Paris, 13 November 1996
In spite of the satisfactory safety level of nuclear power plants in OECD countries and the advances made in technologies basic to the resolution of safety issues, there is a consensus in the international community that there is the potential for yet further improvement. Continued nuclear safety research is necessary and remains an important element in ensuring the safe operation of nuclear power plants.
In a "collective opinion" recently published on the state of the art of nuclear safety research in OECD countries (see Annex), the NEA Committee on the Safety of Nuclear Installations (CSNI) notes that the funding levels of government safety research programmes have been reduced over recent years in several member countries. Care is needed to ensure that this does not have an adverse impact on the ability of government agencies to fulfil their safety responsibilities.
The untimely shutdown of large research facilities and the break-up of experienced research and analytical teams involves the risk of a loss of competence and a reduced capability to deal quickly and efficiently with future safety problems. The lack of large research facilities will make it more difficult to understand complex severe accident phenomena, to verify and validate computer codes, to clarify uncertainties, and to demonstrate the validity of severe accident management strategies.
The aim of nuclear safety research is to provide information to plant designers, operators and regulators in support of the resolution of safety issues, and also to anticipate problems of potential significance. Better understanding of phenomena that have an influence on reactor safety has been one of the major contributors to the improved assurance of nuclear safety. Over the past thirty years, significant amounts of money have been spent in the field of nuclear safety research, advances have been made in many areas and there is now better understanding of problems, phenomena and processes. In particular, research results have been integrated into computer codes, major codes have been validated and our ability to predict the way things happen, e.g. power plant transients, has been transformed over that period. Progress in reactor safety has been substantial, safety improvements have been introduced and safety margins are now quantified with increased confidence. The money was well spent.
NEA and its Committees have an important role to play in ensuring international cooperation in the field of nuclear safety and regulation. The NEA Committee on the Safety of Nuclear Installations (CSNI), which is an international committee made up of senior scientists and engineers, with broad responsibilities for regulation, safety technology and research programmes, reviews the nuclear safety research performed within OECD countries, encourages in-depth exchanges of information, data and experience, develops common technical positions on important safety issues, promotes joint projects, discusses the future direction of safety research, and identifies areas of agreement and areas for further action. CSNI, in collaboration with the Committee on Nuclear Regulatory Activities (CNRA), provides the meeting ground for in-depth exchange of information on reactor safety research and on reactor operations and regulation for the most advanced countries in this technology. The Committees initiate and carry through to completion international cooperation on important safety matters, develop common positions on critical safety issues that need judgment, identify areas where issues can be considered as resolved and areas where further research is needed, and play an important role during the organising phase of OECD Research Projects. The exchange of safety information is effective, without delay and very valuable. Cooperation in the framework of NEA brings together the best minds to collaborate on safety issues, and provides for cost sharing and thus makes each partner's research money go farther. The effect of this work is to add value to national efforts, to extend their scope and to amplify their own results.
A review just completed has shown that, although the safety level of nuclear power plants in OECD countries is very satisfactory and the technologies basic to the resolution of safety issues have advanced considerably, there is an opinion broadly shared throughout the international community that there is the potential for yet further improvement. Although the range of uncertainties is limited, continued nuclear safety research work is necessary to address many of the residual concerns, and it remains an important element in ensuring the safe operation of nuclear power plants. Operating experience, plant ageing, emerging technologies and new design concepts lead to a requirement for additional research to be undertaken. Also, Government Agencies need to ensure that research is undertaken to maintain essential technical national expertise and capabilities so that both operators and regulators can meet their respective responsibilities. A new report identifying areas where there is technical consensus among OECD countries and areas where more work is needed will be published shortly by the CSNI under the title "Nuclear Safety Research in OECD Countries : Areas of Agreement, Areas for Further Action, Increasing Need for Collaboration".
The review shows that there is very good international agreement regarding the results achieved so far, the significance of safety issues, and which safety issues still need to be addressed. These results and remaining issues are discussed in the report mentioned above. Specific priorities in research programmes may depend on national objectives and reactor types but there is largely consensus regarding the most significant safety issues. Their significance may be based upon risk analysis, operational experience, new design concepts or other factors deemed important by national interests. Over the years, in a number of areas CSNI has been able to reach common technical positions and in several cases to close safety issues, thereby eliminating or reducing the associated needs for further research. Examples of common technical positions include the areas of integrity of equipment and structures (aspects of the leak-before-break issue), thermal-hydraulics (development and validation of major codes for loss-of-coolant accidents and the effects of emergency core cooling), aspects of severe accidents (the issue of the source term and accidental radioactive releases, the respective roles of accident prevention and mitigation, progressive implementation by utilities of severe accident management programmes).
There is need to continue to invest in safety research in the future in order to develop understanding and to maintain our capability and expertise, as well as to be able to address emerging safety issues. Further discussion is needed in a number of safety research areas. These include aspects of steam generator and pressure vessel integrity, component ageing, human factors, computer-based control and safety systems, extended application of thermal-hydraulic codes, better understanding and quantification of fuel/coolant interaction related issues, mechanisms of debris coolability, hydrogen combustion and mitigation techniques. Moreover, increasingly strict licensing requirements, and licensing of new reactor designs, have stimulated the need for further confirmatory research; these requirements are likely to become even more demanding in the future.
In a number of technical areas (e.g., human factors, computerized plant control and monitoring, fire protection), other industries are conducting research which has applicability in the nuclear field. Efforts should be made to coordinate and cooperate with these industrial programmes where appropriate.
In the field of nuclear power safety, OECD countries' Government Agencies have broadly similar responsibilities. They need to undertake, fund or sponsor research - or Governments must ensure funds are available - to develop and maintain technical national expertise so as to establish their own position on safety matters and enable them to meet their obligations. However, in several member countries, the funding levels of national Government safety research programmes have been reduced over recent years. Care is needed to ensure that this does not have an adverse impact on the ability of Government Agencies to fulfil their safety responsibilities, especially since the reduction in Government direct or imposed funding of nuclear safety research may not have been offset by increases in the funding of safety research programmes of reactor vendors and operators.
The Committee is concerned that dwindling budgets and support as well as stagnant nuclear programmes may lead to the untimely shutdown of large research facilities and the breaking up of experienced research and analytical teams with the consequent loss of competence and reduced capability to deal quickly and efficiently with future safety problems. Unavailability of large research facilities will make more difficult the understanding of complex thermal-hydraulic and severe accident phenomena, the verification and validation of computer codes, the clarification of uncertainties, and the demonstration of the robustness of severe accident management strategies; it will undermine the confidence to be put in future reactor designs. It will hamper advanced training of engineers and scientists. Maintaining adequate levels of expertise will be one of the key issues of future nuclear power development.
As dramatically demonstrated by the Chernobyl accident, nuclear safety is typically an international issue. Its international aspects assume increasing importance. International collaboration of many forms, sharing information, experience and resources, has long been an important feature of nuclear safety research. The need will be strengthened in coming years as pressures to reduce budget and manpower resources will grow. The review has identified considerable scope for international collaboration in the priority areas; it is most important to continue and intensify the exchange of information and results, to discuss issues, and to conceive, plan, and support joint research projects. It must be stressed, however, that international research projects cannot be a substitute for healthy national programmes; there is a level of effort under which national programmes become ineffective even if they are invigorated by international collaboration.
Cooperation with the Central and Eastern European Countries and the New Independent States of the Former Soviet Union has substantially improved in the last few years. This is especially important in the field of reactor safety and safety research. Collaboration should increase even more in the future, involving both the exchange of information and participation in joint projects.
Note:: The report mentioned in the collective opinion of the CSNI assesses the situation with respect to: