Terrestrial Animal Standard
A large sample of beef was dried and ashed at LLNL and shipped to WOSC. The ash
was spiked with a known amount of algae, blended, and reashed at 400°C. The reashed
beef was blended in a small twin-cone blender, canned, and labeled.
Marine Organism Standard
A large fish sample was collected and ashed at LLNL and then shipped to WOSC.
The ashed sample was spiked with a known amount of algae, blended, and then reashed at
400°C. The reashed sample was then blended in a small twin-cone blender, canned, and
labeled.
CERTIFICATION OF STANDARDS
The first step in certifying the standards was to show that the methods used to
prepare the samples produced a homogeneous sample.
Because the vegetation standard
was the first prepared, the greatest attention was given to it.
Homogeneity was first
tested by measuring 137 Cs in a random selection of ten aliquots of the standard by
nondestructive analysis on a Ge(Li) gamma-ray spectrometer. Because the samples were
not in the counting geometry normally used by WOSC, only relative activities were
measured. As shown in Table 3, there was excellent agreement among the ten samples.
Similarly, the 2.6% relative standard deviation of 10 measurements of
radiochemically and the
4.7%
relative standard deviation
of
16
137
Cs done
measurements of
239+240 54 (Table 4) provide evidence that the procedures used to prepare the samples
produced a homogeneous sample.
Because the marine and terrestrial animal standards
were prepared in the same manner as the vegetation standard by adding algae and
blending, their homogeneity is likewise established.
In the course of this survey, the
homogeneity of the vegetation and animal samples was confirmed by one of the
participating laboratories (EAL). Because the soil standard had no added radioactivity, it
was a slightly different case, but the 5.4% standard deviation about the mean of ten
2394240 5, analyses shows that it was likewise homogeneous (Table 5). Moreover, many
analyses by the participating laboratories have further confirmed its homogeneity.
Certified activities of the standards were established in two ways.
First, the
radioactivity of the algae used to spike samples of vegetation, fish, and beef had been
measured
at
EML,
and
because
it
was
used
to
prepare
samples
for
the
DOE