Qualification Test Program of Polyisocyanurate Rigid Foam for the Use in Type B(U)F Packages

It is a common practice to use polyurethane foam in packages for radioactive material due to its good mechanical properties acting as shock absorber combined with a good thermal protection. The company DUNA-Corradini, developed a polyisocyanurate rigid foam, which is a further development of polyurethane foam providing superior mechanical rigidity, temperature resistance and fire reaction. The intention of DUNA-Corradini and DAHER-NCS is to qualify these foams for nuclear packages, especially for the DN 30 designed by DAHER-NCS as a protective structural package for 30B cylinders. Most of the qualification tests were performed at MPA Stuttgart (Germany) using a guided drop rack. Influence of temperature in a range from -40° to +80° C, humidity, cumulative loads and foam cells orientation were taken into consideration. Another major issue of this qualification program was to investigate the differences between static and dynamic conditions. For the dynamic drop tests, in order to achieve the best comparable results to the drop test conditions defined by IAEA, a drop height of nine meters was chosen. The weight of the drop mass was adjusted to the foam properties to achieve an impact energy comparable to the characteristics in the package. In these drop tests, force and acceleration are measured, as well as deformations detected by optical measurement methods with a sampling rate of 100 kHz over the whole impact. From this curve other quantities, such as energy absorption and compression strength of the foam can be determined. The results of this qualification tests show a very high reproducibility with tight tolerances and little variation of the measured values. This, along with the availability of several densities of the foam (resulting in a well controllable and adaptable compression strength), allows accurate prediction in FE simulations of the overpack behavior and a high standard in quality control of its serial production.