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

Abstract

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, reinforcement 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.

VERA-Grizzly Ex-Core Calculations: Watts Bar Unit 1 Cycles 1-2

“…The simulations were conducted up to a maximum fluence of 5.7 × 10 19 n.cm −2 at E > 0.1 MeV at the surface of the concrete, a value considered conservative for 4-loop PWRs (Esselman and Bruck [2013]). The results of the simulation are consistent with previous literature studies (Pomaro et al [2011], Salomoni et al [2014], Andreev and Kapliy [2014], Le , Giorla et al [2016], Bruck et al [2019], Kambayashi et al [2020]).…”

“…Limited literature is available on the structural significance of irradiation for concrete primarily because irradiated concrete has been mostly studied with the perspective of material design and qualification. Nevertheless, a few structural models for concrete containment and internal structures [Mirhosseini, 2010, Mirhosseini et al, 2014 and for shield structures [Pomaro et al, 2011, Salomoni et al, 2014, Andreev and Kapliy, 2014, Giorla et al, 2016, Bruck et al, 2019, Kambayashi et al, 2020 were recently published.…”

“…Finally, Kambayashi et al [2020] developed a lattice-based meso-scale model of a portion of a prototypical CBS. Aggregates and reinforcing bars are explicitly represented.…”

Catalogue of Radiation-Induced Damage of Rock Aggregates Identified by RBSM Analysis

“…The creep of the rocks was not taken into account in the proposed numerical model. However, this neglected effect may be significant for sedimentary silicate rocks due to the fact that the experimental data were obtained at the average irradiation temperature from 85°C to 215°C (Denisov et al 2012) and since it is known that the creep can reduce the rate of radiation-induced damage (Giorla et al 2017;Kambayashi et al 2020).…”

“…Based on the relevant research (Hilsdorf et al 1978;Field et al 2015;Le Pape et al 2016), the radiation-induced volumetric expansion (RIVE) of rock aggregates in concrete composition is considered to be the principal cause of concrete deterioration under ionizing conditions. Then, the RIVE of rock aggregates may lead to significant concrete damage which may result in cracks in CBS which consequently compromise its shielding and load-bearing properties (Le Pape 2015; Bruck et al 2019;Kambayashi et al 2020). Due to this fact, the RIVE and the related deterioration of rock aggregate mechanical properties need to be predicted.…”