Development and testing of the FAST fuel performance code: Transient conditions (Part 2)

This paper documents the extension of the Fuel And Sheath modeling Tool (FAST) for modeling transient conditions and presents a proof of concept validation exercise. This validation compares the predictions of FAST and ELESTRES/ELOCA fuel performance codes against experimental measurements from a simulated loss of coolant test conducted at Chalk River Laboratories. The comparison includes in reactor measurements of fuel temperature and internal gas pressure along with post irradiation (hot-cell) measurements of cladding deformation and oxidation. The results of this comparison show that the single pellet version of the FAST code was insufficient to fully account for strong axial dependence along an element. This was addressed by modifying the FAST code geometry to allow an arbitrary number of pellets in the fuel-stack. This full element version demonstrated improved agreement with measured cladding deformation, including circumferential ridging effects.