Tham khảo tài liệu 'nuclear power control, reliability and human factors part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Origin and Detection of Actinides Where Do We Stand with the Accelerator Mass Spectrometry Technique 169 Actinides t1 2 y Emitted radiation 234U 105 a 235U 108 a 236U 106 a 238U 109 a 238Pu a 239Pu 104 a 240Pu 103 a 241Pu 14 p- 242Pu 105 a 243Pu 10-4 p- 244Pu 106 a Table 1. Half-lives T1 2 and decay mode of Uranium and Plutonium isotopes in year y units. out. Another large scale source of contamination is due to one of the worst accidents in the history of nuclear energy that occurred on 26 April 1986 at the Chernobyl Nuclear Power Station near Kiev in Ukraine affecting mainly Central and Northern Europe although 137Cs was detectable even in Southern Italy Roca et al. 1989 . 2. small scale includes the operation and decommissioning activities of a NPP which could lead to airborne and liquid releases of radionuclides. At the same level several steps in the fuel cycle up to the reprocessing of spent fuel can release activation and fission products as well as the fissile material itself. Obviously given that the relative concentrations of plutonium and uranium isotopes depend on the nature of the source material and on its subsequent irradiation history all these sources of contamination do not give the same contributions of contamination. As it will be shown in the following useful tools to solve among different contributions are the isotopic ratios 236U 238U 240Pu 239Pu 242Pu 239Pu 244Pu 239Pu and 238Pu 239 240Pu . Table 1 shows the half lives of the relevant isotopes of U and Pu. Different contamination sources The relative concentrations of plutonium and uranium isotopes depend on the nature of the source material and on its subsequent irradiation history all these sources of contamination do not give the same contributions of contamination. Here are shown some example of different contamination sources Being fissile material 239Pu is the most abundant isotope in weapon-grade plutonium. The average ratio of 240Pu .
