The effective gradient method in the fuel bowing problem

An analytical model of reactor fuel element bowing, caused by three main factors: (1) nonuniform fission density across the fuel pin, (2) eccentric arrangement of the pin inside the cladding and (3) nonsymmetrical angular dependence of the cooling temperature, is suggested. The summary action of the factors mentioned gives some vector (bowing temperature gradient) which directly determines the character of the bowing of the fuel elements. The system of ordinary equations obtained allows one to calculate, comparatively easily, the bowing of any element contained in a fuel assembly. 13 refs., 1 fig