CAPINTEC, INC.
CRC
®
-712MX
In general, the attenuation of radiation by a plastic syringe is less than for the standard
ampoule, while for most glass syringes, the attenuation will be greater than for the standard
ampoule.
The anticipated syringe corrections are listed on Table II under the column “Uncertainty Due
to Syringe Correction”. For example, the required correction for I125 activity is estimated to
be about ±25%. This means that you should add 25% to the meter reading if the I125 is in a
glass syringe or subtract 25% if it is in a plastic syringe.
Since the attenuation of low energy radiation is very dependent upon the material of the
container, the value given in the syringe correction column should be used mainly as a guide
giving relative magnitude.
If a measurement of activity in a glass vial is anticipated, the container correction for low
energy
γ
and/or x-ray emitting isotopes will be substantial. It could be about 3 to 5 times that
for a syringe.
If no value is given in this column, the correction is not significant, except for a container
differing greatly from the standard ampoule (e.g. Very thick glass container, vial made of
glass which contains lead, etc.).
UNCERTAINTY DUE TO PUBLISHED DATA
This is the uncertainty on the value of the activity. From calibration numbers calculated from
decay data, the uncertainty given is calculated using only the reported errors on the intensity
of the
γ
and/or x-rays. For calibration numbers measured from NIST (formally NBS) standard
reference materials (known as SRM’s), the uncertainty given is the reported uncertainty on
the activity of the SRM. For these numbers, the reference is given as NIST, and year of
source.
HALF-LIFE
The number before the letter is the value of the half-life. The number following the letter is
the reported uncertainty on the half-life.
Examples:
12.34 D1
means
12.34
days ±0.01
days
12.34 D11
means
12.34
days ±0.11
days
12.340 D1
means 12.340
days ±0.001
days
1.234 D1
means 1.234
days ±0.001
days
A2 - 2
APPENDIX II
January 08
