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Non-toxic Radiopac/Shielding Materials

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The use of radiation is invariably associated with very well established harmful health hazards. The wide application spectrum of the radiation based technology ranging from radio wave to X-ray and gamma ray is well established. Application of high energy electromagnetic radiations i.e. X-ray and γ-ray are inevitable in areas like medical applications (X-ray diagnostic and CT scanner rooms/ establishments, gamma radiation therapy of cancer), energy sector, power generation by nuclear power plants, defence sector (bunkers for army personnel) etc. They pose challenges in terms of the strategic safety planning in view of increased global terrorism etc. Lead has been conventionally used as a radiation shielding material, but is inherently toxic in nature, has high density and does not provide effective shielding against neutron radiation. Further, the element ranks second in the list of most hazardous materials in the UPA list of USA. The use of toxic metals like lead and rare earth materials has been obligatory so far for radiation shielding. Concrete has also been used as a shielding material against γ-ray radiation. However, it suffers from shortcomings like large thickness requirement to serve the purpose and corrosion due to depleted uranium. Accordingly, increased awareness for the environmental safety has necessitated the need for the development of non toxic, i.e. lead free and eco-friendly radiation shielding materials.

In view of the above, a novel process for making advanced new radiopac materials has been developed at AMPRI for the first time in the world. The development involves a unique approach and methodology for making highly effective shielding phases utilizing red mud and fly ash. The shielding materials have been developed by using ceramic as well as ceramic polymer composites in the form of cement, panel and tiles. The shielding efficiency of the developed materials has been evaluated by Radiation Standards and Safety System Division of BARC, and Atomic Energy Regulatory Board (AERB), Mumbai. The HVT (half value thickness), i.e. shielding thickness, of the developed materials has been observed to be the same as that of the conventionally used material i.e. lead for the diagnostic X-ray of 100kV and 60% less in comparison to the conventionally used concrete for shielding gamma radiations. Interestingly, the developed materials are 40-50% in weight compared to that of lead and are cheaper than the latter due to the use of wastes as the raw material. They would also be lighter than concrete keeping despite having comparable density in view their less thickness needed for producing the same degree of shielding effect. The developed materials have also been found to work efficiently for shielding against neutron radiation as well. Further, they meet the ISI and ASTM standards to be used for constructing radiation shielding installations for multifarious applications. The application potential of the X-ray shielding tiles has successfully been demonstrated by fitting them in the X-ray room of Govt. J.P. hospital, Bhopal.   Other potential applications of the developed materials could be in the fabrication of storage devices for radioactive wastes and shipping containers for radioisotopes.

Material

Density, g.cm-3

Half value thicknes, cm (100 KVp diagnostic)

Shielding capability

Thermal Stability, oC

Half value thicknes, cm (γ-ray radiation)

Lead

11.34

0. 085

X-ray

328 (melting point)

1.0

Concrete

2.3

22.5 (Bricks)

γ-ray

~1300

7.0

Developed material

2.0-4.5

0.078

X-ray, γ-ray, neutron radiation

1300

3.0

 

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