Assessment of neutron shielding performance of nano-TiO2-incorporated cement paste by Monte Carlo simulation

Cementitious materials, such as concrete, have been widely used in nuclear reactors and neutron source research facilities as a radiation shielding material because of their cost-effective shielding performance. Therefore, to secure the safety of neutron radiation facilities, it is crucial to improve the radiation shielding performance of cementitious materials. TiO2 nanoparticles (nano-TiO2) are chemically stable and possess a wide range of neutron reactivity cross sections; thus, they have great potential as a filling material to enhance the neutron shielding performance of cementitious materials. In this study, the effects of the use of nano-TiO2 on the physicochemical properties (compressive strength, bulk density, porosity, and hydration products) and neutron shielding performance of cement paste are investigated. Monte Carlo N-Particle Transport Code (MCNP) was used to quantitatively simulate the neutron shielding performance of nano-TiO2-incorporated cement pastes. In the MCNP simulations, thermal (0.025 eV), slow (0.2 eV), intermediate (1 keV), and fast neutrons (10 MeV) were exposed to nano-TiO2-incorporated cement paste walls with different thickness (0, 5, 10, 20, 30, and 50 cm). Nano-TiO2 improved the mechanical properties of the cement paste by decreasing the number of nanosized pores (12 nm - 36 mu m). MCNP simulation further showed that nano-TiO2 enhanced the shielding performance of cement paste at the energy levels of thermal, slow, and intermediate neutrons. Moreover, the neutron shielding performance of cement paste improved as the amount of nano-TiO2 added increased. As the thickness of the shielding wall increased, the effect of added nano-TiO2 increased.