PCI analysis of a stainless-steel cladding fuel rod for a small-sized PWR under power ramping conditions

In order to evaluate the behaviours of a fuel rod for a small sized PWR, PCI analysis has been carried out, with special emphasis on the performances for a rapid power ramping that is important for this type of reactor. The analytical procedures used were divided into two phases. First, the whole-rod-wise calculation was performed by using a general fuel performance code, and the fundamental behaviours of rod were obtained for an averaged operational history over the life of rod. Then, these results were transfered to the second phase analysis, in which very localized PCI behaviours were calculated by using a finite element program. One radial slice was taken out of the axial position of rod where the severest PCI was expected to occur, and it was analyzed in detail for a rapid power ramping condition, taking special consideration for the pellet relocation effect. On the choice of the other calculational conditions, the worst combination of parameters was assumed. It was found, from the results of analysis, that in spite of the conservative calculational conditions, the stresses in clad were well below the clad strength criteria, and excellent performance for power ramping is expected. (author)