Background Information and Definitions

Scope

The information in this data visualization is based on the World Nuclear Industry Status Report (WNISR) Database, a Mycle Schneider Consulting Project, globally updated to 1 January 2026. Additional updates are made continuously as needed. The database covers commercial nuclear power reactors for which construction has or had started but does not include “planned” or “projected” power reactors. It also excludes research, heating, naval, and military reactors that are or were not designed to generate power for the grid.

Sources of Data

The World Nuclear Power Reactor Data Visualization (DataViz) is based on the WNISR Nuclear Reactor Database. Historic data are drawn from the International Atomic Energy Agency’s (IAEA) Power Reactor Information System (PRIS), the World Nuclear Association’s (WNA) online database, and WNISR’s own research. The latest annual WNISR provides over 2,500 bibliographic references, all of which are available on the WNISR website.

Information on reactor characteristics (type, model, capacity, provider, operator) is mainly drawn from IAEA-PRIS, corrected or updated when identified. Provider groupings by country or international consortia, as well as reactor models, have been established by WNISR.

The following are the main discrepancies between IAEA- and WNISR-data relating to reactor constructions:

• IAEA data depends on information provided by Member States; WNISR research attempts to establish which construction projects can be considered “active”. WNISR adds projects to or removes them from the IAEA’s list of reactors “under construction” if primary sources or several credible other sources—either in the open literature or from the WNISR’s international network of experts—corroborate a given status.
• The IAEA sometimes creates “new” construction-start dates, e.g. when there has been a significant interruption in the building of a nuclear power plant as well as in other cases usually involving construction-starts prior to the 1980s. WNISR tries to document interruptions but does not modify the original construction-start date, unless the changes reflect an evolution of the construction-start definition itself.
• Construction data for some reactors in IAEA-PRIS have not only been modified over the years, but some reactors have simply disappeared from the system. Not all those changes are reflected in the WNISR database yet, but they are added as soon as they can be documented.

Definitions

Construction Start

The start of concreting of the reactor building’s base slab is generally considered (IAEA, WNA, WNISR…) the “Construction Start”. Site preparation, excavation, civil works, and other activities are not included in the definition. For floating reactors (Russia and China), as no concrete is poured, WNISR uses the “keel laying ceremony” of the barge as the construction-start date.

Construction Suspension or Abandonment

Over the years, in close to one hundred cases reactor construction has been suspended or abandoned. Suspension and cancellation apply only to “constructions” and not to “projected” or “planned” reactors. Reactors enter the WNISR statistical database only when construction has started according to the above definition.

• Temporary Suspension
  A reactor construction that was once suspended but has resumed.
• Indefinite Suspension
  A construction declared “suspended”—by the operator, authorities, regulators, etc., or listed as “suspended” by IAEA-PRIS—that has not resumed as of the latest update of the DataViz and has no date of a restart. This includes non-official suspensions, for which WNISR has determined that there is de facto no active construction and no prospect of a timely restart.
• Abandoned Construction
  A construction declared cancelled by the operator, authorities, regulators, or any other official decision or listed as “cancelled” in IAEA-PRIS. This includes non-official abandonments for which WNISR has determined that there is de facto no active construction and no prospect for work resumption.

Reactor Startup (Grid Connection)

The WNISR definition of reactor startup is its grid connection. In the case of reactor construction, the expected startup date is not always expressed in terms of grid connection as the information might not be available; it may also refer to “commissioning”, “completion”, “commercial operation”, or other similar terminology. Expected startup is not always connected to a precise date; rather, it can be general as in “early 2026” or “second semester 2026”. WNISR uses “best estimates”, based on a variety of sources, when providing expected startup dates as of 1 January 2026, and regularly updated subsequently.

Construction Time (Duration Since First Construction Start)

The total construction time is the entire length of a reactor’s construction period from first construction start until it is (or is expected to be) connected to the grid or its construction is abandoned (cancelled or indefinitely suspended). Temporary suspension periods are included in the total construction time.

Status

Current Status

The status of reactors is updated as events occur or are made public. The “Current Status” of reactors, indicated below the general world map, reflects the status known as of the latest DataViz update.

Under Construction

The status of a reactor is “Under Construction” when:

• construction has started prior to or as of the latest DataViz update;
• the reactor was not connected to the grid as of the latest update;
• construction of the reactor was not cancelled or suspended as of the latest update, unless otherwise noted.

The number of reactors “Under Construction” by year refers to the total number of reactors that met the following criteria as of 31 December of the respective year:

• construction of the reactor started before or during the year;
• the reactor was not connected to the grid as of 31 December of the year;
• construction of the reactor was not cancelled or suspended as of 31 December of the year;
• in case of suspension, construction resumed before or during the year.

Behind Schedule

“Behind Schedule” applies to reactors “Under Construction” for which the expected startup is later than the expected startup date at construction start. This does not, therefore, include the frequent delays prior to the construction start itself.

Abandoned (Cancelled or Suspended)

A reactor is considered “Abandoned” (Cancelled or Indefinitely Suspended) as of the date of the latest DataViz update when:

• construction started before the date of the latest DataViz update;
• the reactor was declared Cancelled or Suspended (by IAEA-PRIS, operator, builder, authorities, or other authoritative sources) before the date of the latest DataViz update and construction has not resumed; or
• construction is de facto suspended, and no active construction is underway on site with no further prospect of a restart, as of the latest DataViz update.

Cancelled Constructions and Indefinite Suspensions (not resumed) are grouped under the term “Abandoned” constructions.

Operating

A reactor is considered to be “Operating”:

• from the date of grid connection to the date of the latest power production or final disconnection from the grid, or
• from the date of grid connection to the date of entering Long-Term Outage (LTO) status.

A reactor can be retroactively withdrawn from “Operating” status from the day it was disconnected from the grid (either to enter the LTO status or to be closed).

Long-Term Outage (LTO)

A nuclear reactor is considered in Long-Term Outage (LTO):

• when it has not generated any electricity in the previous calendar year and in the first six months of the calendar year under review (when these criteria are met, a reactor’s status is retroactively changed from “Operating” to “LTO” from the date of grid disconnection);
• when a reactor is shut down after its operating license has expired and the process of license renewal is underway.

Closed

A nuclear reactor is considered as “Closed” from the day of latest electricity generation or final disconnection from the grid. A reactor can be retroactively considered “Closed” if it is not restarted after an outage (LTO or other).

Reactor Characteristics

Nuclear Steam Supply System (NSSS)

The Nuclear Steam Supply System (NSSS) consists of a nuclear reactor and all the components necessary to produce high pressure steam, which is used to turn the turbine for electricity generation (IAEA-PRIS Manual). The NSSS is also called the nuclear island.

Nuclear Provider

The indicated nuclear provider is mainly based on the NSSS provider given in IAEA-PRIS as of March 2026. In some cases, the nuclear provider may change during construction. The WNISR database does not immediately account for all these changes. Important changes are introduced in the description of the reactor itself.

Operator

The indicated operators are mainly based on IAEA-PRIS as of March 2026 or later in case of more recent constructions or major changes. Changes of operators are usually not identified as such, even when they differ from IAEA-PRIS.

Capacity

Unless otherwise noted, WNISR uses the net electricity generating capacity as indicated in IAEA-PRIS.

Unless otherwise indicated,

• “Net Capacity” refers to the Reference Unit Power provided in IAEA-PRIS as of DataViz update or for a specific year, and
• “Design Net Capacity” refers to te “Design Net Capacity” provided in IAEA-PRIS.

The list of Events indicates the Net Capacity at the time of the event (Design Capacity for constructions, Reference Unit Power of the year for other events).

Nuclear Production and Share

Data for Nuclear Production and Share in Total Electricity Production are based on the latest available edition of the Energy Institute’s “Statistical Review of World Energy” (with the exception of countries not individually covered in this publication). Production refers to the Net Production, whereas the share is based on gross data.

Imprint

This interactive data visualization tool was developed by the core team of the World Nuclear Industry Status Report (WNISR) Project (data & analysis), Visionscarto.net, and 23Forward (design & programming) with financial support of various WNISR funders.

The current version is based on a first edition hosted by The Bulletin of the Atomic Scientists 2017–2020 with initial support from the Pulitzer Center on Crisis Reporting.

Team

• Arnaud Martin, Web Designer and Full-stack Developer (23FORWARD)
• Philippe Rivière, Journalist and Programmer (visionscarto.net)
• Diala Ashkar, Graphic Designer and Art Director (23FORWARD)
• Julie Hazemann, Information Engineer, WNISR Database Manager
• Éric Mauvière, Statistician and Trainer (icem7)
• Mycle Schneider, Independent Analyst, Coordinator and Publisher of the WNISR

For any question, remarks, or corrections regarding the content of this visualization, please get in touch with julie@worldnuclearreport.org; for all technical issues please inquire with contact@visionscarto.net.