REPRODUCIBILITY OF IMP MEASUREMENTS
DOE/ERSP TECH NOTE NO. 21.0
DATED: 19 February 1980
AUTHOR: Joel Jobst, EG&G, Inc.
Raphael J. Jaffe, EG&G, Inc.
The determination of specific concentrations of transuranic elements in large quantities of soil is
subject to errors and uncertainties. One such uncertainty is attributed to IMP measurements of the
specific concentration of 24lam, which are subject to both systematic variations and counting
statistics.
A simple experiment has been conducted in order to estimate the IMP error. IMP l, equipped with
detector 483, was driven to stake 3-N-0.5 on Pearl. This was a "total lift" area; that is, all brush
and surface soi] had been removed to a depth of several inches. The terrain was relatively flat, the
soil rather moist because a rain had soaked the area in early morning hours. A 300-second
calibration
was done
with
the
standard
EG&G
900-second measurements were made of 3-N-0.5.
calibration
source.
Then
eight
consecutive
A noon calibration was made and nine more
measurements were obtained at 3-N-0.5; finally an evening calibration was made at the close of the
day's work.
The 17 measurements of 2414m and !8%Cs obtained are plotted in Figure B-21-1 in the order in
which they were obtained. These data, and the three calibration measurements, suggest that no
systematic
drift
occurred
during
the
day.
For
the
calibrations,
the
24l am
photopeak
concentrations were 620.5 + 66.4, 604.1 + 64.7 and 609.6 + 65.3 pCi/g. The measured 24. am and
“Cs concentrations obtained for location 3-N-0.5 are shown in Table B-21-1.
Run
241 Am (pCi/g)
137Cs (pCi/g)
632
633
8.1 + 1.4
7.7 + 1.3
9.6 + 1.3
9.6 + 1.3
634
8.4 + 1.4
9.5 + 1.3
635
7.6 + 1.3
9.9 + 1.3
636
637
7.7 + 1.3
8.2 + 1.4
10.3 + 1.4
10.1 + 1.3
638
639
8.3 + 1.4
7.9 + 1.3
10.0 + 1.3
9.7 + 1.3
641
7.9 + 1.3
10.2 + 1.4
642
8.3 + 1.4
9.5 + 1.3
643
644
645
9.0 + 1.4
7.8 + 1.3
7.8 + 1.3
9.5 + 1.3
10.1 + 1.3
10.2 + 1.4
646
7.7 + 1.3
9.8 + 1.3
647
648
649
8.2 + 1.4
8.2 + 1.4
8.9 + 1.4
10.5 + 1.4
B-2]-1
10.0 + 1.3
10.2 + 1.4
a
TABLE B-21-1. AMERICIUM AND CESIUM REPEAT MEASUREMENTS