A research team is selecting a radioactive tracer for a 12-day survey of liquid moving through a closed industrial processing system. Both tracers emit gamma radiation and will be used with the same detector arrangement.
The tracer activity must be at least 1000 Bq1000\ \mathrm{Bq}1000 Bq at the end of the survey so that it can still be detected.
After the survey, all the tracer-containing liquid is collected in a shielded holding tank. The same containment and release conditions apply to either tracer. The liquid must remain contained until the tracer activity falls below 200 Bq200\ \mathrm{Bq}200 Bq.
| Tracer | Activity at the start of the survey | Half-life |
|---|---|---|
| R | 9600 Bq9600\ \mathrm{Bq}9600 Bq | 4 days |
| S | 2400 Bq2400\ \mathrm{Bq}2400 Bq | 12 days |
Calculate the activity of each tracer at the end of the 12-day survey.
The liquid is checked for release exactly 12 days after the survey ends.
Evaluate which tracer should be selected. Use calculations and both activity requirements in your answer.
97 exam-style questions on Edexcel GCSE Physics 6.5 Uses and dangers of radioactivity, covering 6.5.1 Uses of radioactivity, 6.5.2 Dangers of ionising radiation and precautions, 6.5.3 Half-life and radiation dangers, 6.5.4 Safety precautions for radiation exposure, and 6.5.5 Contamination and irradiation. Each one has a worked solution and a mark scheme showing where the marks go.