Radionuclides internal conversion

Sources for activity calibration These sources enable a direct calibration of y-ray spectrometers, for radionuclides for which standards are available. Moreover, with the kits of y-ray sources, the efficiency/energy curve can be plotted in this case, knowledge of decay scheme parameters of the radionuclides involved is needed (y branching ratio, internal conversion coefficient, etc.). 

A process alternative to isomeric transition is called internal conversion (IC). In some cases, the y-energy is absorbed by a K-shell (inner) electron. This electron is ejected out with lower energy. This ejected electron is the internal conversion electron, and the process is called internal conversion. Some diagnostic and therapeutic radionuclides with corresponding half lives are given below. 

It should be noted that for a number of radionuclides the Qp values are more restrictive than those of the earlier Q system. These lower Qp values are primarily associated with radionuclides which emit internal conversion electrons. 

Additional information necessary for radionuclide identification and analysis but not shown in Figs. 9.3-9.9 is given in Sections 9.3.2-9.3.7 it includes the fraction of conversion electrons and X rays in an internal transition and the beta-particle maximum energy. 

Radioactive decay of nuclei is a first-order reaction decay rate (activity A) is therefore dependent on the concentration (content) of the radionuclide and is the product of this concentration (more precisely, the number of atoms of radionuclide N) and the decay constant X (in s" ) A =-(dN/dt) = X.N. The basic unit of activity, according to the System International (SI system) is the Bq (becquerel). One Bq (in s ) is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. Previously, the frequently used unit was the Ci (curie) defined as 3.7 x 10 decays per second. For conversion, the following relationship can be used 1 Ci = 3.7 x lO Bq. Number of radionuclide atoms transformed in time t is f T=NQ.e", where Nq is the initial number of atoms of the radionuclide at the time t=0. During conversion, the number of radioactive atoms of the radioactive nuclide is continuously decreasing. Combining both equations we get the relation expressing the dependence of activity on time A = -(dN/dt) The... 

The need or otherwise for individual or area monitoring for internal exposure will depend on the amount of radioactive material present and the radionuclide(s) involved, the physical and chemical form of the radioactive material, the type of contaimnent used, the operations performed and the general working conditions. For example, workers handling sealed sources, or unsealed sources in reliable containment, may need to be monitored for external exposure, but not necessarily for internal exposure. Conversely, workers handling radionuclides such as tritium, or Pu may need monitoring for internal exposure, but not for external exposure. 

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