HIGHLY DENSE RED MUD SHIELDS FOR X-RAY AND GAMMA-RAY ATTENUATION
20240018050 ยท 2024-01-18
Assignee
Inventors
- Salammal Shabi THANKARAJ (Bhopal, IN)
- Deepti MISHRA (Bhopal, IN)
- Sunil Kumar SANGHI (Bhopal, IN)
- Varsha AGRAWAL (Bhopal, IN)
- Rini PAULOSE (Bhopal, IN)
- Rahul ARYA (Bhopal, IN)
- Sriram SATHAIAH (Bhopal, IN)
- Sanjai Kumar Singh RATHORE (Bhopal, IN)
- Avanish Kumar SRIVASTAVA (Bhopal, IN)
Cpc classification
C04B2235/96
CHEMISTRY; METALLURGY
C04B35/453
CHEMISTRY; METALLURGY
C04B2235/3215
CHEMISTRY; METALLURGY
C04B2235/3298
CHEMISTRY; METALLURGY
International classification
C04B35/626
CHEMISTRY; METALLURGY
C04B35/453
CHEMISTRY; METALLURGY
Abstract
A novel eco-friendly method has been developed for the fabrication of high dense (3.3-5.2 g/cc) red mud based material blocks for shielding high energy X- and -rays. The red mud based material blocks with various densities were fabricated by hot compacting partially melted red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 samples at 1150 C., 1000 C., 1050 C. and 1000 C., respectively. This material can be used to build radiation shielding structures in medical diagnosis, radiotherapy, industrial radiography, particle accelerators, food sterilization plants, nuclear power plants, and radioactive material storage rooms, without further structural support unlike lead (concrete walls). It is economically viable and will suppress the accumulation of hazardous red mud and associated environmental pollutions.
Claims
1-9. (canceled)
10. A red mud based material for attenuation of x-rays and gamma rays, the red mud based material comprising: (a) from 50 wt % to 100 wt % red mud; and (b) from 0 to 50 wt % of: (i) Bi.sub.2O.sub.3; or (ii) Ba(OH).sub.2; or (iii) a 50:50 wt % mixture of Bi.sub.2O.sub.3 and Ba(OH).sub.2.
11. The red mud based material of claim 10, wherein the density of the red mud based material is from 3.3 g/cc to 5.23 g/cc.
12. The red mud based material of claim 10, selected from: red mud having a density of 3.3 g/cc; or red mud:Bi.sub.2O.sub.3 having a density of 5.23 g/cc; or red mud:Ba(OH).sub.2 having a density of 4.6 g/cc; or red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 having a density of 4.7 g/cc.
13. The red mud based material of claim 10, wherein the compressive strength of the material is from 34 MPa to 282.15 MPa.
14. The red mud based material of claim 10, selected from: red mud having a compressive strength of 34.18 MPa; or red mud:Bi.sub.2O.sub.3 having a compressive strength of 282.15 MPa; or red mud:Ba(OH).sub.2 having a compressive strength of 144 MPa; or red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 having a compressive strength of 122 MPa.
15. The red mud based material of claim 10, wherein the half value layer of the material is from 20.96 mm to 34.02 mm at 1.33 MeV (.sup.60Co source).
16. The red mud based material of claim 10, wherein the half value layer of the material at 150 kVp X-ray is from 0.7434 mm to 3.10 mm.
17. A process for preparation of a red mud based material for attenuation of x-rays and gamma rays, the process comprising: (a) taking 50 wt % to 100 wt % of red mud; (b) separately taking 0 to 50 wt % of a component chosen from: (i) Bi.sub.2O.sub.3; or (ii) Ba(OH).sub.2; or (iii) a 50:50 wt % mixture of Bi.sub.2O.sub.3 and Ba(OH).sub.2; (c) grinding the red mud in a ball mill for 4 hours; (d) adding to the ball mill of (c) the component of (b) and grinding for one hour to obtain a mixture; (e) taking the mixture obtained in (d) in a graphite die and sintering at a temperature from 1000 C. to 1150 C. in a hot press at a heating rate of 7 C./min to obtain a partially melted mixture; and (f) compacting the partially melted mixture obtained in (e) by applying pressure of from 23 MPa to 40 MPa for 30 seconds to 60 seconds and cooling at a rate of 10 C./minute to 27 C. to obtain the red mud based material.
18. The process of claim 17, wherein the sintering results in formation of highly dense phases selected from Fe.sub.3O.sub.4, hematite, cancrinite, nepheline, pseudobrookite, gehlenite, silico-ferrite of calcium and aluminum (SFCA), Bi.sub.12SiO.sub.20, 2BiFeO.sub.3, BaTiO.sub.3, and BaFe.sub.12O.sub.19.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0047]
[0048]
[0049]
DETAIL DESCRIPTION OF THE INVENTION
[0050] Accordingly the present invention provides a red mud based material for X- and gamma-ray attenuation which comprises of raw materials like red mud, Bi.sub.2O.sub.3 and Ba(OH).sub.2 in which red mud is initially ball milled for a duration of 4 hrs using 350 gm stainless steel balls (6 Nos) and then equal amount of Bi.sub.2O.sub.3 or Ba(OH).sub.2 or Bi.sub.2O.sub.3:Ba(OH).sub.2 (50:50 ratio) is added with the grinded red mud and then ball milled for another 1 hr to obtain a uniform mixture, then the mixture is taken in a 5 cm die and loaded into the furnace and heated between 1000 C. to 1150 C. at a rate of 7 C./min. Then pressure in the range of 23 MPa to 40 MPa is applied in a hot press to the partially melted mixture at the end of dwelling period and the compressed mixture is cooled at a rate of 10 C./min to fabricate blocks.
[0051] In an embodiment of the present invention, the raw materials used for the preparation of X- and -rays shielding blocks are red mud, Bi.sub.2O.sub.3 and Ba(OH).sub.2.
[0052] In another embodiment of the present invention, pure red mud is grinded in a ball mill for 4 hrs to crush them into fine powders using 350 gm stainless steel balls (6 Nos).
[0053] In yet another embodiment of the present invention, grinded red mud is mixed with commercial grade 50 wt % of Bi.sub.2O.sub.3 or Ba(OH).sub.2 or a mixture of Bi.sub.2O.sub.3 and Ba(OH).sub.2 (50:50 ratio) and then both are together grinded in a ball mill for 1 hr.
[0054] In still another embodiment of the present invention, an amount of the red mud or red mud:Bi.sub.2O.sub.3 or red mud:Ba(OH).sub.2 or red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 with respect to the desired thickness is taken in a die and then loaded into the hot press.
[0055] In still another embodiment of the present invention, the red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 samples are heated to 1150 C., 1000 C., 1050 C. and 1000 C., respectively in a hot press with a heating rate of 7 C./min.
[0056] In yet another embodiment of the present invention, the partially melted red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 samples are compacted by applying 23.4 MPa, 40 MPa, 23.4 MPa and 40 MPa pressure, respectively in a hot press at the end of the dwelling period.
[0057] In yet another embodiment of the present invention, the boehmite, goethite, gibbsite and calcite present in the red mud decomposes during sintering and form new phases like hematite, cancrinite, nepheline, pseudobrookite, gehlenite, perovskite, silico-ferrite of calcium and aluminium (SFCA), Bi.sub.12SiO.sub.20, 2BiFeO.sub.3, BaTiO.sub.3, and BaFe.sub.12O.sub.19.
[0058] In yet another embodiment of the present invention, the developed blocks were tested for density, porosity, X-ray diffraction, heavy element leaching, X-ray (150 kVp) and gamma ray attenuation (Cobalt-60) analysis.
[0059] An embodiment of the present invention provides a red mud based material for X- and -ray attenuation comprising: [0060] a) 50-100 wt % of red mud; and [0061] b) 0 to 50 wt % of Bi.sub.2O.sub.3 or Ba(OH).sub.2 or a mixture of Bi.sub.2O.sub.3 and Ba(OH).sub.2 (50:50 wt %).
[0062] In another embodiment of the present invention, there is provided a red mud based material, wherein the density of said material is in the range from 3.3 g/cc to 5.23 g/cc.
[0063] In still another embodiment of the present invention, there is provided a red mud based material, wherein the density of red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 shields are 3.3 gcc, 5.23 g/cc, 4.6 g/cc and 4.7 g/cc, respectively.
[0064] In yet another embodiment of the present invention, there is provided a red mud based material, wherein the compressive strength of the material is in the range from 34.18 MPa to 282.15 MPa.
[0065] In another embodiment of the present invention, there is provided a red mud based material, wherein the compressive strength of red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 are 34.18 MPa, 282.15 MPa, 144 MPa and 122 MPa, respectively.
[0066] In still another embodiment of the present invention, there is provided a red mud based material, wherein half value layer of the material is in the range of 20.96 mm to 34.02 mm at 1.33 MeV (.sup.60Co source).
[0067] In another embodiment of the present invention, there is provided a red mud based material, wherein half value layer of the material at 150 kVp X-ray is in the range from 0.7434 mm to 3.10 mm.
[0068] Another embodiment of the present invention provides a process for preparation of a mud based material for X- and -ray attenuation comprising: [0069] a. taking 50-100 wt % of red mud; [0070] b. separately taking 0 to 50 wt % of Bi.sub.2O.sub.3 or Ba(OH).sub.2 or a mixture of Bi.sub.2O.sub.3 and Ba(OH).sub.2 (50:50 wt %); [0071] c. grinding the red mud in a ball mill for 4 hrs; [0072] d. adding Bi.sub.2O.sub.3 or Ba(OH).sub.2 or a mixture of Bi.sub.2O.sub.3 and Ba(OH).sub.2 to said ball mill of step (c) and grinding for one more hour to obtain a mixture; [0073] e. taking the mixture obtained in step (d) in a graphite die and sintering at a temperature in the range of 1000 C. to 1150 C. in a hot press at a heating rate of 7 C./min to obtain a partially melted mixture; [0074] f. compacting the partially melted mixture obtained in step (e) by applying pressure in the range of 23 MPa to 40 MPa for 30-60 seconds; and cooling at a rate of 10 C./minutes to 27 C. to obtain the red mud based material.
[0075] In another embodiment of the present invention, there is provided a process for preparation of a mud based material, wherein the heating step results in formation of high dense phases like Fe.sub.3O.sub.4, hematite, cancrinite, nepheline, pseudobrookite, gehlenite, silico-ferrite of calcium and aluminum (SFCA), Bi.sub.12SiO.sub.20, 2BiFeO.sub.3, BaTiO.sub.3, and BaFe.sub.12O.sub.19.
[0076] The novelty of the present invention in the fact that the process of the present invention obviates the drawbacks of the existing red mud based radiation shielding materials mainly on the density and half value layer of the radiation shields.
[0077] In this present investigation, the inventors have compacted a partially melted red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 samples close to their melting point to close the pores and thereby to increase the density. The density of red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 blocks are 3.3 g/cc, 5.23 g/cc, 4.6 g/cc and 4.7 g/cc, respectively. The porosity of the developed red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 blocks are 3.8%, 2.8%, 0.08% and 2.0%, respectively. The half value layer of red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 samples at 1.33 MeV are 34.02 mm, 20.96 mm, 26.80 mm and 24.0 mm, respectively. The HVL of developed red mud:Bi.sub.2O.sub.3 block is more than half of lead (HVL of lead at 1.33 MeV is 12.5 mm) and three times smaller than the concrete (HVL of concrete at 1.33 MeV is 60.5 mm). The HVL of the sample at 150 kVp is 3.10 mm, 0.743 mm, 1.0754 mm and 0.8776 mm for red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 sample, respectively. Moreover, the developed material is lead free and the process is green as it does not emit any green house gases like CO.sub.2 and SO.sub.2 during sintering. The developed material possess the compressive strength between 34 MPa-282 MPa, which is suitable for building the radiation shielding structures without additional structural support like lead. It eventually decreases the thickness of the radiation shield and increases the usable spaces.
[0078] In the process of the present invention, high dense and lead free radiation shielding materials have been developed using iron rich red mud (alumina industrial waste), Ba(OH).sub.2 and Bi.sub.2O.sub.3. The developed radiation shielding materials can be used to shield both the X- and gamma-rays that come out of X-ray diagnostic, radio therapy rooms, food sterilization plants, radioactive material storage rooms, industrial radiography, particle accelerators, and nuclear power plants. The 301.82 mm thick block possesses (red mud:Bi.sub.2O.sub.3) the attenuation equivalent to 180 mm lead at 1.33 MeV, and 6.20 mm thick pellet possess the attenuation equivalent to 2.5 mm lead at 150 kVp. The developed material possesses sufficient strength (34-282 MPa depending on the composition), which is suitable for structural applications. The material eventually requires much less thickness as compared to polymer-metal composites, heavy weight concrete, barite board, and light weight concrete based radiations shields. Moreover, the developed blocks can be directly used to build radiation shielding structure without further structural support unlike lead. It is economically viable and will suppress the accumulation of hazardous red mud and associated environmental pollutions.
[0079] The red mud blocks with various densities were fabricated by hot compacting partially melted red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 samples at 1150 C., 1000 C., 1050 C. and 1000 C., respectively. The red mud is grinded in a ball mill and then mixed with appropriate weight percentage of high Z metal compound. The compound mixture is taken in a die and then heated to a desired temperature at a heating rate of 7 C./min. The partially melted powder is compacted by applying pressures between 23-40 MPa for few seconds and then the samples are cooled at a rate of 10 C./min. The densities of the developed blocks of red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 samples are found to be 3.3 g/cc, 5.2 g/cc, 4.6 g/cc, and 4.7 g/cc, respectively. Gamma attenuation characteristics of the developed shields are studied using Cobalt 60 source by varying the thickness of the shield. The HVL of the sample at 1.33 MeV photon is 34.02 mm, 20.96 mm, 26.80 mm and 24 mm for red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 sample, respectively. The 489.88 mm, 301.82 mm, 385.92 and 345.6 mm thick red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 samples are found to possess the attenuation equivalent to 180 mm lead at 1.33 MeV. The HVL of the sample at 150 kVp is found to be 3.10 mm, 0.7434 mm, 1.0754 mm and 0.8776 mm for red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 sample, respectively. The red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 samples possess the compressive strength of 34.18 MPa, 282.15 MPa, 144 MPa and 122 MPa, respectively. This material can be used to build radiation shielding structures in medical diagnosis, radiotherapy, industrial radiography, particle accelerators, food sterilization plants, nuclear power plants, and radioactive material storage rooms without further structural support unlike lead (concrete walls).
[0080] In the present invention, iron rich red mud is converted into X- and gamma-ray shielding material in a green manner. Red mud is an alumina industrial waste and is left unused in the disposal plants due to inadequate technologies for large scale utilization. It is hazardous due to its extreme alkalinity (>11 pH). The developed material is lead free and economically viable. Moreover, the material consumes less space compared to lead (lead need additional support structures), heavy weight and light weight concretes based radiation shields. It can be used to protect common public, operating personals and environment from harmful X- and gamma-rays, which can emerge out of medical therapy, nuclear power plants, food sterilization plants, radioactive nuclide storage rooms, particle accelerators, and industrial radiography. The red mud based radiation shields will be much cheaper than lead and heavy weight concrete as it is based on industrial waste. Utilization of such secondary resources will reduce primary mining, accumulation of hazardous waste and associated environmental pollution and deforestation.
[0081] Thus, the present application provides a green and eco-friendly method for the conversion of hazardous red mud into X- and -rays shielding materials. The process is schematically illustrated in
[0082] Further, the gamma ray attenuation coefficients of the samples were studied using Co-60 source. The half value layer of red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 sample was found to be 34.02 mm, 20.96 mm, 26.80 mm, and 24.0 mm, respectively at 1.33 MeV.
[0083] Furthermore, the X-ray attenuation of the developed samples was studied using 150 kVp X-rays. The half value layer of the red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 sample was found to be 3.10 mm, 0.7434 mm, 1.0754 mm and 0.8776 mm, respectively at 150 kVp. Table 1 provides the Half value layer of the hot pressed materials at various kVp.
[0084] The compressive strength of the samples were tested as per ASTM C39 standard and the red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 samples possess compressive strength of 34.18 MPa, 282.15 MPa, 144 MPa and 122 MPa, respectively.
[0085] Since red mud, red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 blocks possess sufficient strength as well as X- and gamma ray attenuation, it can be used to build the radiation shielding structure in medical diagnostic, medical therapy, industrial radiography, particle accelerators, food sterilization plant, storage room for radioactive materials, and nuclear power plants, without additional structural support unlike lead.
TABLE-US-00001 TABLE 1 Half value layer of the hot pressed samples. HVL HVL (0.03 mm) (0.5 mm) Sample 100 kVp 125 kVp 150 kVp 1.33 MeV red mud 2.177 2.70348 3.10 34.02 red mud:Bi.sub.2O.sub.3 0.66524 0.70562 0.7434 20.96 red mud:Ba(OH).sub.2 0.81829 0.92968 1.075 26.80 red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 0.74108 0.79956 0.8776 24.00
EXAMPLES
[0086] The following example is given by way of illustration of the working of the invention in actual practice and therefore should not be construed to limit the scope of the present invention.
Example 1
[0087] Red mud was collected and dried in hot-air oven at 90 C. for 15 hrs. 2 kg red mud was grinded in a ball mill for 4 hrs using six numbers of 350 gm stainless steel balls. Red mud was taken in a 50 mm die in which the interior wall of the die and the bottom and top plungers were coated with molybdenum as lubricant. The sample along with the die was loaded in a hot press and then heated to 1150 C. with the rate of 7 C./min. 23.4 MPa pressure was applied after 30 minutes of dwelling at 1150 C. Subsequently, the sample was cooled with the rate of 10 C./min. The density and porosity of the developed block are 3.3 g/cc and 3.8%, respectively. The red mud blocks with various thicknesses ranging from 1-60 mm were fabricated and then the gamma ray attenuation of the samples were studied using Cobalt-60 source.
[0088] The gamma ray attenuation characteristics of the samples were studied using Cobalt-60 (.sup.60Co) source (activity=1 Ci). The intensity of the direct and the transmitted beams were recorded using Barium Fluoride scintillation detector (BaF.sub.2) with the Multi-Channel Analyzer. The bias voltage is 1400 V. The spectra were readout using Epsilon software and the area under the photopeak of 1.33 and 1.17 MeV was integrated using the apple software. The measured spectra were converted from channel number to energy by calibrating using various gamma energy sources like .sup.60Co(1.17 and 1.33 MeV), .sup.22Na(0.511 and 1.274 MeV), and .sup.137Cs (0.662 MeV). This calibration was done every two to three hours of measurement. Source and detector distance was 150 mm. The Half Value Layer (HVL) (i.e., thickness required to attenuate the incoming radiation by 50%) of the samples were determined by varying the thickness of the samples. The half value layer (HVL) of the developed sample was 34.02 mm at 1.33 MeV.
[0089] The X-ray attenuation of shields were determined at various kVp. X-ray machine (Ultisys 52, kV range 40-150 kVp, mA range 10-640 mA) was used as an X-ray source. The residual X-ray that passes through the tile was determined using X2 R/F Sensor at different accelerating voltages. The IEC 61331-1 quality beam was produced by increasing the Al filter stepwise at the tube head. The recommended HVL of Al at 120 kVp is 4.13 mm. All the measurements were done with a 2.64 mm aluminium added filter. The distance between the sample and the X-ray focal spot is one meter. Linear attenuation coefficient () and half value layer (HVL) were calculated using the equation 1 and 2, respectively.
I=I.sub.oe.sup.deq. (1)
HVL=0.693/eq. (2)
[0090] Where, I.sub.o & I are the intensity of direct and transmitted X-rays, respectively, is the linear attenuation coefficient and d is the thickness of the shield.
[0091] The HVL of the sample at 100 kVp, 125 kVp and 150 kVp X-ray is 2.177 mm, 2.7034 mm and 3.10 mm, respectively. The compressive strength of the sample was studied as per ASTM C39 standard. The developed sample possess the compressive strength of 34.18 MPa, which is suitable for civil constructions.
[0092] The leaching of heavy elements from the sintered tiles was determined using Toxicity Characteristic Leaching Procedure (TCLP) as described in ASTM D3987. The eluate was collected from leachant after 1, 7 & 28 days and the presence of toxic elements like Cd, Cr, Pb, etc., in the eluate, was determined in ppm level using Atomic Absorption Spectrometer (Thermo Scientific iCE3500 series). No heavy elements were found to leach from the shield.
Example 2
[0093] The red mud was collected and dried in hot-air oven at 90 C. for 15 hrs. 2 kg red mud was grinded in a ball mill for 4 hrs using six numbers of 350 gm stainless steel balls. Subsequently 2 kg Bi.sub.2O.sub.3 was added to the grinded red mud and then the mixture was further grinded for one hour for uniform mixing. The grinded red mud:Bi.sub.2O.sub.3 mixture was taken in a 50 mm graphite die. The interior wall of the die and the bottom and top plunger was coated with molybdenum. The sample along with die was loaded in a hot press and then heated to 1000 C. with the rate of 7 C./min. 39 MPa pressure was applied in a hot press after 25 minutes of dwelling at 1000 C. Subsequently, the sample was cooled with the rate of 10 C./min. The density and porosity of the developed sample was 5.23 g/cc and 2.8%, respectively. The radiation shielding blocks with various thicknesses ranging from 4-60 mm were developed and then the gamma ray attenuation of the samples was studied using Cobalt-60 source. The half value layer (HVL) of the developed sample is 20.96 mm at 1.33 MeV. The HVL of the sample at 100 kVp, 125 kVp and 150 kVp X-ray is 0.6652 mm, 0.7056 and 0.7434 mm, respectively. The compressive strength of the samples was studied as per ASTM C39. The developed sample possess the compressive strength of 282.18 MPa and no heavy elements were found to leach from the shield.
Example 3
[0094] Red mud was collected and dried in hot-air oven at 90 C. for 15 hrs. 2 kg red mud was grinded in a ball mill for 4 hrs using six numbers of 350 gm stainless steel balls. 2 kg Ba(OH).sub.2 was added to the grinded red mud and then the mixture was further grinded for an hour to have uniform mixture. The grinded red mud:Ba(OH).sub.2 mixture was taken in a 50 mm graphite die. The interior wall of the die and the bottom and top plungers were coated with molybdenum as high temperature lubricant. The sample along with die was loaded in a hot press and then heated to 1050 C. with the rate of 7 C./min. 23.4 MPa pressure was applied in a hot press after 30 minutes of dwelling at 1050 C. Subsequently, the sample was cooled with the rate of 10 C./min. The density and porosity of the developed sample was 4.6 g/cc and 0.08%, respectively. The radiation shielding blocks with various thicknesses ranging from 1.5-50 mm thick samples were fabricated and then the gamma ray attenuation of the samples were studied using Cobalt-60 source. The half value layer (HVL) of the developed sample was 26.80 mm at 1.33 MeV. The HVL of the sample at 100 kVp, 125 kVp and 150 kVp X-ray is 0.8182 mm, 0.9297 and 1.0754 mm, respectively. The compressive strength of the samples was studied as per ASTM C39 standard. The developed sample possess the compressive strength of 144 MPa, which is suitable for civil constructions. No heavy elements were found to leach from the developed shield.
Example 4
[0095] The red mud was collected and dried in hot-air oven at 90 C. for 15 hrs. 2 kg red mud was grinded in a ball mill for 4 hrs using six numbers of 350 gm stainless steel balls. Subsequently 1 kg Ba(OH).sub.2 and 1 kg Bi.sub.2O.sub.3 was added to the grinded red mud and then the mixture was further grinded for one hour for uniform mixing. The grinded red mud:Ba(OH).sub.2:Bi.sub.2O.sub.3 mixture was taken in a 50 mm graphite die. The interior wall of the die and the bottom and top plunger was coated with molybdenum as high temperature lubricant. The sample along with die was loaded in a hot press and then heated to 1000 C. with the rate of 7 C./min. 39 MPa pressure was applied in a hot press after 35 minutes of dwelling at 1000 C. Subsequently, the sample was cooled with the rate of 10 C./min. The density and porosity of the developed sample was 4.7 g/cc and 2.0%, respectively. The radiation shielding blocks with various thicknesses ranging from 1.5-60 mm were developed and then the gamma ray attenuation of the sample was studied using Cobalt-60 source. The half value layer (HVL) of the developed sample is 24 mm at 1.33 MeV. The HVL of the sample at 100 kVp, 125 kVp and 150 kVp X-ray is 0.74108 mm, 0.7996 and 0.8776 mm, respectively. The compressive strength of the sample was studied as per ASTM C39. The developed sample possess the compressive strength of 122 MPa, which is suitable for civil constructions. No heavy elements were found to leach from the shield.
Example 5
[0096] The red mud was collected and dried in hot-air oven at 90 C. for 15 hrs. 2 kg red mud was grinded in a ball mill for 4 hrs using six numbers of 350 gm stainless steel balls. The grinded red mud was taken in a 60 mm hot die steel die. The samples with various thicknesses ranging from 5 mm till 80 mm were fabricated by applying 72 MPa pressure. The developed blocks were sintered at 1150 C. for 30 minutes in a muffle furnace with the heating rate of 7 C./min. Then the samples were cooled to room temperature with the rate of 10 C./min. The density and porosity of the developed samples are 2.13 g/cc and 13%, respectively. The gamma ray attenuation of the sample was studied using Cobalt-60 source. The half value layer (HVL) of the developed sample was found to be 49 mm at 1.33 MeV. The compressive strength of the sample was 20 MPa.
Example 6
[0097] Red mud was collected and dried in hot-air oven at 90 C. for 15 hrs. 2 kg red mud was grinded in a ball mill for 4 hrs using six numbers of 350 gm stainless steel balls. Further 2 kg Bi.sub.2O.sub.3 was mixed with grinded red mud and then the mixture was ball milled for another one hour for uniform mixing. The above mixture was taken in a 60 mm hot die steel die. The samples with various thicknesses ranging from 5 mm till 80 mm were fabricated by applying 72 MPa pressure. The developed blocks were sintered at 1000 C. for 25 minutes with the heating rate of 7 C./min. Then the samples were cooled to room temperature with the cooling rate of 10 C./min. The density and the porosity of the developed block are 2.6 g/cc and 47%, respectively. The gamma ray attenuation of the samples was studied using Cobalt-60 source. The half value layer (HVL) of the developed sample at 1.33 MeV is 40 mm. The compressive strength of the samples is 18 MPa.
Example 7
[0098] The red mud was collected and dried in hot-air oven at 90 C. for 15 hrs. 2 kg red mud was grinded in a ball mill for 4 hrs using six numbers of 350 gm stainless steel balls. Further 2 kg Ba(OH).sub.2 was mixed with grinded red mud and then the mixture was ball milled for another one hour for uniform mixing. The red mud:Ba(OH).sub.2 mixture was taken in a 60 mm hot die steel die. The samples with various thicknesses ranging from 5 mm till 80 mm were fabricated by applying 72 MPa pressure. The developed blocks were sintered at 1050 C. for 30 minutes with the heating rate of 7 C./min. Then the samples were cooled to room temperature with the cooling rate of 10 C./min. The density and the porosity of the developed blocks are 1.9 g/cc and 40%, respectively. The gamma ray attenuation of the samples were studied using Cobalt-60 source. The half value layer (HVL) of the developed sample at 1.33 MeV is 54 mm. The compressive strength of the sample is 7 MPa.
Example 8
[0099] The red mud was collected and dried in hot-air oven at 90 C. for 15 hrs. 2 kg red mud was grinded in a ball mill for 4 hrs using six numbers of 350 gm stainless steel balls. Further 1 kg Ba(OH).sub.2 and 1 kg Bi.sub.2O.sub.3 was added with grinded red mud and then the mixture was ball milled together for another one hour for uniform mixing. The red mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 mixture was taken in a 60 mm hot die steel die. The samples with various thicknesses ranging from 5 mm till 80 mm were fabricated by applying 72 MPa pressure. The developed blocks were sintered at 1000 C. for 30 minutes with the heating rate of 7 C./min. Then the samples were cooled to room temperature with the rate of 10 C./min. The density and porosity of the developed blocks are 2.3 g/cc and 43.7%, respectively. The gamma ray attenuation of the samples was studied using Cobalt-60 source. The half value layer (HVL) of the developed sample is 46 mm at 1.33 MeV. The compressive strength of the sample is 18 MPa.
[0100] Table 2 provides the details of the required thickness of the shield for various composition at 150 kVp and at 1.33 MeV (Co-60 Source).
TABLE-US-00002 TABLE 2 150 KVp Cobalt 60 Attenuation 2.5 mm Attenuation 180 mm Red Coefficient HVL Lead Coefficient HVL Lead Mud Bi.sub.2O.sub.3 Ba(OH).sub.2 (0.002 (0.03 Equivalent (0.0008 (0.5 Equivalent Sample (%) (%) (%) mm.sup.1) mm) (0.25 mm) mm.sup.1) mm) (4 mm) red mud 100 0.224 3.10 25.81 0.02037 34.02 489.88 red 40 60 1.059 0.65 5.46 mud: Bi.sub.2O.sub.3 50 50 0.932 0.74 6.20 0.03306 20.96 301.82 60 40 0.725 0.96 7.97 70 30 0.566 1.22 10.20 red 40 60 0.661 1.05 8.74 mud:Ba(OH).sub.2 50 50 0.644 1.075 8.96 0.02586 26.80 385.92 60 40 0.571 1.21 10.11 70 30 0.515 1.35 11.21 red 50 25 25 0.790 0.877 7.31 0.029 24 345.6 mud:Bi.sub.2O.sub.3:Ba(OH).sub.2 50 35 15 0.776 0.89 7.44 50 15 35 0.764 0.90 7.56
[0101] The main advantages of the present invention are:
[0102] The developed red mud shields of the present application are advantageous due to following reasons: [0103] 1. This novel technique paves the way for conversion of hazardous red mud into X- and -ray shielding material, which can be used as an alternative of toxic lead and heavy weight concrete in a building sectors to fabricate X- and -ray shielding structures. [0104] 2. This technique helps to close the pores tremendously and thereby to achieve high dense red mud blocks having density 5.2 g/cc, which is much higher than the red mud/industrial waste based radiation shield reported so far. [0105] 3. The material is lead free and the process is green as it does not release any greenhouse gases like SO.sub.2 and CO.sub.2 during sintering. [0106] 4. The diffusion bonded red mud:Bi.sub.2O.sub.3, red mud:Ba(OH).sub.2 and pure red mud sample possess 60%, 46.6% and 37% of the attenuation of lead at 1.3 MeV gamma rays (Cobalt-60), respectively. [0107] 5. The HVL of pure red mud block (34.02 mm) is nearly half of light weight concrete (60.5 mm) at 1.33 MeV and possess sufficient strength (34.18 MPa) for building applications. So, it is highly economically viable and occupies less space than the conventional concrete. [0108] 6. The developed material possess the compressive strength of 34-282 MPa, which is higher than the common bricks and concrete. So, the developed blocks can be used to build the radiation shielding structures without any additional structural support unlike lead. [0109] 7. The HVL is nearly 3 times less than the already reported red mud based radiation shielding materials. [0110] 8. The developed shields will be cheaper than lead, since it uses industrial waste as one of the major raw material. It will reduce the usage of toxic lead for radiation shielding applications. [0111] 9. It will generate values to the red mud and will reduce its accumulation and associated environmental problems like soil, air and ground water pollution. [0112] 10. It will occupy less space than lead (need additional support structure), heavy weight and light weight concrete. [0113] 11. The developed material is thermally stable until 1000 C., so its life will be higher than the concrete and polymer based radiation shielding materials.