Analysis to evaluate predictors of fiberboard aging to guide surveillance sampling for the 9975 life extension program

During surveillance of the 9975 shipping package at the Savannah River Site K-Area Complex, several package dimensions are recorded. The analysis described in this report shows that, based on the current data analysis, two of these measurements, Upper Assembly Outer Diameter (UAOD) and Upper Assembly Inside Height (UAIH), do not have statistically significant aging trends regardless of wattage levels. In contrast, this analysis indicates that the measurement of Air Shield Gap (ASGap) does show a significant increase with age. It appears that the increase is greater for high wattage containers, but this result is dominated by two measurements from high-wattage containers. For all three indicators, additional high-wattage, older containers need to be examined before any definitive conclusions can be reached. In addition, the current analysis indicates that ASGap measurements for low and medium wattage containers are increasing slowly over time. To reduce uncertainties and better capture the aging trend for these containers, additional low and medium wattage older containers should also be examined. Based on this analysis, surveillance guidance is to augment surveillance containers resulting from 3013 surveillance with 9975-focused sampling that targets older, high wattage containers and also includes some older, low and medium wattage containers. This focused sampling began in 2015 and will continue in 2016. The UAOD, UAIH and ASGap data are highly variable. It is possible that additional factors such as seasonal variation and packaging site location might reduce variability and be useful for focusing surveillance and predicting aging.