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Radiation Physics and Chemistry 79 (2010) 933–937

Contents lists available at ScienceDirect

Radiation Physics and Chemistry

0969-80

doi:10.1

n Corr

E-m

journal homepage: www.elsevier.com/locate/radphyschem

Natural radioactivity and radiation hazards in some building materials usedin Isparta, Turkey

B. Mavi, I. Akkurt n

Suleyman Demirel University, Fen-Edebiyat Fakultesi Fizik Bol., Isparta, Turkey

a r t i c l e i n f o

Article history:

Received 19 February 2010

Accepted 29 March 2010

Keywords:

Natural radioactivity

Building materials

Gamma ray spectrometry

6X/$ - see front matter & 2010 Elsevier Ltd. A

016/j.radphyschem.2010.03.019

esponding author. Tel.: +90 246 211 4033; fa

ail address: iskender@fef.sdu.edu.tr (I. Akkurt

a b s t r a c t

The activity concentrations of uranium, thorium and potassium can vary from material to material and

it should be measured as the radiation is hazardous for human health. Thus first studies have been

planned to obtain radioactivity of building material used in the Isparta region of Turkey. The

radioactivity of some building materials used in this region has been measured using a g-ray

spectrometry, which contains a NaI(Tl) detector connected to MCA. The specific activity for 226Ra, 232Th

and 40K, from the selected building materials, were in the range 17.91–58.88, 6.77–19.49 and

65.72–248.76 Bq/kg, respectively. Absorbed dose rate in air (D), annual effective dose (AED), radium

equivalent activities (Raeq), and external hazard index (Hex) associated with the natural radionuclide are

calculated to assess the radiation hazard of the natural radioactivity in the building materials. It was

found that none of the results exceeds the recommended limit value.

& 2010 Elsevier Ltd. All rights reserved.

1. Introduction

The human population is always exposed to ionizing radiationdue to background radiation. Besides man-made radiation, themain source of background radiation is natural radioactivity.Natural radioactivity has existed since the beginning of theuniverse due to long half-live of the natural radioelement found inthe earth’s crust. These radionuclides of 226Ra, 232Th and 40K canbe found almost in all types of rocks, granite, sand, cement andgypsum from which building materials are produced.

As natural radiation is the largest contributor to the externaldose of the population, it is important to assess the gammaradiation dose from natural sources (UNSCEAR, 1988). Buildingsare very important in human life as most of the lifetime is spent athome and/or office. The main source of indoor gamma radiation isbuilding materials besides terrestrial and cosmic radiation. It willbe possible to assess any possible radiological hazard bymeasuring radioactivity of building materials. Several works havebeen performed to measure 226Ra, 232Th and 40K activityconcentrations in different building materials.

Amrani and Tahtat (2001) have measured natural andmanufactured building materials collected from Algiers for226Ra, 232Th and 40K using a high-resolution HPGe g-spectrometrysystem. It was found that the 226Ra, 232Th and 40K specificconcentrations were in the range 12–65 Bq/kg,7–51 Bq/kg, 12–65Bq/kg and 36–675 Bq/kg, respectively.

ll rights reserved.

x: +90 246 2371106.

).

Flores et al. (2008) have performed a work to measure theactivity concentration of 44 samples of commonly used rawmaterials and building products collected in five Cuban provinces.The measurements were done using gamma ray spectrometryand the mean values of concentration were in the range of9–857 Bq/kg for 40K; 6–57 Bq/kg for 226Ra and 1.2–22 Bq/kg for232Th.

Krstic et al. (2007) have measured radioactivity of somebuilding materials (gypsum, ceramic, marble, granite, etc.) usingHpGe detector and multichannel analyser. Activity concentrationindex, I, was calculated for each investigated sample. The rangesof I are 0.0297–1.2545 and 0.0376–0.1521 for Macedonian andBulgarian gypsum, respectively. The ranges of I for marble are0.0124–0.6245, 0.0104–1.2089 and 0.0162–0.6747 for Macedonian,Greek and Bulgarian, respectively. The ranges of I for Greek ceramicand granite are 0.3508–1.0152 and 0.0438–1.0062, respectively.

Xinwei et al. (2005) measured eight kinds of building materialscollected from Xi’an, China, and analyzed for the natural radio-activity of 226Ra, 232Th and 40K using g-ray spectroscopy. Theconcentrations of 226Ra, 232Th and 40K in the selected buildingmaterials range from 19.5 to 68.3, 13.4 to 51.7 and 63.2 to713.9 Bq/kg, respectively. The radium equivalent activities (Raeq),external hazard index (Hex) and the internal radiation hazardindex (Hin) associated with the natural radionuclide werecalculated. The Raeq values of all building materials are lowerthan the limit of 370 Bq/kg, equivalent to a g-dose of 1.5 mSv/y.The values of Hex and Hin are less than unity.

It can be seen from all those studies that brick is used in almostall studies as it is a commonly used construction material. Besidesall those studies in the literature, the measurement in building

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1250

1000

750

500

Cou

nts

Co-60Cs-137

1170 kev1332 kev

662 kev

B. Mavi, I. Akkurt / Radiation Physics and Chemistry 79 (2010) 933–937934

materials used in Isparta region is still an open question.Therefore in the present paper, the activity concentrations of226Ra, 232Th and 40K, from the common building constructionmaterials, have been measured and the radium equivalent (Raeq),external hazard index (Hex), absorbed dose in air (D) and effectivedose rate (EDR) have been obtained. Activity of 40K was measuredfrom its intensive line at 1460 keV and for 226Ra activity peakfrom 214Bi at 1760 keV was used. For the case of 232Th activity,peak from 208Tl at energy of 2615 keV was used (Kumar et al.,1999).

3000

2000

1000

4000 8000Channel

120000

0

250

0

Ener

gy (k

eV)

Fig. 1. Calibration spectrum obtained for 137Cs, 60Co source (upper) and related fit

(lower).

Fig. 2. A typical g-ray spectrum obtained for brick.

2. Experimental methods

2.1. Sample preparation

For the measurement of radioactivity the commonly usedbuilding materials such as brick, which is a commonly usedconstruction material; cement; limestone; ytong, which is a kindof light concrete; limra, which is a local construction material;gypsum; ceramic tile and gravel in Isparta city of Turkey havebeen collected and tested for their natural radioactivity content. Atotal of eight samples of building material were crushed and driedat 110 1C in an oven for about 24 h. The samples were then sievedand hermetically sealed in cylindrical plastic boxes, which wereclosed tightly as far as possible to limit the escape of radon. Thesamples were then stored for 30 days before counting so as toensure that 238U attains radioactive equilibrium with theirdaughters.

2.2. Activity measurement

The radioactivity 226Ra, 232Th and 40K in the building materialsamples was determined using a gamma ray spectrometry(Akkurt et al., 2009) consisting of a 3�300 NaI(Tl) detectorconnected to a 16 384 channel multichannel analyser (MCA).The energy resolution of the spectrometer is 8% for 662 keV andthe relative counting efficiency is about 20%. The spectrum isanalyzed using the Genie 2 obtained from Canberra. The detectoris shielded using 6 cm lead on all sides to reduce the backgroundlevel of the system. Before measurement the system should becalibrated. This is done using 137Cs and 60Co radioactive sources,which produce g-ray energy of 662, 1170 and 1332 keV,respectively. With these sources it will be possible to convertchannel number to energy scale. The g-ray spectrum obtainedfrom the mentioned source and related fit has been displayed inFig. 1.

The samples were counted for a period of 40 000 s and thespectra are analyzed for the photo peaks of 226Ra, 232Th and 40K. Atypical spectrum obtained for this kind of measurement has beenshown in Fig. 2, where 226Ra, 232Th and 40K peaks can be clearlyseen.

The activity concentrations for the natural radionuclide in themeasured samples were computed using the following relation(Amrani and Tahtat, 2001):

A¼C

egt mð1Þ

where A is the activity of the isotope in Bq/kg, C is the net countrate under the most prominent photo peaks calculated bysubtracting the respective count rate from the backgroundspectrum obtained for the same counting time. The net countrate in the measurement is calculated from the backgroundsubtracted area of prominent gamma ray peaks. e is the detectorefficiency of the specific gamma ray, which is obtained using aradioactive source with known activity. g is the absolute

transition probability of gamma decay, t is the counting time (s)and m is the mass of the sample (kg).

3. Results and discussion

The activity concentrations of 226Ra, 232Th and 40K in eightdifferent building materials widely used in Isparta (Turkey) havebeen measured. The results have been tabulated in Table 1, wherethey were compared with the previous measurements. It can beseen from this table that the measured values varied from sampleto sample. Some obtained results in this study are higher thanother measurement and some are lower. This could be due to thegeological differences. The results are also displayed in Fig. 3,where the activity variation for 8 different samples can beseen. This is also shown in the 3D plot displayed in Fig. 4. It can beseen that the highest value of the activity concentration of the

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Table 1The measured activity and comparison with other measurement for the same materials (NA: not available).

Sample

code

Material Algeria Bangladesh China Israel Turkey Turkey

S1 Clay brick 40K 675 234 137.4 NA NA 248.8226Ra 65 109 46.2 58.9232Th 51 58 28.4 11.7

S2 Cement 40K 422 506 173.8 138,1 129.7226Ra 41 120 68.3 66,3 NA 26.1232Th 27 132 51.7 39,2 10.4

S3 Limestone 40K 36 63.2 51,1 52.7 76.4226Ra 16 NA 19.5 12,1 11.9 28.8232Th 13 13.4 4,1 5.4 8.9

S4 Yutong 40K NA NA NA NA 287.9–403.2 176.3226Ra 12.3–23.6 17.9232Th 14.1–36.7 19.5

S5 Limra 40K 65.7226Ra NA NA NA NA NA 36,0232Th 11.3

S6 Gypsum 40K 275 161.3 51,4 2.0–186.3 200.2226Ra 50 NA 64.7 10,5 1.2–14.6 27.5232Th 21 48.7 5,9 0.8–18.2 15.6

S7 Ceramic tile 40K 410 NA 776,3 289.7–579.2 106.9226Ra 55 NA 45,7 40.2–96.0 19.1232Th 41 48,2 53.4–68.7 ND

S8 Gravel-aggregate 40K 259 389 286.7 50,4 482.2 101.7226Ra 24 248 28.5 15 21.6 22.5232Th 10 219 19.5 3 25.8 6.8

References Amrani and

Tahtat (2001)

Mustapha et al.

(1997)

Xinwei (2005) Kovler et al.

(2002)

Turhan et al.

(2008)

This study

0

100

200

300

S1

A (

Bq

/kg

)

Ra-226

Th-232

K-40

S2 S3 S4 S5 S6 S7 S8

Fig. 3. The natural radioactivity of the samples.

S1S2

S3S4

S5S6

S7S8

Ra-

226

Th-2

32 K-4

0

0

100

200

300

A(B

q/kg

)

Fig. 4. 3D spectrum for Ra, Th and K activity

Table 2The determined dosimetric quantities for building materials.

samplecode

Material D (nGy/h) AED (mSv/y) Raeq (Bq/kg) Hex

S1 Brick clay 86.97 0.42 94.81 0.26

S2 Cement 45.88 0.22 51.03 0.14

S3 Limestone 42.42 0.21 47.45 0.13

S4 Ytong 52.01 0.25 59.35 0.16

S5 Limra 50.72 0.25 57.11 0.15

S6 Gypsum 58.57 0.28 65.34 0.18

S7 Ceramic tile 26.67 0.13 28.05 0.080

S8 Gravel 36.30 0.18 40.03 0.11

B. Mavi, I. Akkurt / Radiation Physics and Chemistry 79 (2010) 933–937 935

three radionuclides 226Ra, 232Th and 40K are 58.88, 19.49 and248.76 Bq/kg measured in brick, ytong and brick, respectively.On the other hand the minimum values are 17.91, 6.77 and65.72 Bq/kg measured in ytong, gravel and limra, respectively.The results were compared with the worldwide averageconcentrations, which are 40 Bq/kg for 226Ra and 232Thconcentration and 400 Bq/kg for 40K (Steger and Grun, 1999;UNSCEAR, 2000). It was found that all obtained results are lowerthan the world average values except for brick, where it is slightlyhigher for the case of 226Ra concentration.

According to UNSCEAR report, the total air absorbed dose rate(nGy/h) in air 1 m above the ground due to the activityconcentrations of 226Ra, 232Th and 40K (Bq/kg) was calculatedusing the formula (Markkanen, 1995)

DðnGy=hÞ ¼ 0:08CKþ0:92CRaþ1:1CTh ð2Þ

where CRa, CTh and CK are activity concentrations of 226Ra, 232Thand 40K in Bq/kg, respectively. The results of absorbed dose rateare tabulated in Table 2 and displayed in Fig. 5. The absorbed doserate ranged from 26.67 to 86.97 nGy/h. The annual effective doserates (AED) should be obtained to test the health effect of thoseabsorbed dose rates. Using the conversion coefficient from theabsorbed dose in air to the effective dose (0.7 Sv/Gy) and theindoor occupancy factor (0.8) implied that 80% of time is spentindoors, as proposed in UNSCEAR (1993). AED has been obtained

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0

25

50

75

100

S1 S2 S3 S4 S5 S6 S7 S8

D (n

Gy/

h)

Fig. 5. Absorbed dose rate due to the natural radioactivity for all samples.

0

0.1

0.2

0.3

0.4

0.5

S1 S2 S3 S4 S5 S6 S7 S8

(AED

mSv

/y)

Fig. 6. Effective dose rate for all samples.

0

25

50

75

100

S1 S2 S3 S4 S5 S6 S7 S8

Rae

q

Fig. 7. Radium equivalent of the natural radioactivity for all samples showing that

all obtained values are lower than the recommended limit as detailed in text.

00.10.20.30.40.50.60.70.80.9

1

S1 S2 S3 S4 S5 S6 S7 S8

Hex

Fig. 8. Hazard Index for all samples. In the comparison with the recommended

limit value of unity it can be seen that all values are lower than the limit as

detailed in the text.

B. Mavi, I. Akkurt / Radiation Physics and Chemistry 79 (2010) 933–937936

from the following formula (EC, 1999; Cevik et al., 2007; Turhanet al., 2008):

AEDðmSv=yÞ ¼DðnGy=hÞ � 8760ðh=yÞ � 0:8� 0:7ðSv=GyÞ � 10�6

ð3Þ

The obtained AED values ranged from 0.13 to 0.42 mSv/y. Theresults are tabulated in Table 2 and are displayed in Fig. 6.The results were compared with the UNSCEAR limit where theaverage AED from the terrestrial radionuclide is 0.46 mSv/y(UNSCEAR, 2000). The AED values are lower than the limit value.

As the distribution of 226Ra, 232Th and 40K in building materials isnot uniform the uniformity with respect to exposure to radiation hasbeen defined in terms of radium equivalent activity (Raeq) in Bq/kg.In order to compare the specific activity of materials containingdifferent amounts of 226Ra, 232Th and 40K, it is calculated through thefollowing relation (Beretka and Mathew, 1985):

Raeq ¼ CRaþ1,43� CThþ0,077� CK ð4Þ

where CRa, CTh and CK are the activity concentrations of 226Ra, 232Thand 40K, respectively, in Bq/kg. It is assumed that 370 Bq/kg of 226Ra,259 Bq/kg of 232Th and 4810 Bq/kg of 40K produce the same gammaray dose rate (Stranden, 1976; Krisiuk et al., 1971). A radiumequivalent of 370 Bq/kg in building materials produces an exposureof about 1.5 mSv/y to the inhabitants (UNSCEAR, 1982). In Fig. 7 theRaeq for all samples have been displayed. It can be seen from thisfigure that the lowest value of Raeq is 28.05 Bq/kg for ceramic, whilethe highest value is 94.81 Bq/kg for brick. It is also seen that allvalues obtained in this work are lower than the recommendedmaximum levels of radium equivalents for building materials to beused for homes, which is o370 Bq/kg and for industries is 370–740 Bq/kg (UNSCEAR, 2000; Oresegun and Babalola, 1988).

The external hazard index (Hex) is calculated from the equation(Beretka and Mathew, 1985)

Hex ¼CRa

370þ

CTh

259þ

CK

4810ð5Þ

where CRa, CTh and CK are the activity concentrations of 226Ra,232Th and 40K, respectively, in Bq/kg. The value of Hex must beless than unity, which corresponds to the upper limit of Raeq

(370 Bq/kg), in order to keep the radiation hazard under upperlimit. The results have been tabulated in Table 2 and displayed inFig. 8, where it can be seen that all measured results are muchlower than the upper limit of unity.

4. Conclusions

The present work shows that the natural radioactivity levels inthe building construction materials used in Isparta region is wellbelow the acceptable limits. All other quantities of absorbed doserate, annual effective dose, radium equivalent and hazard index,extracted from this activity for important building materials, havebeen measured and they were found within the recommendedsafety limit when used for building construction. From this studyit can be seen that the dose equivalent received by the public inlarge and the workers in particular is lower than the recom-mended safety limits.

Acknowledgments

This work has been supported by the Suleyman DemirelUniversity Foundation (1549-D-07 and 2003-029). One of us(B.M.) was supported by the TUBITAK-BIDEB program.

References

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Cevik, U., Damla, N., Nezir, S., 2007. Radiological characterization of Cayırhancoal-fired power plant in Turkey. Fuel 86, 2509–2513.

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Flores, O.B., Estrada, A.M., Suarez, R.R., Zerquera, J.T., Perez, A.H., 2008. Naturalradionuclide content in building materials and gamma dose rate in dwellingsin Cuba. J. Environ. Rad. 99-12, 1834–1837.

Kovler, K., Haquin, G., Manasherov, V., Ne’eman, E., Lavi, N., 2002. Natural radionuclidesin building materials available in Israel. Build. Environ. 37, 531–537.

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