A Numerical Model for Concrete Strength Change under Neutron and Gamma-ray Irradiation

Abstract

For performance evaluation of existing reinforced concrete members under irradiation conditions, a numerical code called "DEVICE" (Damage EValuation for Irradiated ConcretE), which takes into account the heat, moisture, and radiation transport coupled with cement hydration, is proposed. This code is composed of the established computational cement-based material (CCBM) model and the one-dimensional deterministic transport Sn code "ANISN". In the proposed model, temperature-dependent irradiation-induced expansion of aggregate minerals and resultant strength deterioration of concrete are introduced. Currently, the knowledge and modeling of irradiation-induced expansion of aggregate mineral is limited only for α-quartz. DEVICE was used for evaluating the strength distribution of the decommissioned plant Japan Power Demonstration Reactor (JPDR). Compressive strength distribution in a concrete biological shielding (CBS) wall of the JPDR was obtained by core sampling, and the compressive loading test results were compared with the calculation results. This comparison proved the practicality potential of DEVICE to predict the concrete strength distribution in a CBS. In addition, concrete strength change and its distribution in a CBS of an anonymous two-loop pressurized water reactor was simulated by DEVICE. The contributing factors for the change in the distribution of concrete strength at the inner surface of the CBS are discussed. Furthermore, the ways of integrity evaluation other than the existing allowable fast neutron fluence method are proposed and discussed as follows: 1) mineral composition-based allowable fast neutron fluence; 2) strength prediction at the inner surface based on the expansion of mineral composition of aggregates and the lower limit curve of the ratio of compressive strength of the specimen after irradiation (Fc) to that of the reference specimen (Fco) as a function of concrete expansion; and 3) direct numerical calculation for seismic performance by considering irradiation-induced volume expansion and degradation of concrete.

Development of Soundness Assessment Procedure for Concrete Members Affected by Neutron and Gamma-Ray Irradiation

“…3. It confirms that the Fc/Fco ratio (ratio of strength of irradiated specimen to strength of non-irradiated specimen) decreases monotonically above 1 × 10 19 n/cm 2 , and thus further scientific investigation is necessary to establish a Table 1 Expected neutron fluence and gamma-ray dose after 60-year-operation of Japanese nuclear reactors (Maruyama et al 2016a).…”

“…The gray areas indicate the place of core sampling whose data are used in this study. After (Kakizaki et al 1996, Maruyama et al 2016a. Fig.…”

“…In the framework of this project, we developed a numerical calculation program DEVICE (Damage EValuation for Irradiated ConcretE) (Maruyama et al 2016a), which can quantitatively evaluate the influence of environmental factors (neutrons, gamma-rays, temperature, and humidity) on the distribution of physical properties of concrete members. DEVICE was developed based on a concrete physicalproperty-prediction program known as the Computational Cement-Based Material Model (CCBM) .…”

“…This section builds upon the work of Maruyama et al (2016a). Considering the radiation conditions encountered by concrete, it was decided to employ a deterministic transport theory for the present study.…”

Change in Relative Density of Natural Rock Minerals Due to Electron Irradiation

“…The main reason is considered as an expansion of aggregate, because α-quartz is well-known to show an expansion and density reduction under neutron and electron irradiation (Primak et al 1955;Primak 1958;Bonnet et al 1994;Douillard and Duraud 1996;Bolse 1999;Ewing et al 2000;Field et al 2015). It is hence considered that the natural rock should be sensitive to irradiation, which poses very important issues on the durability of concrete under irradiation as 1) expansion of aggregate, and 2) degradation of concrete performance as a result of 1) (Maruyama et al 2012;Field et al 2015;Giorla et al 2015;Le Pape et al 2015Maruyama et al 2016).…”