Montreal Nuclear Services

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Analysis of PHT System Events



Perform analyses of primary heat transport system events at the Gentilly-2 nuclear power plant.


In order to comply with regulatory requirements from the Canadian Nuclear Safety Commission (CNSC), Hydro-Québec was required to perform detailed safety analyses for primary heat transport system events at the Gentilly-2 nuclear power plant for:

  • Assessing safety improvements such as the addition of new trip parameters
  • Performing new analyses that were not part of the Gentilly-2 Safety Report prior to refurbishment
  • Assessing the impact of fresh fuel at beginning of life

​The industry-standard-tools (IST) codes that were used are CATHENA for the primary and secondary side thermalhydraulics, and fuel heat transfer, ELOCA for detailed analysis of the fuel behaviours, TROLG2 for the primary and secondary circuit control and RFSP/CERBERUS for the 3D core neutronics power. The design basis accidents that were considered are large LOCA, small LCOA and loss of flow. Large LOCAs are always performed with a complete thermalhydraulics/physics coupling. During this project, several loss of flow and small LOCA cases were also performed with coupled codes. In the loss of flow, the initiating events considered were total loss of class IV power, single pump trip and pump seizure.

​For each design basis accident, the work consisted of identifying credible and limiting accident scenarios at different power levels and fuel cycle, define the methodology, perform analyses and verify that results met the acceptance criteria. Another objective was to update the Safety Report for these scenarios. 

​The work was contracted by Hydro-Québec to AECL (Atomic Energy of Canada Ltd).  Gilles Sabourin assumed technical supervision. Pascal Hernu performed the containment and dose calculations. Elisabeth Varin participated extensively in the coupled analyses

NOTE:  This work was performed / lead by MNS personnel during their previous employment


  • CATHENA primary heat transport system model and TROLG2 reactor control model

  • CATHENA/RFSP coupling model.

  • Three Methodology Reports and four Analysis Reports​​​


  • Thermalhydraulics
  • Reactor Core Physics



Gentilly-2, Canada



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