The Influence of Incorporating Plastic within Concrete and the Potential Use of Microwave Curing; A Review

In recent decades, researchers have used plastic to replace natural aggregates (NAs), or as filler and fibre within the concrete. This particular paper puts forward a review that gives comprehensive consideration to the properties and drawbacks, of concrete that contains plastic. As such, it may be hypothesised that poor bond capacity and higher air content due to inclusion of plastic aggregate (PA) within concrete are the predominant factors that reduce the properties in terms of mechanics and durability. In that regard, this study has put forward a new method of curing using microwave irradiation for improvement with respect to those factors. So, that there can be further improvement with regard to overall durability with respect to advanced chemical and hydrophobic resistivity and enhanced performance for conventional concrete with respect to bonding and ductility

Thermal neutron albedo and flux for different geometries neutron guide

This paper presents a study on thermal neutron reflection properties of neutron guide for cylinder, spindle, elliptic and parabolic geometries using 241Am-Be neutron source (5.2 Ci) and BF3 detector, whereas neutron guide is important instrument for transportation of neutrons. To this goal, the required inner and outer radii of neutron guide have been calculated to achieve the highest guided thermal neutron flux based on MCNPX Monte Carlo code. The maximum flux of cylinder geometry with a length 50 cm has been obtained at an inner radius 9 cm and an outer radius 21 cm. Also, the maximum value of thermal neutron albedo is 0.46 ± 0.001 at 12 cm thickness of parabolic guide. Keywords: Thermal neutron, Reflection, Neutron guide, Flux, Parabolic, Albed

Radon concentration in hot springs of the touristic city of Sarein and methods to reduce radon in water

The aim of this research was to measure the efficiency of various simple methods to decrease the concentration of radon in hot springs of the touristic city of Sarein (a touristic city in northwest Iran). With the aid of "RAD7" radon detector, concentrations in water varied from 212 Bq m(-3) to 3890 Bq m(-3). Using 250 mL. vials half-filled with water samples, our research showed that when the temperature of the water increased from 17 degrees C to 27 degrees C, the radon concentration decreased from 3230 Bq m(-3) to 745 Bq m(-3). The mixing of the sample at a speed of 500 rpm for 12 min led to a radon reduction of about 70%. Aerating the water sample with 0.2 L min(-1) of ambient air resulted in a 90% decrease in radon concentration in 6 min. Strong exponential correlations (> 95%) were reported, which verified that the effectiveness of these methods in reducing dissolved gas in the waters used would be high

Fabrication of a superheated emulsion based on Freon-12 and LiCl suitable for thermal neutrons detection

This study develops superheated emulsion detectors that are both sensitive to fast neutrons, and thermal neutrons owing to the exergonic Li36(n,α)H13 capture reaction caused by the 6Li-containing compound dispersed throughout the gel-like medium. The experimental research was conducted on two SEDs. One detector was an ordinary Freon-12 detector and the other was a Freon-12 detector containing 3.4 % (by weight) LiCl. In order to investigate the sensitivity of lithium-containing SEDs to thermal neutrons, two types of SEDs were simultaneously exposed to various flux levels of thermal neutrons from 241Am–Be neutron source inside a cylindrical tank filled with water. A Boron-lined proportional counter was used to estimate the thermal neutron flux and the relevant MCNP code was developed for flux and dose calculations in the prepared set-up around 241Am–Be source. The results demonstrate that there is a proportional relationship between the variations of SED response and the change in thermal neutron flux and dose. Also, the sensitivity of SED was estimated

Electrical Properties of MWCNT/HDPE Composite-Based MSM Structure Under Neutron Irradiation

Because of their low cost, low energy consumption, high performance, and exceptional electrical properties, nanocomposites containing carbon nanotubes are suitable for use in many applications such as sensing systems. In this research work, a metal–semiconductor–metal (MSM) structure based on a multiwall carbon nanotube/high-density polyethylene (MWCNT/HDPE) nanocomposite is introduced as a neutron sensor. Scanning electron microscopy, Fourier-transform infrared, and infrared spectroscopy techniques were used to characterize the morphology and structure of the fabricated device. Current–voltage (I–V) characteristic modeling showed that the device can be assumed to be a reversed-biased Schottky diode, if the voltage is high enough. To estimate the depletion layer length of the Schottky contact, impedance spectroscopy was employed. Therefore, the real and imaginary parts of the impedance of the MSM system were used to obtain electrical parameters such as the carrier mobility and dielectric constant. Experimental observations of the MSM structure under irradiation from an americium–beryllium (Am–Be) neutron source showed that the current level in the device decreased significantly. Subsequently, current pulses appeared in situ I–V and current–time (I–t) curve measurements when increasing voltage was applied to the MSM system. The experimentally determined depletion region length as well as the space-charge-limited current mechanism for carrier transport were compared with the range for protons calculated using Monte Carlo n-particle extended (MCNPX) code, yielding the maximum energy of recoiled protons detectable by the device

The utilization of thorium in Small Modular Reactors – Part I: Neutronic assessment

This work presents a neutronic assessment to convert a Small Modular Reactor (SMR) with uranium core to the thorium mixed oxide core with minimum possible changes in the geometry and main parameters of SMR core. This option is due to most of SMR are designed to be strongly poisoned in the beginning of cycle and to have a long cycle. Thorium can be used as an absorber in the beginning of the cycle and also be used as a fertile material during the cycle, it seems to be a good option to use (Th/U)O2 as SMR’s fuel. The main neutronic objectives of this study is achieving longer cycle length for SMR by using the minimum possible amount of burnable poison and soluble boron in comparison with reference core. The Korean SMART reactor as a certified design SMR has been chosen as the reference core. The calculations have been performed by MCNP code for homogeneous and heterogeneous seed and blanket concept fuel assemblies. The results obtained show that the heterogeneous fuel assembly is the one which gives longer cycle length and used lower amount of burnable poison and soluble boron, and also consumes almost the same amount of 235U

Polyester polymer concrete: Effect of the marble particle sizes and high gamma radiation doses

Polymer concrete (PC) has several advantages when comparing with Portland Cement Concrete (PCC), but its brittle failure characteristics have limited its usefulness for load-bearing applications. Thus, improvements are necessary for specific applications, particularly on the PC components: polymeric resin and mineral aggregates. One alternative is use gamma radiation. In this work, the effects of gamma radiation and the marble particle sizes on compressive properties of polymer concretes (PCs) were studied. The results show the compressive strain and the elasticity modulus depend on the combination of the marble particle sizes and the applied radiation dose. The combination of medium and large particle sizes provides the highest elasticity modulus. Moreover, high radiation doses provoke higher numbers of dispersed particles per unit volume which provide more resistance to crack propagation. (C) 2012 Elsevier Ltd. All rights reserved