IRSN’s experience feedback list for the package design safety assessment

Since more than 20 years, IRSN, the French Institute for radiation and nuclear safety, assesses the safety analysis reports in order to provide technical support to the French Nuclear authorities. In this context, IRSN has recorded the list of specific points most frequently encountered during the assessment of the safety demonstrations to which a special attention should be paid.This experience feedback list has evolved over the last years to take into account the most recent evolutions of the regulations and the last technological knowledge.It appears that some issues shall be taken into account in the first stages of a package development. In particular, IRSN put in the light the necessity to justify the mechanical behaviour of the package, during a 9 m free drop test simulating the accident conditions of transport (ACT), considering the delayed impact of the content and the internal arrangements onto the components of the closure system of the cavity.Furthermore, some internal gaps, which could induce movements of the radioactive contents, should be minimized to justify notably that this phenomenon would not induce an external dose increase greater than 20 % in normal conditions of transport.IRSN also highlighted that justifications relative to the transport of radioactive material under special form, such as sources, within the package cavity cannot be based only on the tests performed according the 2919 ISO norm. Complementary justifications have to be provided especially to conclude on the integrity of the source capsule during the regulatory ACT tests.Furthermore, due to recent tests results, IRSN considers that a specific attention should be paid on the thermal behaviour of packaging made of polyurethane foam in case of fire exposure.Finally, IRSN recommends to avoid the use of bolts with grade 14.9 due to the sensibility of the material to hydrogen embrittlement and the associated risk of fracture at ambient temperature. Concerning the bolts grades 10.9 and 12.9, IRSN considers that a specific attention shall be paid during manufacturing by introducing systematic hydrogen degassing. A relevant final control procedure has also to be put in place to guarantee the conformity of the bolts. IRSN’s experience feedback list for the transport package design is used as a guide by IRSN for the appraisals of the design safety reports and by applicants to improve their design safety reports.