2022-09-15

Low carbon energy or change, take stock of fourth generation nuclear reactor technology


Currently there are 440 nuclear power reactors in the world, with a total generating capacity is enough to supply 10% of the world's electricity, and is now in the construction of the reactor is up to 50 seats, in addition to the increase in the number, in order to improve safety, reduce the cost of nuclear power, nuclear power technology has also continued evolution, "fourth generation nuclear reactor" of the future have the opportunity to cross out of laboratory and boost low-carbon power supply?

In the past, nuclear power was dominated by centralized power plants, each with a capacity of more than 900MW, which cost up to $15 billion and could take up to 20 years to complete and operate. The process also required extensive and tedious administrative procedures that required constant testing, modification and retesting of plant designs and engineering. Operators also have to bear the cost of disposal of spent nuclear fuel after stringent environmental safety regulations.

This situation not only may cause power plant cost overruns, nature also will build long time, if you want to reduce cost, shorten the time required for establishing, methods including standardized design, cover more power plant technology and experience, lean management measures, and through solving the biggest cost of construction, also is the new power plant design is put forward.

Fourth generation power plant design

Today, the nuclear industry's largest companies and various start-ups are searching for new fission reactor designs, many of which have been in development for decades, in hopes of reducing construction and operating costs, improving safety and efficiency, and reducing the risk of nuclear weapons.

Today's nuclear power plants belong to the "third generation". The first generation of nuclear power plants mainly refers to the prototype reactors from the late 1940s to the early 1960s, which are not yet commercially available. The second generation refers to the first batch of commercial light water reactors from the mid-1960s to the mid-1990s. But using more reliable fuel and reactor core, passive cooling system.

Future fourth-generation reactors will naturally be more advanced and diverse, with new reactor technologies, materials and manufacturing techniques expected to reduce costs and improve plant safety.

1. Small Modular Nuclear Reactor (SMR)

As the name suggests, compared with traditional nuclear reactors, small modular nuclear reactors are smaller in size and scale, basically hoping to build a nuclear reactor less than 300MW, or even large-scale manufacturing like automobiles, hoping to introduce factory manufacturing technology to reduce the cost of nuclear power.

The advantage of the technology is that it allows the units to be broken up into many parts and multiple small reactors to be installed on site at once, or to be moved to the site directly after the plant is built, allowing for mass production without the problems of installing massive, time-consuming and expensive nuclear plants in the past. It can also be tailored to customers' needs. For small, relatively remote communities, a small nuclear reactor can be installed to power thousands of homes or businesses, or multiple reactors at a time can be installed to power millions of people in large cities.

Because of its small scale, it can also be used in special applications such as oil exploration and military bases. It is installed underground, on a ship or at sea. It is combined with passive safety system, which does not require active operator intervention or electrical feedback to bring the reactor into a safe shutdown state, nor does it require large concrete structure shielding the nuclear fuel rods.

2. High temperature gas cooled reactor (HTGR)

The high temperature gas cooled reactor is a graphite moderated reactor, which is a nuclear energy technology that has recently matured. Traditional nuclear reactor with enriched uranium or plutonium fuel rods, but high temperature gas cooled reactor fuel is "ball", each composed of uranium, carbon and oxygen "pebbles", they are sealed in three layers of carbon or ceramic material, improve the thermal stability, neutron radiation, corrosion, oxidation, also can avoid the graphite in high temperature burning, inside is nuclear fuel and ACTS as a buffer of graphite, The result is a reactor like a ball pit, filled with thousands of fuel pellets that generate and sustain high-temperature nuclear reactions without the need for control rods.

The pebble fuel will also not melt in the reactor, which can operate at higher temperatures, and the pebble will slowly circulate through the reactor, removed from the bottom once used and replaced with a new pebble.

Iii. Gas-cooled Fast Reactor (GFR)

Gas-cooled Fast reactor is one of the fast breeder reactors. During the operation of such reactors, "fission materials" can be synthesized to make the production of nuclear fuel more than the consumption. The main cooling method is helium, carbon dioxide and other gases, and the power density is higher than that of high-temperature gas-cooled reactors.

Gas-cooled fast reactors produce nuclear fuel by replacing slow neutrons in conventional reactors with fast neutrons and converting thorium or non-fissile uranium isotopes into plutonium or fissile uranium isotopes. The fuel core of the new generation of gas-cooled fast reactors is uranium monocarbide, which can operate at high temperatures and the fuel configuration allows for a higher density of uranium atoms per volume of fuel.

Iv. Sodium Cooled Fast Reactor (SFR)

The sodium-cooled fast reactor uses liquid sodium metal as its coolant. Although the operation process generates a lot of heat energy, even exceeding the heat required to drive the steam generator, the liquid sodium has excellent heat dissipation capacity, so it can still operate smoothly in small reactors, and the passive safety mechanism can also operate smoothly.

Usually the sodium cold fast reactor fuel is wrapped in uranium and zirconium alloy steel, Russia, France and Japan tend to use uranium oxide fuel, in addition sodium cold fast reactor has a closed fuel cycle, uranium and plutonium will be as a part of the fission reaction, recycling within the reactor, supplementary fuel can be used for decades at a time.

V. Lead cooled Fast Reactor (LFR)

Lead cooled Fast reactor (LFR) is a reactor design based on a Russian nuclear submarine and uses lead as the main cooling element. The latest version uses uranium nitride instead of uranium dioxide, and like sodium, lead is a passive safety system that automatically regulates the nuclear reaction if the reactor starts to get out of control.

Vi. Liquid Thorium Fluoride Reactor (FHR)

Liquid thorium fluoride reactors (FHR) are not cooled by helium, but by a molten mixture of lithium fluoride and beryllium fluoride salts. These reactors have 10 times the power density of pebble fuel technology, while fluoride salts enable reactors to operate at much lower temperatures than helium-cooled reactors.

7. Molten Salt Fuel Reactor (MSR)

The fuel in a molten salt fuel reactor (MSR) is not a rod, particle or pebble, but is mixed into a fluoride that flows through graphite or a similar moderator to control the reaction. Molten salt fuel reactors can operate at high temperatures, but they are associated with corrosion problems. Therefore, there are currently many low-temperature versions, but by combining coolant and fuel, it is easier to remove nuclear waste and replenish fuel.

What is the future of nuclear technology?

At present, many countries and governments have set the goal of net zero carbon emission, hoping to achieve carbon neutrality by 2050. In this regard, many countries have high hopes for nuclear energy, especially the new generation of nuclear energy technology can bring new opportunities after 2030, perhaps the fourth generation of reactors mentioned above.

After all by their design purpose is cheaper and faster to build, if have the opportunity to may soon become very common, just the way is still far away, such as Japan's previous efforts to try to "monju reactor", monju reactor is also belong to the "breeder reactor", Japan at a cost of $8.5 billion, but due to the failure accident, regulatory violations, such as controversial, It didn't make a lot of money, and after the 2011 Fukushima disaster, the Japanese public's trust in the plant declined, and the plant was eventually retired in 2016. But there will also be new opportunities for new nuclear designs based on niche applications, and there are already plans for diverse designs such as a small nuclear reactor on the moon.


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