Table 5. Detection limits (la) of selected gamma-emitting radionuclides in
the Bikini Atoll environment as a function of sample size.
pCi/sample - 1000 minutes counting time
Sample size
(g)
3+ 2
10+ 5
70 + 30
160 + 60
40¢
60¢9
1Omag
125sh
137¢s5
155ey
207 pj
241 An
10
15
20
30
1.0
1.6
2.4
3.6
1.0
1.8
3 at
4.5
1.2
1.7
2.9
4.6
0.5
0.8
1.2
1.8
0.9
1.4
2.4
4.0
0.8
1.5
2.2
3.2
1.5
2.5
4.0
7.5
After gamma analysis, a number of samples were selected for radiochemical
analysis for 90Sr, 137cs, 113mcq, 238,239,240py, 24lam, 210p9, 210Ph, and
210Bi.
Activities of these radionuclides were measured using either alpha-
spectrometer systems or low-background beta detectors.
Measurements of these
radionuclides were conducted because some were judged to be of potential
Significance for dose assessments and others were analyzed to meet specific
programmatic objectives.
The !3/Cs was often radiochemically separated from
muscle tissue and analyzed
RRR
a
spectrometry, which,
to confirm the measurements
made by gamma
in turn, provided a useful laboratory calibration for
quality control.
Quality of data has always been an important aspect of our analytical
measurements.
As a standard practice, 5 to 10% of our time is devoted to
quality-assurance work in all
projects involving analytical measurements.
This quality-assurance work includes
e
Analysis of background samples and blanks.
e
Instrument calibration.
°
Duplicate sampling and analysis.
°
National and international interlaboratory standardization.
°
Replicate measurements.
.
Analysis and calibration traceable to National Bureau of Standards
samples.
e
9000564
Appropriate statistical analysis of the results.
10