CAPINTEC, INC CRC
®
-25R
The accuracy of the chamber response calculation for a particular radioisotope, hence the
accuracy which can be attained by using a calculated Calibration Setting Number depends
not only on the accuracy of the available primary standards used to determine Figure A1-1,
on the nuclear data, on the variation in the chamber sensitivity and electrometer gain setting,
but also on the sample configuration due to low energy photon absorption.
The calibration Setting Numbers for pure and equilibrium state radioisotopes for the CRC
®
Calibrators are listed in this Appendix. Appendix IV contains tables of multiplication factors
for obtaining the activity of a parent nuclide when it is not in equilibrium with the daughter
nuclide. A general equation for this situation is also given in that appendix.
Since the determination of the Calibration Numbers and the calibrations (normalization) of
the instrument are performed using standard reference materials issued by the NIST and/or
the LMR, the Calibration Numbers for radioisotopes are given for sample configuration
similar to those issued by the NIST.
All of the NIST standards, with the exception of Xe133, were of the liquid solution form.
Approximately 5g of radioactive liquid were sealed in borosilicate glass ampoules having a
diameter of about 17mm, a length of 40mm, and a wall thickness of 0.6mm. The Xe133
standard was sealed together with inactive xenon gas in a borosilicate glass ampoule having
a volume of about 5ml, a length of 45mm, a diameter of 15mm, and a wall thickness of
1.3mm.
June 09 APPENDIX II A2 - 3
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