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Nuclear Fission Reactors

Nuclear fission reactors are devices that produce and control the release of energy from nuclear fission reactions (the splitting of atoms of elements such as uranium or plutonium). In nuclear power reactors the energy released is used as heat, primarily to produce steam directed to a turbine to generate electricity. However, the heat can also be used for non-electric applications, for example district heating or desalination. In nuclear research reactors the radiation produced by the nuclear fission reaction is used for research, testing materials or producing medical isotopes. Nuclear power reactors – predominantly light water reactors – are a major source of baseload electricity in many countries. Currently (2026) nuclear reactors provide about 9% of global electricity, but more than 20% of global low-carbon electricity (about 9% of total global electricity).

Overview

Nuclear fission reactors use uranium-235 as fuel, which undergoes fission when bombarded with neutrons. The resulting energy is released in the form of heat, which is transferred to water or other coolant circulating through the reactor core. In light water reactors, and some gas-cooled reactors, the heated coolant is used to generate steam, which drives turbines to produce electricity. Some gas-cooled reactor designs use the heated gas to directly drive a turbine, with no steam involved. The heated coolant can also be used directly to provide industrial or process heat such as for district heating or desalination. Nuclear fission reactors are typically large and complex structures, requiring extensive safety and security measures. Supply chain considerations involve the availability of uranium fuel, specialised reactor components, and skilled labour. Logistical challenges include the transportation and installation of heavy equipment and the management of nuclear waste. Accessibility for developing countries interested in including nuclear power in their energy mix is influenced by the high upfront cost, technical complexity, and regulatory requirements.

Maturity

Nuclear fission reactors are a mature technology, with a long history of commercial operation.

Safety considerations

The nuclear safety risks associated with nuclear fission reactors are related to direct exposure to radiation and contamination through the release of radioactive materials into the environment. This can be due to malfunctions or accidents, or the mismanagement of radioactive waste or spent fuel. Robust safety systems and regulations are essential to minimise these risks.

Security considerations

Stringent security measures are essential to ensure proper control and prevent, detect or respond to theft, sabotage, unauthorized access, illegal transfer or other malicious acts involving the nuclear fuel, other radioactive material or the nuclear facility itself.

Safeguarding considerations

The applicable IAEA safeguards agreement is implemented, involving, for example, inspections, nuclear material accounting, and containment and surveillance measures, to verify the peaceful use of nuclear materials..