The need for long-term predictions of the performance of old nuclear power plants concrete shielding all around the world has recently relaunched the issue of predictive modeling of the deterioration ...mechanisms associated to irradiated concrete, both theoretically and numerically. A robust numerical model for describing concrete affected by prolonged nuclear irradiation, based on a coupled thermo-hydro-mechanical formulation, is proposed and the main features that are phenomenologically responsible for the degradation of concrete material at the mesoscale level are discussed. The study is conducted at the mesoscale to account for the antagonist action of the cement paste and aggregates when irradiated. Radiation-induced damage is assimilated to mechanical damage in the proposed formulation in that radiation-induced volumetric expansion of aggregates is conceived as the source of triggering of damage in the surrounding paste. The numerical results for plain concrete samples exposed to severe radiation fluences and high temperature are juxtaposed with experimental data, showing that the model agrees satisfactorily with the general tendency of the irradiated concrete stiffness evolution and dehydrated water mass of the sample. On the other hand, the model tends to underestimate its global radiation-induced volumetric expansion.
► We present the effect of radiation on concrete as shielding material. ► The coupling between hydro-thermal-mechanical fields and radiation damage is shown. ► Attention is focused on numerical ...modelling of concrete in 3D domains. ► A new estimate of the radiation damage parameter is given. ► A risk assessment of concrete-radiation interactions is developed.
Concrete is commonly used as a biological shield against nuclear radiation. As long as, in the design of nuclear facilities, its load carrying capacity is required together with its shielding properties, changes in the mechanical properties due to nuclear radiation are of particular significance and may have to be taken into account in such circumstances. The study presented here allows for reaching first evidences on the behavior of concrete when exposed to nuclear radiation in order to evaluate the consequent effect on the mechanical field, by means of a proper definition of the radiation damage, strictly connected with the strength properties of the building material. Experimental evidences on the decay of the mechanical modulus of concrete have allowed for implementing the required damage law within a 3D F.E. research code which accounts for the coupling among moisture, heat transfer and the mechanical field in concrete treated as a fully coupled porous medium. The development of the damage front in a concrete shielding wall is analyzed under neutron radiation and results within the wall thickness are reported for long-term radiation spans and several concrete mixtures in order to discuss the resulting shielding properties.
In this work we report the ongoing characterization of the Sos Enattos former mine (Sardinia, Italy), one of the two candidate sites for the Einstein Telescope (ET), the European third-generation ...underground interferometric detector of Gravitational Waves. The Sos Enattos site lies on a crystalline basement, made of rocks with good geomechanical properties, characterized by negligible groundwater. In addition, the site has a very low seismic background noise due to the absence of active tectonics involving Sardinia. Finally, the area has a low population density, resulting in a reduced anthropic noise even at the ground level. This location was already studied in 2012-2014 as a promising site for an underground detector. More recently, in March 2019, we deployed a new network of surface and underground seismometers at the site, that is currently monitoring the local seismic noise. Most of the energy carried by the seismic waves is due to the microseisms below 1 Hz, showing a significant correlation with the waves of the west Mediterranean sea. Above 1 Hz the seismic noise in the underground levels of the mine approaches the Peterson's low noise model. Exploiting mine blasting works into the former mine, we were also able to perform active seismic measurements to evaluate the seismic waves propagation across the area. In conclusion we also give a first assessment about the acoustic and magnetic noise in this underground site.
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