Cook Plant preoperational studies, 1969 / John C. Ayers ... [et al.].

REPORT OF RADIOASSAY OF FIELD SAMPLES
Submitted by, CHARLES C. KIDD
INTRODUCTION
Radioassay of macrobenthos samples collected in July, 1968 during an environmental survey of Lake Michigan in the vicinity of The Big Rock Nuclear Power
Plant indicated that levels of gross beta and gamma radioactivity in Pontoporeia
affinis might possibly reflect the influence of radionuclides released in the
waste from the plant. However, the samples taken at that time did not contain
many amphipods. Moreover, there were insufficient sampling locations to discern
any pattern or trend in levels of radioactivity. On October 18, 1968 the writer
returned to the area and working off The Great Lakes Research Division's ship
"The Mysis", obtained more benthos samples from nine sampling points (see figures
#1 and #2) in the vicinity of The Big Rock Nuclear Power Plant. The objective
of the study described in this report is to detect any pattern in the distribution of radioactivity as results from the radioassay of the amphipods collected.
The degree to which Pontoporeia affinis responds to the low levels of radioactivity
encountered in the study area is reflective of their usefulness as biological
indicators of environmental radioactivity.
METHODS AND MATERIALS
Bottom samples were taken with a Ponar Dredge. The dredge was lowered four
times at each sampling point. This represented a sampling area of approximately
0.25 square meters. Sampling depth ranged from 70 feet to 300 feet. All samples
were washed free of mud and put in 1-pint Mason Jars. A small amount of Formalin
was added to preserve each sample. In the laboratory the Pontoporeia were picked
from each sample and weighed. They were then wet digested in nitric acid. The
neutralized residue was dried on stainless steel planchets and analysed for
200 minutes in a gamma spectrometer. The samples were also analysed for 200

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