Spent nuclear fuel integrity during dry storage

Information on spent fuel integrity is of interest in evaluating the impact of long-term dry storage on the behavior of spent fuel rods. Spent fuel used during cask performance tests at the Idaho National Engineering and Environmental Laboratory (INEEL) offers significant opportunities for confirmation of the benign nature of long-term dry storage. The cask performance tests conducted at INEEL between 1984 and 1991 included visual observation and ultrasonic examination of the condition of the cladding, fuel rods, and fuel assembly hardware before dry storage and consolidation of the fuel; and a qualitative determination of the effect of dry storage and fuel consolidation on fission gas release from the spent fuel rods. A variety of cover gases and cask orientations were used during the cask performance tests. Cover gases included vacuum, nitrogen, and helium. The nitrogen and helium backfills were sampled and analyzed to detect leaking spent fuel rods. At the conclusion of each performance test, periodic gas sampling was conducted on each cask as part of a cask surveillance and monitoring activity. A spent fuel behavior project (i.e., enhanced surveillance, monitoring, and gas-sampling activities) was initiated by the U.S. Department of Energy (DOE) in 1994 for intact fuel in a CASTOR V/21 cask and for consolidated fuel in a VSC-17 cask. The results of the on going gas sampling activities are reported in this paper. (author)