Abstract
Passive gamma ray spectrometry and neutron capture prompt gamma activation analysis (PGAA) were used to investigate powdered cow's milk samples [termed optimal (1), optimal (2) and optimal (3)] collected from local markets in the city of Cairo, Egypt. Standard material with a total average activity of 0.830 +/- 0.2 mu Ci and a certified reference material [IAEA (A-14)] were used to study the accuracy of a passive multi-gamma ray measurement method. Three powdered milk samples of the same geometry and volume were used in this analysis. The specific activity of Ra-226 ranged from 24.5 +/- 2.1 to 114 +/- 1.2 Bq/kg, Th-232 from 8 +/- 1 to 14 +/- 1.2 Bq/kg and K-40 from 444 +/- 28 to 1826.1 +/- 3.1 Bq/kg, all of which were higher than the activities corresponding to the United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR) (50, 50 and 500 Bq/kg for Ra-226, Th-232 and K-40, respectively). The average dose rate at 1 cm for K-40 ranged from 8.21E-02 +/- 0.12 to 3.3E-1 +/- 0.22 mSv/h/cm. We also showed that (208)T1(81), Pb-212(82) and Bi-212(83) should be considered products of thorium. k(0)-PGAA was carried out using an integrated and calibrated prompt gamma ray system with a neutron flux of 10(6) n/cm(2) per second. The thermal to epithermal neutron flux ratio (f) and cadmium ratio were measured using a thin gold foil technique (ration = 160). Different Cl concentrations were prepared as standards for k(0)-PGAA. The elemental concentrations of Na, Mg, Al, Ca, Mn, Fe, Cu, Ga, Zn, As, Se, Cs, Cd, In, Th and I were measured in the three powdered milk samples. The mean f standard deviation ranges of the elements were as follows: Na = 1069 +/- 49-1583 +/- 53 ppm, Mg = 347 +/- 13.64-385 +/- 16.71 ppm, Al= 45 +/- 1.30-72 +/- 2.40 ppm, Fe =5500 +/- 110-7123 +/- 130 ppm, Zn =107 +/- 3-123 +/- 6 ppm, Ca = 4200 +/- 72-5483 +/- 81 ppm, Mn =1269 +/- 69-1784 +/- 72 ppm, Pr =1.7 +/- 0.02-2.6 +/- 0.07 ppm, Ga = 265 +/- 5-293 +/- 8 ppm, Cu =57 +/- 0.5-64 f 0.9 ppm, In =1000 +/- 38.64-1574 +/- 41.34 ppm, Cd = 6.1 +/- 2.71-12.6 +/- 4.11 ppm, I= 53 +/- 0.09-62 +/- 1.18 ppm, Cs = 4 +/- 1.56-11 +/- 4.22 ppm, As = 26 +/- 0.66-29 +/- 0.89 ppm, Se =126 +/- 4.8-144 +/- 5.7 ppm, Th = 47 +/- 1.0-78 +/- 6.0 ppm. (C) 2016 The Authors. Production and hosting by Elsevier B.V. on behalf of Taibah University.