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High performed new heavy concrete samples were designed and produced that absorption parameters were determined for gamma and neutron radiation by using Monte Carlo Simulation program GEANT4 code. In the sample production, many different materials were used such as; chromite (FeCr2O4), wolframite [(20Fe,80Mn) WO4], hematite (Fe2O3), titanium oxide (TiO2), aluminum oxide (Al2O3), limonite (FeO (OH) nH2O), barite (BaSO4), materials. Furthermore, calcium aluminate cement (CAC) was utilized for high temperature resistant. In the current study, five different new heavy concrete samples were produced then physical and chemical strength of them tested. High-temperature-resistant tests were made at 1000°C and good resistance against high temperature was observed. Neutron equivalent dose measurements were made for by using 4.5 MeV energy 241Am-Be fast neutron source. Results compared with paraffin and conventional concrete. It was found that the new heavyweight concretes had the better absorption capacity than paraffin and conventional concrete. Gamma radiation absorption measurements also were carried out at the energies of 160, 276, 302, 356, and 383 keV by using 133Ba point radiation source. It has been suggested that the new produced concretes can be used for radiation safety in the nuclear applications.

Radiation is often used in applications such as in energy production, in medicine diagnosis and treatment, in material research and investigation. In addition, it is also used in such areas as agriculture, archeology (in carbon determination), space exploration, military, geology, and many others (U.S. NRC, 2010). Radiation leaks may occur during these applications (Lamarsh, & Baratta, 2001); therefore, it must be properly shielded. In radiation shielding works, conventional materials such as concrete, steel, alloy, ceramic, glass, and polymers are widely used (Aygün et al., 2019; Kumar, Sayyed, Dong, & Xue, 2018; Sayyed, Akman, Kumar, & Kaçal, 2018). In these studies, concrete is among the most widely used materials (Li et al., 2017). Concrete is a composite material which glued in such a way that aggregate particles (sand, gravel, stone, and filler) with cement or a binder. Traditional concrete is not as effective in nuclear shielding material radiation, but it is a very common used building material. The traditional concrete lead bricks for radiation shielding characteristic may vary and is dependent on the chemical composition of the concrete. New types of concrete samples have been developed by different the aggregated used for preparing concrete, depending on the available natural and artificial materials (Mukhtar, Shamsad, Al-Dulaijan, Mohammed, & Akhtar, 2019; Chen, 1998). Heavy concrete is the most common material used in radiation shielding equipment. Heavy concrete is obtained by adding high-density aggregates into normal concrete. Normal-weight concrete density varied between 2200 and 2450 kg/m3 while heavy concrete’s density is ranging from about 2900 and 6000 kg/m3 (Nawy, 1997). Some natural minerals such as hematite, magnetite, limonite, serpentine, siderite and barite can be used as aggregates in heavy concrete production. In literature, numerous experimental and theoretical researches have been conducted to develop new heavy concrete. Different minerals like siderite, limonite were used to produce heavy concrete in order to provide gamma radiation shielding. It was reported that the gamma radiation absorption capacity of heavy concretes is high (Basyigit et al., 2011). Boron-containing multi-layered new heavy concretes were produced and radiation shielding properties were determined. It is reported that these concretes are very high in 14 MeV neutron absorption capacity (Sato, Maegawa, & Moshimatsu, 2011). In a different study, some metal oxides such as Al2O3, AS2O3, BaO, CaSO4, CdO, Cr2O3, CuO, Fe2O3, K2O, MgO, MnO, Na2O, NiO, P2O5, PbO4, SrO, TiO2 was used in the heavy concrete production, and it was stated that the use of these new heavy concretes in nuclear reactors is appropriate (Abdo, 2002; Erdem, Baykara, Doğru, & Kuluöztürk., 2010; Mortazavi, Mosleh-Shirazi, & Baradaran Ghahfarokhi et al., 2010). Seltborg et al.produced heavy concretes by using, such as calcium (Ca), strontium (Sr), barium (Ba), radium (Ra) magnesium (Mg) elements. They determined these heavy concretes can be used to shield gamma and neutron radiation in nuclear reactors (Seltborg et al., 2005). In the present study of tungsten oxide (WO3) gamma radiation mass attenuation coefficient in the concrete, the effect on the coefficient was investigated. Appropriate geometry found by using MCNPX and XCom simulation programs. It is found that shielding properties when nanoparticle WO3 doped in concrete more than microparticle WO3 (Tekin, Singh, & Manici, 2017). In another study, high-density concrete (ρ = 4.71 g/cm3) was made by using steel balls and in aggregate the debris of the demolished concrete buildings in the earthquake region in Fukushima. Good shield properties were determined this of heavy concrete and it is shown that can be used in storage radioactive waste (Sanjay, Yusuke, Kimura, Fujikura, & Araki, 2018). Heavy concrete was made using lead-zinc slag waste instead of sand which can be used gamma radiation shielding. Shielding and strength properties were investigated of this concrete and compared with conventional concrete. It is reported that lead–zinc slag waste concretes better radiation shielding and strength characteristic than conventional concretes (Mohamed, 2017). Medical cyclotron is a system designed for radiopharmaceutical production, which high-level radiation emit. Shielding wall thickness was calculated by using Monte Carlo simulation when cyclotron system used to operate that may occur radiation. Consequently, for shielding, radiation at 200-cm-thickness concrete wall need was determined (Jang, Kim, & Kim, 2017). Some mining wastes suitable for heavy concrete production. For instance, Gallala et al. have produced new heavy concrete by using barite-fluorspar mine waste (BFMW) aggregates and investigated their gamma radiation shielding, mechanical strength properties. The results clearly showed when ratio 25% BFMW added to concretes has better gamma radiation shielding and compressive strength properties than conventional concrete (Gallala et al., 2017). Tekin et al., using MCNPX code, demonstrated that high strength concrete containing nanoparticles of WO3 and Bi2O3 had enhanced shielding capacity for gamma radiation (Tekin, Sayyed, & Issa, 2018). Five different concrete types were made using magnetite aggregates and 0%, 2%, 4%, 6%, and 8% of titanium dioxide (TiO2) nanoparticles for nuclear power plant shielding material. Some of the protecting parameters such as MAC (mass attenuation coefficients) HVL (half-value layer), TVL (tenth value layer), and linear attenuation coefficients (LAC) were determined for 662, 1173, and 1332  keV energy of gamma ray used. It is reported, the significant effect on radiation shielding properties occurred within 8% of TiO2 nanoparticles (Iman et al., 2019). Some natural minerals can be using heavy concrete in production. Different concrete types which including natural perlite mineral and B4C have been experimentally investigated and gamma radiation shielding parameters have been determined (Agar et al., 2019)

In this study, new concrete samples were designed and produced using Monte Carlo simulation program Geant4 code. The production of heavy concrete for radiation shield was made based on the concrete production process such as mixture proportion, ratio of water to cement, cement hydration. Furthermore, new concrete candidates with good radiation shielding ability at high temperature have been produced and it has been shown that raw materials such as chromite, wolframite can be used in production.

In Monte Carlo simulation program, the Geant4 code is used to determine the interactions between radiation and materials. In addition, it can be used to predict nuclear events that may occur at the point of radiation and detector interaction. Geant4 software is the most developed, for analyses biological effects of radiation-induced and their modification nuclear shielding engineering. Also, Monte Carlo program Geant4 to simulate can be used to predict the transport, accumulation of incident particles through the walls of a nuclear power plant (Agostinelli et al., 2003). It is used in applications in nuclear physics, particle accelerator designing, space investigation, and medical physics. Detailed information can be found at www.Geant4.org.

2.2. Sample preparation

New heavy concrete samples were produced by using different natural aggregates such as chrome ore (FeCr2O4), wolframite [(Fe,Mn)WO4], hematite (Fe2O3), limonite (FeO (OH) nH2O), barite (BaSO4). Nickel oxide (NiO) was used to fill the pores that could form in the concrete. The chromium ore (FeCr2O4) mineral has a density of average 4.79 g/cm3 and it melts in temperature 1650–1660°C (Jay, Meegoda, Zhengbo, & Kamolpornwijit, 2007). The chrome ore sample was taken from the Kayseri city Yahyalı district chrome mine. This chrome ore contains such minerals 53.19% Cr2O3, 16.80% MgO, 11.15%Al2O3, 15.11%Fe, 2.72%SiO2, 0.007%S, and 0.005% P according to Eti (Chromium Ferrochrome Foundation). Wolframite is a mineral with a density of 7.1–7.5, average 7.3 g/cm3 and 11.70% MnO, 16.85% FeO, 71.46% WO3 including (Tolun., 1951). This ore was obtained from an Uludağ tungsten mine, which is located in the province of Bursa and is approximately 2200–2300 m high from the sea. According to the pioneering simulation work, both gamma and neutron radiation absorption cross-sectional values were determined higher in chromite and wolframite minerals. Furthermore, these minerals have both refractory properties and high mechanical strength and plenty of reserves. Therefore, these minerals were used in the production of heavy concrete. Hematite, titanium oxide, aluminum oxide, limonite, siderite, barite, materials are always used materials for the production of heavy concrete, but for that, the chromite and wolframite minerals are not very commonly used. The usage of natural chromite and wolframite minerals provided will be with this work in the nuclear industry. Chromium oxide (Cr2O3) was used to fill capillary cavities that may form in concretes. When concrete components were selected, the high macroscopic cross-sectional values were taken into account.
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