As a low-carbon energy source, nuclear energy is useful in the fight against climate change. However, the nuclear power industry is faced with the dual challenge of declining uranium resources and radioactive waste management. The solutions to these issues lie in innovation and the development of more fuel-efficient fourth-generation reactors.
Generation IV reactors
The reactors currently in operation belong to Generation II. The Generation III reactors under construction, such as the Flamanville European Pressurized Reactor (EPR) in France, do not represent a technological leap forward, but rather take advantage of the experience gained from the previous generation while enhancing security systems. Generation III reactors have been designed to eliminate the need to evacuate residents from the surrounding area, even in the event of a serious accident.
Research is being conducted to develop safer Generation IV reactors that use uraniumGray, very dense radioactive metal that is relatively abundant in the Earth's crust and oceans in the form of UO2... more efficiently and reduce the risk of nuclear proliferation. The Generation IV International Forum (GIF), which brings together 13 countries1, is among those involved in such research at the international level.
Countries around the world are working together to conduct research on Generation IV nuclear reactors.
GIF has selected six reactor technologies:
- Three types of fast neutronType of particle, along with the proton, that makes up the nucleus of an atom. Neutrons have no net electric charge. reactors, which are able to consume their entire fuelFuel is any solid, liquid or gaseous substance or material that can be combined with an oxidant... supply while recyclingAny waste treatment process that uses materials from identical or similar end-of-life products or manufacturing waste to produce new products. the plutonium produced by nuclear reactors currently in operation. This technology is defined by the type of coolant used: helium, sodium or lead (see Close-Up: "Inside a Conventional Nuclear Reactor").
- Very-high-temperature reactors, which can produce heatIn the field of statistical thermodynamics today, heat refers to the transfer of the thermal agitation of the particles making up matter... for industrial needs, and supercritical-water-cooled reactors, which offer improved powerIn physics, power is the amount of energy supplied by a system per unit time. In simpler terms, power can be viewed as energy output... plant efficiency. Unlike fast neutron reactors, these two technologies neither reduce the amount of uranium consumed nor do they recycle plutonium.
- Molten salt reactors, which use a molten salt mixture as both the coolant and fuel.
Characteristics of fast neutron reactors
With the same amount of natural uranium as a current reactor, fast neutron reactors can produce at least 60 times more energy, dramatically increasing the lifespan of the world's uranium reserves from a few hundred years to hundreds of thousands of years.
Fast neutron reactors also offer the advantages of transmutation, reusing minor actinides (the main contributors to the half-life and toxicity of radioactive waste) to reduce the volume of the most radioactive waste by a factor of ten and its toxicity by a factor of 100.
During the transmutation process, the heavy nucleus of an element, such as plutonium, neptunium, americium or curium, which would normally remain radioactive for hundreds of thousands of years, is split into two lighter nuclei with a radioactive lifespan of just a few centuries. In less than 500 years, the levels of radioactivity are equivalent to those of the natural uranium currently used for the production of nuclear fuel (see Close-Up: “The Nuclear Fuel Cycle").
France, pioneering fast neutron technology
France began conducting research into fast neutron reactors in 1959 and commissioned the Superphénix nuclear reactorLocated in the core of a nuclear power plant, the reactor is a type of huge boiler. It has four main components... in 1986. The reactor was operational for eleven years and served as the first testing ground for the use of sodium as a coolant (see sidebar).
France and fast neutron reactors In 1959, the French Atomic Energy Commission (CEA) began construction on the Rapsodie 40 MWth fast neutron prototype reactor, which started up in 1967 and was closed in April 1983. The Phénix 250 MWe prototype industrial reactor was operational from December 1973 to February 2010 and is currently being dismantled. More recently, the Superphénix 1240 MWe reactor was linked to the grid in January 1986. Operations were disrupted by numerous technical difficulties and strong opposition. A ministerial decree issued on December 30, 1998 definitively closed the reactor.
Neutrons lose less energy in collisions with sodium atoms, reducing the amount of radioactive waste. This technology also greatly improves safety, particularly in the case of loss-of-heat-sink accidents. However, sodium is highly reactive to water and air.
France is developing a 600 MWe Advanced Sodium Technical Reactor for Industrial Demonstration (Astrid), scheduled to come on stream in 2040. This fast neutron sodium-cooled reactor will convert more than 80% of the natural uranium into energy while also burning depleted uranium stored in France and plutonium contained in used fuel2.
The power of the Sun
In a complete break with current technology, researchers are also working on nuclear fusionReaction in which two atoms join to form one heavier atom, releasing energy... reactors (see Feature Report: "Nuclear Fusion"). The goal is to reproduce the energy of the Sun in a reactor by joining together very small nuclei - isotopes of hydrogenThe simplest and lightest atom, the most abundant element in the universe. (deuterium and tritium). A first prototype reactor should demonstrate the technical feasibility of this process within the next 15 years.