The research paper published by IJSER journal is about GAMMA-RAY SPECTROMETRIC ANALYSIS OF FLY-ASH SAMPLES OF COAL FIRED POWER PLANTS 1

ISSN 2229-5518

GAMMA-RAY SPECTROMETRIC ANALYSIS OF FLY-ASH SAMPLES OF COAL FIRED POWER PLANTS.

Ashutosh Pathak* , Archana Sharma*, Brijesh Pathak**, S.Pathak**

*Department Of Chemistry, University of Rajasthan, Jaipur (India)
**Baba Farid College, Deon, Bathinda, (India)
** (shivanshupathak@yahoo.co.in)

ABSTRACT

Suratgarh super thermal power station, Suratgarh and Guru Nanak thermal power station, Bathinda are the two potential sites selected for the study of radionuclides in fly ash samples by γ-ray spectrometer. The activities of Cs-137, K-40, Ra-226 and Th-232, ( in Bq/Kg.) are 17.8, 98.8, 29.1 and 120.9 respectively for Suratgarh thermal power plant and 25.7, 96.6, 25.0 and 123.2 respectively for Bathinda power plant.
The absorbed dose rate (nGy h-1) obtained for Suratgarh power plant is 90.57 and for Bathinda power
plant is 89.98. The effective dose rate (mSv y-1) in case of former is 0.111075 and for latter is 0.11035.
Radium equivalent activity (Raeq) and External hazard index (Hex) are calculated for by-products to assess the radiation hazards arising due to the use of fly ash in the construction of dwellings. The values of Raeq.(Bq/Kg) and Hex for Suratgarh thermal power plant are 209.58 and 0.5658 respectively and for Bathinda thermal power plant are 208.6 and 0.56318 respectively. These results are below safe use values.

Introduction : In India coal fired thermal plants produce around 69,616 MW of electricity which is 54.1% of the total electricity produced in the country. Coal , when burnt in power plants, mainly produces two type of solid wastes namely fly ash and bottom ash. Bottom ash is the coarse –grained material which is collected at the bottom of boiler and is disposed off to a nearby ash pond (waste disposal site). Due to lack of sophisticated emission control devices, most of the fly ash is released into the atmosphere. Since the ash produced is used for variety of purposes viz. production of cement and bricks, so it is essential to study the radiological characteristics of its components. The radiological hazards of fossil fuels were first studied by Eisenbud and Petro [1].
Although many studies are going on across the nation and world [2-5] on the radioactive hazards of fly
ash emitted from various coal fired thermal plants, yet data for Suratgarh Super Thermal Power Station , Suratgarh (Raj.) and Guru Nanak Thermal Power Station , Bathinda (Pb.) are not available. So the activities of Cs-137 , K-40, Ra-226 and Th-232 (in Bq Kg-1) present in the fly ash samples have been studied in this context using -ray spectrometer. Along with this the absorbed dose rate (nGy h-1), effective dose rate (mSv y-1), Radium equivalent activity (Raeq) as well as External hazard index (Hex) are calculated for the by products to
assess the radiation hazards arising due to the use of fly ash in the construction of dwellings.

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The research paper published by IJSER journal is about GAMMA-RAY SPECTROMETRIC ANALYSIS OF FLY-ASH SAMPLES OF COAL FIRED POWER PLANTS 2

ISSN 2229-5518

Location of sites : Guru Nanak Thermal Power station is located on Bathinda- Malout road, Bathinda (Punjab) and Suratgarh Thermal Power Station is located at Village Raiyanwali which is 4 Km distant from Suratgarh Tehsil, Distt. Sri Ganganagar (Rajasthan)

Experimental : The samples were collected and stored in polythene bags. They were dried in an oven for 24 hrs. at 600 C to remove moisture. They were then kept in radon impermeable containers and were st ored for 40 days before counting for Ra and Th daughter products to attain radioactive equilibrium .
The activities of Cs-137, K-40, Ra -226 and Th-232 were calculated using-ray spectrometer at D.R.D.O. Lab, Jodhpur (Rajasthan). The detector consisted of NaI (Tl) crystal coupled to a 5x4 inch photomultiplier tube. A 256 channel data set covering the  energy range 0-4 KeV was attached to detector . The energy reason for K-40, Ra-226, Th 232 and Cs -137 were 1.46 MeV, 1.76 MeV, 2.6 MeV and 0.662 MeV respectively. The standard samples were prepared by mixing Pthalic acid powder obtained from BARC Lab. Mumbai. The samples were counted for about 200 to 400 Min.
The absorbed gamma dose rates for the uniform distribution of radionuclides (Cs-137, K-40, Ra-226 and Th-232) were calculated on the basis of directions given by UNSCEAR[3]. Conversion factor to transform specific activities Ak, ARa and ATh of K, Ra and Th respectively, in absorbed dose rate at 1 m above the ground (in nGy h-1 by Bq Kg-1)are calculated by Monte Carlo method and the values are [6].
D(nGy h-1) = 0.0417 Ak +0.462 ARa+ 0.604 ATh .
The annual effective dose rate is calculated using the formula
Effective dose rate (mSv y-1) = D (nGy h-1) x 8760 (h y-1) x 0.2 x 0.7 (Sv Gy-1) x 10-6
where the conversion coefficient from the absorbed dose in air to the effective dose (0.7 Sv Gy-1) and the outdoor occupancy factor (0.2) as proposed by UNSCEAR are used.
About 83.59% of the fly ash and bottom ash of these thermal plants is used for the pro duction of dwelling materials such as cement and bricks , so in order to assess the radiological hazard of fly ash, the radium equivalent (Raeq) and external hazard index (Hex) are calculated using the relation given by Beretka and
Mathew [7].
Raeq = ARa + 1.43 ATh + 0.077 AK
Hex = ARa /370 + ATh / 259 + AK/ 4810
Where ARa, ATh and AK are the activities of Ra-226, Th 232 and K 40 in Bq Kg-1 respectively. For safe use , the values of Raeq should be less then 370 Bq Kg-1 and that of Hex should be equal to unity.

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The research paper published by IJSER journal is about GAMMA-RAY SPECTROMETRIC ANALYSIS OF FLY-ASH SAMPLES OF COAL FIRED POWER PLANTS 3

ISSN 2229-5518

Result and discussion : The various data pertaining to above study are presented in the following table . These results reveal that the activities of K-40, and Ra 226 (Bq Kg-1) in the samples of Suratgarh power plant
are higher (98.8 and 29.1 respectively) as compared to Bathinda power plant (96.5 and 25.0 respectively).

The absorbed dose rate (nGy h-1) for Suratgarh power plant exhibits higher value (90.57) as compared to Bathinda power plant (89.98). The effective dose rate (mSv y-1) in case of the former is 0.111075 and for the latter is 0.11035.
Lastly , a glance at the values of Raeq (Bq Kg-1) and Hex reveals that these are greater in the samples of
Suratgarh power plant (i.e. 209.58 and 0.5658 respectively) than for Bathinda power plant (208.6 and 0.56318
respectively). But the results in either case are below safe use values.

Acknowledgement : We are grateful to the authorities o f Thermal Power Plant for providing the samples. We also thanks Dr. Deepak Gopalani and his team for analyzing the samples at D.R.D.O. Lab, Jodhpur (Raj.)

References :

1 Eisenbud , M. and Petro, H.G. Radioactivity in the atmospheric effluents of power plants that use fossil fuels. Science, 1964, 144 ,288-289.
2. Baba.A., Assessment of radioactive contaminants in by-products from yatagan (Mugla, Turky) coal fired power plants. Environ. Geol., 2002,41, 916-921.
3. Bech, H.L., Radiation exposures due to fossil fuel combustion. Radiat.phys.chem., 1989, 34,285-293
4. Iyengar, M.A.R. , Rajan, M.P., and Ramachandran, T.V., Radioactivity aspects of Indian coals. Curr. Sci.
1995, 69, 592-596.
5. Fengling Wang, Xiaodan Jia and, Xinwei Lu Natural radioactivity of coal and its by-products in Baoji coal
–fired power plant, China. Curr. Sci. 2006, 91, 1508-1511
6. UNSCEAR, Sources and effects of ionizing radiation. United Nations Scientific Committee on the Effects o f
Atomic Radiation, United Nations, New York , 2000

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International Journal of Scientific & Engineering Research Volume 3, Issue 7, July-2012 4

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7. Beretka, J. and Mathew, P.J., Natural radio activity of Australian building materials, industrial wasted and by-products. Health phy., 1985,48,87-95.

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