specific activity [spǝ`sif·ik ak`tiv·ǝd·ē] NUCLEONICS 1. The activity of a radioisotope of an element per unit weight of element present in the sample. 2. The activity per unit mass of a pure radionuclide. 3. The activity per unit weight of a sample of radioactive material.In these three cases, specific activity can be expressed in such units as millicuries per gram, disintegrations per second per milligram, or counts per minute per milligram. |