Magnetite Concrete Research Articles

Mechanics, γ-ray shielding properties and acoustic emission characteristics of radiation shielding concrete exposed to elevated temperatures

High temperature can cause serious damage to building structures, so it is important in order to re-evaluate the residual properties of radiation shielding concrete (RSC) exposed to elevated temperatures for ensuring security of medical, industrial and defense building structures. Thus, the deterioration of the mechanical, γ-ray shielding properties and acoustic emission characteristics of barite concrete (BC) and magnetite concrete (MC) exposed to elevated temperatures were studied. Research indicated that the performance of aggregates played a crucial role in the thermal stability, residual physical and mechanical properties of concrete exposed to elevated temperatures. BC was subjected from bursting and even spalling at 300 °C, while its physical and mechanical properties deteriorated drastically. However, MC still had favorable integrity and relatively high residual mechanical properties at 800 °C. The maximum deterioration temperature of BC exposed to elevated temperatures occurred at about 300 °C, while that of MC occurred at 450–600 °C. The degradation of the γ-ray shielding properties of RSC exposed to elevated temperatures was significantly lower than its mechanical properties.

Effect of Magnetite Concrete on Splitting Tensile Strength and Gamma Ray Shielding Performance Exposed to Repeated Heating at High Temperature

Radiation shielding concrete is one of the most used materials in the construction of nuclear power plants and will be subjected to high temperatures for a long time during its service life. This study aims to investigate deterioration of radiation shielding concrete with multiple heating at different temperatures. A microwave oven was used as a heating apparatus to simulate irradiation, and 200, 300, and 400 °C were selected as experimental cycle temperatures. The apparent characteristics, mass loss, splitting tensile strength, and gamma ray shielding properties of the commonly used magnetite shielding concrete were investigated. The results showed that the splitting tensile strength and gamma shielding performance of concrete were dramatically reduced at first heating. Then, as the heating times increased, the splitting tensile strength and gamma shielding properties of the concrete continued to deteriorate, and the higher the increase in heating temperature, the more severe the deterioration of the concrete. During the service period of radiation shielded concrete, the magnitude of temperature under the service conditions will affect the deterioration degree of concrete, and the continuous change of temperature will continuously lead to the deterioration of concrete.

Influence of SiC on the thermal energy transfer and storage characteristics of microwave-absorbing concrete containing magnetite and/or carbonyl iron powder

A microwave-absorbing concrete with favorable heat transfer and storage was investigated to improve the efficiency of deicing concrete pavement during microwave heating and off in cold winter. The concrete was prepared using magnetite and/or carbonyl iron powder (CIP) as the absorbing material. The effect of SiC as the heat transfer and storage material on microwave absorption efficiency, thermal conductivity and thermal diffusivity of concrete were studied. In addition, the pore structures of concrete were investigated to analyze its influence on the thermal properties of concrete.The results showed that the SiC slightly affected the microwave absorption capacity of magnetite concrete (MC) and magnetite-CIP concrete (MCC). The SiC could effectively improve heat transfer and storage ability of concrete. When the content of SiC was 7%, SiC improved the thermal conductivity and effusivity of MC and MCC were improved by 86.4% and 110%, and 84% and 97.3%, respectively. Meanwhile, adding CIP and SiC could improve the porosity and pore diameter of concrete to make it dense, which might be an influence factor to improve the thermal properties of concrete. Under the same conditions, the thermal conductivity and storage capacity of concrete showed the same change trend. In addition, the coefficient of temperature nonuniformity (CTN) and coefficient of max temperature gradient (CMTG) as new indexes was used to evaluate the influence of SiC on the thermal properties of concrete. Therefore, to improve concrete absorption of more heat during microwave heating, and transfer and store heat quickly for road deicing, the magnetite-CIP-SiC concrete (MCSC) might be the most suitable.

Effect of elevated temperature on the magnetite and quartz concrete at different W/C ratios as nuclear shielding concretes

• Several tests were carried out to obtain heavyweight concrete's physical, mechanical and microstructural properties after being exposed to 20, 150, 300, 500 and 800 ℃. • The thermal stability of MG concrete is relatively high, up to 500 ℃, compared to QU, and the number of cracks developed for the high w/b ratio concretes. • Due to the good thermal stability of magnetite concrete up to 800 ℃ and the high progression of cracks; due to the high evaporation and dehydration ratio as well as decomposition of paste in quartz concretes. • Correspondingly, after temperature loading with 800 ℃, QU-III and MG-III showed the lowest declination values of flexural strength, thus explaining the slow disintegration of C S H in QU and postponement of the second phase of C S H decomposition in MG with high w/c ratio. Nuclear buildings are exposed to hazardous radiation and high temperature during their operation and in the case of fire. Heavyweight concrete is used in constructing nuclear buildings for the advantages of strength, durability, heat resistance, and shielding against radiation. The physical, mechanical and microstructure properties of the heavyweight magnetite concrete (MG) were investigated and compared to the reference normal weight quartz concrete (QU) as the concrete. Each type of concrete has been studied for 42, 47 and 52% water-cement ratios. Results indicated that the thermal stability of MG is relatively high, up to 500 ℃, compared to QU concrete. The loss in MG's mass was relatively lower than the QU concrete. Changes in the porosity were quite similar in QU and MG, but the effect of the growth in the porosity on the compressive strength of MG was relatively lower than in QU. At 20 ℃, the compressive and flexural strength values for the (QU) mixes decreased with raising the water-cement ratio, while it developed in the magnetite (MG) concrete as the w/c percentage increased. The result showed that the residual mechanical properties of ordinary QU were improved as the w/c ratio increased. The microstructure investigations of QU and MG before and after the heat treatment identified some changes in the concrete structure. These changes represented the appearance of microcracks, decomposition of C S H, and voids at 500 and 800 ℃. Therefore, it affected the physical and mechanical properties of QU and MG.

Radiation shielding properties of siderurgical aggregate concrete

The world is changing, and consequently so are policies on the use of natural resources. One of the most convenient ways to reduce the consumption of natural aggregates in the production of more sustainable construction materials is the use of recovered industrial by-products. In this study, concretes are designed using siderurgical aggregates from electric arc furnaces, taking advantage of their high density to use them as radiation shielding concrete. To verify the suitability of these aggregates, four concrete mixes were designed with different aggregates: limestone, siderurgical magnetite aggregates (the most commonly used in the nuclear field). The comparison of the different mixes was carried out focusing on the physical–mechanical properties in the field of ionizing radiation shielding (gamma radiation and neutron shielding) by means of simulations. In addition, an analysis was performed to establish how the w/c ratio and the amount of CEM affect shielding properties. In terms of linear attenuation coefficient and neutron transmission rate, the concrete with siderurgical aggregates shows intermediate capability in comparison with the limestone aggregate and magnetite concrete. The increase in the amount of cement and the w/c ratio caused a decrease in the linear attenuation coefficient and a reduction in the neutron transmission rate, but the variation in the w/c ratio did not have a significant impact on the neutron transmission rate.

Determination of photon-shielding features and build-up factors of nickel–silver alloys

In this study, a comprehensive study on photon and fast neutron interactions was conducted to determine the possible uses of four different copper-based Nickel–Silver (NS) alloys as alternative protective materials. For this purpose, photon interaction parameters (μ, μm, X1/2, σT, Zeff, Neff, Ceff) of NS alloys which have Cu65Ni18Zn17, Cu62Ni18Zn20, Cu64Ni12Zn24 and Cu55Ni18Zn27 compositions were presented experimentally in the photon energy range of 30–1333 keV using ideal transmission geometry conditions. In order to compare experimental and theoretical results and to a comprehensive evaluation in wide energy range (0.015–15 MeV), these parameters were also calculated using WinXCOM based Phy-X/PSD software. It was found that there is a good agreement between experimental and theoretical results, and that the maximum relative difference is approximately 1.2%. In order to test the suitability of the radiation shielding capacities of the studied alloys for nuclear applications, all parameters were also calculated theoretically for ordinary concrete (OC), basalt (BM) and steel magnetite (SM) concretes. Furthermore, the exposure build-up factors for the alloys and concretes were calculated using G-P fitting method at photon energy range from 0.015 to 15 MeV up to 40 mean free path (MFP) penetration depth. Moreover, the fast neutron removal cross-sections of the materials were determined using Phy-X/PSD software. According to the data obtained, it has been observed that the shielding capacities of NS alloys are far superior to selected concretes for both photon radiation and fast neutrons. It was revealed in this study that NS alloys may be an alternative shielding material candidate due to their high density, high melting points (about 1100 °C) and good mechanical strength.

Influence of polymer modification on the microstructure of shielding concrete.

In this paper an analysis of the influence of polymer modification on the microstructure, shielding properties against neutrons, and compressive strength of heavy-weight magnetite concrete is carried out. The modifications involve the addition of acrylic or epoxy dispersions as well as micro- or/and macrofibers. A computer image analysis method is used to evaluate the microstructure of concretes and parameters of pore structure are calculated; these parameters include relative volume fraction, relative specific surface area, and pore arrangement ratios, including a proprietary ratio based on Voronoi tessellation. An assessment of significance of differences between stereological parameters of reference concrete and polymer modified concretes, as well as the impact of polymer form (dispersion or fibers) on shielding properties and compressive strength is carried out using Student’s t-test. The results show that except for the effect of the addition of both polypropylene micro- and macrofibers on the relative volume of pores, all other modifications result in statistically significant changes in the values of stereological parameters. Nevertheless, it is shown that neither polymer dispersions nor fibers have a statistically significant impact on shielding properties, but that they do influence compressive strength.

A comprehensive study on the effect of water to cement ratio on the mechanical and radiation shielding properties of heavyweight concrete

Recently, due to application of nuclear technology and the issue of protection against nuclear radiations with harmful environmental impacts such as gamma rays, heavyweight concrete is widely used in industry. On the other hand, water to cement (w/c) ratio is one of the chief factors affecting concrete behavior. Thus, in the present research, it has been attempted to explore the impact of various w/c ratios on the mechanical and shielding characteristics of heavyweight magnetite concrete. The parameters which were evaluated in this study are compressive and tensile strengths, modulus of elasticity, linear attenuation coefficient, mean free path, tenth value layer and half value layer. The Cs137 and Co60 radiation sources with different energy levels were applied. The obtained results indicated that mechanical and shielding characteristics and microstructure of heavyweight magnetite concrete improve with the reduction of w/c ratio.

An experimental investigation on combined effects of nano-WO3 and nano-Bi2O3 on the radiation shielding properties of magnetite concretes

This study has investigated the effect of adding nano-WO3, nano-Bi2O3 and the combination of these two nanoparticles on the shielding properties of heavy-weight concrete (HC). All prepared concrete specimens are exposed to gamma radiation with Cs137 and Co60 sources and the linear attenuation coefficient (LAC) was calculated as a function of the percentage of nanoparticles added to the concrete for the energy levels of 662, 1173 and 1332 KeV. The results show that the addition of these nanoparticles to HC improves the protective and mechanical properties, so that adding only 6% of the combination of nano-WO3 and nano-Bi2O3 to HC mixture (A): the LAC of gamma-ray increases by 6.57, 3.54 and 4.92% at the energy levels of 662, 1173 and 1332 KeV, respectively, (B): the compressive strength increases by 8.3%, (C): the Ultrasonic Pulse Velocity (UPV) increases by 6.2%. Also, the values of half-value layer (HVL), tenth-value layer (TVL) and mean- free path (MFP), which are considered to be the most important radiation transmission thicknesses in the design of the shield, are also calculated and presented for all mixtures.

Research on the Dynamic Mechanical Properties of Magnetite Concrete under Impact Load

In order to investigate the dynamic compression characteristics of magnetite concrete under impact load, the large-diameter Φ100mm Hopkinson pressure bar test device was used to test the impact compression of magnetite concrete specimens under different strain rates, whose the experimental results were valid and consistent, and the stress-strain curves of magnetite concrete were obtained at different strain rates. The results show that: (1)the stress-strain relationship of magnetite concrete materials is nonlinear; (2)that magnetite concrete materials are obvious rate sensitive materials, whose strain rate sensitivity is lower than that of plain concrete, and the compressive strength of concrete increasing with the strain rate’s increasing; (3)the failure pattern of specimen appears the splitting damage at low strain rate and the block destroy at high strain rate.

Study of concrete activation with IFMIF-like neutron irradiation: Status of EAF and TENDL neutron activation cross-sections

The aim of this paper is to check the performance of last versions of EAF and TENDL libraries (EAF2007, EAF2010, and TENDL2014) in the prediction of concrete activation under the neutron irradiation environment expected in IFMIF, an accelerator-based neutron source conceived for fusion materials testing. For this purpose Activity and dose rate responses of three types of concrete (ITER-Bioshield kind, barite and magnetite concretes) have been studied. For these quantities, dominant nuclides and production pathways have been determined and, then, a qualitative analysis of the relevant activation cross-sections involved has been performed by comparing data from mentioned libraries with experimental data from EXFOR database. Concrete activation studies have been carried out with IFMIF-like neutron irradiation conditions using the ACAB code and EAF and TENDL libraries. The cooling times assessed are related to safety and maintenance operations, specifically 1 hour, 1 day and 12 days. Final conclusions are focused on the recommendations for the activation library to be used among those analyzed and cross-section data to be improved.

Determination of gamma and fast neutron shielding parameters of magnetite concretes

In this study, some gamma shielding parameters such as mass attenuation coefficient (μρ), effective atomic number (Zeff), electron density (Nel) and buildup factors have been investigated for concretes with and without magnetite aggregate. The measurements have been carried out using 1.25 MeV (mean energy of 1.1732 MeV and 1.3325 MeV photons of a 60Co radioactive source) gamma photons. The theoretical values of μρ have been calculated in the energy range from 1 keV to 100 GeV by WinXCom computer code and these values were used in order to calculate the values of Zeff and Nel. And fast neutron shielding parameter namely effective removal cross-sections (ΣR, cm−1) have been calculated. In addition, Energy absorption buildup factors (EABF) and exposure buildup factors (EBF) values of concrete samples have been calculated for photon energy 0.015–15 MeV up to 40 mfp (mean free path) penetration depths. The results of this study showed that the magnetite concrete is more efficient than the ordinary concrete for fast neutrons and gamma rays.

Overview of Material Challenges in IFMIF Test Cell Design

As the core region of IFMIF, the test cell (TC) suffers intense neutron and gamma irradiations. Major material challenges of the TC faced during engineering design phase are outlined and the current key material allocations are described. Actively cooled magnetite concrete is selected as the major biological shielding material for the TC, and actively cooled closed liner made of 316L stainless steel is selected to cover the complete TC internal surfaces. Material selections for sealing gaskets and electric insulations inside the TC are preliminarily defined based on dose rate maps at different locations. Metal based sealing gaskets and glass/ceramic electric insulations are applied in the areas with high dose rate, while organic based gaskets and conventional insulation materials can only be arranged behind sufficient biological shielding. Leak tight welding seams between removable interface shielding plugs and the TC liner are located in the region with very low helium generation rate (<0.01 appm/fpy) in steel so that cutting and re-welding during the complete IFMIF life span is guaranteed.

Shielding calculation for the CSNS target station

In this paper we firstly calculate the one-dimension shielding models to give the basic data for the Chinese Spallation Neutron Source (CSNS) target station. Then the three-dimensional shielding calculations have been performed for the detailed design of the CSNS target station. The gaps and void spaces in the CSNS target station are considered for precise estimation. We find that 4.8-meter-radius steel adding 1.2-meter-thick magnetite concrete can satisfy the shielding requirement in the horizontal direction. The dose rate on the top of the ceiling is a little higher than 2.5μSv/h due to streaming effect, which originates from the moderator transfer lines. A thin sandwich structure will be adopted for decreasing residual radioactivity dose rate on the altitude directions after considering the engineering cost and maintenance. All these calculations lie on the Monte Carlo simulation code MCNPX2.5.0.

Comparison of shielding properties for ordinary, barite, serpentine and steel–magnetite concretes using MCNP-4C code and available experimental results

In this paper shielding properties of ordinary, barite, serpentine and steel–magnetite concretes in 511, 662 and 1332keV gamma ray energies were studied using MCNP-4C code and compared with available experimental results. The simulated and measured values were compared and the results showed reasonable agreement for all concretes. Steel–magnetite has higher linear and mass attenuation coefficients, and lower transmission factor, HVL and TVL values relative to other concretes in each photon energies studied in this research.

Homogeneous and Multilayered Shields for Neutrons and Gamma-Rays

Measurements were carried-out to compare the attenuation properties of homogeneous shields and shields of two layers and three layers for fast neutrons and total gamma rays. These were performed by measuring the fast neutron and total gamma-ray spectra behind homogeneous shields of magnetite–limonite, ilmenite–ilmenite and magnetite–magnetite concretes. The two layers assembly consists of iron and one of the above mentioned concretes, while the three layers shield consists of water, iron and one of the previously mentioned concretes. All measurements were carried-out using a neutron-gamma spectrometer with stilbene scintillator coupled to a fast photomultiplier tube. Separation between pulses of recoil protons and recoil electrons was achieved by a pulse shape discrimination technique. The obtained data are presented in the form of neutron and gamma spectra measured behind homogeneous shields and shields of two layers and three layers. The spectra measured behind homogeneous shields were used to derive the total macroscopic cross-sections for neutrons and the total attenuation coefficients for total gamma rays.

Measurements of neutron shielding properties of heavy concretes using a Cf-252 source

This investigation reports the experimental results of neutron transport and shielding properties of heavy concretes made from locally available ilmenite and magnetite sand. The experiment has been carried out with a 252Cf source and a BF 3 detector as a long counter. The thickness dependent removal cross section has been investigated and found to vary from 0.0936 cm −1 at 5 cm to 0.0346 cm −1 at 100 cm and 0.0990 cm −1 at 5 cm to 0.0366 cm −1 at 100 cm for ilmenite and magnetite concretes respectively. The results illustrate the effectiveness of ilmenite and magnetite heavy concretes so far as their sheilding properties are concerned. These materials may be used as a neutron shield in reactors, accelerators and neutron sources.

1040 重量コンクリートの施工と遮蔽に関する実験(材料・施工)

1040 重量コンクリートの施工と遮蔽に関する実験(材料・施工)

Magnetite Concrete for Radiation Shielding

A concrete containing only magnetite ore concentrate, cement, and water is found to have appreciably better shielding properties than ordinary concrete, and to possess good strength and ease of handling. Exceptionally high moisture content, although gradually lost by diffusion, decreases by only about 50 percent in thirty years in an eight-foot thick wall. Its use is desirable under certain conditions because of space economy due to its high density.