{"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":"
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 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 <\/a><\/p>\n <\/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 <\/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 Solution:<\/strong><\/p>\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 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>\nCurie – Examples<\/strong><\/h2>\n
Example – Calculation of Radioactivity<\/h2>\n
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