Creep and Shrinkage in Reactor Containment Shells

The nonuniformity of creep and shrinkage caused by drying, and to a lesser extent by temperature gradients, causes significant self-straining in containment shells. This condition can be of two types: (1) Local, within the cross section of the wall, or (2) global, due to differences in the deformation of the cylindrical shell and foundation slab, or the dome, the ring, and the hoop tendon buttresses. By approximate calculations, in which cracking is neglected, these effects are shown to be quite significant as compared with other loads in service conditions, whose effect is also normally evaluated without consideration of cracking. For quantitative design predictions, the stress relief due to cracking must be considered. By means of a numerical example, it is demonstrated that the age-adjusted effective modulus method permits a very simple analysis of these effects.