Montreal Nuclear Services
Perform fuel cooling and ECC conditioning analyses for pressure tube/calandria tube rupture with consequential end fitting failures.
In the Gentilly-2 Safety Report, a pressure tube rupture initiating event is considered. However, the calandria tube is assumed to stay intact following the pressure tube rupture and the moderator is credited as the ultimate heat sink.
Experiments have shown that it is possible that in some cases a pressure tube rupture can be followed by a calandria tube rupture and end fitting ejections, leading to a moderator drainage.
The work consisted in identifying the scenarios to analysed, developing methodologies and assumptions and performing the simulations. A close link with the probabilistic safety assessment (PSA) was required to identify the scenarios.
Coupled thermalhydraulics/containment simulations (CATHENA-GOTHIC) were performed to assess the temperature of the reactor building sump water, which is pumped by the low pressure emergency core cooling system. Public dose calculations were also performed.
An analysis was also performed to verify that the ECC conditioning signal was reached in all cases, using again thermalhydraulics and containment codes.
The work was contracted by Hydro-Québec to AECL (Atomic Energy of Canada Ltd). Gilles Sabourin assumed technical supervision. Pascal Hernu performed containment analysis (including heat sink, ECC conditionning signal, radionuclide transport and retention) and analysis of doses to the public. Michel Saint-Denis was the PSA specialist.
NOTE: This work was performed / lead by MNS personnel during their previous employment
Development of a detailed methodolog
Modifications to the CATHENA thermalhydraulic model for a detailed representation of the ECC low pressure system.