ROBATEL-CEA'S NEW ANSWER TO THE ISSUE OF EVACUATION OF CEA'S HISTORICAL WASTE: TIRADE-R76 PACKAGE

For the evacuation of its high and intermediate level waste drums (HILW) stored in its ancient facilities, the CEA has commissioned ROBATEL Industries to design and manufacture 4 casks of a new fissile B(M) type package (named TIRADE or R76). TIRADE/R76 transport cask shall replace the actually used DGD/R66 packaging (already designed by ROBATEL Industries for the CEA in 1996) because of increasing difficulties to obtain new certificates of approval. The new cask has to meet two main objectives for the CEA: the transport of the primary ILW drums to CEA’s reconditioning facilities before long-term storage, and secondly the transport of HLW drums to DIADEM, a new facility where all CEA’s HLW waste will be collected. However, these waste drums contain organic materials thought to produce hydrogen, a highly flammable and explosive gas, by combined phenomena of radiolysis and thermolysis. These phenomena are strongly driven by nature and residual heat of the radioactive contents as well as temperatures reached during transport. The current DGD/R66 packaging cannot meet the CEA’s future transport needs because the specifications of the HILW waste drums to be transported are not compatible with the data underlying the initial safety studies, especially with respect to the residual heat to be considered. Therefore, the new TIRADE/R76 cask will present significantly increased performances especially regarding its mechanical behavior towards the risk of an internal hydrogen explosion. The purpose of this paper is to present the original approach adopted by the CEA and ROBATEL Industries to develop this new package design. In addition to the safety justifications that aim to demonstrate the absence of risk of explosion in the package during the transport, the packaging has been nevertheless designed to withstand a possible internal explosion. These studies were conducted on the basis of physical explosion tests on an instrumented life-size model that allowed then to analyze the package’s mechanical behavior by numerical simulations. The CEA and ROBATEL Industries thus suggest a pragmatic and robust safety justification of the future TIRADE/R76 transport cask incorporating in its design an additional internal explosion test, not specifically required by the regulations.