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Reactor Safety Criticality Coding for Multi-Unit CANDU NPP

Expert ranking of multi-unit CANDU nuclear plant components using safety criticality coding criteria
Component criticality coding at a Nuclear Power Plant (NPP)
Utilities code the components at a NPP in terms of their criticality to Reactor Safety; Production; and Cost, Conventional Safety and the Environment. The coding for each category is combined to create an overall criticality code for a component.  The overall criticality code for a component is used to prioritize maintenance activities, procurement and other operational activities.
Incorrect riticality coding may result in inappropriate maintenance and procurement strategies for components. This can negatively affect reactor safety and production.
Scope of work
Kinectrics was asked to rank the components at a multi-unit CANDU NPP using the utility’s reactor safety criticality coding criteria, which included considerations such as:
  • The degree of impairment to a system should the component fail;
  • The importance of the component to the results of the Probabilistic Safety Assessment;
  • The importance of the component to the integrity of the containment boundary; and
  • The participation of the component in the NPP’s safety-related system testing program.
Kinectrics was asked to deliver a reactor safety criticality coding database within a very tight timeline.
Kinectrics developed a strategy to create parallel work streams based on the utility’s reactor safety criticality coding criteria. In each parallel work stream, an analyst developed coded component lists based on a single unit or single train of a system.  Tools were developed to replicate the coding across other trains and units, and to identify discrepancies between trains or units for detailed review and resolution.
The results from each parallel work stream were integrated into a single database, and conflicts were resolved.
The tight timeline was achieved by deploying a team of 18 analysts and system experts to prepare and independently review the component lists and databases. Client review was integrated directly into list and database preparation to ensure the timely acceptance of the component lists and databases.

Results and client benefits
The Kinectrics team coded approximately 80,000 components. The Reactor Safety criticality coding database was delivered within the very tight timeline specified by the client:
  • The database is now consistent with the utility’s Reactor Safety criticality coding criteria.
  • The rationale for the criticality coding can now be tracked for specific components through elements of an electronic database.
  • Kinectrics suggested improvements in the criticality coding scheme to further focus the coding on reactor safety importance. 
The client has integrated the Reactor Safety coding database into its operational programs.