The OL3 EPR construction site in October 2013 (Source: TVO)

The management of a nuclear power plant (NPP) construction project is a challenging, long, resource-consuming and complex activity. For instance, the on-going construction project of Olkiluoto 3 (Finland) involved a peak number of about 4500 on-site workers from many different contractors. After full completion of the project, the construction will have involved more than 10,000 on-site workers in total, of more than 50 different nationalities.

Moreover, starting new-build now is very demanding since much of the earlier experience and resources have progressively been lost from the nuclear industry. Circumstances are quite different from the 1970s when most of the operating plants were constructed. Then, vendors had large experienced organizations ready to go ahead, and had less need to rely on subcontractors. In addition, there was no shortage of skilled manufacturing capacity in the market, and designs were often based on work done in similar ongoing or completed projects.

"Lessons learned from past construction periods and from ongoing construction projects are very important for the increased number of utilities and regulators involved in the construction of new nuclear plants"

Consequently, lessons learned from past construction periods and from ongoing construction projects are very important for the increased number of utilities and regulators involved in the construction of new nuclear plants, in order to reduce the probability of previous construction or commissioning problems happening again. Efforts to collect lessons learned from pre-operational experience have already been performed in the past. But as there was no recent comprehensive study published on lessons learned from events related to pre-operational phases, nuclear safety authorities participating in the European Clearinghouse on Operational Experience Feedback for NPPs decided to launch an up-to-date in-depth analysis of both past and recent experience related to the pre-operational stages of NPPs. This article focuses on its cross-cutting recommendations for the management of a construction project.


Experience related to pre-operational stages of NPPs was captured by screening the following three data sources:

  1. The US Licensee Event Reports (US-LERs) publicly available on a website of the United States Nuclear Regulatory Commission
  2. The International Reporting System (IRS) jointly operated by the International Atomic Energy Agency and by the Nuclear Energy Agency of the OECD.
  3. The OECD/NEA’s recently-established dedicated working group Working Group on Regulation for New Reactors (WGRNR).
"582 event reports have been found applicable to construction experience"

These three data sources provide a worldwide coverage of more than three decades of events reported. We have screened 1090 IRS reports, 857 US-LERs and 100 WGRNR reports dating back to the start of the databases (the 1980s as far as the IRS and LER databases are concerned) and ending on 30 November 2009. After screening, a total of 582 event reports have been found applicable to construction experience. They were analysed individually to identify the main trends (most common recurring and safety-significant events), the lessons learned for specific activities of the construction projects, and cross-cutting recommendations.

Four top findings

A trend analysis of the IRS applicable reports has been performed, leading to the main conclusions below. It is to be noted that the event reports often did not provide enough detailed information about the root causes to perform accurate statistics. As a result, the following conclusions are to be seen as trends.

65% of the events are related to some extent to the management of the project. Among management-related events, the most recurring subfamilies are in the areas of quality management (one-third of all management related events), management of subcontractors and suppliers (18%), and management of the work environment (housekeeping, cleanliness, foreign material exclusion policy).

"The average detection time of the initial deficiencies is about eight years after the start of commercial operation"

The average detection time of the initial deficiencies is about eight years after the start of commercial operation, but this interval depends on the components involved. More specifically, the failures of active components like diesels or pumps are detected more quickly (partially because of their plant surveillance programmes) than the failures of passive components such as civil structures, pipes or welds. These latter components are generally affected by slow degradation phenomena initiated by an original construction or manufacturing defect.

The proportion of common cause failures (CCF) can be quite high for some structures, systems and components: more than 50% for civil work and fire protection and 45% for electrical components (the average CCF rate being 34%). A CCF consists in the failure of two or more structures, systems and components due to a single specific event or cause.

More than 75% of the events are detected fortuitously, and the rate of fortuitous detection is particularly high for some items: civil work, electrical components, I&C, pipes and valves. In some items like civil structures (for example, building structures, anchorages and supports) we find a combination of long detection time, a high rate of common cause failure and a high rate of fortuitous detection.

The importance of management

The above conclusions underline the importance of minimizing the deficiencies during the construction, manufacturing and commissioning phases of a new reactor, because they can remain major latent failures or contributors to failures over a long time, with significant consequences for safety when the reactor starts to operate. This emphasizes the necessity to detect the deficiencies during pre-operational stages and in particular during the commissioning of the plant, as it may be difficult to identify them during operation.

In addition, these trends highlight the role of management to further reduce the gravity and/or reduce the occurrence of events in the plants. For NPP construction, project management is a key area to influence the final quality and safety of the facilities, by acting in the following areas:

  • Definition of the project top priorities and values (that should include safety culture)
  • Putting in place a reliable quality management system
  • Ensuring efficient communication between all parties involved in the project
  • Ensuring unambiguous partition of responsibilities
  • Setting up efficient and reliable management of suppliers and subcontractors.

See part 2 for detailed examples of some of the most common recurring and safety significant events.

Marc Noël and Benoit Zerger, European Clearinghouse on Operational Experience Feedback for Nuclear Power Plants, Institute for Energy and Transport, Joint Research Centre, European Commission

The work in this paper is based partly on research previously reported in ‘European Clearinghouse: Analysis of Construction and Commissioning Events – Topical Report (2010)’, European Commission, Joint Research Centre, Institute for Energy, Petten, Netherlands.