A germanium crystal has been used to measure the absolute intensity of gamma rays from the decay of 238Pu, 212Pb, 212Bi, and 208Tl in a 1 ½-W SNAP-15A heat source. In practically all cases, agreement with other measurements is excellent. In addition, the amount of 236Pu impurity originally present in the sample can be measured with an accuracy of 4%. It is estimated that the 236Pu content in a fuel sample that is several months old can easily be measured with an accuracy of 10%.