[en] This report provides a description of the state-of-the-art in the development and use of Risk Monitors at nuclear power plants in the Member States. The work has been carried out jointly by IAEA and OECD WGRisk. The information presented in this report has been obtained from three questionnaires on the development and use of Risk Monitors, software and Regulatory perspectives; from OECD and IAEA Workshops on Risk Monitors; and from IAEA consultants meetings and WGRisk Task Group meetings. Some of the work carried out to produce the report has been funded by the United Kingdom Nuclear Installations Inspectorate. The aim is to produce a report that describes the state of the art in the development of Risk Monitors and their use at nuclear power plants. This will: - define the terminology that relates to Risk Monitors as used in this report, - describe the state of the art in the development and use of Risk Monitors at nuclear power plants, and indicate future developments, - provide information on the software packages available for Risk Monitors, - identify the issues that need to be addressed in the development of a Living PSA for use in a Risk Monitor application and give guidance on how these issues can be resolved, - give information on the issues relating to the design of the Risk Monitor operator interface so that it gives a tool that can be used by all station staff, - discuss the issues that relate to the qualitative and quantitative risk measures addressed by Risk Monitors such as the definition of the Operational Safety Criteria which define the risk levels, the calculation of the Allowed Configuration Time and the definition of the qualitative risk levels that relate to the availability of safety systems, - give insights into the costs involved, the benefits that can be obtained from Risk Monitors and their limitations, and - discuss the regulatory perspective on the use of Risk Monitors to provide risk information that can be used during nuclear power plant operation. As well as providing information on the state of the art, the report will also identify good practices in each of these areas. Section 2 defines the terminology used in the report. Section 3 describes the differences between a Living PSA and a Risk Monitor, and provides a historical perspective on the growth of the use of Risk Monitors in the worldwide. Section 4 gives an overview of the Risk Monitor software packages currently available or under development. Section 5 discusses the changes that need to be made to the Living PSA before it can be used in a Risk Monitor application. Section 6 relates to the use of Risk Monitors at nuclear power plants. It identifies the users of the Risk Monitor and the functions that they carry out, and how the information on the plant configuration and environmental factors is input into the Risk Monitor. It describes the outputs provided by the Risk Monitor and how this relates to the actions that need to be carried out by the plant staff to control the risk. Section 7 discusses the Operational Safety Criteria that define the boundaries between the risk bands displayed by the Risk Monitor and used by the plant operators. Section 8 discusses the calculation of the Allowed Configuration Time for a new plant configuration and how this relates to the Allowed Outage Time given in the plant Technical Specifications. Section 9 describes the qualitative risk measures addressed by many of the Risk Monitors. Section 10 discusses the costs involved in implementing a Risk Monitor at a nuclear power plant and the benefits that would be obtained by the plant operator. Section 11 discusses the issues and limitations related to the use of Risk Monitors. Section 12 gives the views of the Regulatory Authorities in some of the Member States on the development and use of Risk Monitors. Section 13 gives the conclusions drawn from the work and Section 14 lists the references cited in the report. Appendix 1 gives detailed information on the current status of Risk Monitors worldwide. It identifies the Risk Monitors currently in service and those that will be installed within the next 1-2 years. Appendix 2 provides a detailed description of the Risk Monitor software packages currently in existence or under development. This is based on information that has been provided by the software developers