Failure of pressurized reactor vessels due to severe pressure transients

A particular family of severe accidents, will be considered, namely uncontrolled pressure transients, to assess whether it is possible to guarantee that the incident sequence leads to limited structural damage or to the loss of sealing of the vessel. With a detailed study of the deformation behavior of flanges and O-Rings, based on both finite element analysis and simple model, the sealing at the flange/O-Ring interface of an AP600-like vessel is investigated. The theoretical pressure level at which the sealing is lost depends on both bolt tightening and O-Ring design. The obtained results demonstrate that, under some circumstances, the sealing is lost and, consequently, the primary circuit is depressurized, before that a serious structural damage of the vessel occurs. A simple methodology that permits rapid and reasonably accurate analysis for assessing the sealing of AP600-like vessel was developed. This methodology is easily applicable to other plant-types. (author). 4 refs., 8 figs., 1 tab