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CAPINTEC, INC CRC
®
-25R
APPENDIX III
MULTIPLICATION FACTORS FOR NON-
EQUILIBRIUM RADIOISOTOPES
Note: These Multiplication Factors apply to the R Chamber only.
The activity in a non-equilibrium sample can be determined by using the following equation:
A
B
B A
B A
B A
A
R
R
n2 1 t
T T
T T
- exp - 1
T T
T
F + 1
A" " Pure for Number Cal. with Reading Meter
= A" " of Activity
⎥
⎦
⎤
⎢
⎣
⎡
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
× ×
×
−
−
where “A” and “B” are parent and daughter nuclide respectively, T's are half lives, and R
A
and R
B
are the chamber responses to the isotopes A and B, “t” is the elapsed time after the
pure parent isotope was produced, and “F” is the decay branching ratio.
B
The chamber response,”R,” may be obtained from the calibration number “N,” using the
following equation:
0797 . 0
1075.8
N
= R
+
When the half-life of the parent nucleus (T
A
) is much shorter than that of the daughter
nucleus (T
R
), the parent decays down to the daughter. After about 10
×
T
A
, we can assume
that only the daughter is left (except if the original activity of the parent was exceptionally
high). The equation above for the Activity of “A” can be used to obtain the activity of the
parent while it has measurable activity.
Multiplication factors obtained by using the equation are given in the following tables for
selected isotopes.
July 07 APPENDIX III A3 - 1