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ISSN 2229-5518

Determination of natural radioactivity and radiological hazards for Cement and Gypsum in Sulaimani Area (Kurdistan Region – Iraq)

Adil M. Husain, Kamal O. Abdullah, Salahaddin A. Ahmed

Abstract: Activity concentration of 238U, 232Th and 40K in twelve samples of cement and gypsum is used as a building material in Sulaimani Governorate-Kurdistan Region-Iraq, these samples were measured using γ-spectrometry based on scintillation detection. Also activity concentration of 222Rn was determined using solid state nuclear track detector (SSNTD) technique through the CR-39 detector and radium equivalent activities (Raeq), absorbed dose rate (D), external and internal hazard indices (Hex and Hin) and level index of γ- radiation hazard (Iγ) were calculated to assess the potential radiological hazard associated with these samples. The activity concentration of 238U, 232Th and 40K for the cement samples were found to range between (4.458 ± 0.304 - 51.573 ± 11.955, 6.330 ± 1.253 – 19.188 ±

6.612 and 54.950 ± 6.050 -81.648 ± 10.958) Bq/Kg, respectively. Values of average radium equivalent activities (Raeq), absorbed dose

rate (D), external and internal hazard indices (Hex and Hin) and γ- index hazard (Iγ) are ranged as (36.74-78.028) Bq/Kg, (32.093 ± 4.235-

69.369 ± 13.110) nGy/hr, (0.099-0.21), (0.111-0.349) and (0.131-0.267) but the radon concentration are ranged inside the air of the tube between (75.514±3.876 - 286.082±28.583) Bq/m3, while inside the studied sample materials is ranged between (30618.211±295.7 -

8081.946±40.101) Bq/m3, the natural radioactivity concentrations. The higher values appeared in the cement samples and the lower one in

the gypsum except in thorium concentration, fortunately they are not higher than the limit of worldly values, therefore the studied samples

(cement and gypsum) in Sulaimani building materials can be used in construction safely from the radioprotection.

Keywords: Natural radioactivity, Cement, Gypsum, γ-spectrometry, SSNTD.

1. Introduction:

——————————  ——————————

Natural radiation sources can be classified into [1]:
1- Gamma and radioactive nuclides present in the crust of earth, building materials and air.
2- Internal sources, comprising the naturally occurring radionuclides which are taken into the human body.
The main radioactive materials in naturally occurring radioactive materials are long –lived radionuclides such as

238U, 235U, 232Th and 40K. Natural radioactivity and terrestrial

gamma dose originated from naturally occurring radioactive in the building materials depend essentially on geological and geographical conditions, therefore concentrations of natural radioactivity in the material especially in soil vary from one region to another in the world [2, 3].
Studies of natural radioactivity in building material such (Cement and Gypsum) are necessary not only because of their radiological effect, but they also act as an excellent biochemical and geochemical tracer in the environment. The presence of radium associated with the emanation of radon, the inhalation of radon and short-lived daughter products decay is a major contributor to the total radiation dose in an exposed subject. Therefore the lung dose due to radon may be cause to increase the lung cancer [4]. Among all the radon isotopes, only 222Rn is important which produced from the decay product of 226Ra, deriving from the uranium series of natural radionuclides and has a half-life of 3.8 d [5]. Indoor radon comes from several major sources, especially from the soil underlying and surrounding building foundations and building materials.

1,2,3 Physic Dep.-Faculty of Science and Science Education- University of Sulaimani-Kurdistan region-Iraq

adilj aff@gmail.com, kamaloa13@gmail.com, salahaddinahmed@gmail.com .
All types of building materials like cement, gypsum, concrete, brick, sand, granite, limestone, etc. cause direct radiation exposure because of their uranium, thorium and potassium content [6].
In the present work, the concentrations of natural radionuclide were measured in 12 samples of cement and gypsum, which considered as a building material samples that, is used commonly in Sulaimani Governorate and its surroundings by means of gamma-ray spectrometry. The potential radiological hazards associated with those materials (cement and gypsum) were assessed by calculating the radium equivalent activity (Raeq ), indoor absorbed gamma dose rate (D), external and internal hazard indexes (H ex, H in ) and level index of gamma radiation hazard (Iγ ). In addition, the same samples were analyzed for the radon concentrations using passive radon detector (CR-39). The obtained results were compared with the recommended values to assess the radiation hazards to human due to building materials (cement and gypsum) and also compared to the corresponding values of the building materials from different countries which done through using the same technique.

2. Experimental procedure:

2.1 Sampling:

The majority of building materials (cement and gypsum) is
produced in Sulaimani (Kurdistan Region-Iraq) from both factories Tasluja and Bazyan and also from the other neighbor countries Turkey and Iran used in sulaimani.

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The samples weight were about 1Kg putting in a Marnelli beaker, hermetically sealed and stored for 1 month to take place the equilibrium between 226Ra and its decay products of short half-life before being taken in gamma spectrometry analysis [7].
The measurement of radon concentrations was carried out by using (SSNTD) solid state nuclear detector (CR-39) samples

Rα can be calculated from the equation (6) [14]:

Rα = (0.005 Eα + 0.285) Eα 3/2 ------------ (6)

= 4.019 cm (for energy Eα = 5.49 MeV)
The value of diffusion constant (η) according to dimensions of
the present system equals to (0.057744) Tr.cm-2 .d-1 / Bq . m-3
To calculate 222Rn concentration in the samples, equation (7)
can be used [12]:

λRn 𝐶𝑎 𝐻 𝑇

with 130 g were prepared after drying and placed on the

𝐶𝑠 =

𝐿 -------------- (7)

bottom of a sealed polyethylene bottle (cylindrical plastic) and
the (CR-39) detector with pieces of area 1cm x1. 5cm on the
other side of cylindrical plastic suspended, then stored for two
Where C s - Rn222 concentration in the samples (Bq\m3)
C a – Rn222 concentration in air space inside the tube
(Bq\m3)
months to allow radioactive equilibrium between 222Rn and

λ Rn

- Decay constant of Rn222
(0.1814 day-1)

226Ra. Exposed detector was collected and etched chemically

using 6.25 M NaOH at 70Co for 6 hrs after washing these detectors in distilled water, the track density on CR-39 (tr.
/cm2) was counted using an optical microscope with magnification 400x [8].

2.2 Gamma-ray measurements:

In gamma-ray spectrometry measurement, a (2 inch x 2 inch) NaI (TI) detector was used with energy resolution 9.46%

H – Height of air space in the tube (29.5 cm)

L – Thickness of the sample in the tube (3 cm)

T - Time of irradiation (60 days)

2.4 Estimation radiation hazard index:

The most widely used radiation hazard index is called the radium equivalent activity Raeq which is a weighted sum of activities of the 3 radionuclides based on following relation as showing in equation (8) [5,7]:
at the energy of 662 keV for 137Cs line. The detector is
Raeq
= 1.43 A Th
+ A Ra
+ 0.077 A k
-------------- (8)
surrounded by an 8cm thick lead shield to reduce the gamma-
radiation background. Each sample of cement and gypsum was measured for 6 hrs. The photo peak of 238U was measured from 609 keV gamma-line of 214Bi, 232Th from 911 keV gamma- line of 228Ac and 40K from 1460 keV gamma-energy. The concentrations of 238U, 232Th and 40K in each sample by ppm were calculated form the calibration curve which done for each of the above nuclides alone from the obtained standard sources were counted with the NaI(TI) detector and their spectrums yield, when they are used in the establishment of calibration curve, through their net area and by fitting these calibration curves we obtained these relations as shown in equations (1),(2) and (3) [9]:
Y = 0.0022x – 0.2492 ----------- (1) for 238U
Where: A Th is the activity concentration of thorium
A Ra is the activity concentration of radium
A k is the activity concentration of potassium

2.5 Estimation of dose rate (D):

The average absorbed dose rates D (nGyh-1) in air 1m from
terrestrial sources of gamma- radiation in the samples can be calculated from the equation (9) based on Gide lines provided by UNSCEAR 2000 [5]
D(nGyh-1) = 0.462 A Ra + 0.621 A Th + 0.0417 A K ------------ (9) Where: D is the dose rate in (nGyh-1)

2.6 Estimation of (External and Internal) hazard index (Hex

and H in ):

The external hazard index Hex is defined as shown in eq. (10) [5,15]:
Y = 0.0223x – 1.617 ----------- (2) for 232Th
H ex
= A Ra
/ 370 + A Th
/ 259 + A K
/ 4810 --------------- (10)
Y = 9x10-6 x – 0.0004 ----------- (3) for 40K
Then to measure the specific activity by using the conversion factor for each radionuclides (238U, 232Th and 40K) can be used for 1 ppm of U corresponds to 12.35 Bq/Kg for Th corresponds to 4.1 Bq/Kg and for K corresponds to 259.2 Bq/Kg [10].

2.3 Radon concentration measurement:

The concentrations of 222Rn in the air of tube, as shown in
Fig.(1), that contain cement and gypsum samples by using CR-
39, can be calculated from the equation (4) [11,12]:
Ca = ρ / η T ------------- (4)
Where ρ is the track density on the exposed detector CR-39
(Tr/cm2)
Another hazard due to radon effect on respiratory organs called internal hazard index H in can be determined from the eq. (11):
H in = A Ra / 185 + A Th / 259 + A K / 4810 -------------- (11)

2.7 Estimation of level of gamma hazard index (Iγ ):

But the level index of gamma-radiation hazard which was associated with natural radionuclides in specific investigated can be calculated from equation (12) [5]:
Iγ = 0.0067 A Ra + 0.01 A Th + 0.00067 A K ------------- (12)
T is the exposure time of the samples (60 d)
η is the detection efficiency and can be calculated from this relation eq.(5) using the dimensions of the tube [8]:
η = 1 𝑟 (2 cos 𝜃
− 𝑟 ) ----------- (5)

4 𝑡

𝑅𝛼

where r - Tube radius for the diffusion volume (3.6 cm)
𝜃𝑡 - Threshold angle for the CR-39 detector (35o) [13]

Rα - Range of α- particle in air from Rn

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CR- 39

Sample

7.2 cm

29.5 cm

3cm

hazard indices are given in Table (3-4), from the obtained results the lowest value of Raeq was 36.74 Bq/Kg calculated in (Gypsum1) sample from Iran while the highest value is 78.028
Bq/Kg in (Cement White 8) from Turkey. The calculated values of the total dose rate range from (32.093 to 69.369) nGy/hr and Fig.(5) shows all the ranges for each samples. The values of Hex and H in varied in the range from (0.099 to 0.21) and from (0.111 to 0.349), respectively. For the safe use of a material in the construction places, H ex and H in must be less than the unity [7] and all the calculated values are less than the unity. Also the calculated values of Iγ for the studied samples varied in the
Fig. (1) Schematic Diagram of Long-Tube for SSNTD
Technique.

3. Result and discussion:

3.1 Radon measurements:

The obtained radon and uranium concentrations of the studied samples through using SSNTD technique are given in Table (3-1). The radon concentration is ranged inside the air in the tube between (75.514±3.876 - 286.082±28.583) Bq/m3 and the studied samples ranged between (30618.211±295.7 -
8081.946±40.101) Bq/m3. The highest value of the radon concentration appears in the cement-5 sample from Sulaimani (Kurdistan Region-Iraq) and the lower value of the Gypsum-1 sample from Iran as showing in Fig.(2). Table (3-2) shown the radon concentrations values in the cement and gypsum samples. Fortunately, these values approximately lower than the world values with comparison to the other works [16], also the highest values appear in the cement-5 and gypsum-3 samples, the mentioned samples were located in the same area of Sulaimani governorate, furthermore these regions enriched with marlstone and sandstone which contain a concentration of uranium according to geology information [9].

3.2 Radionuclide concentrations:

Table (3-3) shows the radionuclide concentrations of 238U,

232Th and 40K, using gamma- spectroscopy technique, the

lowest specific activity of 238U was (4.45835±0.304) Bq/Kg appeared in the gypsum-1 sample from Iran. The 232Th specific activity value record 6.3304±1.253 Bq/Kg appeared in the cement-2 sample from Sulaimani (Kurdistan Region – Iraq). The 40K predicted the lowest activity (54.9504±6.050) Bq/Kg, which appeared in the gypsum-3 sample from Sulaimani (Kurdistan Region – Iraq), while the highest value is recorded to these radionuclide; the 238U in the cement-6 sample from Iran, the 232Th in gypsum-1 sample from Iran and the 40K in the cement-3 sample from Sulaimani (Kurdistan Region – Iraq), as
range between (0.131-0.267), for all types of samples it’s observed they are less than the critical value of unity as showing in the Figures(6 & 7) for cement and gypsum, respectively. By comparison, these results with the other works which made in the same region they are approximately close together [7] but lower than the other [16] as shown in the Table (3-5).

Table (3-1) Radon and Uranium Concentrations in the samples

350

300 Cement

shown in Figures (3 & 4) for cement and gypsum, respectively.
Although the distribution of radionuclides U, Th and K in
building materials, especially in cement and gypsum is not uniform they could be considered a bit higher in the cement samples while it’s less in the gypsum sample by comparing to the other works [7] while it’s vice versa in the other [16] as shown in Table (3-3).

3.3 Dose Calculations:

The calculated values of the radium equivalent activity, total absorbed dose rate (D) and external, internal with gamma

250

200

150

100

50

0

Gypsum

1 2 3 4 5 6 7 8

Samples No.

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Fig.(2) Radon Concentrations (Bq/m3) in Cement and Gypsum samples

100

U Th

80 K

60

40

20

0

1 2 3 4 5 6 7 8

Samples No. for Cement

Fig.(3) Uranium, Thorium and Potassium Concentrations (Bq/Kg) in

Cement samples

Table (3-2) Radon, Uranium, Thorium and Potassium concentrations in the samples Cement and Gypsum in the other work

Table (3-3) Uranium, Thorium and Potassium concentrations in the samples.

Table (3-4) Raeq , total absorbed dose rate, external, internal and gamma hazard indices calculations.

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Table (3-5) Raeq , total absorbed dose rate, external, internal and gamma hazard indices in the other work.

70 0.4

U

60 Th

K

50

0.3

Hex Hin Iy

40

0.2

30

20

0.1

10

0

0 1 2 3 4 5

Samples No. for Gypsum

0.0

1 2 3 4 5 6 7 8

Samlpes No. for Cement

Fig.(4) Uranium, Thorium and Potassium Concentrations
(Bq/Kg) in Gypsum samples
Fig.(6) Radiological hazards in Cement sample

80

70 Cement

Gypsum

60

50

0.16

0.14

0.12

Hex Hin Iy

0.10

40

0.08

30

0.06

20

0.04

10

0

1 2 3 4 5 6 7 8

Samples No.

0.02

0.00

0 1 2 3 4 5

Fig.(5) Total absorbed dose rate D (nGy/hr) in Cement and
Gypsum samples

Samples No. for Gypsum

Fig.(7) Radiological hazards in Gypsum samples

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4. Conclusion

The radon concentration, natural radionuclide content, external and internal hazard indices of some building material such as cement and gypsum were determined which commonly used in Sulaimani area in Kurdistan Region-Iraq, using SSNTD and gamma spectroscopy techniques. The result of measuring obtained activity concentrations to estimate qualify and quantify radiological hazards which associated with the studied samples. It is concluded that the studied samples of Sulaimani building materials can be used in construction safely from the radioprotection.

5. References

1- Laith A. et al. (2011), Natural radioactivity levels of limestone rocks in northern Iraq using γ-spectroscopy and SSNTD. (289): 709-715
2- Poschl M. (2007), Radionuclides concentration in food and the

Environment, Taylor & Francis Group, USA.

3- Turhan, S. (2008), Assessment of the natural radioactivity and radiological hazards in Turkish cement and its raw materials. J. Environmental Radioactivity, 99 (2), 404-414.
4- UNSCEAR (1993), Exposure from natural sources of radiation. United Nation, New York.
5- (UNSCEAR 2000), Sources and Effects of Ionizing Radiation, Report to general assembly, with scientific annexes, United Nations. (http://www.unscear.org)
6- Cetin, E. et al. (2012), Natural radioactivity levels of granites
used in Turkey, Radiation Protection Dosimetry, 151(2): 299-
305.
7- Oktay, B. et al. (2011), Assessments of natural radioactivity and radiological hazards in construction materials used in Elazig, Turkey. Radiation Measurement, (46): 153-158
8- Omer N. (1999), Electrochemical Etching, Msc. dissertation,
University of Mousl.
9- Kamal O. and Rasheed M. (2013), Natural Radioactivity Measurements of soil and water in Sulaimani Governoraye, Ph.D. Dissertation, University of Sulaimani.
10- Samuel S. M. (2004) Introductory Nuclear Physic, 2nd
Edition, University of Toronto.
11- Azam,A. et al. (1995).Radium Concentration and Radon
Exhalation Detectors . Nuclear Geophysics, 9 (6) : 653- 657.
12- Ahmad M. (2011).“Employment SSNTD (CR-39) to Detect Radioactive Pollution of DU in a Particular Region from Salahadeen Governorate” Proceeding in Ist Scientific
Conference to College of Science University of Tikrit.Iraq, (295-
300).
13- Barillon R. et al. (1993) “Comparison of Effectiveness of three Radon Detectors ( LR- 115,CR-39 and Si. Diode pin) Placed in Cylindrical Device- Theory and Experimental Techniques ,Nuclear Track” Radiation Measurement, 22(1-4) ;
281-282.
14- Michael F. Annunziata (2007),” Radioactivity Introduction and History”, Ist edition USA.
15- Sroor A. et al.(2001),Natural Radioactivity and Radon Exhalation rate of Soil in Southern Egypt, Applied Radiation and Isotopes, 55: (873-879).
16- Laith, N. et al. (2013),Measurement Of Natural Radioactivity in Building Materials used in Iraq. Australian J. of basic and Applied Science, 7(1): 56-66.

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