Radiation Protection and Environment

ORIGINAL ARTICLE
Year
: 2016  |  Volume : 39  |  Issue : 1  |  Page : 3--6

Radiation shielding of polymer composite materials with wolfram carbide and boron carbide


Alparslan Erol1, Isa Pocan1, Emre Yanbay1, Onur Alp Ersoz2, Fatma Yurt Lambrecht2,  
1 Department of Engineering, Turkish Military Academy, Cankaya, 06240 Ankara, Turkey
2 Department of Nuclear Applications, Ege University, Institute of Nuclear Sciences, Bornova, 35100 Izmir, Turkey

Correspondence Address:
Emre Yanbay
Department of Nuclear Applications, Institute of Nuclear Science, Ege University, Bornova, 35100 Izmir
Turkey

Abstract

In general, lead is used as shielding material for protection against radiation. In spite of its high density, lead is toxic and lead aprons are very heavy for personal shielding. Thus, there is a need for nontoxic, light, and environmental friendly radiation-shielding materials. Polymers cannot be effective against gamma radiation on their own. High-density metal wolfram carbide could be useful against gamma radiation, and boron carbide could also be useful for neutron shielding. In this study, high-density polyethylene, boron carbide, and wolfram carbide can be mixed in certain amounts and composite discs can be obtained in this way. According to results, a new shielding material is efficient for gamma radiation.



How to cite this article:
Erol A, Pocan I, Yanbay E, Ersoz OA, Lambrecht FY. Radiation shielding of polymer composite materials with wolfram carbide and boron carbide.Radiat Prot Environ 2016;39:3-6


How to cite this URL:
Erol A, Pocan I, Yanbay E, Ersoz OA, Lambrecht FY. Radiation shielding of polymer composite materials with wolfram carbide and boron carbide. Radiat Prot Environ [serial online] 2016 [cited 2020 Apr 5 ];39:3-6
Available from: http://www.rpe.org.in/text.asp?2016/39/1/3/185147


Full Text

 INTRODUCTION



Ionizing radiation could be dangerous for human life depending on its energy. However, there are three principles for protection against the hazards of radiation. These are time, distance, and shielding. Staying as less time as possible around the radiation sources and staying as far as possible away from the radiation sources can cause less radiation exposure. Shielding is the best technique for a radiation worker to protect himself/herself from the hazardous effects of radiation. There are various shielding techniques depending on the type of radiation. Alpha particles are so heavy that they cannot move very far away in the air and their penetration is very low. Thus, there is no need for special shielding techniques against alpha particles. Human skin can easily block them. Unlike alpha particles, beta particles can move easily in the air and their penetration is higher than alpha particles. In general, elements of the low atomic number such as aluminum should be used as beta radiation shielding. Hydrogenous polymers and boron could play an important role for neutron shielding. [1],[2] However, gamma rays could easily penetrate through the human body. Therefore, high-density materials are used for gamma ray protection. [3]

In general, lead and lead compounds are used for protection against gamma rays. Nevertheless, lead is toxic and aprons are so heavy for personal shielding. [4] Therefore, the materials which are environment friendly and nontoxic can be used with both personal and material lighter shield. This has increased the interest in the polymer composite radiation-shielding material. However, polymers are inefficient to stop gamma rays on their own. [5],[6] High-density wolfram carbide has no toxic effectiveness and could stop gamma rays.

Nowadays, researchers are generally studying various polymers and high-density metals for radiation protection.

Yue et al. have been studying wolfram and styrene-butadiene-styrene copolymer and have obtained a new shielding material by mixing metal and copolymer. [7]

In the study by Ivanova et al., high-density polymer metal composites are used for radiation protection in radiotherapy. In the preparation of this composite, wolfram powder and polymer were created by mixing high-density and low X-ray transmittance. [8]

Soylu et al. had been investigating the efficiency of wolfram carbide-doped polymer on gamma ray shielding. In this study, 50%, 60%, and 70% wolfram carbide-doped polymer composite discs had been produced and exposed to I-131, Am-241, and Cs-137 gamma sources, respectively. According to the results, the best efficiency of composite materials was determined against the Cs-137 source. [9]

Eder had been studying tin, bismuth, and wolfram instead of lead alternatively. In this study, he mixed metals with polymers in different ratios and obtained materials that were exposed to X-rays. He found that the ability of absorption decreased depending on the increase of the voltage of the tube. [10]

McAlister had been studying a polymer that was named T-Flex which was mixed with wolfram and iron powders and he produced a shielding material. This shielding material was exposed to various radiation sources and he compared the theoretical results that were obtained with X-COM and experimental results. [11]

In this study, we aimed at the production of a durable, healthy, flexible, light-shielding material, which contains boron and wolfram carbide. Four different samples were prepared in this context. The shielding ability of these samples was tested with a Geiger-Müller (GM) detector with Cs-137 and I-131 radioisotopes where the best results of the products were obtained.

 MATERIALS AND METHODS



Preparation of samples

The composite discs were produced using a high-density metal warm compaction (WC) powder (<10 μm), boron carbide, and high-density polyethylene. WC (density = 15.63 g/cm 3 ) was supplied by Sigma-Aldrich (Multinational chemical, life science and biotechnology company. Europe and USA).

The materials in the metal polymer composites were used as a radiation-shielding material that could be mixed homogeneously. First, WC powder, B 4 C powder, and polymer powder were mixed homogeneously by mechanical mixture method. After that, powder mixture was pressed by hot-press technique and then, four 1 mm thickness and 8 cm diameter discs were formed by cold-press technique in the prepared pattern which is presented in [Table 1]. Thus, four different types of discs have been made and are presented in [Table 2].{Table 1}{Table 2}

Mechanical and homogeneity tests

Tests were performed with the use of Shore-D test with an Geratech LX-D Analog Shoremetre (Geratech, manufacturer of measuring equipments, Germany) at the Department of Mechanical Engineering of the Dokuz Eylül University so that the elasticity of discs could be determined.

The discs were sent to the Department of Mechanical Engineering of the Dokuz Eylül University to determine their homogeneity. The homogeneity of the composite discs was analyzed with a scanning electron microscope (SEM).

Gamma detection

The shielding potential of the material was determined by working with radioisotopes with different gamma energies. The shielding of the prepared discs was measured in orderly Cs-137 (662 keV) and I-131 (364 keV) point sources, inserted 20 cm away of GM detector. With each source, empty counting was made without placing prepared discs in 300 s. Then, polymer composite discs and the equivalent lead disc were placed separately on a detector window and were counted 6 times for 300 s too.

 RESULTS AND DISCUSSION



According to the SEM images shown in [Figure 1] and [Figure 2], metal powders were dispersed homogeneously in the polymer for all discs.{Figure 1}{Figure 2}

According to [Table 3], Shore-D test has shown that the composite discs are elastic and soft. Then, they are easily shapeable.{Table 3}

The 5 μCi and 662 keV activity Cs-137 point source with energy gamma counting and shielding effectiveness results are shown in [Figure 3]. When the measurements were evaluated, it was found that Disc 1 and Disc 2 have the best shielding effectiveness while Disc 1 and Disc 2 have a constant ratio of WC, the shielding effectiveness was increased by increasing the B 4 C ratio. In addition, the shielding effectiveness was compared to the equivalent disc as lead; Disc 1 was 4.32% and Disc 2 was 2.03% more efficient than the equivalent lead disc.{Figure 3}

According to [Figure 4], 5 μCi and 364 keV activity I-131 point source with energy gamma counting and shielding effectiveness results are given. When the measurements were evaluated, it was found that Disc 1 has the best shielding effectiveness. In addition, the shielding effectiveness was compared to the equivalent disc as lead; Disc 1 was 0.81% more efficient than the lead disc.{Figure 4}

At the end of gamma rays detection, we obtained the best results with Disc 1. Equivalent lead disc (1 mm thickness, 8 cm diameter) and Disc 1 were compared as far as their weight was concerned. The weight of Disc 1 was 9.4 g while the weight of the lead disc was 28 g.

 CONCLUSIONS



According to results, wolfram carbide-doped boron carbide polymer composite could be a candidate for protection against gamma ray applications. It has been proved that new shielding materials have managed to stop the efficiency against high-energy gamma rays better than lead. On the other hand, the new shielding material is elastic, soft, and easily shapeable. Another advantage of the composite is its lightness. The wolfram carbide-doped boron carbide polymer composite is lighter than lead. Thereby, this material is used in commercial utilization as a gamma shielding equipment.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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