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Area Radiology and radiological physics / Ionizing radiations : quantities and units

IEV ref881-04-47

Symbol
τ

en
mean life
the average life expectancy of a nucleus of a particular radionuclide which is the time in which the number of nuclei of the radionuclide is reduced to the fraction 1/e (≈ 0,368) of its initial value

NOTE – It is related to the decay constant λ and the half-life T 1 2 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGe aGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaq Fn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpe WZqaaeaaciWacmGadaGadeaabaGaaqaaaOqaaiaadsfadaWgaaqcba waaSWaaSqaaKGaGfaacaaIXaaabaGaaGOmaaaaaKqaahqaaaaa@397C@ by:

τ= 1 λ = T 1 2 ln2 T 1 2 0,693 1,433 T 1 2 MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHXgaruavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeaaciWacmGadaGadeaabaGaaqaaaOqaaGWaciab=r8a0jabg2da9maalaaabaGaaGymaaqaaiabeU7aSbaacqGH9aqpdaWcaaqaaiaadsfadaWgaaWcbaWaaSqaaWqaaiaaigdaaeaacaaIYaaaaaWcbeaaaOqaaiGacYgacaGGUbGaaGOmaaaacqWIdjYodaWcaaqaaiaadsfadaWgaaWcbaWaaSqaaWqaaiaaigdaaeaacaaIYaaaaaWcbeaaaOqaaiaaicdacaGGSaGaaGOnaiaaiMdacaaIZaaaaiabloKi7iaaigdacaGGSaGaaGinaiaaiodacaaIZaGaaGPaVlaaykW7caWGubWaaSbaaSqaamaaleaameaacaaIXaaabaGaaGOmaaaaaSqabaaaaa@532B@


fr
vie moyenne, f
temps moyen au cours duquel le nombre de radionucléides d'un système atomique donné est réduit à la fraction 1/e (≈ 0,368) de sa valeur initiale

NOTE – La vie moyenne est liée à la constante de désintégration λ et à la période radioactive T 1 2 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGe aGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaq Fn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpe WZqaaeaaciWacmGadaGadeaabaGaaqaaaOqaaiaadsfadaWgaaqcba waaSWaaSqaaKGaGfaacaaIXaaabaGaaGOmaaaaaKqaahqaaaaa@397C@ par la relation:

τ= 1 λ = T 1 2 ln2 T 1 2 0,693 1,433 T 1 2 MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHXgaruavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeaaciWacmGadaGadeaabaGaaqaaaOqaaGWaciab=r8a0jabg2da9maalaaabaGaaGymaaqaaiabeU7aSbaacqGH9aqpdaWcaaqaaiaadsfadaWgaaWcbaWaaSqaaWqaaiaaigdaaeaacaaIYaaaaaWcbeaaaOqaaiGacYgacaGGUbGaaGOmaaaacqWIdjYodaWcaaqaaiaadsfadaWgaaWcbaWaaSqaaWqaaiaaigdaaeaacaaIYaaaaaWcbeaaaOqaaiaaicdacaGGSaGaaGOnaiaaiMdacaaIZaaaaiabloKi7iaaigdacaGGSaGaaGinaiaaiodacaaIZaGaaGPaVlaaykW7caWGubWaaSbaaSqaamaaleaameaacaaIXaaabaGaaGOmaaaaaSqabaaaaa@532B@


ar
متوسط العمر

es
vida media

it
vita media

ko
평균수명

ja
平均寿命

pl
czas życia średni

pt
vida média

sv
medellivstid

Publication date: 1983-01
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