Since 1996, IRSN, the technical support of the French Competent Authority for the safety of transports of radioactive materials, has recorded the list of the difficulties most frequently encountered during the appraisal of the safety reports of package designs. This so-called "REX (experience feedback) list" takes into account the most recent evolutions of the regulations and the last technological knowledge (the risk of perforation of a package by a punch after a 1 m free drop when the package is in oblique position, the 9 m drop test of a package with slap-down, the thermal dissipation under canopies, the brittle fracture analysis at - 40°C...). IRSN's experience feedback list for the transport package design, which is published annually, is used as a guide by IRSN for their appraisals of the design safety reports and by applicants to improve their design safety reports.