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Emergency power systems at Canadian nuclear power plants, including portable alternating current power sources

An abstract of the technical document presented:
Emergency Power Systems at Nuclear Power Plants Symposium
Munich, Germany
April 23–24, 2015

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


The presentation provides a brief description of electrical power systems at Canadian nuclear power plants (NPPs), which are designed to satisfy the high safety and reliability requirements for nuclear systems. This is generally based on the following principles:

  • two-group design philosophy (Group 1 and Group 2 electrical power systems)
  • five distinct classes of power (Classes I–IV are designated as Group 1, and the emergency power system as Group 2)
  • the capability to transfer power between units in a multi-unit plant

The presentation focuses on the Canadian practice of setting up emergency power systems as follows:

  • two separate groups of onsite power generators: Class III standby generators (SGs) and emergency power generators (EPGs)
  • up to four Class III standby generators to cope with loss of Class IV power, and at least two EPGs to cope with specific external events (i.e., earthquakes, tornadoes, fires)
  • EPG capacity
  • EPG mission time
  • EPG start-up and running capability tests
  • EPG loading capability test
  • fuel management supply system
  • EPG maintenance
  • aging management implementation (programs, condition assessments, obsolescence)
  • inspections and regulatory oversight

Following TEPCO’s Fukushima Daiichi accident in 2011, CNSC staff tasked all Canadian NPP operators with deploying additional emergency power supplies to the already robust CANDU electrical power systems, as part of the emergency mitigating equipment (EME). This included requirements for backup portable diesel generators, storage facilities, fuelling supplies and EME guidelines for testing, maintenance and training.

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