During the 2010 outage of Angra 2 Power Plant the expansion joints of the containment penetration JMK05D0201 (LCQ50) which belongs to the blowndown system were found very distorted as shown in Fig. 1. The cause was an inadvertent over pressurization made during monthly tests to verify the set pressure. In order to leave the damaged expansion joint installed during one cycle, Eletronuclear conducted an elastic-plastic analysis which has demonstrated the joint could be in the position up to the next Angra 2 outage, in March 2012.
Considering that the option to replace the damaged expansion joint by another one is extremely complex, Eletronuclear decided to keep it in place and cover it by an expansion joint designed to resist all loads predicted in the original design specification. This new design is a two-sided (bipartite) bellows with longitudinal field welds.
This paper presents the fatigue and stress analysis of the bipartite overlapping expansion joints considering the loads defined in the design specification. Based on the results obtained, fatigue is not a concern and stress/strains are kept under acceptable values for all loading conditions. In addition, it also was demonstrated that the original design of the blowdown system was not impacted by the proposed design of the bipartite joint.