Quality Assurance in Fabrication and Operation of Dual Purpose Casks for Spent Nuclear Fuel in Germany

In Germany spent nuclear fuel is stored under dry conditions in dual purpose casks (DPCs). Until a final repository will be available, the casks are kept in central and on-site interim storage facilities. In addition, the transportability of the DPCs at any time is required. Therefore, quality assurance in design, fabrication and operation of the DPCs is of particular importance. The system of quality assurance measures applied in Germany is presented.For the legal scope of transport the approval certificate holder is responsible for the determination of quality assurance measures, whereas for legal scope of storage the storage license holder is responsible. Hence, for almost the same technical object, two independent regular frameworks have to be applied. The measures can be categorised as system-related and design-related and are independently approved and monitored by the competent authority BAM and its authorised inspection experts. The qualification of the applicant is reviewed in the context of the design approval procedure. The qualification of manufacturer and producers is checked and documents are pre-assessed before the start of manufacture. Manufacturing inspections are carried out according the pre-assessed documents. The manufacturing inspections are completed by the inspection before commissioning. Periodic inspections during operation ensure that the properties specified in the approval certificate are preserved over package life time. The type and the time interval of periodic inspections depend on the use of the package. For transport after interim storage a system of specific tests and inspections is prescribed.How transportability can be retained over 20 years of interim storage is exemplified by the package CASTOR® THTR/AVR with SNF inventory of decommissioned gas cooled high temperature research reactor in Jülich, Germany. The 20 years storage license ended in 2013, therefore a transport has to be taken into consideration. The transport preparation includes repair and testing of trunnions, examination of bolting torque of lid bolts and leak-tightness tests of lid systems. A large part of the transport preparation has completed. It will be reported on lessons learned in inspections before transport and on the current status of transport preparation.