Nuclear Plant Failure

Primary reference(s)

USNRC, 1975. Reactor Safety Study: An Assessment of Accident Risks in US Commercial Nuclear Power Plants (Vol 88). United States Nuclear Regulatory Commission (USNRC). Accessed 8 November 2020.

Additional scientific description

Nuclear reactors are used to heat water to produce enormous amounts of low-carbon electricity and can be powered by a variety of different fuels. The fissioning of atoms in the chain reaction releases a large amount of energy as heat. The generated heat is removed from the reactor by a circulating fluid, typically water. This heat is then used to generate steam which drives turbines for electricity production (World Nuclear Association, 2020).

Electricity is essential for modern life, however, almost one billion people live without access to electricity. Global challenges such as climate change, pollution and environmental degradation require nations to generate electricity renewably (World Nuclear Association, no date). During the 20th century, the main energy sources for generating electricity were fossil fuels, hydroelectricity and since the 1950s, nuclear energy. Despite the growth and demand for renewable energy, fossil fuels remain the dominant source globally. Nuclear power is an environmentally friendly form of electricity generation. Although proponents of nuclear energy claim this is a renewable and safe form of energy, when nuclear plant failures do occur, they can have significant human, environmental, and socio-economic impacts (World Nuclear Association, no date).

In 2018, nuclear power generated 10.5% of the world’s electricity (World Nuclear Association, 2020).

Nuclear reactors are a reliable source of energy and are capable of running for 24 hours a day for many months and possibly up to years without interruption, providing large amounts of clean electricity. Most nuclear reactors can operate for many years, over 60 years in some cases (World Nuclear Association, 2020).

Reactors derived from designs originally developed for propelling submarines and large naval ships generate about 85% of the world’s nuclear electricity. The most common power reactor types use water, with more than 90% of the world’s reactors being water-based (World Nuclear Association, no date).

The nuclear plant failures in Chernobyl and Fukushima are notable examples of major disasters.

Chernobyl, Ukraine (former Soviet Union) 1986: Chernobyl, is considered the world’s worst nuclear disaster to date. A sudden power surge resulted in explosions and nearly complete destruction of the reactor. Fires broke out in the building which contributed to the extensive radioactive releases. The initial steam explosion and fire killed two people with a further 28 dying from radiation poising within three months. Massive amounts of radiation spread across the Soviet Union and Europe, and displaced 220,000 people as well as contributing to significant health, environmental and socio-economic impacts (WHO, 2016; World Nuclear Association, 2019).

Fukushima, Japan 2011: The 2011 Great East Japan Earthquake and tsunami that struck Japan on 11 March 2011, destroyed four reactors at the Fukushima nuclear power plant due to the loss of cooling as a result of the tsunami. There were no deaths or serious injuries as a direct result of radioactivity.

Metrics and numeric limits

Design certification of reactors is the responsibility of national regulators. There is international collaboration among national regulators to varying degrees, and there are various sets of mechanical codes and standards related to quality and safety (World Nuclear Association, 2019).

Examples of drivers, outcomes and risk management

Despite recent nuclear disasters such as Chernobyl and the devastation that brought, there is very little risk of nuclear power plants releasing radioactive materials to nearby communities. There has been strong awareness of the potential hazard of both nuclear criticality and release of radioactive materials from generating electricity through nuclear power, which has led to increased safety measures, an increase in well-trained reactor operators, thorough testing and maintenance, and policy and regulations put in place by organizations such as the Nuclear Regulatory Commission (USNRC, 2011; World Nuclear Association, 2019). The design and operation of nuclear power plants to date, aims to minimise the likelihood of accidents, and avoid major human consequences through implementation of nuclear safety measures and risk-informed decision-making (USNRC, 2011).

The International Atomic Energy Agency (IAEA) reports that nuclear power plants are equipped with multiple safety systems able to deal with a wide range of abnormal operating conditions. They also have well-proven emergency operating procedures that help operators to achieve a stable and safe end state. However, the most severe circumstances can result in damage to the nuclear fuel and the containment structures, possibly leading to a release of radioactivity to the environment. Yet even in these events the consequences can still be mitigated using available and, in some cases, dedicated plant equipment (IAEA, no date).

To protect the public and the environment from the consequences of a nuclear power plant accident, each plant operator establishes a severe accident management programme, which is kept under constant review and development. The main objective of the guidelines used to design such programmes is to utilise any available equipment at the nuclear power plant to terminate core damage, maintain containment integrity and minimise the release of radioactivity from the site (IAEA, no date).

The severe accident management guidelines vary according to plant design, local regulations and site characteristics. The IAEA has developed a toolkit to help operators develop their own guidelines and offers its Member States modular training programmes (IAEA, no date).

Although they are unlikely to be needed, severe accident management programmes are a critical part of the Defence in Depth concept, which is a hierarchical deployment of different levels of equipment and procedures in a graded approach to protect against a wide variety of incidents, accidents, equipment failures, human errors and events initiated outside the plant. In general, severe accident management programmes are designed to: evaluate generically the capability of existing plants to tolerate a severe accident; identify events that can lead to severe accidents and formulate preventive and mitigation strategies; and identify short-term and long-term measures for handling severe accidents (IAEA, no date).

The IAEA provides extensive materials on nuclear power plant safety systems which are designed to mitigate a range of abnormal operating conditions. In the unlikely case of a severe accident, plant operators use guidelines developed specifically for the purpose. The IAEA has a toolkit to help operators develop these guidelines and offers training to its Member States (IAEA, no date).

In addition, the IAEA organises the International Conference on Radiation Safety: Improving Radiation Protection. In 2020 it was held virtually, from 9 to 20 November. The Conference was organised in cooperation with the European Commission, the Food and Agriculture Organization of the United Nations, the International Labour Organization, the Nuclear Energy Agency of the Organisation for Economic Co-operation and Development, the Pan American Health Organization, the United Nations Environment Programme and the World Health Organization (IAEA, 2020).