Innovation is the motor force for a continuous development of nuclear technologies that will lead to new reactors with even greater capabilities than they currently have. These advances will involve not only electricity generation plants but also high temperature heat production plants, heating, hydrogen and seawater desalination plants.
In nuclear industry, scientific knowledge and technology are continuously advancing and forcing the evolution of safety requisites and norms based on the new knowledge and acquired experience. The nuclear sector is one of the most technologically advanced, comparable only to the aeronautical and aero spatial industries.
Nuclear reactors of the future
Nowadays, nuclear reactors are classified according to the technological leap they constitute. This gives way to three large groups that include a series of generations: I, II, III, III+, which are the currently existing ones, and IV for the future ones.
- I and II generation plants: the first nuclear plants, such as Shippingport (first PWR plant in history) and all the Spanish nuclear plants.
- III and III+ generation plants: the result of the logical development and II generation plants. They feature “evolutionary improvements” based on the acquired experience, and especially affect safety, reliability and plan operability systems, costs and design standardization.
- IV generation plants: they encompass a series of projects, programs and initiatives for the development and test of various highly innovative nuclear systems that offer very remarkable advantages in respect to the current nuclear plants. At this point most of them are at the design stage, and their development pose great challenges, especially as regards materials and fuels.
As a consequence of this, while the implementation of third-generation nuclear power plants is now possible, fourth-generation plants require an investment of time and resources in research and development for these designs.
Nowadays, nuclear reactors are classified according to three large groups that include a series of generations: I, II, III, III+, which are the currently existing ones, and IV for the future ones
III+ nuclear power plants
These are reactors with an evolutionary improvement from III generation, including passive safety systems that act upon physical phenomena such as natural convection and gravity, and act on their own when the plant is sidetracked from its normal mode of operation. They do not need to be activated by anything, and they do not need any type of external electric energy.
Reactors of this generation can be sub-divided into two groups:
- Boiling water evolutionary reactors, including the ABWR (Advanced Boiling Water Reactor) from Toshiba and General Electric, Westinghouse’s BWR 90+, General Electric’s ESBWR and Areva’s SWR-1000.
- Advanced pressurized water reactors, including AP-600, AP-1000 and Westinghouse’s PWR System 80+, Mitsubishi’s APWR and Areva’s EPR.
IV Generation nuclear plants
These are a series of rather generic designs, expectedly to be introduced into the market in approximately 25 years, in most cases, and in 10 years in the case of the PBMR.
It is a great improvement because rather than advancing in the same direction as III Generation (applying enhancements to the already existing) it pretends to create new designs without forgetting the lessons learnt from the past. For this reason, IV Generation designs do not stem from existing reactors but from establishing new principles to be fulfilled.
The new principles established for IV Generation nuclear energy systems are:
- Sustainability: the designs must promote the long-term availability of systems and the use of fuel for worldwide energy production, minimizing volume and the radioactive waste management period.
- Economy: designs must offer more economic advantages than other energy sources during their useful life cycle, equating their financial risk level with that of other energy projects.
- Safety and reliability: designs must stand out because of their safety and reliability, reduce to a minimum the possibility of damage to the reactor’s nucleus and its magnitude and eliminate the need to adopt emergency measures offsite.
They include the novelty that designs do not need to be exclusively oriented towards generating electric energy in plants, but that some may be applied to other fields such as hydrogen generation, large transport systems or simply heat generation.
The main reactor systems currently under study are:
- Gas-cooled fast reactor (GFR); a fast neutron spectrum reactor capable of using as fuel a great part of current waste, cooled by helium and with a closed fuel circuit.
- Very high temperature reactor (VHTR): helium-cooled reactor moderated by graphite with an open uranium fuel cycle. It may be adapted to the production of hydrogen.
- Super critical water-cooled reactor (SCWR): A reactor cooled by high pressured water and high temperature that works beyond water’s thermodynamic critical point.
- Sodium-cooled fast reactor (SFR): Fast-spectrum reactor. It can consume current radioactive waste as fuel, cooled by sodium. The fuel cycle is closed for an efficient management of actinides and the conversion of fertile uranium.
- Lead-cooled fast reactor (LFR): A fast-spectrum reactor, cooled by liquid bismuth/lead metal with a closed fuel cycle for an efficient conversion of fertile uranium and actinide management.
- Molten-salt reactor (MSR): It produces fission energy in a mix of molten salt fuel in circulation with a complete actinide recycled fuel cycle.