Around the world, the prospects for nuclear power generation are increasing – opportunities made clear by the number of currently under-construction nuclear plants that are smaller than those currently in the limelight. Offering advantages in certain situations, these smaller plants can more readily serve smaller grids as well as be used for distributed generation (with power plants located close to the demand centers and the main grid providing back-up). Smaller plants are also easier to finance, particularly in countries that are still in the early days of their nuclear power programs.
In recent years, development and licensing efforts have focused primarily on large, advanced reactors, due to their economies of scale and obvious application to developed countries with substantial grid infrastructure. Meanwhile, the wide scope for smaller nuclear plants has received less attention. However, of the 30 or more countries that are moving toward implementing nuclear power programs, most are likely to be looking initially for units under 1,000 MWe, and some for units of less than half that amount.
With that in mind, let’s take a look at some of the current designs.
There are many plants under 1,000 MWe now in operation, even if their replacements tend to be larger. (In 2007 four new units were connected to the grid – two large ones, one 202-MWe unit and one 655-MWe unit.) In addition, some smaller reactors are either on offer now or likely to be available in the next few years.
Five hundred to 700 MWe. There are several plants in this size range, including Westinghouse AP600 (which has U.S. design certification) and the Canadian Candu-6 (being built in Romania). In addition, China is building two CNP-600 units at Qinshan but does not plan to build any more of them. In Japan, Hitachi-GE has completed the design of a 600-MWe version of its 1,350-MWe ABWR, which has been operating for 10 years.
Two hundred and fifty to 500 MWe. And finally, in the 250- to 500-MWe category (output that is electric rather than heat), there are a few designs pending but little immediately on offer.
IRIS. Being developed by an international team led by Westinghouse in the United States, IRIS – or, more formally, International Reactor Innovative and Secure – is an advanced third-generation modular 335-MWe pressurized water reactor (PWR) with integral steam generators and a primary coolant system all within the pressure vessel. U.S. design certification is at pre-application stage with a view to final design approval by 2012 and deployment by 2015 to 2017.
VBER-300 PWR. This 295- to 325-MWe unit from Russia was designed by OKBM based on naval power plants and is now being developed as a land-based unit with the state-owned nuclear holding company Kazatomprom, with a view to exporting it. The first two units will be built in Southwest Kazakhstan under a Russian-Kazakh joint venture.
VK-300. This Russian-built boiling water reactor is being developed for co-generation of both power and district heating or heat for desalination (150 MWe plus 1675 GJ/hr) by the nuclear research and development organization NIKIET. The unit evolved from the VK-50 BWR at Dimitrovgrad but uses standard components from larger reactors wherever possible. In September 2007, it was announced that six of these units would be built at Kola and at Primorskaya in Russia’s far east, to start operating between 2017 and 2020.
NP-300 PWR. Developed in France from submarine power plants and aimed at export markets for power, heat and desalination, this Technicatome (Areva)- designed reactor has passive safety systems and can be built for applications of from 100 to 300 MWe.
China is also building a 300-MWe PWR (pressurized water reactor) nuclear power plant in Pakistan at Chasma (alongside another that started up in 2000); however, this is an old design based on French technology and has not been offered more widely. The new unit is expected to come online in 2011.
One hundred to 300 MWe. This category includes both conventional PWR and high-temperature gas-cooled reactors (HTRs); however, none in the second category are being built yet. Argentina’s CAREM nuclear power plant is being developed by CNEA and INVAP as a modular 27-MWe simplified PWR with integral steam generators designed to be used for electricity generation or for water desalination.
After many years of promoting the idea, Russia’s state-run atomic energy corporation Rosatom has approved construction of a nuclear power plant on a 21,500-ton barge to supply 70 MWe of power plus 586 GJ/hr of heat to Severodvinsk, in the Archangelsk region of Russia. The contract to build the first unit was let by nuclear power station operator Rosenergoatom to the Sevmash shipyard in May 2006. Expected to cost $337 million (including $30 million already spent in design), the project is 80 percent financed by Rosenergoatom and 20 percent financed by Sevmash. Operation is expected to begin in mid-2010.
Rosatom is planning to construct seven additional floating nuclear power plants, each (like the initial one) with two 35- MWe OKBM KLT-40S nuclear reactors. Five of these will be used by Gazprom – the world’s biggest extractor of natural gas – for offshore oil and gas field development and for operations on Russia’s Kola and Yamal Peninsulas. One of these reactors is planned for 2012 commissioning at Pevek on the Chukotka Peninsula, and another is planned for the Kamchatka region, both in the far east of the country. Even farther east, sites being considered include Yakutia and Taimyr. Electricity cost is expected to be much lower than from present alternatives. In 2007 an agreement was signed with the Sakha Republic (Yakutia region) to build a floating plant for its northern parts, using smaller ABV reactors.
On a larger scale, South Korea’s SMART is a 100-MWe PWR with integral steam generators and advanced safety features. It is designed to generate electricity and/or thermal applications such as seawater desalination. Indonesia’s national nuclear energy agency, Batan, has undertaken a pre-feasibility study for a SMART reactor for power and desalination on Madura Island. However, this awaits the building of a reference plant in Korea.
There are three high-temperature, gas-cooled reactors capable of being used for power generation, but much of the development impetus has been focused on the thermo-chemical production of hydrogen. Fuel for the first two consists of billiard ball-size pebbles that can withstand very high temperatures. These aim for a step-change in safety, economics and proliferation resistance.
China’s 200-MWe HTR-PM is based on a well-tested small prototype, and a two-module plant is due to start construction at Shidaowan in Shandong province in 2009. This reactor will use the conventional steam cycle to generate power. Start-up is scheduled for 2013. After the demonstration plant, a power station with 18 modules is envisaged.
Very similar to China’s plant is South Africa’s Pebble Bed Modular Reactor (PBMR), which is being developed by a consortium led by the utility Eskom. Production units will be 165 MWe. The PBMR will have a direct-cycle gas turbine generator driven by hot helium. The PBMR Demonstration unit is expected to start construction at Koeberg in 2009 and achieve criticality in 2013.
Both of these designs are based on earlier German reactors that have some years of operational experience. A U.S. design, the Modular helium Reactor (GT-MHR), is being developed in Russia; in its electrical application, each unit would directly drive a gas turbine giving 280 MWe.
These three designs operate at much higher temperatures than ordinary reactors and offer great potential as sources of industrial heat, including for the thermo-chemical production of hydrogen on a large scale. Much of the development thinking going into the PBMR has been geared to synthetic oil production by Sasol (South African Coal and Oil).
The IRIS developers have outlined the economic case for modular construction of their design (about 330 MWe), and it’s an argument that applies similarly to other smaller units. These developers point out that IRIS, with its moderate size and simple design, is ideally suited for modular construction. The economy of scale is replaced here with the economy of serial production of many small and simple components and prefabricated sections. They expect that construction of the first IRIS unit will be completed in three years, with subsequent production taking only two years.
Site layouts have been developed with multiple single units or multiple twin units. In each case, units will be constructed with enough space around them to allow the next unit to be constructed while the previous one is operating and generating revenue. And even with this separation, the plant footprint can be very compact: a site with three IRIS single modules providing 1000 MWe is similar to or smaller in size than one with a comparable total power single unit.
Eventually, IRIS’ capital and production costs are expected to be comparable to those of larger plants. however, any small unit offers potential for a funding profile and flexibility impossible to achieve with larger plants. As one module is finished and starts producing electricity, it will generate positive cash fl ow for the construction of the next module. Westinghouse estimates that 1,000 MWe delivered by three IRIS units built at three-year intervals financed at 10 percent for 10 years requires a maximum negative cash flow of less than $700 million (compared with about three times that for a single 1,000-MWe unit). For developed countries, small modular units offer the opportunity of building as necessary; for developing countries, smaller units may represent the only option, since such country’s electric grids are likely unable to take 1,000-plus- MWe single units.
Distributed generation. The advent of reactors much smaller than those being promoted today means that reactors will be available to serve smaller grids and to be put into use for distributed generation (with power plants close to the demand centers and the main grid used for back-up). This does not mean, however, that large units serving national grids will become obsolete – as some appear to wish.
One aspect of the global Nuclear Energy Partnership program is international deployment of appropriately sized reactors with desirable designs and operational characteristics (some of which include improved economics, greater safety margins, longer operating cycles with refueling intervals of up to three years, better proliferation resistance and sustainability). Several of the designs described earlier in this paper are likely to meet these criteria.
IRIS itself is being developed by an international team of 20 organizations from ten countries (Brazil, Croatia, Italy, Japan, Lithuania, Mexico, Russia, Spain, the United Kingdom and the United States) on four continents – a clear demonstration of how reactor development is proceeding more widely.
Major reactor designers and vendors are now typically international in character and marketing structure. To wit: the United Kingdom’s recent announcement that it would renew its nuclear power capacity was anticipated by four companies lodging applications for generic design approval – two from the United States (each with Japanese involvement), one from Canada and one from France (with German involvement). These are all big units, but in demonstrating the viability of late third-generation technology, they will also encourage consideration of smaller plants where those are most appropriate.