Structural effects of radiation-induced volumetric expansion on unreinforced concrete biological shields

Limited literature (Pomaro et al., 2011, Mirhosseini et al., 2014, Salomoni et al., 2014, Andreev and Kapliy, 2014) is available on the structural analysis of irradiated concrete biological shield (CBS), although extended operations of nuclear powers plants may lead to critical neutron exposure above 1.0 × 10+19 n cm−2. To the notable exception of Andreev and Kapliy, available structural models do not account for radiation-induced volumetric expansion, although it was found to develop important linear dimensional change of the order of 1%, and, can lead to significant concrete damage (Le Pape et al., 2015). A 1D-cylindrical model of an unreinforced CBS accounting for temperature and irradiation effects is developed. Irradiated concrete properties are characterized probabilistically using the updated database collected by Oak Ridge National Laboratory (Field et al., 2015). The overstressed concrete ratio (OCR) of the CBS, i.e., the proportion of the wall thickness being subject to stresses beyond the resistance of concrete, is derived by deterministic and probabilistic analysis assuming that irradiated concrete behaves as an elastic materials. In the bi-axial compressive zone near the reactor cavity, the OCR is limited to 5.7%, i.e., 8.6 cm (312 in.), whereas, in the tension zone, the OCR extends to 72%, i.e., 1.08 m (4212 in.). These results, valid for a maximum neutron fluence on the concrete surface of 3.1 × 10+19 n cm−2 (E > 0.1 MeV) and, obtained after 80 years of operation, give an indication of the potential detrimental effects of prolonged irradiation of concrete in nuclear power plants.