PERGAMON Radiation Measurements 31 (1999) 491--495

Radiation Measurements

N A T U R A L R A D I O A C T I V I T Y A N D R A D O N E X H A L A T I O N

R A T E S I N B U I L D I N G M A T E R I A L S U S E D I N E G Y P T

M. SHARAF*, M. MANSY*, A. EL SAYED** AND E. ABBAS*

* National Institute for Standards, Radiation Measurement Department, Giza, Egypt.

** Cair6 University, Faculty of Science, Biophysics Department, Giza, Egypt

ABSTRACT

Natural and fabricated building materials commonly used in Egypt were surveyed for both natural radionuclides content and radon exhalation rate. These include raw as well as construction products. Concentration of natural radionuclides in all samples were determined by v-ray spectroscopy with I-IPGe detector. For Radon exhalation rate measurements of fabricated samples, the seal can-technique has been applied using CR-39 plastic track detectors. The radiation hazard indices of the total natural radioactivity in the studied samples were estimated. The results were compared with the corresponding results of different countries and were found to be lying within the average world values. Radon exhalation rate in the studied samples varied between 197 (cement brick) and 907 mBq m: h "1 (blast furnace slag cement). The results of this survey suggest that, using blast furnace slag cement for pre-coating the internal walls of buildings in the Urban region of Egypt is discouraged and the replacement of clay brick by cement brick will be more healthy for the public.

KEYWORDS

Natural radioactivity; radon; building material.

INTRODUCTION

Natural occurring radionuclides in building materials are sources of external and internal radiation exposure in dwellings. The external radiation exposure is caused by 3,-radiation originally from the member of uranium and thorium decay chains and from 4°K. The internal radiation exposure, affecting the respiratory tract, is due to radon and its daughters which are exhaled from building materials. In the last two decades the interest of studying radioactivity in building materials has increased noticeably worldwide (OECD, 1979; UNSCEAR, 1993). A very few attempts were carried out in Egypt to estimate the natural radioactivity levels in building materials and radon exhalation rate (Hassib, 1993; Hussein et al., 1991; El Tahawy et al., 1995). In several countries industrial wastes have been used as building materials (UNSCEAR, 1982). Many of these waste materials have levels of radioactivity that can be significantly higher than the background levels (OECD, 1979; UNSCEAR, 1982). In Egypt the blast furnace slag (bfs), waste product from iron processing is used by 35% in the manufacture of bfs- cement which intern used as a precoating material for the internal walls of the building. In the present work the primary attention was given to the measurements of the natural radioactivity and exhalation rates in different types of Egyptian cement products. Second emphasis was suggested for the natural and fabricated building materials commonly used in Egypt. Also the radiation hazard indices for the studied materials were calculated and compared with the corresponding results of different countries.

1350-4487/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PII: S 1350-4487(99)00206-1

492 M. Sharaf et al. /Radiation Measurements 31 (1999) 491-495

MATERIAL AND METHODS

Samples

Seventy seven samples building materials (38 natural materials and 39 fabricated products) were used for the measurements of activity concentrations. These samples were collected from different regions; sand and gravel from El Giza provenance quarries in El Haram region, limestone from Gayara at the south east of Cairo and bfs from Tora factory. Black-, yellow-, mixed-clay and Rrothind-, kamak-, sea water resistant-cements also bfs-cement were collected from Hellwan, Tora and El Kawmia factories. From Miser and techno Crete factories, clay-, cement-, and sand brick were collected. Concrete blocks were prepared according to the Egyptian Code for concrete construction. The samples were crushed, sieved through 2 mm meshes, homogenized and dried at 80 OC until acquiring constant weight. An aliquot of 1000 cc of each homogenized sample was weighted and stored in one liter plastic marinelli beaker for 4 weeks, in growth period to ensure secular equilibrium between radium and its daughters.

Measurement of the radioactivity concentration

The concentrations of *%a, u%‘h and “OK in the studied materials were measured directly using a typical high resolution y-spectrometer based on a shielded I-IF%-detector coaxial type. The spectrometer was calibrated in the energy range 186-2500 keV using 226Ra source and chemically pure KC1 (El Tahawy et al., 1992).

Measurement of the radon exhalation rate

For the measurement of exhalation rate the can technique (Abu Jarad et al., 1980) was applied in which a cylindrical stainless steel can (10 cm height and 7 cm diameter) was sealed by plasticin to the individual building material. In each can CR-39 plastic detector of 1x1 cm size was kept at the top inside the can for exposure period of one month. CR-39 detectors were taken and etched in 6.25 N NaOH solution at 70 “C for 8 hours in constant temperature water bath. The resulting OL tracks were counted under an optical microscope of magnification 400X. The track density was determined and converted into activity concentration using Somogy' s conversion factor for CR-39 (Somogy et al., 1986). The radon exhalation rate (Ex) has been calculated using the relation (Abu Jarad et al., 1980)

CViZ/A

ITx = T+ (l/A)(e-* - 1) (1)

where C is the integrated radon exposure as measured by the plastic detector, V is the volume of the can h is the decay constant of radon, A is the area covered by the can and T is the exposure time .

RESULTS AND DISCUSSION

The activity concentrations of 4%, ?h and 22% (Ck, C!T~, C ,) and the Radium equivalent activity @Q are given in Table 1. The obtained results indicate that the specific activity for all studied building materials are less than the corresponding values 500,50 and 50 Bq/kg for “K, 23?h and 226Ra respectively. (OECD, 1979 and UNSCEAR, 1993). The only exception was found for the raw bfs and bfs-cement where the radium contents are 323.9f18.6 Bq/kg and 107f8.2 Bq/kg respectively. y radiation hazard can be assessed according to the values of Ra, (Beretka and Mathew, 1985), representative level index; Iyr (OECD, 1979) and external hazard index; I& (O’Brien et al., 1995). &, is calculated using the formula

Ra, = CR, + (10/7)& + (10/13O)C,

Cb, CTh and CK are the specific activities of 2%a, 232Th and “OK respectively. Iyr is given by

I, = (CR, /HO) + (c, /lOO) + (CT, /1500)

(2)

(3)

M. Sharufet al. ! Radiation Measurements 31 (1999) 491-495 493

0’ Brien et al. (1995) suggested that the contribution of building materials to the external equivalent dose to the gonads can be limited to 1.5 mGy/year by applying the constraint

(C,,/185)+(C,,/259)+(C,/4810) 2 1 (4)

All the values of Iyr (see Table 1 ) were found to be lower than one, except for the samples of bfs. Using equation 4 the a, for all studied samples ranged between 0.0701 for sand brick and 1.9325 for the raw bfs samples which is nearly twice the criterion limit.

Table 1. Ck, Cm, C Ra ,Reg and I, of raw and industrial building materials (BM) used in Egypt

sample Bq/kg Bqlkg Bq/kg Bq/kg Raw Sand 10 47.3f 9 3.3k1.3 9.2ti.5 16.6 0.119

Gravel 7 62.4+12 3.5f1.6 9.8X2.0 19.7 0.142 limestone 5 19.3+ 2 4.4HJ.8 20.4f2.8 25.4 0.170

bfs 5 158+16 39.8f7.2 323f18.6 392.3 2.569 black clay 4 3 12f12 24.9f3.9 25.W2.5 85.5 0.647

yellow clay 5 282zt15 23.5k3.5 25.6ti.4 79.8 0.593 mixed clay 4 301+12 22.6f3.9 23.9ti.2 79.4 0.586

1 -Industrial Protland 3 48.6*4.0 ll.l+l. 1 31.3fi.6 50.9 0.353 cement karnak 3 76.8ti.5 14.0f1.4 40.2ti.6 66.2 0.459

water resist 3 30.6~t2.5 9.9k1.2 ,28.8+3.2 45.3 0.311 bfs 3 49.3k4.8 19.41t1.8 107.9kS.2 185.4 1.261

2-Industrial clay 8 227.7ti7 24.1f4.4 24.5k4.6 76.5 0.556 brick cement 6 60.9rt7.2 2.6H.9 lO.lti.2 18.5 0.133

sand 6 66.9ti.2 4.2kl.l 10.7?2.5 21.7 0.157 3 -concrete 5 76.4zlz8.7 8.1k1.7 19.1ti.8 36.6 0.272

In Table 2 the CR, CTh, Ck and Ra, were compared with the corresponding values determined in other different countries. It is clear that, there is a reliable agreement between the present data and the previous data of El Tahawy and Higgy, 1995 for clay brick and lying within the average world values for the other materials except cement which has the lower values. Measurements of the radon exhalation rate from fabricated building materials showed that bfs-cement exhales the highest radon concentration (907 mBq me2 h-l), while the cement brick gives a minimum value (180 mBq me2 h-l); see Fig. 1.

1200

-2 1000 - 907

P

D- E 800 -

s! B 600 -

s 402 400

367 371 ‘S - m 268 294

_!J! 231 180 r lz 200 -

0 , 1

Fig. 1. The average radon exhalation rate in building materials in Egypt

494 M. Sharaf et al. /Radiation Measurements 31 (1999) 491-495

Table 2. Comparison of Ck, Cn,, C Ra and R&,in Bq/kg of different building materials (BM) in different countries with the present work.

Types of BM Countries CK C!T~ Cr+ Raeq Reference

Sand Australia 44.4 40.0 3.7 65.3 Beretka & Mathew, (1985) China 573.0 47.2 39.4 151.0 Yu et al., (1992)

Hog Kong 841.0 27.1 24.3 128.0 Yu et al., (1992) Brazil 807.0 18.0 14.3 102.0 Malanca et al., (1993)

Netherland 200.0 10.6 8.1 38.6 Ackers et al., (1985) USA 18.5 33.3 37.0 86.0 Ingersoll., (1983)

Pakistan 520.0 31.9 21.5 107.0 Tufail et al., (1992)

Gravel Egypt 47.3 3.3 9.2

Australia 171.0 14.8 13.9 . 16.6 Present work

48.2 Sorantin & Teger (1983)

Limestone

Cement

Clay Brick

Brazil 933.0 _-__- 10.3 82.1 Malanca et al., (1993) Netherland 140.0 12.6 9.7 38.5 Ackers et al., (1985)

USA 14.8 33.3 33.3 82.0 Ingersoll, (1983) Pakistan 51.3 9.9 24.8 42.9 Tufail et al., (1992)

Egypt 62.4 3.5 9.8 19.7 Present work Australia ______ 11.1 _____ 15.9 Beretka & Mathew (1985) Austria 34.0 2.8 9.0 15.6 Sorantin & Teger (1983) Brazil 205.0 7.0 24.3 50.1 Malanca et al., (1993) Egypt 19.3 4.4 20.4 25.4 Present work

Australia 115.0 48.1 51.8 129.0 Beretka & Mathew (1985) Austria 210.0 14.2 26.7 63.1 Sorantin & Teger (1983) China 169.0 62.0 69.3 189.0 Zigiang et al., (1988) Brazil 564.0 58.5 61.7 189.0 MaIanca et al., (1993)

UK 141.0 7.0 22.0 42.8 OECD, NEA (1979) Germany 241.0 118 Q6 70.3 OECD, NEA (1979) Sweden 241.0 47.0 55.0. 141.0 OECD, NEA (1979) Norway 241.0 18.0 30.0 74.3 OECD, NEA (1979) Finland 241.0 26.0 44.0 99.7 OECD, NEA (1979) Pakistan 212.0 26.8 31.3 85.9 Tufail et al., (1992)

Egypt 48.6 11.1 31.3 50.9 Present work Australia 681 88.8 40.7 220 Beretka & Matbew (1985) Austria 635 44.7 38.3 152 Sorantin & Teger (1983) China 717 52.0 41.0 171 Zigiang et al., (1988) Brazil 747 65.3 51.7 203 Malanca et al., (1993)

UK 703 44.0 52.0 169 OECD, NEA (1979) Germany 673 67.0 59.0 207 OECD, NEA (1979) Sweden 962 127.0 96.0 352 OECD, NEA (1979) Norway 1140 47.0 63.0 257 OECD, NEA (1979) Finland 962 62.0 78.0 241 OECD, NEA (1979) Pakistan 631 53.7 43.2 169 Tufail et al., (1992)

Egypt 258 24.1 24.0 78 El Tahawy & Higgy (1995) Egypt 227 24.4 24.5 077 Present work

CONCLUSION

The obtained results indicate that the specific activity for all studied samples are less than the corresponding world values except the bfs-cement which has the highest value. This can be attributed to the fact that its raw materials which contains high radium specific activity 323 Bq/lcg is used by 35% in its fabrication process. Therefore using bfs-cement for the precoating the internal walls of the new buildings is discouraged because it will increase the contribution to the annual effective dose resulting from the inhalation radon and its progeny. Also according to the low radon exhalation rate results of the cement bricks (180 mBq mm2 he’), it is then reasonable to courage the replacement of clay bricks by cement bricks in the new buildings which will be less hazard for the public.

M. Shamf et al. /Radiation Measurements 31 (1999) 491-495 495

REFERENCES

Abu-Jarad F., Fremlin J.H. and Bull R. (1980) A study of radon emitted from building materials using plastic alpha track detectors. P&r. Med. Biol. 25,683-694.

Ackers J.G., Den Boer J.F., De Jong P. and Wolschrijn R.A. (1985) Radiation and radon exhalation rates of building materials in the Netherlands. The Science of the total Environment 45, 15-165.

Beretka J. and Mathew P.J. (1985) Natural radioactivity of Australian building materials, Industrial Wastes and by Products. Health Phys. 4887-95.

El Tahawy M.S. and Higgy R.H. (1995) Natural radioactivity in different types of bricks fabricated and used in Cairo region. Appl. Radiat. Isot. 46, 1401-1406.

El-Tahawy M.S., Farouk M.A., Hammad F.H. and Ibrahiem N.M. (1992) Natural potassium as standard source for the absolute efficiency calibration of germanium detectors. Nucl. Sci. J. 29, 361-363.

Hassib G.M. (1993) Assessment of radon concentration in Egyptian dwellings by using a passive technique. Nucl. Tracks Radiat. Meas. 22,341-344.

Hussein M.I. and Kawy M. (1991) Indoor gamma level in some Egyptian cities. 5& International Symposium On the Natural Radiation Environment (NRE-v Salzburg, Book OfAbstracts, 161.

Ingersoll G.j. (1983) A survey of radionuclide contents and radon emanation rates in building materials in USA. Health Phys. 45,363-368.

Malanca A., Pessina V. and Dallar G. (1993) Radionuclide content of building materials and Gamma dose rates in dwellings of Rio Grade Do Norte, Brazil. Radiat. Prot. Dosim. 48, 199-203.

0’ Brian R.S., Peggie J.R. and Leith IS., (1995) Estimates of inhalation doses resulting from the pos- sible use of phospho-gypsum plaster-board in Australian homes. Health Phys. 68, 561-570.

OECD (1979) Exposure to radiation from natural radioactivity in building materials. Nuclear Energy Agency (NEA)Report by NEA Group of Experts OECD, Paris.

Somogy G., Hafez A., Hunyadi I. and Toth-Szillagyi (1986) Measurements of exhalation and diffusion parameter of radon in solids by plastic track detectors Nucl. Track 12,701-704.

Sorantin H. and Steger F. (1983) Natural radioactivity of building materials in Austria. Radiat. Prot. Dosim. 7,59-61.

Tufail M., Ahmed N., Mirza S.M. and Khan H.A. (1992) Natural radioactivity from building materials used in Islamabad and Rawalpindi, Pakistan. The Science of the total Environment. 121,282-29 1.

UNSCEAR (1982) Sources and effects of ionizing radiation and biological eficts. United Nations Scientific Committee on the Effects of Atomic Radiation. Report to the general assembly, with annexes. United nations sales publication E.82. Ix. 8. Untied Nations New York.

UNSCEAR (1993) Exposure from natural sources of radiation. United Nations Scientific Committee on the Effects of Atomic Radiation . Report to the general assembly, 93 -8287 11.

Yu K.N., Guan Z.J., Stokes M.J. and Young E.C.M. (1992) The assessment of the natural radiation dose committed to the Hong Kong people. J. Environment Radioactivity 17, 3 l-48.

Ziqiang P., Yin Y. and Mingqiang G. (1988) Natural radiation and radioactivity in China. Radiat. Prot. Dosim. 24.29-38.