A study of the shielding performance of fibers coated with high-Z oxides against ionizing radiations

doi:10.1016/j.nima.2020.164174

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Volume 973, 1 September 2020, 164174

https://doi.org/10.1016/j.nima.2020.164174 Get rights and content

Abstract

The aim of the present study is to fabricate an economical, easily workable and environmentally friendly X-ray and gamma ray-shielding composites using a coating method. Nano- and micron-size powders of WO₃, PbO and Bi₂O₃ were used as a substitution base for the shielding materials. After the synthesis of those materials, they were coated on fabric samples which were then exposed to an X-ray tube at 40, 70 and 120 kV voltages, 10 mAs, and 40 SID (i.e. the distance from the X-ray beam source to the specimen). They were also exposed to the gamma rays of a ¹³⁷Cs source. Attenuation percentages (AP), mass attenuation coefficients and effective atomic numbers ( $Z_{eff}$ ) were calculated for different samples. It is evident from this study that polymer composites containing Bi₂O₃, WO₃ and PbO can be coated on fabrics, which is an effective method to produce flexible and wearable textiles such as aprons. The results indicated that, at low energy values, the attenuation of the samples which contain nano-particles is higher than that of those containing micro-particles. Also, at the energy level of 662keV, there is no difference between the samples containing micro and nanoparticles of WO₃ and Bi₂O₃. However, a matrix containing microparticles of PbO has a higher mass attenuation coefficient than a matrix containing nano-particles of PbO. The study was partly dedicated to the comparison of the experimental and theoretical (MCNP4C) attenuation percentages of the micro samples of Bi₂O₃, WO₃ and PbO in exposure to ionizing radiation. As it was observed, at 40 kV, the experimental and theoretical results were almost the same for the three samples. At 70 kV and 120 kV, however, these results were significantly different in the case of the sample containing Bi₂O₃ micro-particles.

Introduction

Nowadays, irradiations with gamma ray and X-ray are widely done for the diagnosis and treatment of many diseases in medical physics [1]. These rays may have ionizing effects on the atoms and molecules in cells and cause free radicals to spread and reach the nearby molecules, leading to injuries to important cell components [2]. To keep the radiation staff and others safe from the exposure to ionizing radiation, public places and working areas should be shielded or protected. Owing to its high density (8.90 g/cm³), high atomic number (Z $=$ 82), cheapness and abundance, lead (Pb) has been considered as a good X-ray-shielding material. However, lead aprons are relatively heavy, and their toxicity poses an environmental problem. Among high-Z elements, tungsten (W, Z $=$ 74) and bismuth (Bi, Z $=$ 83) are two alternatives which have a very low toxicity, [3], [4], [5], [6], [7], [8], [9]. As another class of alternatives, non-toxic lead-free polymer composites have aroused great interest in many areas, especially medical fields. These composites are preferred for their lightweight, workability and ability to effectively attenuate radiation. Also, due to their low density and ease of construction, this new type of materials, which are based on nanoparticle-filled polymer compounds, is more favored and employed than others [10], [11], [12].

Attenuation or absorption of high-energy radiations by composite shields has been reported frequently. As it has been observed, the increased surface area on nano-scale materials decreases the need for raw materials. Therefore, the study and the use of nanoparticles have flourished for conservation purposes [10], [13], [14], [15], [16].

Polymer nanocomposites containing non-lead fillers are gaining considerable attention as radiopaque materials. They are easy to handle due to their flexibility, paving the way for a wide range of applications [10], [15], [17].

Photon attenuation parameters can be determined experimentally by using radiation sources with particular energy levels and through transmission spectra. Monte Carlo N-Particle Transport Code (MCNP4C) has been used to simulate gamma and X-ray attenuation. MCNP4C is, indeed, a widely benchmarked simulation code for real cases. It is based on the Monte Carlo technique of tracking thousands of particles over a wide range of energy (up to 100 MeV).

The aim of this study is to develop a coating which can be directly applied to the surface of textiles through conventional textile processes and with a focus on protection against ionizing radiations in medical applications. For this purpose, EPVC composites containing Bi or W compounds were prepared, appropriate methods to adhere them to fabrics were investigated, and their ability to shield diagnostic X-rays (40, 70 & 120 kVp) and gamma radiation (Cs 137 source, 0.662 MeV) was evaluated. Also, for comparison purposes, EPVC composites containing Pb compounds were investigated, and the MCNP4C results were compared with the experimental data.

Section snippets

Materials and methods

At the first step, some micro powder of the studied oxide was purchased from Aldrich and Merck. The nano-powder was synthesized by hydrothermal and chemical methods [11]. Using SEM images, the characterization of the materials was performed. The corresponding data are provided in Table 1.

Emulsion polyvinyl chloride (EPVC) is an excellent polymer by virtue of its good characteristics, including stiffness, low price, physical properties, mechanical performance and thermal stability. In addition,

Attenuation theory

The basic theory of attenuation is summarized in Formula (1) as follows: $D = D_{0} exp (- μ x)$ where D, $D_{0}$ , $μ$ and x are the measured dose after a shield, the measured dose without any shield, the attenuation coefficient and the shield thickness respectively.

The attenuation percentage (AP) could be calculated by Formula (2) as follows: $AP = \frac{D_{0} - D}{D_{0}} * 100$ where D and $D_{0}$ denote the doses measured with and without a shield. Using AP, the attenuation ability of the shield could be obtained independently of

MCNP4C simulation code

MCNP4C code is a Monte Carlo radiation transport code used for modeling the transport and the interaction of radiation with matter. It utilizes nuclear cross-section libraries and physical models for particle interactions and yields the required quantity with a certain error (Shirmardi et al., 2013).

The geometry of an X-ray and gamma system is composed of a source collimator and a detecting collimator. The two collimators are made of two lead cylinders, and a fiber shield is located between the

Scanning electron microscopy

Scanning electron microscopy (SEM) was conducted to investigate the surface morphology of the prepared samples using VEGA\\TESCAN SEM, Czech Republic. Fig. 3 presents the back-scattered SEM (BSEM) image of the fiber without coating. Also, the BSEM of the coated fibers can be seen in Fig. 4. All of the samples were sputter-coated with a thin layer of gold to minimize sample charging. The BSEM images were taken under extreme vacuum conditions.

As shown in Fig. 4, the dispersion of the particles

Conclusion

In this study, the attenuation percentages, mass attenuation coefficients and effective atomic numbers ( $Z_{eff}$ ) of different coating materials were calculated. It was found that Bi₂O₃, WO₃ and PbO in a suitable polymer composite can be coated on fabrics as an effective method to produce flexible and wearable aprons. The attenuation ability of the studied materials proved to be sufficient. They can, thus, be used as alternatives to Pb-containing shields. It should be noted that the results were

CRediT authorship contribution statement

Leila Gholamzadeh: Conceptualization, Methodology, Resources, Project administration, Writing - review & editing, Supervision. Nadia Asari-Shik: Investigation, Formal analysis, Writing - original draft. Mohsen Khajeh Aminian: Formal analysis, Validation, Writing - review & editing. Mahdieh Ghasemi-Nejad: Software, Formal analysis.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

The authors thank the RRC (Radiation Research Center) of Shiraz University for its friendly cooperation.

Funding

This work was supported by INSF (Iran National Science Foundation) under the grant number 96000566.

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A study of the shielding performance of fibers coated with high-Z oxides against ionizing radiations

Abstract

Introduction

Section snippets

Materials and methods

Attenuation theory

MCNP4C simulation code

Scanning electron microscopy

Conclusion

CRediT authorship contribution statement

Declaration of Competing Interest

Acknowledgment

Funding

Appl. Radiat. Isot.

Radiat. Phys. Chem.

Appl. Radiat. Isot.

J. Alloys Compd.

Monte Carlo dosimetric characterization of the Cs-137 selectron/LDR source: Evaluation of applicator attenuation and superposition approximation effects

Med. Phys.

Radioisotopes and their Applications in Nuclear Physics

A novel design for production of efficient flexible lead-free shields against X-ray photons in diagnostic energy range

J. Biomed. Phys. Eng.

Radiation attenuation properties of shields containing micro and Nano WO3 in diagnostic X - ray energy range

Int. J. Radiat. Res.

Nano-W dispersed gamma radiation shielding materials

Adv. Eng. Mater.

A review on silicone rubber

Natl. Acad. Sci. Lett.

An alternative X-ray shielding material based on coated textiles

Text. Res. J.

Radiation attenuation properties of shields containing micro and Nano WO₃ in diagnostic X - ray energy range