Gap formation between steel liner and cylinder wall in reactor containment buildings

In Sweden, holes have been drilled through the containment walls of four reactors. Following drilling, gaps were observed between the inner concrete surface and the steel liner. Such gaps may adversely affect containment performance by altering its mechanical behavior under accident loading.

This report suggests that the observed gap formation between the steel liner and the inner concrete wall is a consequence of uneven shrinkage effect together with the hole making process of drilling and releasing of prestressing force. Furthermore, the conclusion that in a defect free concrete the risk of gap formation in a concrete containment wall with a steel liner embedded is low.