RBMK reactors: history, characteristics and prospects

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RBMK reactors (Reaktor Bolshoy Moshchnosti Kanalniy, or high-power pressure tube reactor) are a type of nuclear reactor developed in the Soviet Union in the 1960s and 1970s. They are best known for their association with the Chernobyl disaster in 1986.

History

The development of RBMK reactors began in the 1960s, with the construction of the first reactor of this type in Leningrad in 1970 (1). The main aim of this technology was to produce electricity and plutonium for military use, thanks to the flexibility offered by the reactor’s design. At the time of their development, RBMK reactors were seen as an economical and efficient alternative to light water reactors, such as pressurized water reactors (PWRs) and boiling water reactors (BWRs), which were the most widespread in Western countries (2).

Features

RBMK reactors use graphite as neutron moderator and light water as coolant (3). This combination makes it possible to use low-enriched uranium as fuel, which was an economic and strategic advantage for the Soviet Union at the time (4). The reactor core consists of several thousand pressure tubes containing the fuel rods and coolant. These tubes are surrounded by graphite, which acts as a moderator to maintain the chain reaction (5).

One of the distinctive features of RBMK reactors is their large size and high power ratings, ranging from 1,000 to 1,500 megawatts electrical (MWe) (6). This high power is achieved by using a large number of pressure tubes and fuel rods, which are regularly reloaded during operation. This design also provides the flexibility to adjust reactor power by inserting or removing control rods (7).

RBMK reactors have a number of safety features, including emergency cooling and control rod monitoring systems. However, these systems have been criticized for their inefficiency and vulnerability to certain accidents, notably due to the reactor design and the use of graphite as a moderator (8). The Chernobyl disaster highlighted these safety issues and led to major changes in the design and operation of existing RBMK reactors (9).

Key events

At its peak, the Soviet Union had 17 RBMK reactors in operation or under construction (10). Following the Chernobyl disaster in 1986, several reactors were shut down or modified to improve safety. By 2021, only 10 RBMK reactors remained in operation, mainly in Russia (11). These reactors have gradually been replaced by more modern, safer technologies, such as VVER-type pressurized water reactors (12).

The Chernobyl disaster was the worst nuclear accident in history, with devastating consequences for the environment and human health. The explosion and subsequent fire released large quantities of radioactivity into the atmosphere, contaminating vast areas of Ukraine, Belarus and other European countries (13). Estimates of direct and indirect deaths linked to the disaster vary, but the World Health Organization (WHO) estimates that around 4,000 deaths are attributable to the accident and subsequent radiation-induced illnesses (14).

Due to the specific design of the RBMK reactors, the International Atomic Energy Agency (IAEA) has classified them as high-risk reactors (15). Following the Chernobyl disaster, safety measures were implemented to improve the safety of the remaining RBMK reactors. These include modernizing control systems, improving staff training and adding containment systems to reduce the risk of radioactive leaks (16).

Outlook

Despite the safety improvements made to RBMK reactors following the Chernobyl disaster, the future of this technology remains uncertain. Russia, which operates the majority of the remaining RBMK reactors, plans to gradually replace them with new-generation reactors, such as the VVER-1200 (17). These new reactors offer significant improvements in terms of safety, energy efficiency and radioactive waste management (18).

Conclusion

RBMK reactors played an important role in the development of the nuclear industry in the Soviet Union, generating electricity and plutonium for military purposes. However, the Chernobyl disaster and the safety problems inherent in this technology led to a gradual decline in the number of RBMK reactors in operation. Today, efforts are focused on modernizing and replacing these reactors with safer, more efficient technologies.

Sources :

  1. International Atomic Energy Agency (IAEA), “RBMK Reactors: An Overview,” 2009.
  2. World Nuclear Association, “RBMK Reactors,” 2021. https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/appendices/rbmk-reactors.aspx
  3. Ibid.
  4. Ibid.
  5. Ibid.
  6. Ibid.
  7. Ibid.
  8. International Atomic Energy Agency (IAEA), “RBMK Reactors: An Overview,” 2009.
  9. World Nuclear Association, “RBMK Reactors,” 2021.
  10. Ibid.
  11. Ibid.
  12. Ibid.