,
."C"
RADIOACTIVITY OF BUILDING MATERIALS AVAILABLE IN CANADA L. Zikovsky and G. Kennedy* 226Rawas determined by measuring its 186-keV peak and the 352- and 609-keV peaks of 214Pband 214Bi.The 186-keV peak gave an apparent radium concentration that was too high because of the contribution of 235Uwhich emits gamma rays of the same energy. The 352- and 609-keV peaks gave an apparent radium concentration that was too low because of the emanation of radon (214Pband 214Biare radon decay products) from materials. The results were corrected for these phenomena. For the 186-keV peak, it was assumed that 58% (Kahn et al. 1983) of the gammaray activity was due to 226Ra,and the concentrations were divided by 1.72. For 214Pband 214Bi,it was assumed that the mean emanation coefficient was equal to 8.6% (Kominek and Mrnustik 1989), and the concentrations calculated from these peaks were multiplied by 1.094. The results obtained from the 186-keV peak and the 352- and 609-keV peaks were generally in good mutual agreement. For 232Th,the 9 1 1-keV peak of 228Acand the 239keV peak of 212Pbwere used. For the 9 1 1-keV peak, no interference was identified, while for the 239-keV peak, 227Thand 224Racould possibly add activity to the ~ e a k . ~ ~is ~a Tdecay h product of 235U,whose activity was calculated from the 186-keV peak. 224Raoriginates from 232Th.Appropriate corrections, usually very minor, were made for both of these. The results calculated from the 9 1 1-keV and 239-keV peaks were quite similar. For 40K,the 1461-keVpeak was used. The building materials studied were bought in stores in the Montreal area. Different brand names were sought. The origin of the material was frequently indicated on the material or its packaging. Samples of concrete used in foundations were recovered from different construction sites around Montreal. They were the leftovers dumped from mixing trucks near new unfinished houses. Samples were weighed and their dimensions were measured for the purpose of calculating the counting efficiencies. The typical sample weight was between 1 and 2 kg. The materials were sometimes cut with a diamond saw in order to fit into the leadshielded space around the detector.
~
Absfvuef-Concentrations of 232Th,226Ra,and 40Kwere measured in 47 samples of seven different building materials available in Canada. The radioactivities were low for woods and natural gypsums and up to 160 Bq kg-' 232Th,121 Bq kg-' 226Ra, and 990 Bq kg-' "OK for bricks and tiles. Annual gonadal doses generated by these materials vary from 0.01-1.4 mSv. Health Phys. 63(4):449-452; 1992 Key words: Canada; exposure, population; dose, external; radioactivity, indoor
INTRODUCTION KNOWLEDGE of the concentrations of radioelements in building materials is important in the assessment of population exposures, as most individuals spend 80% of their time indoors. The average indoor absorbed dose rate in air from terrestrial sources of radioactivity is estimated to be 70 nGy h-I (UNSCEAR 1988). Indoors elevated external dose rates may arise from high activities of radionuclides in building materials. Large-scale surveys of concentrations of radioelements in construction materials were summarized by the United Nations (UNSCEAR 1977, 1988) but very little information was found on the situation that exists in Canada. Consequently, this study was undertaken with the purpose of measuring radioactivity in Canadian building materials.
MATERIALS AND METHODS The radioactivity of building materials was measured with a Ge(Li) detector with an active volume of 114 cm3.The detector was coupled to an amplifier and a multichannel analyzer. The typical counting time was 1 d. Absolute counting efficiencies were calculated with a modified version of a computer program previously published (Zikovsky and Chah 1988). The building materials were counted in their original shape as it was not necessary to grind them to produce a standard counting geometry. ~
* Energy Engineering Institute, Ecole Polytechnique, Montrhl, Quibec, Canada, H3C 3A7. (Manuscript received 22 July 199I ; revised manuscript received 31 January 1992, accepted 6 April 1992 00 17-9078/92/$3.00/0 Copyright 0 1992 Health Physics Society
RESULTS AND DISCUSSION The concentrations of 232Th,226Ra,and 40Kmeasured in a selection of building materials available in 449
450
Health Physics
October 1992, Volume 63, Number 4
Table 1. Concentrations (in Bq kg-') of 232Th,226Ra,and 40Kin the building materials. The counting error is shown in parentheses. Material Country 232Th 226Ra 40K AGDE" I1 I2 I3 I4 Cb Acoustic panel C Brick-brown C Brick-grey C Brick-red C Brick-red Brick-refractory C C Brick-yellow C Concrete C Concrete C Concrete C Concrete C Concrete Concrete C C Concrete C Concrete C Concrete C Concrete C Concrete C Concrete Concrete C Fiberglass-pink C Fiberglass-white C Fiberglass-yellow C Glass C Glass C Granite C Gravel-large C Gravel-small C Gravel-medium C Gypsum-chemical C Gypsum-chemical C Gypsum-chemical C Gypsum-natural C Gypsum-natural C Gypsum-natural C Gypsum-natural C Marble C Slate C Tile-beige B' Tile-blue Id Tile-brown B Tile-brown P Tile-grey B Tile-grey B Tile-grey I Tile-grey I Tile-red Ef Tile-red I Tile-white B Tile-white B Tile-white B Tile-white B Tile-white B Vermiculite C Wood-pine C Wood-spruce C a AGDE = annual gonadal dose equivalent (mSv). C = Canada. B = Brazil. I = Italy. P = Portugal. E = England.
340 (10) 300 (10) 450 (20) 800 (10) 340 (20) 335 (9) 200 (10) 380 (20) 340 (20) 320 (10) 330 (20) 570 (20) 560 (30) 560 (20) 640 (30) 600 (10) 450 (20) 800 (20) 470 (20) 320 (10) 240 (20) 76 (6) 33 (3) 195 (10) 8 (1) 1030 (30) 180 (10) 280 (15) 205 (10) 66 (5) 120 (10) 52 (5)
."C"
RADIOACTIVITY OF BUILDING MATERIALS AVAILABLE IN CANADA L. Zikovsky and G. Kennedy* 226Rawas determined by measuring its 186-keV peak and the 352- and 609-keV peaks of 214Pband 214Bi.The 186-keV peak gave an apparent radium concentration that was too high because of the contribution of 235Uwhich emits gamma rays of the same energy. The 352- and 609-keV peaks gave an apparent radium concentration that was too low because of the emanation of radon (214Pband 214Biare radon decay products) from materials. The results were corrected for these phenomena. For the 186-keV peak, it was assumed that 58% (Kahn et al. 1983) of the gammaray activity was due to 226Ra,and the concentrations were divided by 1.72. For 214Pband 214Bi,it was assumed that the mean emanation coefficient was equal to 8.6% (Kominek and Mrnustik 1989), and the concentrations calculated from these peaks were multiplied by 1.094. The results obtained from the 186-keV peak and the 352- and 609-keV peaks were generally in good mutual agreement. For 232Th,the 9 1 1-keV peak of 228Acand the 239keV peak of 212Pbwere used. For the 9 1 1-keV peak, no interference was identified, while for the 239-keV peak, 227Thand 224Racould possibly add activity to the ~ e a k . ~ ~is ~a Tdecay h product of 235U,whose activity was calculated from the 186-keV peak. 224Raoriginates from 232Th.Appropriate corrections, usually very minor, were made for both of these. The results calculated from the 9 1 1-keV and 239-keV peaks were quite similar. For 40K,the 1461-keVpeak was used. The building materials studied were bought in stores in the Montreal area. Different brand names were sought. The origin of the material was frequently indicated on the material or its packaging. Samples of concrete used in foundations were recovered from different construction sites around Montreal. They were the leftovers dumped from mixing trucks near new unfinished houses. Samples were weighed and their dimensions were measured for the purpose of calculating the counting efficiencies. The typical sample weight was between 1 and 2 kg. The materials were sometimes cut with a diamond saw in order to fit into the leadshielded space around the detector.
~
Absfvuef-Concentrations of 232Th,226Ra,and 40Kwere measured in 47 samples of seven different building materials available in Canada. The radioactivities were low for woods and natural gypsums and up to 160 Bq kg-' 232Th,121 Bq kg-' 226Ra, and 990 Bq kg-' "OK for bricks and tiles. Annual gonadal doses generated by these materials vary from 0.01-1.4 mSv. Health Phys. 63(4):449-452; 1992 Key words: Canada; exposure, population; dose, external; radioactivity, indoor
INTRODUCTION KNOWLEDGE of the concentrations of radioelements in building materials is important in the assessment of population exposures, as most individuals spend 80% of their time indoors. The average indoor absorbed dose rate in air from terrestrial sources of radioactivity is estimated to be 70 nGy h-I (UNSCEAR 1988). Indoors elevated external dose rates may arise from high activities of radionuclides in building materials. Large-scale surveys of concentrations of radioelements in construction materials were summarized by the United Nations (UNSCEAR 1977, 1988) but very little information was found on the situation that exists in Canada. Consequently, this study was undertaken with the purpose of measuring radioactivity in Canadian building materials.
MATERIALS AND METHODS The radioactivity of building materials was measured with a Ge(Li) detector with an active volume of 114 cm3.The detector was coupled to an amplifier and a multichannel analyzer. The typical counting time was 1 d. Absolute counting efficiencies were calculated with a modified version of a computer program previously published (Zikovsky and Chah 1988). The building materials were counted in their original shape as it was not necessary to grind them to produce a standard counting geometry. ~
* Energy Engineering Institute, Ecole Polytechnique, Montrhl, Quibec, Canada, H3C 3A7. (Manuscript received 22 July 199I ; revised manuscript received 31 January 1992, accepted 6 April 1992 00 17-9078/92/$3.00/0 Copyright 0 1992 Health Physics Society
RESULTS AND DISCUSSION The concentrations of 232Th,226Ra,and 40Kmeasured in a selection of building materials available in 449
450
Health Physics
October 1992, Volume 63, Number 4
Table 1. Concentrations (in Bq kg-') of 232Th,226Ra,and 40Kin the building materials. The counting error is shown in parentheses. Material Country 232Th 226Ra 40K AGDE" I1 I2 I3 I4 Cb Acoustic panel C Brick-brown C Brick-grey C Brick-red C Brick-red Brick-refractory C C Brick-yellow C Concrete C Concrete C Concrete C Concrete C Concrete Concrete C C Concrete C Concrete C Concrete C Concrete C Concrete C Concrete Concrete C Fiberglass-pink C Fiberglass-white C Fiberglass-yellow C Glass C Glass C Granite C Gravel-large C Gravel-small C Gravel-medium C Gypsum-chemical C Gypsum-chemical C Gypsum-chemical C Gypsum-natural C Gypsum-natural C Gypsum-natural C Gypsum-natural C Marble C Slate C Tile-beige B' Tile-blue Id Tile-brown B Tile-brown P Tile-grey B Tile-grey B Tile-grey I Tile-grey I Tile-red Ef Tile-red I Tile-white B Tile-white B Tile-white B Tile-white B Tile-white B Vermiculite C Wood-pine C Wood-spruce C a AGDE = annual gonadal dose equivalent (mSv). C = Canada. B = Brazil. I = Italy. P = Portugal. E = England.
340 (10) 300 (10) 450 (20) 800 (10) 340 (20) 335 (9) 200 (10) 380 (20) 340 (20) 320 (10) 330 (20) 570 (20) 560 (30) 560 (20) 640 (30) 600 (10) 450 (20) 800 (20) 470 (20) 320 (10) 240 (20) 76 (6) 33 (3) 195 (10) 8 (1) 1030 (30) 180 (10) 280 (15) 205 (10) 66 (5) 120 (10) 52 (5)
