Which unit is used to measure the rate of radioactive decay associated with contamination?

Which unit is used to measure the rate of radioactive decay associated with contamination?

• A. Becquerel
• B. Sievert
• C. Disintegrations per minute (dpm) or counts per minute (cpm)
• D. Gray

Answer: (C)

Measuring contamination relies on the decay rate of the radioactive material. The practical way to express that rate in field surveys is in disintegrations per minute or counts per minute, because these per-minute quantities directly reflect how many decays are being detected each minute on a surface or in a sample. This is the rate of decay you want to monitor to assess contamination levels and decide on actions. Becquerel is the SI unit for activity (decays per second), which is correct in principle but not as convenient for quick contamination surveys that are often interpreted in minutes. Gray and Sievert measure dose metrics—how much energy is absorbed or the biological effect—rather than the actual decay rate of the contaminant itself.

Measuring contamination relies on the decay rate of the radioactive material. The practical way to express that rate in field surveys is in disintegrations per minute or counts per minute, because these per-minute quantities directly reflect how many decays are being detected each minute on a surface or in a sample. This is the rate of decay you want to monitor to assess contamination levels and decide on actions.

Becquerel is the SI unit for activity (decays per second), which is correct in principle but not as convenient for quick contamination surveys that are often interpreted in minutes. Gray and Sievert measure dose metrics—how much energy is absorbed or the biological effect—rather than the actual decay rate of the contaminant itself.