Available online at www.sciencedirect.com Radiation Measurements 36 (2003) 561–565 www.elsevier.com/locate/radmeas Determination of the uranium content of Egyptian phosphate ores by passive and active detectors A.F.Saad a ; ∗ ,T.M.Talaat a ,S.T.Atwa b; 1 ,G.Espinosa c ,M.Fujii d a Physics Department, Faculty of Science, Zagazig University, Zagazig, Egypt b Chemistry Department, Faculty of Science, Zagazig University, Benha-Branch, Benha, Egypt c Institute de Fisica UMAN. Apdo.Postal 20-364,01000 Mexico, D.F., Mexico d Faculty of Engineering, Aomori University, 2-3-1 Kobata, Aomori, Japan Received 21 October 2002; received in revised form 13 May 2003 Abstract Uranium contents of phosphate ores and fertilizers collected from El-Sobaeya and El-Suez mines in Egypt were determined by measuring the radon emanated from these samples. In our method, neither direct contact of CR-39 track detectors to the samples nor thermal neutron activation process is required. The concentration of 222 Rn in the emanation container (Genitron Instruments GmbH) is dependent on the uranium deposited in the phosphate sample. The CR-39 and a pulse ionization chamber, Alpha GUARD PQ-2000 (Genitron Instruments GmbH) were simultaneously used for radon detection. The detection eciency of CR-39 was calibrated with the Alpha GUARD. The uranium content determinations were performed using a high-resolution inductively coupled plasma mass spectrometer for comparison. The measurements revealed a very high uranium content, 355 ppm for ore and 118 ppm for fertilizer from El-Sobaeya mine, while it was 7 ppm for fertilizer from El-Suez. Although the uranium content of ores from El-Sobaeya mine is within permissible limit for the manufacturing of fertilizers, the phosphate ore from El-Suez is much safer for fertilizers. c  2003 Elsevier Ltd. All rights reserved. Keywords: Uranium content; CR-39; Diusion cup; Filter paper; Alpha GUARD; Plasma mass spectrometer 1. Introduction Oneofthemostthreateningproblemstothehumanhealth is uranium-containing materials. Uranium and phosphate ores are closely existing together in nature. Phosphate fertil- izers are one of the most commonly used materials all over the world in the agriculture eld. The examination of the radioactivity of a large number of minerals has revealed that phosphoric samples have a much higher radioactivity level than that in the common rocks of the earth’s crust (Strutt, 1908). The phosphate ore is a rich natural source of uranium. So, the uranium contents of natural ores were estimated from the measurements of nuclear tracks in solids by many investigators (Fleischer ∗ Corresponding author. Fax: +2 055 2303252. E-mail address: abdallahsaad@hotmail.com (A.F. Saad). 1 Present address: Department of Science and Mathematics, College of Education for Girls, Al-lieth, Saudi Arabia. et al., 1975; Fisher, 1970; Chakarvarti and Nagpaul, 1980; Virk et al., 1982; Veli ckovi c et al., 1982; Gamboa et al., 1984; Qureshi et al., 2001). Since 238 U produces 222 Rn, it is reasonable to use radon measurements for uranium exploration. In this work, we propose a method for determining the uranium content of Egyptian phosphate ores by using a CR-39 nuclear track detector simultaneously with an Alpha GUARD pulse ion- ization chamber. This method is based on measurement at an equilibrium condition that takes place in a closed system between uranium and radon nuclides. 2. Materials and methods The minerals studied were phosphate ores and fertilizers collected from two dierent sites in Egypt, El-Sobaeya and El-Suez. The samples were two mined rocks and four fer- tilizers. The sample weight was 100 g as a powder material 1350-4487/03/$-see front matter c  2003 Elsevier Ltd. All rights reserved. doi:10.1016/S1350-4487(03)00203-8