-7- emitters present in the samples were determined from the gamma curves by use of the method of Conally (1956). A three-inch by three-inch NaI (T1) crystal was used in conjunction with a 256channel analyzer. Tests for the accuracy of the gamma spectrum method were made with standards and with radioactive spikes the disintegration rates of which had been determined from beta counts. Accuracy of + 20 per cent, based on known spike mixtures, was obtained for six of the isotopes (W485, co27, cs137, zr95, Co>8 and co®9) present in the samples. ‘The lowest limit of de- tection of any given isotope in the. samples was approximately one per cent of the total gamma activity. The determinations of the levels of Rul03..Ry,106 and cet41. gelt4 are not as accurate as those obtained for the other isotopes because of the overlapping gamma peaks. The ratio of Rut to Rul06 was calculated in the following manner. The .624 MEV peak of Rut06 was determined in selected samples and the contribution of the isotope was calculated. .513 MEV peak from the same This value was subtracted from the com- posite .498 MEV gamma peak of Ru203 and the .515 MEV peak of Rul06 in selected samples, and the remainder was assumed to be contrib- uted by RulO3, The ratio of Cel41 to celt4 was calculated in a similar way. The 0.08 MEV and 0.03 MEV peaks of Cel44 were determined in selected samples and the contribution of the .134 MEV Ce 144 f IG