Over the past 60 years, the size of nuclear reactor units has grown from 60 MW to more than 1600 MW, and this bigger-is-better mindset shows no sign of abating in those countries that continue to embrace nuclear post-Fukushima.
However, there is a growing lobby putting the case for SMRs, which is sometimes used to stand for small and medium reactors, but is now more commonly used as an acronym for 'small modular reactors'.
The International Atomic Energy Agency (IAEA) defines "small" as less than 300 MW, and these reactors are increasingly being put forward as a solution to the energy demands of many countries, especially those in developing regions. The IAEA believes that SMRs are an attractive option for countries with small grids and less-developed infrastructure - indeed, a 2009 assessment by the IAEA under its Innovative Nuclear Power Reactors and Fuel Cycle programme concluded that there could be up to 96 SMRs in operation around the world by 2030.
SMR research and development is well underway around the world, and several examples are already in operation.
A 2011 report by the University of Chicago Energy Policy Institute concluded that the development of SMRs could create an opportunity for the US to recapture a slice of the global nuclear technology market.
On the back of that study, last year the US Department of Energy called for applications from industry to support the development of one or two light-water reactor designs, and allocated $452 million over five years. The winning design came from Babcock & Wilcox (B&W) mPower, and will be developed with Bechtel and TVA. The B&W mPower reactor is an advanced integral pressurized water reactor designed to generate 180 MW of electricity.
|Christofer Mowry (left), president of B&W mPower, with Peter Lyons (centre), the US Department of Energy's assistant secretary of Nuclear Energy
Credit: B&W .
"This award represents another key milestone in the work to establish the world's first commercially viable SMR nuclear plant," said E James Ferland, president of B&W.
In China, Chinergy is starting to build the 210 MW HTR-PM, which has twin 250 MW high-temperature, gas-cooled reactors, and in India there are 220 MW pressurised heavy water reactors (PHWR) based on Canadian technology. The Nuclear Power Corporation of India is now working on 540 MW and 700 MW versions of its PHWR, and is offering both 220 and 540 MW versions internationally.
Fuel for life
The energy business advisors Douglas-Westwood are advocates for the use and development of SMRs. The company's director Steve Robertson says: "SMRs have a part to play. These units will offer utilities a number of benefits, including short lead-times, scalability, the option to fuel for life, built-in storage for the life of the plant, simple and safe plant design and a more-straightforward financing process."
Robertson says "scenarios that particularly favour SMRs include smaller countries with growing energy demand and grid restrictions, remote communities such as islands, and essential services such as military facilities, hospitals, desalinisation plant - together with major power-hungry industrial projects."
Peter Riley of De Montfort Law School in the UK says that for the small reactor to be an economic prospect it is necessary to have a significant market to justify investment in manufacturing.
"Novel applications will contribute to this market: much of the electrical distribution systems in the future will be decentralised, in particular in regions with large land masses or areas where approvals for transmission lines are strongly opposed; extra loads will be imposed on the grid system and small power stations local to load centres provide an answer."
He says the load centres will be small towns, factories, battery charging stations, hydrogen production plants, wind farms, desalination plants, gas extraction sites and replacements for "old worn out coal fired power stations that will demand power from a few to hundreds of megawatts - an ideal application for SMRs".
"While being the building blocks for SMRs, the opportunity also exists for the deployment of small reactors in remote and underdeveloped regions and may be the catalyst to more general use thus providing a sound base for manufacturing," adds Riley.
He states that while novel in the commercial world, militarily both Russia and the US have deployed small reactors to provide electricity to bases in the Arctic. "In a remote corner of Siberia at the Bilibino co-generation plant, four 62 MW units using a graphite-moderated boiling water design produce steam for district heating and 11 MW and has operated since 1976; the US operated mini military power plants in McMurdo Sound from 1962 to 1972, generating 79 million kWh; a military developed BWR of 67Mwe operated at Big Rock Point for 35 years to1997."
Riley says that underdeveloped regions and small island communities do not have the infrastructure and institutional controls to give confidence in the operation and management of nuclear systems. "A possible solution to this would be to deploy stand-alone small reactors and to retain full operational control and responsibility in the reactor manufacturer."
|A scale model of Westinghouse's SMR Reactor Vessel
However, he cautions that the rules concerning the liability of the operator - the manufacturer in this scenario - may require modification. To enable such support, he says international laws and rules regarding justification and non-proliferation safeguards would have to be satisfied.
"International conventions on nuclear liability and national legislation give the supplier considerable protection from the risk of nuclear damage by holding the operator liable for damages regardless of fault, and require appropriate insurance by the operator," states Riley.
He adds that the Fukushima accident of March 2011 demonstrated the level of liability suffered by the operator of a large nuclear complex, and it is currently estimated at $7.2 billion with a total cost of $125 billion.
Riley says that the deployment of small reactors depends on the need for power, the commitment of the manufacturer, political and commercial will.
|B&W's nuclear manufacturing plant
"The relative simplicity of small reactors, enhanced safety and proliferation resistance will support the case for them and will help to overcome obstacles to their deployment, support justification for the practice and exclusion from the regime of international liability conventions."
Robertson agrees that there are challenges for SMRs. "Uncertainty within the political environment is the single biggest threat to an economical international nuclear industry.
"The economics of SMRs are also yet to be proved. Furthermore, a first-of-a-kind plant will not prove the economic benefits that will come from building many reactor cores off-site in factories to a common approved design, and shipped to site by rail, truck or barge."
But, he maintains, "If the economics of SMRs can be realized, then they have a good future, expanding the nuclear option to smaller countries and new markets and applications".
No source of power is ideal for all situations, argues Robertson, and he firmly believes that individual countries need a balanced portfolio approach to energy: "Fossil fuels, renewables and nuclear all have their pros and cons, and SMRs could have considerable value in many situations."
Licensing and liability
Small reactors may not attract the regulatory rigour of current commercial plant, where the underlying principle of the international conventions and national legislation on nuclear liability is that the regime is meant for extraordinary risk, writes Peter Riley.
The legislation provides for amendment where the risk is low and excludes the operator of marine reactors from liability.
The installation state has the discretion to exclude certain installations if the risk is low. Since there is no guidance in either international or national laws as to what constitutes a low risk installation, public consultation by the regulatory authority followed by a Justification of Practice would be necessary based on a pre-licensing or generic design assessment
In addressing policy and licensing, the US-NRC has identified issues relating to facilities comprising small multi modules: separate license decisions may be necessary for each module as construction proceeds; for factory built units a manufacturing license may be required in addition to design certification; and where modules are manufactured outside the US jurisdictional issues may arise in relation to manufacturing licenses.
The NRC observes that the Price-Anderson Act for nuclear facilities is not applicable to small reactors of less than 100 MW and may not be applicable to non-electricity generating reactors.
The need to recommend amendment to the Act is being considered, to bring modular facilities in line with the public liability, financial protection and insurance requirements of that required for commercial nuclear plant.
It is important in this context that the opportunity to amend international and national legislation that may benefit the operator of small reactors in non-modular applications is not prejudiced by weighty regulation brought on by amendments to US legislation, in the attempt to satisfy consistency with existing commercial operations.
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