For the last 50 years, nuclear power plant operators worldwide have shared their experiences on safety-related events through international incident reporting systems to learn from these incidents and contribute to the prevention of accidents. The seventh edition of the IAEA/NEA Nuclear Power Plant Operation Experience has now been published, providing an overview of lessons learned by operators during the 2015-2017 period.
Accidents do not come out of nowhere: by paying attention to events with minor or no real consequences (so called ‘near misses’) during safe operation, events with more serious consequences can be prevented from occurring. The report summarizes lessons learned also from such events and supports plant operators in identifying measures and actions to prevent future incidents.
The report gathers data from 35 countries which contribute to the International Reporting System for Operating Experience (IRS) database (see How are events reported in the IRS?). The database, jointly operated and managed by the IAEA and the Nuclear Energy Agency (NEA) of the Organisation for Economic Co-operation and Development (OECD), aims to increase awareness of potential and actual problems in nuclear power plant operations. Accessible to operators, regulators and technical support organizations, the IRS works as a global contact network and forum.
“The new report is a valuable reminder of safety significant subjects for experts and it is written in an easy-to-understand language for the general public and media. It allows the best possible insights into actual nuclear safety questions,” said Michael Maqua, Head of the Department of Plant Engineering at the Facility and Reactor Safety Organization (GRS), a technical support organization in charge of IRS management on behalf of the nuclear regulatory body in Germany (BMU).
The report groups events into three categories: human performance, equipment issues and management and oversight.
During the period 2015-2017, 246 reports were submitted to the database, describing the events that occurred, analysing their causes and highlighting corrective actions and lessons learned. The new report presents a summary of these lessons to help further improve nuclear safety worldwide. In Germany, for example, GRS analyses the applicability to German plants of these lessons and, when relevant, develops specific recommendations, Maqua said.
By analysing the data, experts can identify recurring events, which may need to be addressed at a more systemic level to further enhance plant safety.
Human performance events
According to the new report, human performance continues to be the main contributor to safety-related events. More than 60% of all the submitted reports for the period fall into this category. The evaluation is based on human errors or the behaviours of nuclear power plant personnel, including licensed operators, maintenance and engineering personnel and contractors.
Problems with equipment were included in many of the reports countries submitted. These may occur for several reasons, including design deficiencies, manufacturing defects, improper installation, premature ageing and degradation or improper equipment alignment. According to the new publication, issues related to the ageing of nuclear power plant components continue to emphasise the importance of robust ageing management programmes.
Events related to management and oversight
Management and oversight improvements can make a significant contribution towards reducing the number of reported events, reveals the new report. Just over 30% of the reports submitted included events in this category: events either caused or aggravated by organisational deficiencies, management direction, decision making or lack of supervisory oversight. The majority of procedure-related issues were identified to have been caused by the inadequacy and incompleteness of procedures and the impact of deficient procedures was found to be greater on less experienced personnel, who are more reliant on these procedures.
The importance of learning from past experiences was highlighted in the publication as a practice that could have helped to prevent major accidents such as Three Mile Island, Chornobyl or Fukushima Daiichi. However, even nowadays insufficient use of operating experience has been recognised by the IAEA’s Operational Safety Assessment Review Team (OSART) missions as a root cause in a number of significant events occurring at nuclear power plants, said Dian Zahradka, Senior Nuclear Safety Officer at the IAEA.
“The IRS aims to support management of regulators and operating organisations in recognising and managing the potential risks to safe and reliable operation by learning from other nuclear operators throughout the world and raising the bar of safety performance and operations,” he said. “It provides information on safety significant events from the global nuclear community via reports accessible to all, and this latest publication makes the most recent lessons learned easily available.”
How are events reported in the IRS?
Reporting to the IRS is based on the voluntary commitment of the participating countries. Each of the 35 IRS participating countries with a nuclear power plant under construction or in operation submit events to the IRS when the event is considered by the national co-ordinator to be of international interest. Events of safety significance and events from which lessons can be learnt should be reported according to the IRS guidelines.
The event report contains basic information, including the title and date of the event, the characteristics of the plant and an abstract. It also includes a narrative description of the event, a safety assessment (the direct causes, consequences and implications), the results of a root cause analysis (if available), corrective actions and lessons learned that can be easily searched and retrieved.
Often, a written description of the event is supported by photographs and graphics such as diagrams of affected parts of the plant. When an event or series of events indicates a generic problem, the national co-ordinator may produce a “generic event report.”