credit to : (Article in IAEA Newsbriefs, Vol. 6, No.2 (49), March/April 1991)
In the five years since the Chernobyl nuclear plant accident in April 1986, governments working through the 1AEA and other international organizations have reinforced their cooperation in areas of nuclear safety and radiological protection. Key achievements cover areas including:
- Post-Accident Analysis And Review. The Chernobyl accident's causes, consequences, and radiological impact have been thoroughly analyzed by international experts. In August 1986, more than 600 participants met at a post-accident review conference of the IAEA; a concluding summary report attributed the accident mainly to flagrant disregard by operating personnel of safety rules and procedures that placed the reactor in an unstable state resulting in an explosion. In view of design characteristics peculiar to the Chernobyl type of reactor, a limited number of which are operating only in the Soviet Union, the accident did not call into question the design or safety of the world's other types of nuclear plants. Chernobyl's immediate consequences were severe - the accident destroyed the plant, killed 31 workers and fire-fighters, seriously injured nearly 300 workers, and released a great amount of radioactive material that severely contaminated a large area around the plant. The radiological impact was assessed in 1988 by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). In Byelorussia, among the most heavily affected areas, UNSCEAR found that the highest average dose a person sustained in the first year after the accident was about equal to that due to I year's exposure to natural background radiation. Outside the USSR, this dose was about a third of that received in a year from natural background radiation.
The situation in the most heavily affected Soviet republics -- Byelorussia, Russia, and the Ukraine -- continues to command international attention. In response to concerns of Soviet citizens living there, USSR authorities in late 1989 requested the IAEA to coordinate an international assessment of Chernobyl's health and radiological consequences, and to review Soviet countermeasures to protect public health and safety. Results of that assessment, which involves UNSCEAR, the World Health Organization (WHO), and other organizations, will be published in May 1991. Separately, assistance projects have been initiated by UN bodies including WHO and the United Nations Scientific, Educational and Cultural Organization (UNESCO).
- Plant Safety Reviews And Technical Exchanges. More countries are inviting teams of international experts to review the operational safety of their nuclear plants. As before the Chernobyl accident, national regulators and utilities carry the primary responsibility for the safety of their country's nuclear plants: no supranational safety authority has been formed. But to complement national efforts and to visibly reinforce them, governments are using international safety services expanded or created over the past 5 years. Under one IAEA programme, 37 missions to plants in more than 20 countries have been conducted since 1986. An interrelated project is placing special emphasis on design and operational reviews of older nuclear plants, currently WWER-440/230 units operating in Eastern Europe and the Soviet Union. Ten reactors of this type have been selected for on-site reviews in 1991.
Operational experience, training methods, and safety practices also are being more widely shared by nuclear utilities through a programme of technical exchange visits coordinated by the World Association of Nuclear Operators (WANO), a non-governmental organization that nuclear utilities formed after the Chernobyl accident. Since September 1989, some 50 exchanges involving nuclear plant operating personnel from Western countries, the USSR, and Eastern Europe have been coordinated.
- Event Analysis And Safety Assessment. Global collaboration to prevent serious nuclear plant accidents includes greater use of resources for analyzing and sharing technical details about unusual events that have occurred. Under a project initiated in 1986, fourteen IAEA expert missions have assisted nuclear authorities in nine countries with such safety assessments. Mission experts specifically review the root causes of past significant incidents and accidents, and the effectiveness of corrective actions, making recommendations as needed. Through another post-Chernobyl IAEA programme started in 1989, six countries have requested international peer reviews of nuclear plant safety studies they have done using the methodology of probabilistic safety assessment; others have requested help in conducting such studies as part of comprehensive plant safety reviews.
National nuclear authorities also are exchanging more reports on safety-significant events at nuclear plants through a computerized global Incident Reporting System (IRS). Operated since 1983 by the IAEA and Nuclear Energy Agency of the Organisation for Economic Co-operation and Development (NEA/OECD) to supplement national and regional systems, the IRS was upgraded after the Chernobyl accident to improve capabilities for collecting, analyzing, and disseminating information.
- Emergency Notification And Assistance. A global system is in place to ensure the prompt reporting of nuclear accidents having potential transboundary consequences and to coordinate provision of technical and medical assistance in emergencies. More than 70 IAEA Member States have signed two international conventions that were drafted and adopted within 5 months of the Chernobyl accident: the Convention on the Early Notification of a Nuclear Accident and the Convention on Assistance in the Case of a Nuclear Accident or Radiological Emergency. The IAEA, which is the depositary of these conventions, started operating an Emergency Response System (ERS) in January 1989 to receive and pass on reported information, including radiological data, to governmental authorities, and to help coordinate assistance if required. ERS is supported by the Global Telecommunication System of the World Meteorological Organization (WMO). Since the Chernobyl accident in 1986, no nuclear plant accident has occurred that required international notification or assistance.
- Supporting Health And Environmental Networks. Other global networks are supporting efforts to strengthen national capabilities for preventing and responding to radiological emergencies. They include the Radiation Emergency Medical Preparedness and Assistance Network of the World Health Organization (WHO), which is being developed among WHO's regional collaborating centres. Another is the Global Environmental Radiation Monitoring Network that was set up jointly with the United Nations Environment Programme (UNEP) to buttress data capabilities covering radioactivity levels in air, soil, and precipitation. Also in place, and expanded over the last 5 years, are IAEA radiation protection services tailored to the practical needs of developing countries. Under one service in which WHO participates, more than 40 countries have requested advisory missions since 1986 to establish or improve their radiation protection programmes.
Permissible radioactivity levels for foodstuffs in international trade also have been issued. The Codex Alimentarius Commission of WHO and the Food and Agriculture Organization (FAO), using the IAEA's expertise and advice, adopted recommended levels in 1989. These global guidelines should help to prevent repetition of what happened in 1986, when national governments set widely varying levels that confused people and undermined their confidence in authorities.
- Liability For Nuclear Damage. Legal experts from more than 50 countries are heading efforts to establish a more equitable and adequate international regime for compensation of victims in the event of a nuclear accident. In 1988, countries adopted a joint protocol to expand the scope of application of the two existing international conventions on civil liability for nuclear damage, which are wider auspices of the IAEA and NEA/OECD. Issues related to international civil and State liability, including possible revision of the existing conventions, remain under discussion.
- Event Reporting. A standardized global approach has been developed for rapidly and clearly informing people about the significance of nuclear accidents. Twenty-seven countries are now using this International Nuclear Event Scale on a trial basis. Modelled on national systems, the scale uses seven levels to categorize a nuclear event, based on the extent of radiological effects and the performance of the plant's emergency safety systems and structures: for example, a major nuclear accident, such as Chernobyl, is Level 7, whereas an operational or functional anomaly at a nuclear plant is Level 1. Events are analyzed and categorized by national authorities in participating countries. The scale was developed in 1990 by the IAEA and NEA/OECD in cooperation with WANO.
- Safety Codes And Principles. International safety recommendations for nuclear plants have been carefully reviewed and updated where required. international advisers to the IAEA's Nuclear Safety Standards Programme (NUSS) issued revised documents in 1988 that particularly reflect experience gained in accident prevention and management. NUSS, which includes some 60 codes and guides, covers areas such as nuclear plant construction, operation, and emergency planning. Basic safety principles for nuclear plants also were published in 1988 by the IAEA’s International Nuclear Safety Advisory Group (INSAG). The report responded to the need for a concise, integrated, and comprehensive statement of principles underlying advanced national policy and industry practices worldwide.
