Contents lists available at ScienceDirect Progress in Nuclear Energy journal homepage: www.elsevier.com/locate/pnucene Effect of mineral admixtures in concrete on biological shield wall radiation in APR1400 Samson Ayodeji Olubiyi a , Seong-Cheol Lee b,* , Chang-Joo Hah c a Research and Infrastructure Development Directorate, Nigeria Atomic Energy Commission, Garki, Abuja, Nigeria b Department of Civil Engineering, Kyungpook National University, Daegu, Republic of Korea c Department of NPP Engineering, KEPCO International Nuclear Graduate School, Ulsan, Republic of Korea ARTICLE INFO Keywords: Concrete mix design Flux Removal cross section Irradiation Biological shield wall ABSTRACT Although many researchers investigated the effect of radiation on concrete mechanical properties, a little at- tention was given to the effect of concrete mix design on the radio-activation of biological shield wall, which could be important on decommissioning of nuclear power plants. In this paper, to investigate the effect of concrete mix design, radiation in biological shield wall of the Advanced Power Reactor 1400 MWe (APR1400) was investigated with consideration of several concrete mix designs. As an analytical variable, three different concrete mix designs were considered according to mix proportions of Ordinary Portland Cement (OPC), Fly Ash (FA), and Ground Granulated Blast Furnace Slag (GGBS), which were broadly adopted on construction site. For irradiation analysis of concrete, the compositions of concrete mix were analyzed to obtain the mass of each element in each concrete mix design. Flux distribution along depth of concrete shield wall was evaluated from flux at the outside of the Reactor Pressure Vessel (RPV) which was obtained through regression analysis for flux distribution in the RPV. After 60 years of service life and 10 years of cooling period, the analysis showed that concrete mixed with FA was 9% more radio-activated than concrete in which OPC only or both OPC and GGBS were mixed. The result of this paper will be useful for design of concrete shield wall considering radioactive waste amount generated through decommissioning. 1. Introduction Decommissioning of a nuclear power plant after their active life is essentially connected with handling of a large amount of radioactive components and structures. These structures, including the concrete biological shield wall, have significant contribution on large amount of waste in the decommissioning of a nuclear power plant (NPP) (Zagar and Ravnik, 2000). In order to reduce the volume of the waste and to successfully plan the dismantling of the concrete shield, activation of the structure should, at least, be known in advance (Pauzi et al., 2012). Since concrete is the most common material used for reactor biological shielding mostly because of its satisfactory mechanical properties and availability, it is important to investigate the effect of concrete mixture design on its radio-activation. Concrete is considered to be composed of coarse materials that are embedded in a hard matrix of material filling the space between the aggregate particles in the mixture (Malkapur et al., 2015). It has been used for various purposes; support for buildings, shielding in nuclear installations, and construction of containment in nuclear power plant (Allen et al., 2011). Concrete structures have been found to deteriorate overtime as a result of exposure to several conditions such as freeze and thaw, heat, cracking, acids, chlorides, sulfates, carbonates, calcium leaching, and radiation. These conditions are compounded by the ageing of the concrete structures as most nuclear facilities are designed for more than 40 years of active life (Hilsdorf et al., 1978), particularly APR1400 Pressurized Water Reactor (PWR) which was designed to operate for 60 years. Under nuclear irradiation, the atomic structure of material aggregates in the crystalline form becomes distorted, thereby causing lattice deformation of the material aggregate (Hilsdorf et al., 1978). Consequently, the material becomes more brittle and may eventually lead to break down of atomic bonds. The material finally becomes radioactive and degradation sets in as a result of further ex- posure to these conditions overtime. The overall use of concrete in nuclear facilities for containment and shielding purposes has equally made its performance critical to the safety of the facility with regards to the effect of radiation and degradation (Naus, 1986). There has been extensive research on the effect of radiation on concrete used as shielding in a NPP. For example, Mirhosseini et al. (2014) studied the effect of nuclear radiation on the behavior of reinforced concrete ele- ments. They concluded that the ultimate strength and ductility of https://doi.org/10.1016/j.pnucene.2018.04.022 Received 28 November 2017; Received in revised form 7 April 2018; Accepted 24 April 2018 * Corresponding author. Department of Civil Engineering, Kyungpook National University, 80 Daehakro, Bukgu, Daegu, 41566, Republic of Korea. E-mail address: seonglee@knu.ac.kr (S.-C. Lee). Progress in Nuclear Energy 107 (2018) 110–115 Available online 01 May 2018 0149-1970/ © 2018 Elsevier Ltd. All rights reserved. T