Individual:
http://rdf.iit.demokritos.gr/2014/iaeaSafetyGlossary/id20
Annotations (2)
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nreo:canonicalLabel "activity" (en)
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skos:definition "1. The quantity 'A' for an amount of radionuclide in a given energy state at <br/>
a given time, defined as:<br/>
'N'<br/>
'A'('t') = dd't'<br/>
where d'N' is the expectation value of the number of spontaneous nuclear <br/>transformations from the given energy state in the time interval d't'. (From <br/>Ref. [1].)<br/>
The rate at which nuclear transformations occur in a 'radioactive material'. The <br/>equation is sometimes given as: <br/>
'N'<br/>
'A'('t') = - dd't'<br/>
where 'N' is the number of nuclei of the radionuclide, and hence the rate of <br/>change of 'N' with time is negative. Numerically, the two forms are identical.<br/>The SI unit of activity is the reciprocal second (s–1), termed the <i>becquerel <br/></i>(Bq). (From Ref. [1].)<br/>Formerly expressed in 'curies '(Ci); 'activity' values may be given in Ci (with the <br/>equivalent in Bq in parentheses) if they are being quoted from a reference <br/>that uses Ci as the unit.<br/>
<i><b>specific activity.</b></i> Of a material, for the purposes of the Transport <br/>Regulations, the 'activity' per unit mass of the material in which the <br/>radionuclides are essentially uniformly distributed. (From Ref. [2].)<br/>Of a radionuclide, the 'activity' per unit mass of that nuclide. Of a material, <br/>the 'activity' per unit mass or volume of the material in which the <br/>radionuclides are essentially uniformly distributed.<br/>
The distinction in usage between 'specific activity' and <i><b>activity concentration</b></i> is <br/>controversial. Some regard the terms as synonymous, and may favour one or <br/>the other (as above). ISO 921 [7] distinguishes between 'specific activity' as the <br/>'activity' per unit mass and 'activity concentration' as the 'activity' per unit volume. <br/>Another common distinction is that 'specific activity' is used (usually as <i>activity<br/></i>per unit mass) with reference to a pure sample of a radionuclide or, less <br/>strictly, to cases where a radionuclide is intrinsically present in the material <br/>(e.g. carbon-14 in organic materials, uranium-235 in 'natural uranium'), even if <br/>the abundance of the radionuclide is artificially changed. In this usage, <i>activity <br/>concentration</i> (which may be 'activity' per unit mass or per unit volume) is used <br/>for any other situation (e.g. when the 'activity' is in the form of 'contamination' in <br/>or on a material).<br/>In general, the term 'activity concentration' is more widely applicable, is more <br/>self-evident in meaning, and is less likely than 'specific activity' to be confused <br/>with unrelated terms (such as ‘specified activities’). <i><b>Activity concentration</b></i> is <br/>therefore preferred to 'specific activity' for general use in 'safety' related <i>IAEA <br/>publications</i>.<br/>
2. See 'facilities and activities'.<br/>" (en)
Types (1)
Usage (46)