{"id":24885,"date":"2019-07-21T18:53:02","date_gmt":"2019-07-21T18:53:02","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=24885"},"modified":"2023-06-09T08:05:03","modified_gmt":"2023-06-09T08:05:03","slug":"curie-unit-of-radioactivity","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-protection\/units-of-radioactivity\/curie-unit-of-radioactivity\/","title":{"rendered":"Curie – Unit of Radioactivity"},"content":{"rendered":"
\n

The original unit for measuring the amount of radioactivity was the curie<\/strong> (symbol Ci), a non-SI unit of radioactivity<\/strong> defined in 1910. A curie<\/strong> was originally named in honor of Pierre Curie<\/strong> but was considered at least by some to be in honor of Marie Curie as well. A curie was originally defined as equivalent to the number of disintegrations that one gram of radium-226<\/strong> will undergo in one second<\/strong>. Currently, a curie is defined as 1Ci = 3.7 x 1010<\/sup> disintegrations per second<\/strong>. Therefore:<\/p>\n

1Ci = 3.7 x 1010<\/sup> Bq = 37 GBq<\/strong><\/p>\n

One curie is a large amount of activity. The typical human body contains roughly 0.1 \u03bcCi (14 mg) of naturally occurring potassium-40. A human body containing 16 kg of carbon would also have about 0.1 \u03bcCi of carbon-14 (24 nanograms). Activities measured in a nuclear power plant (except irradiated fuel) often have usually lower activity than curie, and the following multiples are often used:<\/p>\n

1 mCi (milicurie) = 1E-3 Ci<\/strong><\/p>\n

1 \u00b5Ci (microcurie) = 1E-6 Ci<\/strong><\/p>\n

While its continued use is discouraged by many institutions, the curie is still widely used throughout the world’s government, industry, and medicine.<\/p>\n

Curie – Examples<\/strong><\/h2>\n

The relationship between half-life<\/strong> and the amount of a radionuclide required to give an activity of one curie is shown in the figure. This amount of material can be calculated using \u03bb<\/strong>, which is the decay constant<\/strong> of certain nuclide:<\/p>\n

\"Curie<\/a><\/p>\n

\"Radioactivity<\/a>The following figure illustrates the amount of material necessary for 1 curie<\/strong> of radioactivity. Obviously, the longer the half-life, the greater the quantity of radionuclide needed to produce the same activity. Of course, the longer-lived substance will remain radioactive for much longer. As can be seen, the amount of material necessary for 1 curie of radioactivity can vary from an amount too small to be seen (0.00088 gram of cobalt-60), through 1 gram of radium-226, to almost three tons of uranium-238<\/a>.<\/p>\n

<\/div>\n

Example – Calculation of Radioactivity<\/h2>\n

\"Iodine<\/a>A sample of material contains 1 microgram of iodine-131. Note that iodine-131 plays a major role as a radioactive isotope present in nuclear fission products<\/a>. It is a major contributor to health hazards when released into the atmosphere during an accident. Iodine-131 has a half-life of 8.02 days.<\/p>\n

Calculate:<\/strong><\/p>\n

    \n
  1. The number of iodine-131 atoms is initially present.<\/li>\n
  2. The activity of the iodine-131 in curies.<\/li>\n
  3. The number of iodine-131 atoms will remain in 50 days.<\/li>\n
  4. The time it will take for the activity to reach 0.1 mCi.<\/li>\n<\/ol>\n

    Solution:<\/strong><\/p>\n

      \n
    1. The number of atoms of iodine-131 can be determined using isotopic mass as below.<\/li>\n<\/ol>\n

      N<\/strong>I-131<\/sub><\/strong> = m<\/strong>I-131<\/sub><\/strong> . N<\/strong>A<\/sub><\/strong> \/ M<\/strong>I-131<\/sub><\/strong><\/p>\n

      N<\/strong>I-131 <\/sub><\/strong>= (1 \u03bcg) x (6.02\u00d710<\/strong>23<\/sup><\/strong> nuclei\/mol) \/ (130.91 g\/mol)<\/strong><\/p>\n

      N<\/strong>I-131<\/sub><\/strong> = 4.6 x 10<\/strong>15<\/sup><\/strong> nuclei<\/strong><\/p>\n

        \n
      1. The activity of the iodine-131 in curies can be determined using its decay constant<\/strong>:<\/li>\n<\/ol>\n

        The iodine-131 has a half-life of 8.02 days (692928 sec), and therefore its decay constant is:<\/p>\n

        \"\"<\/a><\/p>\n

        Using this value for the decay constant, we can determine the activity of the sample:<\/p>\n

        \"\"<\/a><\/p>\n

        3) and 4) The number of iodine-131 atoms that will remain in 50 days (N50d<\/sub>) and the time it will take for the activity to reach 0.1 mCi can be calculated using the decay law:<\/p>\n

        \"\"<\/a><\/p>\n

        As can be seen, after 50 days, the number of iodine-131 atoms and thus the activity will be about 75 times lower. After 82 days, the activity will be approximately 1200 times lower. Therefore, the time of ten half-lives (factor 210<\/sup> = 1024) is widely used to define residual activity.<\/p>\n<\/div><\/div>\n

        <\/span>References:<\/div>
        \n

        Radiation Protection:<\/strong><\/p>\n

          \n
        1. Knoll, Glenn F.,\u00a0Radiation Detection and Measurement 4th Edition,\u00a0Wiley,\u00a08\/2010. ISBN-13: 978-0470131480.<\/li>\n
        2. Stabin, Michael G., Radiation Protection and Dosimetry: An Introduction to Health Physics, Springer, 10\/2010.\u00a0ISBN-13: 978-1441923912.<\/li>\n
        3. Martin, James E., Physics for Radiation Protection 3rd Edition,\u00a0Wiley-VCH, 4\/2013.\u00a0ISBN-13: 978-3527411764.<\/li>\n
        4. U.S.NRC,\u00a0NUCLEAR REACTOR CONCEPTS<\/li>\n
        5. U.S. Department of Energy, Nuclear Physics and Reactor Theory.\u00a0DOE Fundamentals Handbook,\u00a0Volume 1 and 2.\u00a0January\u00a01993.<\/li>\n<\/ol>\n

          Nuclear and Reactor Physics:<\/strong><\/p>\n

            \n
          1. J. R. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading,\u00a0MA (1983).<\/li>\n
          2. J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.<\/li>\n
          3. W. M. Stacey, Nuclear Reactor Physics, John Wiley & Sons, 2001, ISBN: 0- 471-39127-1.<\/li>\n
          4. Glasstone, Sesonske. Nuclear Reactor Engineering: Reactor Systems Engineering,\u00a0Springer; 4th edition, 1994, ISBN:\u00a0978-0412985317<\/li>\n
          5. W.S.C. Williams. Nuclear and Particle Physics.\u00a0Clarendon Press; 1 edition, 1991, ISBN:\u00a0978-0198520467<\/li>\n
          6. G.R.Keepin. Physics of Nuclear Kinetics.\u00a0Addison-Wesley Pub. Co; 1st edition, 1965<\/li>\n
          7. Robert Reed Burn, Introduction to Nuclear Reactor Operation, 1988.<\/li>\n
          8. U.S. Department of Energy, Nuclear Physics and Reactor Theory.\u00a0DOE Fundamentals Handbook,\u00a0Volume 1 and 2.\u00a0January\u00a01993.<\/li>\n
          9. Paul Reuss, Neutron Physics.\u00a0EDP Sciences, 2008.\u00a0ISBN: 978-2759800414.<\/li>\n<\/ol>\n<\/div><\/div>