Developing an insulation material for Type B shipping containers

The Y-12 National Security Complex develops Type B shipping containers for various U.S. Department of Energy (DOE) missions. For the past 10 years, new shipping container designs used a cast ceramic material as the insulation in the outer drum for the purpose of impact limiting and thermal resistance. The material used in these containers has been a commercial product known as Kaolite 1600™, which is a pre-mix concrete product. During current fabrication of the Y-12 container known as the MD-2, the Kaolite 1600™ 'after-casting' density was slightly above the required density in the container design specifications. After repeated sample castings of Kaolite 1600™, an acceptable density could not be achieved. Over a subsequent 6-month period, Y-12 worked with the supplier to understand the discrepancies and several attempts were made to re-create the original product. The end result was that changes in the batch mixing process and origin of raw materials produced a slightly different final product, and the original product could not be re-created by this manufacturer. Kaolite 1600™ still meets the needs of industrial users, but no longer meets the precise property requirements needed for Y-12 containers. It became apparent that Y-12 would have to substitute this material in the MD-2 and all future container fabrications. To replace Kaolite 1600™, Y-12 initiated a program to develop a new, but similar material. A mixture was made with essentially the same ingredients as Kaolite 1600™, but mixed to more exacting proportions. The new mixture, termed Packcrete, has comparable material properties to Kaolite 1600™, as seen in laboratory testing. Specific mechanical and thermal tests were designed to show equivalent properties to Kaolite 1600™, as analyzed in the MD-2 Safety Analysis. Moving forward, Y-12 plans to fabricate MD-2 prototypes with Packcrete and subject them to full-scale regulatory drop and burn testing in accordance with US Code of Federal Regulations (10 CFR 71.71 and 71.73). (author)