Design Assessment of a dual purpose cask for damaged spent nuclear fuel

A German package design approval certificate was recently issued for a dual purpose cask package design for encapsulated damaged spent nuclear fuel (SNF). A comprehensive assessment procedure was carried out by the competent authority BAM with respect to the mechanical and thermal design, the activity release of radioactive material and quality assurance aspects for manufacturing and operation. The objective of this procedure was to verify the documentation including analyses of the Package Design Safety Report (PDSR) fulfils the requirements of the IAEA regulations. Up this approval, German package designs considering standard fuel assemblies with defined specifications and properties for transport and interim storage. Due to the nuclear power phase-out in Germany all kinds of SNF e.g. damaged spent fuel rods shall be packed in transport and interim storage casks. Therefore specific requirements shall be considered in accordance with international experiences including IAEA technical reports. The main requirement for damaged SNF is a tight encapsulation with specific defined properties under transport and storage conditions. Due to the interim storage period the encapsulation shall be long term durable. Thus qualified specific loading and drying procedures are necessary. BAM assessed these drying procedures taking into account long-term behavior of the encapsulation and the suitability of the drying equipment. This special equipment shall be qualified in a “cold handling”. In addition, it shall be shown that the behavior of the test equipment used in the qualification process is comparable with the original equipment, e.g. test fuel rods or test encapsulation. In the development of the drying process experience was obtained in how to put the requirements of the IAEA into practice. The present paper gives an overview of the assessment procedures and experience made by BAM and point out the main resulting requirements on drying processes for these kinds of encapsulations.