Mechanical behaviour of a gamma radiography device subject to the plate drop test, with or without its additional overpack[Comportement mécanique d'un gammagraphe soumis à une compression dynamique (chute de plaque), avec ou sans son suremballage]

The IAEA Regulations for the Safe Transport of Radioactive Material (No. SSR-6 Rev. 1, 2018 edition) define, in paragraphs 659 and 685 respectively for Type B and fissile packages, the conditions to carry out a dynamic crush test (9-meter drop test of a 500-kg plate onto the package) in place of the 9-meter free drop test. Those conditions include a mass not greater than 500 kg, an overall density not greater than 1 000 kg/m3 based on the external dimensions and, for type B packages, the radioactive contents (other than special form radioactive material) greater than 1 000 A2. Package designs sometimes fulfil only one of these conditions (mass or density) or present characteristics that are very close to them, and thus are subject to a 9-meter free drop test as part of the demonstration of their ability to withstand accidental conditions of transport. For those, even if not regulatorily required, IRSN (now ASNR) has studied the consequences of a dynamic crush test. This study considers a gamma radiography device whose mass is much less than 500 kg, but its overall density is much higher than 1 000 kg/m3. After ensuring that the numerical model reproduces with accuracy the actual 9-meter free drop tests of this device with and without its additional overpack, IRSN has compared the associated numerical results with those simulating dynamic crush tests for the same configurations. The objectives are to evaluate: • the behaviour of the gamma radiography device, with and without its overpack, especially within the context of emergency preparedness and response involving an accident on such a package; • the safety margins offered by its additional overpack. The study addresses particularly the risk of source ejection, the general deformation of the radiological protection (depleted uranium block), and the possible consequences on the emergency teams.