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Offsite and Onsite Power Supplies at Canadian Nuclear Power Plants

Abstract of the technical paper presented at:
24th International Conference on Nuclear Engineering (ICONE 2016)
Charlotte, North Carolina, USA
June 26–30, 2016

Prepared by:
Jasmina Vucetic and Nadine El Dabaghi
Canadian Nuclear Safety Commission


This presentation provides an overview of the electrical power systems (EPS) at Canadian CANDU plants, and includes related regulatory oversight activities. The systems are designed to satisfy the high safety and reliability requirements for nuclear systems. They rely on diverse, multiple and independent sources (defence-in-depth strategy) as follows:

  • offsite power: supply from grid
  • onsite power: supply from (1) the unit itself, (2) other units in a multi-unit plant, (3) the standby power supply, (4) batteries, (5) emergency power supply, and (6) alternate AC power supply

Furthermore, the presentation addresses the following requirements to improve the availability and reliability of offsite and onsite AC power supplies to CANDU plants:

  • grid reliability (switchyard between the stations and the grid)
  • classification of the EPS power supply
  • Group 1 EPS (four distinct classes of power according to the acceptable duration of voltage interruption to the loads that they supply)
  • Group 2 EPS (emergency power supply – a minimum of two generators to cope with specific external events (i.e., earthquakes, tornadoes, fires))
  • dual bus configuration for EPS (odd and even divisions)
  • alternate AC power supply (post-Fukushima enhancement – additional backup portable diesel generators to cope with station blackout conditions)

To obtain a copy of the abstract’s document, please contact us at or call 613.995.5894 or 1.800.668.5284 (in Canada). When contacting us, please provide the title and date of the abstract.

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