Background. The authors conducted a study to analyze the stress distribution in an End Cover – Buttress Strap – Cylindrical connection according to Users’ Spec.

Materials and methods. The authors created axi-symmetric finite element models in order to demonstrate the reaction loads and stress distribution on contact surfaces as well as stress distribution in the various regions of the model. They applied different design scenarios according to an operational (users’) spec to the models. The parameters investigated were the reaction loads at contact points and local and linearised stresses. Also each individual buttress groove was studied. Ratcheting and fatigue assessment were also addressed aligned with the stress results.

Results. The study results showed the behaviour of each buttress element under the operating loads. It also showed the location with the greatest local stress levels as well as the locations most vulnerable to ratcheting and fatigue cracking. A safety margin assessment also was carried out picturing the pressure-temperature enhancement possibilities.

Conclusions. The study indicates potential future design options for enhancing buttress type connections. It also contributes to the understanding of existing reactor damage and corrosion assessment, impacts which may be useful in the remaining life assessment and process optimisation. Fracture study also defines the most critical inspection points during the life of the reactor.

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