EEI/EPRI FUEL DENSIFICATION PROJECT.

The EEI/EPRI Fuel Densification Program was initiated in March 1973 to investigate the principal causes of in-reactor densification in sintered UO//2 pellet fuel. This research program conducted by Battelle, Pacific Northwest Laboratories was initiated in response to an industry-wide problem and was sponsored by the Edison Electric Institute (EEI) and eleven nuclear-oriented industrial organizations. The objectives of this program were to investigate in-reactor densification of sintered UO//2 pellet fuel and relate densification behavior to pellet characteristics and irradiation conditions. The densification behavior of well-characterized UO//2 pellets was evaluated in a parametric study in which fuel pellet characteristics and experimental parameters were optimized to study those phenomena of primary interest. Another major feature of the program was the extent of pre- and post-treatment characterization of the fuel pellets utilizing specialized techniques. A significant results of this program was the demonstration that sintered UO//2 pellet fuels with specific ranges of microstructural characteristics are stable with respect to densification. The results of the experimental program also show that for the fuel types studied, the propensity for sintered UO//2 pellet fuel to undergo irradiation-induced densification can be correlated with fuel microstructure. In addition to providing data that relates to an improved understanding of in-reactor fuel densification, the results of this study provided supportive data related to the design and production of sintered UO//2 pellet fuel that is stable during irradiation.