Lead Free X-Ray Shielding Tiles

Radiation shielding materials are the integral part of civil construction in medical X-ray diagnostic rooms, nuclear power facilities, particle accelerator, synchrotron radiation sources, radiotherapy rooms, etc., to protect public, operation personals and environment from radiation hazard. The global medical radiation shielding market is projected to grow at a Compound annual growth rate of 5.02% to reach US$1,750.875 million by 2025, from US$1,305.038 million in 2019.

Lead and heavy weight concretes are widely used to shield such high energy radiations. Worldwide 12 million tons of lead has been produced. Among that 6% of lead has been used for radiation shielding application. Although India is one of the top most producer of lead, India is importing 2,00,000 tones of lead every year. Among that, India is using 12,000 tones for radiation shielding purposes. It costs nearly Rs. 225/kg. So, overall India is importing Rs. 2700 million i.e. 40 million USD worth lead for radiation shielding purposes, which can be saved through this technology.

In addition, alumina industries are spending Rs 800/tonne (12 USD) to safeguard red mud. So it is expected to further save Rs. 7.2 billion, which has been spend on safe guarding red mud. Utilization of such secondary resources will reduce primary mining, accumulation of industrial waste, deforestation, and environmental pollution.

Radiation is a serious concern in medical diagnostic systems, nuclear power facilities, particle accelerator, synchrotron radiation sources, food sterilization plants, radiotherapy facilities, etc.  Prolonged exposure and accumulation of such high energy ionizing radiations like X- rays, gamma-rays and particle emissions (alpha, beta, proton, electron and neutron) may result in cell mutations, genetic disorder, organ failure etc. To avoid the occupational hazardous of employees, public and environment from the radiation is a great concern. Commonly, lead based radiation shielding materials are widely used to attenuate high energy gamma and X-rays, because of its high atomic number (82), high density (11.34 g/cc), malleability and low cost. But, lead is highly toxic and contact with this toxic material could lead to severe health problem. Lead is known to interfere with a number of body functions and it is primarily affecting the central nervous, hematopoietic, hepatic and renal system producing serious disorders. Lead poisoning happens when too much lead gets into the body through the skin, inhalation, eating and drinking.

Apart from lead other materials like high atomic number based iron, tin, antimony, tungsten, Bismuth etc., filled polymer composites and thick walled heavy weight concretes are also used to attenuate high energy ionizing radiations. The high Z material incorporated polymer composites are expensive. Heavyweight concretes are used to fabricate by incorporating heavy density aggregates in cement matrix. But the concretes are not stable above 300°C due to the breakage of C-S-H gel.

CSIR-Advanced Materials and Processes Research Institute (CSIR-AMPRI)  was converted iron rich red mud (hazardous alumina industrial waste) into X-ray shielding tiles, which can be used to shield X-rays instead of toxic lead sheet and concretes in the X-ray diagnosis, computerized tomography scanner (CT scan) and Cath labs. The red mud tiles were made through ceramic route by adding 30 – 45 wt% of BaSO₄/Bi₂O₃ and 5 – 10 wt% kaolin clay binder with it. The green tiles were fabricated by applying 300 kg/cm² pressure in a hydraulic press and then sintered between 1050 - 1150°C. The developed tile posses the flexural strength of 22 N/mm². The 6.29 mm and 11.698 mm thick red mud:Bi₂O₃:kaoline clay tile and red mud:BaSO₄: kaoline clay  tile, respectively, possess the attenuation equivalent to 2 mm lead at 125 kVp X-ray. The developed tiles were accredited by Atomic Energy Regulatory Board of India and listed as an alternative material of toxic lead in their website (https://aerb.gov.in/images/PDF/layout_guidelines.pdf).

 The developed tiles were demonstrated in M/S Saideep Healthcare and Research Pvt. Ltd., Ahmednagar. Nearly 2500 ft² joint free X-ray shielding tiles were fabricated and installed in two X-ray diagnoses, one CT scanner and one Cath lab of it, which is in operation since 2018.

This innovation will suppress the accumulation of hazardous red mud, which is underutilized (2-3% has been used in building sectors) and associated environmental problems like ground water, soil and air pollution. It will also reduce the usage of toxic lead sheet in hospitals and its import.

Commonly, 2mm thick toxic lead is used to shield diagnostic X-rays that can emerge out of X-ray diagnosis, CT-scanner and Cath labs. The radiation shielding tiles developed by us is lead free, non-toxic and made using industrial waste. The 12mm thick tile posses the attenuation equivalent to 2mm lead and 12mm barite board. It is three times cheaper than lead and barite boards. It occupies less space as compared to the lead and concrete. It will reduce the usage of toxic lead, primary mining, and accumulation of industrial waste and associated air, soil and ground water pollution. It is thermally stable and easily repairable.

 This red mud based lead free radiation shielding tiles are approved by the Atomic Energy Regulatory Board (AERB) of India.