BEHAVIOUR OF METALLIC SEALS IN CASTOR® -CASKS UNDER NORMAL AND ACCIDENT CONDITIONS OF TRANSPORT: QUALIFICATION REQUIREMENTS

The Federal Institute for Materials Research and Testing (BAM) is the responsible German authority for the design assessment of mechanical and thermal aspects of transport casks for radioactive materials. BAM checks applicants’ proof in their safety reports and assesses the conformity to the applicable modal regulations based on the Regulations for the Safe Transport of Radioactive Materials (TS-R-1) [1]. Containment components are classified at the highest level “No. 1” according to the German regulation for quality assurance and control of packagings for transport of radioactive materials - TRV 006 [2]. This means that comprehensive quality assurance and control are required for these components. BAM has developed quality assurance and assessment criteria for seals as an important component of containment systems. These criteria include qualification of the manufacturer, fabrication of test seals, a full qualification program for the mechanical, thermal, short- and long-term behavior of the seals, quality assurance during fabrication of original seals, arrangements after assembling and loading casks and re-inspection tests of the containment system during their usual operation. The Gesellschaft für Nuklear-Service mbH (GNS) applied for qualification of the design and the properties of metallic double jacket spring seals as components of containment systems for CASTOR® -casks. As a result, some modified design criteria for the behavior of a system consisting of metallic seals, lids, bolts and cask body have been developed. These design criteria concern the elastic compression and expansion behavior and the standard-helium-leakage-rate. This paper presents BAM requirements for a sealing qualification process and gives advice for implementation based on qualification tests performed by GNS. The results of special research by GNS were used as proof concerning tightness behavior of seals with aluminium and silver outer jackets under the influence of mechanical loading, particles and corrosion.