Радиоактивтіктің бірлік массасына шаққандағы белсенділігі

Activity per unit mass of a radionuclide
specific activity radioactivity

In the context of radioactivity, activity or total activity (symbol A) is a physical quantity defined as the number of radioactive transformations per second that occur in a particular radionuclide. The unit of activity is the becquerel (symbol Bq), which is defined equivalent to reciprocal seconds (symbol s 1). The older, non SI unit of activity is the curie (Ci), which is 3.7 radioactive decay per second. Another unit of activity is the rutherford, which is defined as 1 radioactive decay per second. Specific activity (symbol a) is the activity per unit mass of a radionuclide and is a physical property of that radionuclide. It is usually given in units of becquerel per kilogram (Bq/kg), but another commonly used unit of specific activity is the curie per gram (Ci/g). The specific activity should not be confused with level of exposure to ionizing radiation and thus the exposure or absorbed dose, which is the quantity important in assessing the effects of ionizing radiation on humans. Since the probability of radioactive decay for a given radionuclide within a set time interval is fixed (with some slight exceptions, see changing decay rates), the number of decays that occur in a given time of a given mass (and hence a specific number of atoms) of that radionuclide is also a fixed (ignoring statistical fluctuations).

One gram of rubidium 87 and a radioactivity count rate that, after taking solid angle effects into account, is consistent with a decay rate of 3200 decays per second corresponds to a specific activity of 3.2. Rubidium atomic mass is 87 g/mol, so one gram is 1/87 of a mole. Plugging in the numbers:

IsotopeHalf lifeMass of 1 curieSpecific Activity (A) of 1 kg 232Th 1.405 years 9.1 tonnes 4.07 MBq (110 μCi or 4.07 Rd) 238U 4.471 years 2.977 tonnes 12.58 MBq (340 μCi, or 12.58 Rd) 235U 7.038 years 463 kg 79.92 MBq (2.160 mCi, or 79.92 Rd) 40K 1.25 years140 kg 262.7 MBq (7.1 mCi, or 262.7 Rd) 129I 15.7 years5.66 kg 6.66 GBq (180 mCi, or 6.66 kRd) 99Tc 211 years58 g 629 GBq (17 Ci, or 629 kRd) 239Pu 24.11 years16 g 2.331 TBq (63 Ci, or 2.331 MRd) 240Pu 6563 years 4.4 g 8.51 TBq (230 Ci, or 8.51MRd) 14C 5730 years0.22 g 166.5 TBq (4.5 kCi, or 166.5 MRd) 226Ra 1601 years 1.01 g 36.63 TBq (990 Ci, or 36.63 MRd) 241Am 432.6 years 0.29 g 126.91 TBq (3.43 kCi, or 126.91 MRd) 238Pu 88 years 59 mg 629 TBq (17 kCi, or 629 MRd) 137Cs 30.17 years 12 mg 3.071 PBq (83 kCi, or 3.071 GRd) 90Sr 28.8 years 7.2 mg 5.143 PBq (139 kCi, or 5.143 GRd) 241Pu 14 years 9.4 mg 3.922 PBq (106 kCi, or 3.922 GRd) 3H 12.32 years 104 μg 355.977 PBq (9.621 MCi, or 355.977 GRd) 228Ra 5.75 years3.67 mg 10.101 PBq (273 kCi, or 10.101 GRd) 60Co 1925 days883 μg 41.884 PBq (1.132 MCi, or 41.884 GRd) 210Po 138 days223 μg 165.908 PBq (4.484 MCi, or 165.908 GRd) 131I 8.02 days8 μg 4.625 EBq (125 MCi, or 4.625 TRd) 123I 13 hours518 ng 71.41 EBq (1.93 GCi, or 71.41 TRd) 212Pb 10.64 hours719 ng 51.43 EBq (1.39 GCi, or 51.43 TRd)

The specific activity of radionuclides is particularly relevant when it comes to select them for production for therapeutic pharmaceuticals, as well as for immunoassays or other diagnostic procedures, or assessing radioactivity in certain environments, among several other biomedical applications.