What is the method used to measure INTERNAL exposure to radioactive materials?

The method commonly used to measure INTERNAL exposure to radioactive materials is referred to as CPM, which stands for Counts Per Minute. This measurement is crucial because it quantifies the rate at which radioactive particles are detected, allowing for an assessment of the amount of radioactivity present in a person's body due to the ingestion or inhalation of radioactive materials.

CPM provides a direct indication of the radiation emitted from the radioactive substances that may have entered the body, facilitating accurate monitoring and assessment of internal contamination. By analyzing CPM readings, medical and safety personnel can gauge exposure levels and determine necessary safety measures or medical interventions.

In contrast, the other options are associated with different aspects of radiation safety and measurement. MPCA (Multi-layered Particle Counter Analysis) would relate to particle measurements rather than direct internal exposure, RMS (Radiation Monitoring System) pertains to overall radiation levels in an environment rather than specifically internal exposure, and ALARA (As Low As Reasonably Achievable) is a principle in radiation safety aimed at minimizing exposure but does not provide a measurement method for internal contamination. Thus, CPM directly addresses the need for measuring internal exposure to radiation.