post-Fukushima design and safety requirements and winning public acceptance. (This is why the British competition is so important for the SMR sector: it will result in the answering of these questions, at least for the winning design or designs.)
As of 2014, the IAEA reports, there were 45 SMR designs under development, although only four were under construction. Of these one was an industrial prototype (the CAREM-25, in Argentina), one an industrial demonstration plant (the HTR-PM, in China) and two were floating units (the KLT-40S and RITM-200, both in Russia). However, in its analysis of SMRs (updated in December 2015), the WNA listed the CAREM-25, the HTR-PM and the KLT-40S as being under construction.
The CAREM-25 will have an output of 25 MWe (capable of meeting the needs of a popu- lation of 100 000) and should enter operation in 2017/18. Developed locally, at least 70% of the inputs, components and services for the project will be provided by Argentinian industry. Two KLT-40S reactors, with a capacity of 35 MWe each, have been installed in the 21 500 t floating NPP Akademik Lomonosov, which is due for delivery at the end of the third quarter of this year. The RITM-200 design is developed from reactors powering Russia’s nuclear-powered icebreakers and is intended to replace the KLT designs in floating NPPs. The first two operational RITM-200 reactors will, in fact, be used to power new 33 540 t icebreaker Arktika, which will enter service late next year. Each RITM-200 will have a capacity of 50 MWe.
The HTR-PM (the abbreviation stands for High Temperature Reactor-Pebble Bed Modules), is an HTGR and is described by the WNA as the most advanced of the SMR projects. It is an upscaled version of the experimental 10 MWt HTR-10 pebble-bed fuel reactor, which was started up in 2000 and reached full power in 2003 and has successfully demonstrated the passive safety features of the design in what the WNA describes as “an extreme test”: the circulation of the cooling helium was deliberately stopped while the reactor was working. While the tempe- rature within the reactor increased, it did not exceed the safe limit of 1 600 oC and the reaction shut itself down in three hours. The HTR-PM will be composed of two 250 MWt/210 MWe reactor modules (each module designated HTR-200). The original concept was for a single 450 MWt/ 200 MWe unit, but that would have required a redesign of the reactor’s core configuration, so that idea was abandoned in favour of smaller modules retaining the core configuration of the HTR-10.
The HTR-PM is a pebble-bed modular reactor (PBMR) – that is, its fuel comes in the form of small spheres, called pebbles, each of which has a few grams (in the case of the HTR-10, five grams) of low-enriched uranium (in the HTR-PM, to a level of 8.9%) in its centre. South Africa, of course, had its own PBMR project. Both the South African and Chinese PBMRs were derived from licensed German technology, but the South African and Chinese designs reportedly have different reactor core configu- rations. The South African programme was effectively terminated in 2010, after R9.244- billion had been spent on it, 80% of which came from taxpayers. Had the South African project been continued, it would now be the most advanced SMR programme in the world and would have been in pole position for the British competition.
Of the other SMR designs listed by the IAEA, as of September 2014 (the agency’s most recent available survey), 15 were still in conceptual design, two had completed conceptual design, one had completed preliminary design and six were in basic design. The WNA lists ten designs as “development well advanced” and 16 as being “at earlier stages (or shelved)”.
The most advanced and/or promising of these include designs from China, the Republic of (South) Korea, Russia and the US. Most of these are PWRs, although some are fast neutron reactors (which are smaller and simpler than LWRs but require a new safety case). The PWR SMRs include the Nuclear Power Institute of China’s 100-MWe-capacity ACP100, the Korea Atomic Energy Research Institute’s 100 MWe SMART (System-Integrated Modular Advanced Reactor) and Russia’s OKBM 300 MWe VBER-300 (which the WNA describes as “little reported”). American SMR PWR designs include Babcock & Wilcox’s 180 MWe mPower, NuScale Power’s 50 MWe NuScale and Westinghouse’s 225 MWe Westinghouse SMR. All these US designs are integral PWRs – that is, all their pumps and steam generators are inside their reactor vessels, instead of outside, as in conventional PWR designs. (The reactor vessel contains the reactor core.)
Out of Africa, into Africa
South Africa is currently considering the construction of a number of NPPs using large (above 900 MWe) PWRs. “I think there is a place for both big reactors and SMRs,” says nuclear physicist (and Engineering News columnist) Dr Kelvin Kemm, speaking in his capacity as CEO of Nuclear Africa. “SMRs are Generation IV reactors, while the big PWRs we are considering are Generation III+. A lot of the Generation IV requirements are based on South Africa’s PBMR experience.”
“There is significant South African input into many of the SMR designs from engineers who had worked on the PBMR project,” reports Arint South Africa MD François Mellet. Some of these engineers now live and work overseas, while others remain in this country but consult for overseas companies.
“I love the SMR technology,” enthused Mellet. “One of the big things about it is that it is small! An SMR can be easily contained and erected pretty much anywhere where its output is required. And that can be done in 50 MWe increments – even 4 MWe increments. Do it properly and you won’t even need significant transmission lines.”
Currently, with most of the country’s power being generated in Mpumalanga, among the coalfields, electricity in South Africa has to be carried along transmission lines that extend for thousands of kilometres. Such long transmission lines require costly and sometimes difficult maintenance and involve noticeable power losses.
Even though Cape Town has the country’s only operational NPP, at Koeberg, it still gets about half its power from the distant coalfields. “The distance from the coalfields to Cape Town is the same as the distance from Rome to London,” highlights Kemm. “What we are doing is like, in Europe, all of Western Europe being supplied with electricity by Austria. We cannot keep expanding the supply of coal- powered electricity because of the transmission distances involved.” “South Africa really shouldn’t have such large transmission networks,” opines Mellet.
In Kemm’s view, large PWRs are ideal to meet the needs of the country’s coastal cities (“Port Elizabeth and East London,” he notes, “are currently out on an electricity limb, largely powered by coal and Koeberg”), where the supply of cooling water (which does not go through the reactor and does not become radioactive) would be no problem. Coal would continue to power the country’s economic heartland, Gauteng, which lies close to the coalfields. “SMRs would be ideal for places outside the major centres – for example, mining towns,” he suggests. “You can’t put a big nuclear power station in the Free State [province], because of the lack of water. But SMRs would be possible in the interior.”
Mellet highlights that some SMR designs are not water-cooled and so would be ideal for the country’s interior. “If we base them at [electricity] load centres, we could eliminate transmission lines and all their associated losses. SMRs offer more flexibility, more options.”
Moreover, SMRs do not have to be restricted to the production of electricity. “In Europe, there is great interest in using these [SMR] units for desalination plants,” he notes. Kemm agrees: “SMRs can be used for desalination. High-temperature SMRs – and the PBMR was a HTGR design – could be used for process heat, which is potentially a massive market. Because they are small, SMRs can be safely located, under existing rules, closer to industry. I believe this will come about. Industry currently uses a huge amount of electricity just for heating things!”
SMRs could also potentially be of great benefit to other African countries. “African countries are often geographically huge by European standards but often have small populations,” points out Kemm. “They need more and more electricity. Currently, many rely on hydropower, but, when the rains fail, they are able to generate less electricity: they can lose as much as 50% of their generating capacity in a drought. And most don’t have coal, oil or gas reserves. Moreover, national grids are often impractical and unaffordable, certainly as a starting point. Often, their real need is for local grids and SMRs are ideal for local grids. Eventually, local grids could, if required, be linked together to form a national grid.”
According to the IAEA, about ten African countries are currently considering, or preparing for, nuclear energy programmes. They include Kenya, Morocco and Nigeria. “Many of these countries would be ideal customers for SMRs,” he affirms. This could provide South Africa with a major economic opportunity, assuming the country also invests in SMRs (which would include the development of a local manufacturing capability). South Africans could then provide expertise to, as well as manufacture SMR components and systems for, and, in due course, perhaps manufacture and sell nuclear fuel to, other African countries. But Kemm has a warning. “We must not act like colonialists. We must not seek to just sell South African products to other African countries. We need to help their development. We need to transfer technology to them.”
“The biggest problem is that we don’t have any SMRs operating at the moment,” observes Mellet. “So we can’t really convince people about their merits. South Africa is not a developing country with regard to nuclear technology, but we will have to purchase something that is already there. That is why everyone is looking to the UK. There is strong political support there for the SMR concept – the aim is to meet that country’s needs and recreate its nuclear industry.”