- 12 : 241 tos . has been used to estimate the Pu activity in other compartments. The calculations have also been made using a ratio of 2414/239 ,240p, of 3.0 which is slightly more than X + I¢(i.e., 1.85 + 1.0 = 2.85). b. Lagoon surface water has an average 239, 240 Pu concentration of 39 £Ci/1 (Ref. 2, Ref. 1). Using a ratio of 1.85 7#4py/239>?40, the 241bu activity is 72 £Ci/1l. The ratio of 24d to 239,240, is 0.11 (Ref. 3); therefore, the 241am activity is 4.3 f£Ci/1. The maximum 241 Am activity which will result from decay of present levels of 24d is 72 (0.026) = 1.87 fCi/l. over present 241any activity. The total 241 This is a 43% increase Am which will result ts 6.2 £Ci/l which is 16% of the 799>74%pu activity. Plankton Concentrations in pCi per gram wet weight of 241 Am and 239, 2405, in plankton samples are 0.23 and 0,39 respectively (Ref. 1). Using the factor 1.85 for 241/739 22405, the a concentration would be 0.72 pCi/g. Maximum growth from this level of 7*!pu will be 0.72 this Relative to the present 2a dA level of 0.23 pCi/g represents an 8% increase. 0.249 pCi/g. Relative to the The total 24.am is 0.23 + 0.019 239,240 or 64%. Pu levels this is 0.249/0.39 Ml (0.026) = 0.019 pCi/g. 0.64 ~ However, a more realistic situation is that the plankton will always reflect the same ratio of water concentrations, 241 Am to 239 ,240 Pu as they do to the present Therefore, the increased 241an water concentrations resulting from the “grow in" from 241nu will lead to 24]a concentrations in plankton which are 85% of the 239 , 240 Pu concentrations.