High-temperature creep deformation evaluation in CANDU pressure tubes under a station black-out

In this work the deformation of pressure tubes in CANDU6 nuclear reactor under a Station BlackOut event is analyzed. Firstly, the thermal–hydraulic simulation of the whole reactor is carried out using RELAP5Mod3 in order to get the spatial and temporal temperature profiles along the axial coordinate for five representative coolant channels in the core. Then, these temperature fields are mapped into a mechanical model for the PT to estimate the creep deformation by ballooning. Without consider the CT, the pressure tube to Calandria tube contact was estimated with relative accurate added to the contact location and area of contact in time. To address the mechanical model a novel 3D code based on correlations of Shewefelt effective strain for Zr–2:5%Nb alloy is developed in OpenFoam-5.0. This pressure tube to Calandria tube contact causes a large heat transfer from the coolant to the moderator giving an additional heat sink, which should be carefully considered during the progression of the Station BlackOut event.