Lake Michigan environmental survey : final report / [edited] by John C. Ayers.

this basis, the estimated Cs-137 in Lake Michigan in 1970 is 5940 Ci and in
1975, 5790 Ci. The estimated concentration of Cs-137 in Lake Michigan at the
present time is 1.2x10 9 uCi/ml (5940 Ci/4.8xl108 ml), excluding losses to
sediment or to lake outflow.
Tritium is formed from ternary fission in atomic weapons at the rate of
0.7 Ci per kiloton of TNT explosive yield; the yield for fusion weapons is
6,700 Ci/kT.(14) To date, approximately 1,700x10 Ci of H-3 have been con(14)
tributed to the environment from weapon testing. Much of this tritium is
oxidized to water and removed from the troposphere by precipitation. (2122)
The concentration of H-3 in precipitation is not constant, but swings from a
peak level in the spring to a low level in the winter. (2022) The maximum H-3
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content in precipitation, 3x10-5 uCi/ml, occurred in the spring and early
summer of 1963 in northwestern Canada.(22) Since then the H-3 concentration
has been decreasing continuously. Recently (1968), snow at the Dresden reactor contained 5x10 7 uCi/ml.(
There are no specific figures for the concentration of tritium in Lake
Michigan. The Public Health Service found in 1968 that the H-3 concentrations
in water downstream from large nuclear installations ranged between 2xlO to
10-5 uCi/ml. (14'3) Kahn reports that the concentration of H-3 in the Illinois
River at the Dresden reactor in 1968 was 2 ~ 2xlO7 uCi/ml.( 26)
Big Rock Nuclear Power Plant
Big Rock Nuclear Power Plant, a boiling water reactor owned and operated
by the Consumers Power Company, is the only operating power reactor on Lake
Michigan. This plant has released 33.1 Ci of gross beta-gamma radioactivity
into Lake Michigan from 1962 to 1968.(30) Occasional analyses have indicated
that most of this activity has consisted of Zn-65, Co-58, Cs-137, Ba-140 and
La-140. In 1968, 7.5 Ci of gross beta-gamma activity was discharged. If this
were also true for 1969 and 1970, the total radioactivity released to date is
some 50 Ci gross beta-gamma activity. It is estimated that the maximum quantity of tritium that could have been released during 1968 is 34 Ci. Thus,
the H-3 released to Lake Michigan since the plant went critical in 1962 can
scarcely exceed 300 Ci.

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