Rating Definitions

CNSC inspector

A CNSC inspector at the Pickering Nuclear Generating Station. The white tower is part of an emergency
injection cooling system, one of the facility's many safety features. Pickering, Ontario, Canada

Updated January 27, 2022

Safety performance rating

The performance ratings used in the 2020 report on the safety of Canada's nuclear power plants are defined as follows:

Satisfactory (SA)

Licensee meets all of the following criteria:

  • Performance meets CNSC staff expectations
  • Licensee non-compliances or performance issues, if any, are not risk-significant
  • Any non-compliances or performance issues have been, or are being,
    adequately corrected

Below Expectations (BE)

One or more of the following criteria apply:

  • Performance does not meet CNSC staff expectations
  • Licensee has risk-significant non-compliance(s) or performance issue(s)
  • Non-compliances or performance issues are not being adequately corrected

Unacceptable (UA)

One or both of the following criteria apply:

  • Risk associated with a non-compliance or performance issue is unreasonable
  • At least one significant non-compliance or performance issue exists with no associated corrective action

Rating methodology

CNSC site staff member

A CNSC site staff member inspects an instrument panel at the pumphouse that draws cooling water from Lake Ontario, at the Darlington Nuclear Generating Station.
Bowmanville, Ontario

The determination of the rating in each safety and control area is based on considerations of individual findings from inspections, event reports and desktop reviews.

Step 1: Identify findings

The findings are identified for each specific area using information from a variety of sources, including inspections, event reviews and desktop reviews. Findings are evaluated against a set of compliance criteria developed for each specific area that measure the degree of conformity with legal requirements.

Step 2: Assess findings

CNSC staff evaluate the findings against the compliance criteria and assign one of five possible finding assessments, high, medium, low, negligible or positive. The finding assessment category depends on the degree of negative impact on the effectiveness of the specific area as given in the manner defined in table 1 below.

Table 1: Findings assessment categories
Findings Category Definition
High Major negative impact on effectiveness of safety and control measures in the specific area; evidence of breakdown.
Medium Significant negative impact on effectiveness of safety and control measures in the specific area.
Low Small negative impact on effectiveness of safety and control measures in the specific area.
Negligible Insignificant impact on effectiveness of safety and control measures in the specific area.
Positive Evidence that the specific area is effective.

Step 3: Rate the specific areas

CNSC staff consider the relevant findings for the specific area and determine the effectiveness using a CNSC-developed guideline. The findings are judged in the context of the performance objective for the relevant SCA. The assessed effectiveness categories for all findings of a specific area are converted into a performance rating of FS, SA, BE, or UA (see performance rating definitions above).

Step 4: Rate the safety and control areas

The specific area ratings are converted to a number. Individual specific area ratings are then averaged to determine the SCA rating.

Determining the Integrated Plant Rating

The integrated plant rating (IPR) is determined for each station through averaging the values for ratings obtained in all 14 safety and control areas for each station.

The industry average SCA and IPR ratings are determined through averaging the seven individual ratings for the stations: Bruce A, Bruce B, Darlington, Pickering A, Pickering B, Gentilly-2 and Point Lepreau.

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