Consideration of Hazards in Safety Analysis

Abstract of the technical presentation presented at:
IAEA Workshop on the Consideration of Hazards in Deterministic Safety Analysis
July 24-28, 2023

Prepared by:
Noreddine Mesmous
Canadian Nuclear Safety Commission

Abstract:

This technical presentation summarizes the Canadian Nuclear Safety Commission (CNSC) regulatory requirements and guidance for the consideration of hazards in safety analysis.

The presentation is based on the following CNSC regulations and regulatory documents:

• General Nuclear Safety and Control Regulations
• Class I Nuclear Facilities Regulations
• Radiation Protection Regulations (all requirements related to dose)
• REGDOC-1.1.1, Site Evaluation and Site Preparation for New Reactor Facilities
• REGDOC-1.1.2, Licence Application Guide: Licence to Construct a Reactor Facility
• REGDOC-1.1.3, Licence Application Guide: Licence to Operate a Nuclear Power Plant
• REGDOC-2.5.2, Design of Reactor Facilities
• REGDOC-2.4.1, Deterministic Safety Analysis
• REGDOC-2.4.2, Probabilistic Safety Assessment
• REGDOC-2.4.4, Safety Analysis for Class IB Nuclear Facilities

Hazard analysis is recognized to be an important part in demonstration of the safety case for a nuclear facility. Hazard analysis is a systematic evaluation (identification, characterization and assessment) of hazards (internal, external, human-made and natural events) that could cause the identified hazards to initiate faults in the facility (postulated initiating events - PIEs) that could develop into accidents.

A comprehensive Probabilistic Safety Assessment (PSA) considers the probability, progression and consequences of equipment failures or transient conditions, to derive numerical estimates for the safety of the plant. Core damage frequency is determined by a Level 1 PSA (small release frequency), and large release frequency is determined by a Level 2 PSA.

Deterministic Safety Analysis (DSA) is an analytical study used to demonstrate how safety requirements are met for a broad range of operating conditions and various initiating events. The objectives of DSA are to confirm that the design of an NPP meets design and safety requirements; derive or confirm operational limits and conditions that are consistent with the design and safety requirements for the NPP; assist in establishing and validating accident management procedures and guidelines; and assist in demonstrating that safety goals, which are established to limit the risks posed by the NPP, are met.

In summary, CNSC regulatory requirements ensure that the aspects and provisions applicable to hazards are adequately addressed in safety analysis. Based on these analyses, the capability of the design to withstand PIEs and accidents shall be confirmed, the effectiveness of the items important to safety demonstrated, and requirements for emergency response established. The results of the safety analyses shall be fed back into the design.

To obtain a copy of the abstract’s document, please contact us at cnsc.info.ccsn@cnsc-ccsn.gc.ca or call 613-995-5894 or 1-800-668-5284 (in Canada). When contacting us, please provide the title and date of the abstract.