56 4.3 Methods for Measuring Gamma-RayEmitting Radionuclides 4.3-1 Instrumentation and radiochemical calibrations for 2M a, 2078, 135ey, 6064, 226,, and 13766. Aliquots of the sediment samples were prepared for gamma spectrometric analysis according to Fig. 6, Section 4.1. The gamma-ray energies ef the several radionuclides measured are shown in Table 11. Americium-241 concentrations in surface sediments were determined by counting its gamma radiation with a 1 cm 2 Ge(intrinsic)? detector and a 400channel multichannel analyzer. Rismuth-207, 5ey, 1376.6 | 606, and 2262, concentrations reported in surface sediments and al] the gamma-emittina radionuclides in the core sediments were measured with one of two 7.3%, Ge(Li)° detectors and 4096~channel analyzers. TABLE 11. Energies of y-rays detected from the radionuclides measured by ganma spectroscopy. Isotope 241 am 2075 55, 1376 60¢4 226R4 Eneroy of y-ray detected (MeV) 0.060 0.570; 0.085; 0.662 1.173; 0.186; 1.063 0.105 1.332 0.295, 0.352, 0.609, 1.121 (from 214Pb daughter) a. Applied Detector Corporation, Menlo Park, California. b. Absolute detection efficiency for 1.33 MeV gamma rays relative to a 30% efficient NaI detector. C. Nuclear Diodes Inc., Prairie View, Illinois. (Presently Edax International)