The global nuclear industry is on the verge of significant changes. The model of establishment of nuclear power plants more than fifty years ago and their exploitation during this period, has been exhausted. Moreover, the expected nuclear Renaissance never took place, and for one reason or another, there was a serious public resistance in a number of countries against nuclear energy. What are the reasons that led to this situation? What are the prospects and opportunities for nuclear energy to overcome this crisis and realise its huge potential to deliver consumers worldwide with secure and abundant energy?
The Challenges Facing Nuclear Power Today
The active zones of the modern water reactors operate under large pressures, which creates the need for many active and passive protection systems to manage the risks. Thus, safety is achieved at significant costs and the role of the human factor for this safety is also significant. All three major accidents in the history of nuclear energy, 1979 Three Mile Island NPP, 1986 Chernobyl NPP and 2011 Fukushima are results of human errors provoked by an already existing technological risk. Although modern nuclear reactors already rely on passive protection systems, and the ban on building reactors with characteristics such as the Chernobyl type, their complexity and scale represent a significant technological challenge, which leads to increase of their cost.
Water reactors use only 1% of the energy contained in one kilogram of uranium. This leads to accelerated depletion of natural uranium reserves, although they are relatively large. According to some forecasts, even at the current level of nuclear capacity in the world, after 2050 we can expect a significant increase in the price of the fresh nuclear fuel associated with the depletion of uranium ore reserves. The recycling of the SNF (MOX) is also not an effective process, because the resulting secondary SNF from MOX fuel can not be recycled again. Looking ahead, this inefficiency significantly limits the possibility of expanding the share of nuclear energy in the global energy mix. Any attempt to massively introduce new capacities of today’s type would lead to an increase in the cost of fuel and thus a reduction in the competitiveness of nuclear power plants.
The impact of the globalised economy must be identified as a factor for nuclear energy development. Modern nuclear power plants were created in relatively closed national markets with highly centralized energy systems, where energy consumption was sustainable and predictable over time. Today we have a global market where the address of entire industrial sectors can be changed in less than ten years. At the same time, new energy technologies have entered the market, which do not require large capital expenditures and their commissioning time is very short. This causes major nuclear power plants to appear cumbersome and inflexible in the ever changing economic environment. It is very difficult to plan such large capacity in the timeframe of operation of modern reactors, which is allready 60 years.
There are difficulties in the realization of new nuclear projects. Their scale is so large that it reduces their market to several highly developed countries or to major emerging economies, which have significant financial resources accumulated in other sectors of the economy. At the same time, the energy market in developed countries is oversaturated, and in the developing economies it is limited by other, cheaper to date energy sources. In fact, there are no economic prerequisites for significant growth of new nuclear capacity outside some big fast developing countries. Very few are investors who have the financial resources to start a new nuclear project, and also they require state guarantees against the political and economic risk associated with building large nuclear facilities. All this makes plans to expand the share of nuclear energy in the global energy mix to seem unlikely.
The Future of Nuclear Energy
IV Generation Nuclear Reactors
The International forum for IV generation of nuclear reactors (GIF) was initiated by the US Department of Energy in 2000, and officially founded in mid-2001. It is an international group representing the governments of 14 countries where nuclear energy is important now and is also considered vital for the future. The Group is committed to the co-development of the next generation of nuclear technologies. Initially, six technologies were selected, but one of them branched out in two directions, so below are listed the current seven. The Modification of the original projects is now being discussed due to the Fukushima incident, and in some cases the extension of the preparatory phase.
High temperature fast neutron gas-cooled reactors (GFR)
CIn helium-cooled reactors that are in operation or are under construction, GFR (gas-cooled fast reactors) will be high temperature installations with 850 °C. They use technology for VHTR (very high temperature reactors), suitable for energy production, thermochemical production of hydrogen or other technological heat. The reference GFR block is 2400 MWt/1200 Mwt with a thick steel pressure housing and three loops of 800 MWt each. The first loop will produce electricity with a helium turbine with indirect cycle, in the second loop the helium will power directly Brayton gas turbine, and the steam cycle is the third loop. The reactor will have a breeding core with fast neutron spectrum and no breeding shell. Nitride or carbide fuels will include depleted uranium and other fissile or fissile materials such as ceramic needles or plates, with a plutonium content of 15 to 20%. As with sodium fast reactors, the fuel used will be processed locally and all the actors will be recycled many times to minimise the production of long-term radioactive waste.
Lead-cooling Fast Reactor (LFR)
The LFR (lead-cooled fast reactor) is a flexible fast neutron reactor that can use depleted uranium, thorium, and burn up the actinides from SNF from the current water moderated reactors. The cooling of liquid metal (Pb or Pb-Bi eutectic) is at atmospheric pressure by natural convection. The fuel is metal or nitride, with full recycling of actinides from regional or centralized SNF processing plants. LFR will come in a wide range of sizes from factory-produced battery-type with 15-20 years of life for small networks or developing countries, to modular 300-400 MWe units and large single installations of 1400 MWe. Operating temperature of 550 °C is easily achievable, but 800 °C is provided with modern materials to ensure corrosion resistance to lead at high temperatures, which would allow the production of thermochemical hydrogen. A two-stage development program leading to industrial implementation is foreseen: up to 2025 for reactors operating at relatively low temperature and power density, and then up to 2040 for more high temperatures.
Molten-Salt Reactors (MSR)
The general principle of MSR is that the fissionable material is dissolved in a fluoric molten salt coolant. There are many concepts for reactors with molten salts, which in general can be divided into two main groups: breeders operating in the spectrum of fast neutrons, and converters operating in the spectrum of thermal neutrons. The first type requires high concentrations of fissionable material in molten salts, which, as with any fast neutron reactor, produces more fissionable material than the nuclei of the fissile material, such as uranium-238. The advantages are that the products of nuclear reactions that inhibit the production of new neutrons are removed from the molten salt as well as the new fissionable material produced. This ensures a very efficient combustion of the fuel without accumulation of large quantities of long-lived radionuclides, and at the same time the production of new fuel. A major challenge to this concept are the materials used in the active area, which must withstand long-term high temperatures and corrosive factors. The second type, which works in the spectrum of thermal neutrons, uses for moderator graphite and for the fuel uranium-235 and/or thorium. Achieves the same very high degree of depth of combustion, but because it does not require continuous removal of fissionable material, as in the fast neutron version, the materials and construction of the installation is far simpler and achievable to be already existing projects.
Sodium-cooled Fast Reactor (SFR)
SFR (sodium-cooled fast reactor) uses liquid sodium as a cooling agent for the reactor, which allows high power density with low coolant volume at low pressure. Current developments are based on about 390 reactor years of fast neutron reactors cooled with sodium for five decades in eight countries, initially being the main technology that is of interest to GIF. Three variants are available: modular type 50-150 MWe with actinides embedded in U-Pu metal fuel, which requires electrometallurgical processing (pyroprocessing), integrated in place; version 300-1500 MWe with pool reactor; and version 600-1500 MWe with a contour reactor and conventional fuel MOX. BN-800 in Belyarsk in Russia came into operation in 2015, and until December 2018 produced 13.7 million MWh without any accidents. The BN-800 is a predominantly experimental fuel reactor for fast neutron reactors. GIF notes that the technology is planned for wide application in very close time for the management of SNF. Another similar reactor in Kalpakam of 500 MWe in India is expected to reach criticality in 2019.
Super-Critical Water Reactors (SCWR)
The Super-critical Water-cooled Reactor (SCWR) is a very high pressure water-cooled reactor that operates on the thermodynamic critical point of the water (374 ºC, 22 MPa) to produce heat efficiency by about one-third higher than today’s light water reactors. The super-critical water (25 МPa and 510-550 °C) directly drives the turbine, without a secondary steam system, which simplifies significantly the entire construction of the installation. Two variants are considered: pressure vessel and pressure pipes. Passive safety features are similar to those of simplified boiling water reactors. The fuel is uranium oxide enriched in the case of an open fuel cycle option. The reactor nucleus may use a thermal neutron spectrum with a light or heavy water moderation, or be a fast reactor for the complete recycling of acinides based on conventional processing of SNF. As SCWR is based both on the considerable experience gained in the operation of water-boiling reactors and on the experience of hundreds of fossil fuel power plants, which are fuelled with super-critical steam, the technology of this type of reactor is expected to be rapidly developed and operation of a demonstration reactor from 30 to 150 MWe to start at 2022 year. Japanese studies confirmed the target heat efficiency of 44% at the core outlet temperature of 500 °C and assessed the potential cost reduction by 30% compared to current light water reactors. Safety is expected to be similar to ABWR. Canada is developing a heavy water pressure pipe design.
Small Modular Reactors (SMR) are based on technologies that have been used for a long time in the military sphere, but are now ready to enter the economy. Currently there are more than 60 projects, some of which will have built and functioning commercial prototypes from 1 to 5-7 years. Most of them use technologies from generation IV, which make them several orders of magnitude more secure than the most modern major nuclear reactors. The SMRs are foreseen to be included in closed combustion cycles. They are in the investment range of small economies and private investors, while at the same time expanding the possibilities for the utilization of nuclear energy in various industrial applications and city heating. They are built quickly and easily adapted to current market conditions. Here We present briefly only those SMRs, which are closest to industrial realization.
Russian KLT-40S from OCBM African is a development of the KLT-40 reactor, well proven in Russian icebreakers. It is Designed for desalination of seawater, as well as for the production of electricity in remote locations. The Reactor has a power of 150 MWt and produces 35 MWe (gross), as well as up to 35 MW heat for desalination or central heating. It is designed to work 3-4 years before refueling, as the storage of SNF becomes on board. At the end of a 12-year working cycle, the ship is taken to a central facility for overhaul and unloading of SNF. Two reactors will be mounted on a barge of 20 000 tons. Although the core of the reactor is cooled normally by forced circulation (four-way), the construction relies on the convection for emergency cooling. The fuel is uranium aluminum silicon with enrichment levels up to 20%. The first floating nuclear power plant, Academician Lomonosov, will start regular operation in 2019.
Russian OCBM Africanov develops a new compact reactor for icebreakers and for servicing floating nuclear power plants. It is a light water reactor with a power 175 MWt with four contour cooling and external circulator pumps. It has intrinsic safety characteristics using a low-enriched (<20%) uranium fuel. The charging is every seven years with a capacity factor of 65%, and over 40-year service life. Designed to provide power of 30 MWe, the LK-60 icebreakers will be powered by two of them. The gas-tight reactor facility has a mass of 1100 tonnes and is 6 m × 6 m × 15.5 m. Rosatom expects the first three ships LK-60 in Arctic to be commissioned in 2019. The version for the floating nuclear power plants is RITM-200M with a power of 55 MWe, without recharging on site due to the long fuel cycle. Operating life is 40 years, with a possible extension up to 60 years. It is Foreseen the installation of RITM-200 on land, with two or more modules of 175 MWt/50 MWe, fuel enriched to almost 20% and 5-7 years fuel cycle.
The Chinese HTR-PM is a high-temperature reactor with helium cooling and pebble-bad technology. TWO reactors, each with a power of 250 MWt, drive a steam turbine with a power of 210 MWt. The fuel is in spheres with a diameter of 60 mm and is enriched to 8.5% (520 000 pieces in both reactors), which gives 90 GWd/t. The outlet Temperature of the core is 750 ºC for helium, the steam temperature is 566 °C, and the temperature of the core inlet is 250 °C. Thermal efficiency is 40%. The Projected cost of the demonstration reactor is $430 million. In serial production the overnight cost is expected to fall to $1500/kW and the cost of electricity to be about $0.05/kWh. Commissioning is expected in 2019. The demonstration reactor in the province of Shandong must pave the way for 600 MWe reactor blocks (6×250 MWt, total 655 MWe). The life of the reactor is intended to be 40 years with a load coefficient of 85%. The capital expenditures per kW are expected to be 75% of those of the smaller HTR-PM. A series of HTR modules will be factory-manufactured and installed in China.
SMR of NuScale (USA) is a convection cooling light water reactor, the only moving parts being the actuators of the control rod. Uses standard fuel for PWR, enriched to 4.95% in normal PWR fuel cartridges (but with a length of only 2 m) with a 24-month charging cycle. Each module is installed in a water basin below ground level and is a cylindrical body with a diameter of 4.6 m, height 22 m, weight 650 t, which contains a reactor with a steam generator over it. In one standard power plant there will be 12 modules with a total power of 720 MWe. The Project life span is 60 years. There is completely passive cooling at work and after shutdown for an indefinite period of time without even requiring DC power supply. The NRC concluded in January 2018 that the design of NuScale eliminates the need for backup power from class 1E present requirement for all U.S. nuclear power plants. It has a good ability to follow the load of the grid. In 2014, the Overnight price was $5078/kWe net, as LCOE was expected to be $100/MWh for the first unit (or $90 in serial production). In June 2018, the the company announced that its reactor could generate 20% more energy than originally planned. This will lower the capital costs to around $4200/kw and will reduce LCOE by 18%.
SMR of Holtec International is a 160 MWe light water reactor called the Holtec Inherently Safe Modular Underground Reactor (HI-SMUR). Uses fuel similar to that in larger PWR, including MOX. The 32 full-length fuel cartridges are in a single fuel cartridge that is loaded into the 31-metre reactor casing. Holtec gives a one-week break for recharging every 42 months. The reactor has completely passive cooling and after emergency stop for an indefinite period, as well as a negative temperature coefficient so that it is switched off at high temperatures. The reactor will also be available with additional air cooling, which makes it suitable for installation in rigid regions. The SMR-160 is designed to quickly change its power, up or down, with the ability to increase power from 30% to full power at a speed of 2.5% per minute. The entire reactor system will be installed below ground level, with storage for SNF for 100 years. A 24-month construction period is foreseen for each module, which will cost 800 million dollars ($5000/kw). The period of operation is at least 80 years, but the company expects it to be extended to 120 years.
PRISM (Power Reactor Innovative Small Module) is fast neutron reactor of GE Hitachi (GEH). This is sodium cooled compact modular pool type reactor. After 30 years of development it represents the GEH vision for the IV generation reactors to close the fuel cycle in USA. Each PRISM unit consists of two modules of 311 MWe (840 Mwe) each, (or earlier three modules of 155 MWe, 471 Mwe), each with one steam generator, which together drive a turbogenerator. Pool-type modules below ground level operate at temperature around 500 °C. The Intermediate sodium contour transfers heat to the steam generators. The metal Pu & DU fuel is obtained from SNF from the current light water reactors. All transuranic elements are removed from SNF by electrometallurgical processing and are added to the fresh fuel for PRISM. The reactor can also work as a burner, and as a breeder. The radiation of the high-radioactive waste, left after burning SNF in PRISM, is leveled with the natural background after 300 years. One PRISM module will burn 72 kg/plutonium per year.