Numerical Analysis of a Concrete Biological Shielding Wall under Neutron Irradiation by 3D RBSM

抄録

In nuclear power plants, concretes used for biological shielding walls are exposed to radiation such as neutrons and gamma rays over the long-term operation of the plant. Previous studies have reported that neutron irradiation causes aggregate expansion due to the metamictization of quartz and feldspar leading to reduced density and a loss of the compressive strength and Young' s modulus of the concrete. Therefore, it is crucial to understand the current state of a concrete biological shield (CBS) and predict its future soundness. In this study, a rigid-body spring model, which can easily evaluate fracture behavior by using springs between each element, is used to conduct numerical analyses on a CBS. A three-phase (mortar, aggregate, and interfacial transition zone) model of a 2000 mm thick CBS is used to investigate the varying deformation responses depending on the presence or absence of reinforcing bars (rebar), creep, and an inner steel plate with five types of analyses, i.e. analysis to understand the impacts of temperature distribution, re-inforcement bars, an internal steel plate, and creep of mortar. The results show that cracking and delamination occur inside the CBS, resulting in a lack of cracking on the outside. They also show that the cracks are reduced by rebar and creep, resulting in cracks extending from the innermost edge to a depth of approximately 150 mm.