CDPH Lead Inspector/Assessor California State Practice Exam

Which radioisotope is NOT used in XRF machines?

1. Cadmium-103

2. Cobalt-57

3. Cadmium-109

4. Cobalt-60

The correct answer is: Cadmium-103

Cadmium-103 is not utilized in X-ray fluorescence (XRF) machines primarily because it does not emit the type of radiation that is useful for the detection of elements through XRF analysis. XRF typically relies on radioisotopes that produce X-rays or gamma rays with appropriate energies to excite the atoms in the material being analyzed. Cobalt-57, Cadmium-109, and Cobalt-60 are used in XRF due to their specific gamma-ray production capabilities, which effectively interact with the atoms in a sample, causing them to emit secondary X-rays that can be detected and analyzed for elemental composition. In summary, the selection of radioisotopes for XRF must be based on their ability to generate the necessary radiation that facilitates accurate and efficient elemental analysis, which is why Cadmium-103 is excluded from that list.