Thermal analysis of 9977 radioactive material package

摘要

The 9977 package is a certified type B transportation packaging that was designed to transport radioactive materials with a decay heat load of up to 19 W. The packaging was recently modified to accommodate increased content heat load (up to 38 W) by employing an aluminium heat dissipating sleeve outside the containment vessel (CV), as well as an aluminium spacer inside the CV holding two 3013 containers. This paper provides highlights of thermal analyses of the modified 9977 package that were performed to evaluate its compliance with the 10 CFR 71 regulatory safety requirements. Parametric studies were also performed to examine effects of (ⅰ) surface properties, e.g. light absorptivity and emissivity, of the packaging; (ⅱ) total decay heat loads, ranging from 18 to 38 W; and (ⅲ) distribution of decay heat load inside the CV on the temperature of the Viton O-ring seal. The results of thermal analyses show that for the normal condition of transport with insolation, increasing absorptivity and decreasing emissivity increase the temperature of the O-ring; decreasing heat load decreases the temperature of the O-ring, whereas changing heat load distribution has little effect on the temperature of the O-ring. Likewise, changing the thermal conductivity of the spacer inside the CVhas little effect on the temperature of the O-ring. Briefly discussed is the possible extension of the annual maintenance interval of the 9977 package, based on previous work and the data obtained in the long-term leak performance tests conducted by the Savannah River National Laboratory.