emitters present in the samples were determined from the gamma
curves by use of the method of Conally (1956).
A three-inch by
three-inch NaI (Tl) crystal was used in conjunction with a 256channel analyzer.
Tests for the accuracy of the gamma spectrum
method were made with standards and with radioactive spikes the
disintegration rates of which had been determined from beta
counts.
Accuracy of + 20 per cent, based on known spike mixtures,
was obtained for six of the isotopes (W185, co°7, csi37, zr95,
co58 and co®9) present in the samples.
The lowest limit of de-
tection of any given isotope in the samples was approximately one
per cent of the total gamma activity.
The determinations of the
levels of RulO3. Ryl06 and Get41_gelt4 are not as accurate as those
obtained for the other isotopes because of the overlapping gamma
peaks.
The ratio of Rul03 to RulO® was calculated in the following
manner.
The
.624 MEV peak of RyL06 was determined in selected
samples and the contribution of the .513 MEV peak from the same
isotope was calculated.
This value was subtracted from the com-
posite .498 MEV gamma peak of Rul03 and the .515 MEV peak of Rul0®
in selected samples,
and the remainder was assumed to be contrib-
uted by RulO3,
The ratio of cel4l to cel4t4 was calculated in a similar
way.
The 0.08 MEV and 0.03 MEV peaks of Cel44 were determined in
selected samples and the contribution of the .134 MEV Ce 144
a