Generation IV reactor

Generation IV reactors

Generation IV reactors are new designs for nuclear power plants. They could replace the ones we use today. These new reactors are being made to be safer, work better, and help the environment. An international group called the Generation IV International Forum chose six types of these reactors to study.

These reactors could work better than older ones. They might start being used in factories before 2030. Some designs use special metals to cool the reactor. Others use melted salt, and some work at very high temperatures.

Most nuclear power plants today use older designs. But China did something important in December 2023. They operated the world's first Generation IV reactor. This reactor is in Shandong. It uses a special technology called a pebble-bed high-temperature gas-cooled reactor. China also plans to build the first nuclear power station using thorium molten salt technology. This could be ready by 2029.

Generation IV International Forum

The Generation IV International Forum (GIF) is a group of countries that work together to create new kinds of nuclear reactors. These reactors are designed to be safer, better for the environment, and more efficient than older ones. GIF helps countries share research and ideas about these new designs.

As of 2021, countries such as Australia, Canada, China, and many others are part of GIF. The group began in January 2000, led by the Office of Nuclear Energy of the U.S. Department of Energy. In May 2019, a private company named Terrestrial Energy joined, becoming the first private company to be a member. In October 2021, the group decided to focus on using nuclear heat for cleaning water and making hydrogen on a large scale.

Timelines

The GIF Forum has plans for six new types of nuclear reactors. These plans have three steps. First, they test basic ideas to see if they work. Next, they improve these ideas in real conditions. Finally, they build and test a full-sized model.

In 2000, GIF said each reactor would need at least six years and several billion dollars to build a test model after the improvement step. By 2013, they changed these dates, and they don’t have specific goals for when these reactors will be ready for everyday use. GIF thinks it will take at least 20 to 30 years before these new reactors can be used widely.

Reactor types

Many types of reactors were studied. The list was narrowed to focus on the most promising ones. Some use slow, or thermal, neutrons, and some use fast neutrons. The very high temperature reactor (VHTR) can provide high-quality heat for industry. Fast reactors can burn certain materials to reduce waste and can create more fuel than they use. These systems aim for better safety, sustainability, efficiency, and cost.

Thermal reactors

A thermal reactor is a nuclear reactor that uses slow, or thermal, neutrons. A neutron moderator is used to slow down the neutrons from fission, making them more likely to be captured by the fuel.

Very-high-temperature reactor (VHTR)

The very-high-temperature reactor (VHTR) uses a core with graphite and a fuel cycle that uses uranium, with helium or molten salt as coolant. This design aims for a temperature of 1,000 °C. The core can be either a prismatic-block or a pebble bed design. The high temperatures allow uses such as providing heat for industry or making hydrogen.

Molten-salt reactor (MSR)

A molten salt reactor (MSR) is a type where the coolant or the fuel itself is a molten salt mixture. It runs at high temperature and low pressure.

Supercritical-water-cooled reactor (SCWR)

The supercritical water reactor (SCWR) is a reduced moderation water reactor concept. It uses supercritical water as the working fluid. SCWRs are basic light water reactors that run at higher pressure and temperatures with a direct heat exchange cycle. They aim to produce electricity at lower cost.

Fast reactors

A fast reactor uses fission neutrons directly without slowing them down. Fast reactors can be set up to "burn," or fission, certain materials, greatly reducing the amount of waste from current reactors, or they can create more fuel than they use.

Gas-cooled fast reactor (GFR)

The gas-cooled fast reactor (GFR) uses a fast-neutron spectrum and a closed fuel cycle. It is cooled by helium and has an outlet temperature of 850 °C. It uses a direct gas turbine cycle for high efficiency. Different fuel forms are being studied.

Sodium-cooled fast reactor (SFR)

Sodium-cooled fast reactors (SCFRs) have been used in several countries since the 1980s.

Lead-cooled fast reactor (LFR)

The lead-cooled fast reactor (LFR) uses a fast-neutron-spectrum lead or lead/bismuth coolant with a closed fuel cycle. Proposals include small, medium, and large reactors. The fuel contains certain materials, and the reactor cools by natural convection, reaching high temperatures for uses like making hydrogen.

Assessment

The GEN IV Forum changes how we think about nuclear reactor safety. The goal is to make serious accidents impossible. These reactors use both active and passive safety systems.

Gen IV reactors have several benefits over older types. They make nuclear waste that stays radioactive for a few hundred years instead of thousands. They can produce much more energy from the same amount of fuel. They can use different fuels, including fuels that are not sealed (like in MSR and LFTR designs). They can also use old nuclear waste to make electricity, creating a closed fuel cycle. These reactors are safer because they work at normal pressure and can shut down automatically.

One concern with some designs, like the SFR, is the use of metallic sodium as a coolant. If it touches water, it can react strongly. Argon is used to prevent this. Some designs use lead or molten salt as coolants because they are safer.

Several experimental Gen IV designs have been tested. For example, reactors at the Fort St. Vrain Generating Station and HTR-10 are similar to proposed Gen IV VHTR designs. The pool type EBR-II, Phénix, BN-600, and BN-800 reactors are similar to proposed pool type Gen IV SFR designs.

Some experts say that with new reactors, unexpected situations can happen that are hard to plan for, and human mistakes can still occur. Building and operating new reactors can be difficult and risky, even with proven technology.

Design projects

Radiation resistant materials

The development of generation IV reactors has led to interest in new materials that can resist radiation. These materials help keep nuclear plants safe and working longer. One recent discovery is the High-entropy alloy, which has shown great promise. Other materials, like high entropy carbide ceramics, also resist radiation well.

Even though these materials are exciting, they are still new and need more study. Scientists are continuing to study these materials to learn more about their strength and durability.