Radiation-induced Alteration of Meta-chert

Abstract

Concrete aggregate identified as "meta-chert" was irradiated with gamma-rays and neutrons. To identify the volume expansion of the aggregate under neutron irradiation, the following analyses were performed for pristine and irradiated α-quartz and metachert: X-ray diffraction (XRD)/Rietveld analysis, dimension change, water pycnometry, He-pycnometry, light optical microscopy (LOM), and scanning electron microscopy (SEM). From the difference of volume expansion observed from dimension change and water/helium pycnometry, the crack opening inside the aggregate subjected to irradiation was elucidated, and this was confirmed by LOM and SEM analysis. The crack contribution to the expansion of the aggregate was significant for neutron fluence > 6.99 × 10 19 n/cm 2 , for E ≥ 0.01 MeV. Based on the XRD analysis, changes in lattice parameters were identified and the cell volume expansion was compared with the data obtained by helium pycnometry. Based on the density change calculation and phase calculation data, the density of X-ray amorphous phase was consistent with that of expanded crystal α-quartz.

Study of Mechanical Properties of Silicate Minerals by Molecular Dynamics Simulation

“…As the physical properties of concrete depend on the properties of the aggregate, it is the behavior of the internal rock minerals that determines the properties of the aggregate. Aggregates in concrete have a decisive influence on the physical properties of concrete due to mineral strength, mineral bond strength, and mineral volume changes (Maruyama et al 2022;. In concrete structures around reactor buildings and pressure vessels, amorphization of minerals in aggregates due to neutron irradiation has occurred (Maruyama and Muto 2016;Silva et al 2018).…”

“…Le Pape et al ( , 2020 proposed an empirical RIVE model by organizing and reanalyzing those data. In addition, recent experiments have confirmed that cracking associated with mineral expansion affects concrete deterioration (Maruyama et al 2022(Maruyama et al , 2023. Therefore, it will be important in the future to investigate not only mineral expansion but also aggregate expansion with respect to cracking in concrete deterioration.…”