Table of Contents
Nuclear Reactor Generations
Nuclear reactors are often categorised into “generations” based on their design, safety features, and technological advancements. While there isn’t a universally accepted definition for each generation, here’s a general overview of the main generations of nuclear reactors:
The first generation of nuclear reactors includes the early prototypes and experimental reactors developed in the mid-20th century. These reactors primarily used natural uranium and heavy water (e.g., the CANDU reactor) or graphite (e.g., the RBMK reactor) as moderators. They had limited safety features compared to modern designs.
Examples of Generation I Reactors:
- Magnox Reactor – Calder Hall (1956–2003)
- Magnox Reactor – Chapelcross-1 (1958-2004)
An example is a Magnox Reactor:
Second-generation reactors represent a significant step forward in safety and efficiency. They include Pressurised Water Reactors (PWRs), boiling water reactors (BWRs) and Advanced Gas-cooled Reactors (AGRs), which are the most common commercial reactor types. These reactors have improved safety systems and more standardised designs. They continue to operate in many countries today.
Examples of Generation II Reactors:
- Dungeness B: Located on the Kent coast, Dungeness B consists of two AGR units (Dungeness B-21 and B-22). It has been in operation since the 1980s but is currently no longer operating.
- Hartlepool: Situated in County Durham, Hartlepool nuclear power station has two AGR units (Hartlepool-1 and Hartlepool-2), and it began operating in the mid-1980s.
- Sizewell B: Sizewell B is a PWR located on the Suffolk coast. It has been operational since the early 1990s and is currently the only PWR in operation in the UK.
An example is a PWR:
Third-generation reactors are designed with a strong focus on safety enhancements and improved efficiency. Notable examples include the the Advanced Boiling Water Reactor (ABWR). These reactors incorporate passive safety systems and improved control mechanisms.
Examples of Generation III Reactors:
- Kashiwazaki-Kariwa Nuclear Power Plant (Japan): Units 6 and 7 of the Kashiwazaki-Kariwa Nuclear Power Plant in Japan are ABWRs. These units have been in operation since the late 1990s and early 2000s, respectively.
- Shin Kori Units 3 and 4: These APR-1400 reactors are located at the Shin Kori Nuclear Power Plant in Ulsan. Both units have been completed and are in commercial operation.
An example is a BWR:
Sometimes referred to as “third-plus generation,” these reactors are an evolution of third-generation designs, aiming to further enhance safety and reduce environmental impact. They often incorporate advanced materials and more efficient fuel cycles. The Generation III+ reactors include the AP1000 (a PWR) and the ESBWR.
Examples of Generation III+ Reactors:
- Hinkley Point C: Hinkley Point C is a significant nuclear power project in the UK, featuring two EPR (European Pressurized Reactor) units. EPR (a PWR) is considered a Generation III+ design, combining features from both Generation III and Generation IV technologies. As of my last update, Hinkley Point C was under construction in Somerset, England.
- Vogtle Electric Generating Plant: Vogtle Units 3 and 4, located in Georgia, USA, are the first AP1000 reactors under construction in the United States. The construction project faced delays but was ongoing as of my last update, with Unit 3 expected to enter service in the future.
An example is an AP1000:
Fourth-generation reactors are still under development and are designed to be more sustainable, safe, and capable of using different types of fuel. They aim to reduce nuclear waste, improve safety, and operate at higher temperatures for better efficiency. Examples include the Integral Fast Reactor (IFR), High Temperature Gas Reactors (HTGR) and the Sodium-cooled Fast Reactor (SFR).
To date no commercial Generation IV reactors built anywhere in the world, however there are some examples of research reactors testing materials and technologies associated with Generation IV technology:
- The High Flux Isotope Reactor (HFIR) research reactor located at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, United States. HFIR is one of the world’s most powerful research reactors and is primarily used for neutron scattering research, isotope production, and materials irradiation studies.
Fifth-generation reactors are theoretical at this stage and are envisioned to be even more advanced in terms of safety, sustainability, and fuel flexibility. They may use novel coolants, such as molten salt, and advanced fuel cycles. These reactors are expected to have enhanced proliferation resistance and reduced long-term waste issues.
Take a look at our page on Advanced Modular Reactors (AMRs) page to find out more about some of the potential Generation V technologies.
It’s important to note that the transition between nuclear reactor generations is not always clear-cut, and the categorisation is subject to debate. Reactor designs and generations may also vary by region and organisation. The focus on safety and environmental sustainability has been a common theme in the evolution of nuclear reactor technology, with each generation seeking to address the limitations of the previous one.
Matt Moore
