Creep and shrinkage of Intermediate Level Long Life containers concrete comparison between gamma-irradiated and non-irradiated material

Abstract : Many of the facilities and structures involved in the radioactive waste repository call for reinforced concrete (RC) in their construction. RC is used for containers as well as for surface and deep geological structures. In this paper we will focus on concrete containers (about 2 cubic meter) which would receive 1 to 4 waste containers (steel or concrete waste packages) of Intermediate Level Waste Long Lived (ILW-LL). With regards to the present disposal concept these containers would be placed one above the others up to 4 levels in the repository cells. In such context, Andra has to demonstrate the continuous mechanical integrity of the structure all over the operating / reversibility period.Classical mechanical properties of this concrete, as compressive strength, tensile limit and Young modulus are well known in classical non irradiated environment and must be confirmed in irradiated environment. This present study deals with the assessment of creep, shrinkage and others physical properties both under and out gamma irradiation, the samples being at the same thermal and hydric conditions.Specific experiment has been developed to address these parameters using cylindrical concrete dedicated to creep measurement and prisms dedicated to shrinkage.Samples are split in two groups, half irradiated and half non-irradiated. Gamma-irradiation has been carried out at the dose level representative of such ILW-LL wastes ($\approx$30 Gy/h) during 8 months to reach a total dose near to 180 kGy in average.The results show only a very small dimensional differences between irradiated and non-irradiated concrete samples in the same order of magnitude both for creep and shrinkage samples. Irradiation at such dose does not induced significate mechanical deterioration of the cementitious material.