S4.11.5 For the adult
Radiation and safety
A worker stands near a strong gamma source for an hour and then walks away. Is the worker now radioactive?
What this chapter teaches
Irradiation is exposure to a source outside the body, and it stops when the source is removed. Contamination is radioactive material on or in the body or an object, and it keeps irradiating and can spread. Alpha is the greater harm inside the body and gamma the greater risk from outside. A dose is reduced by distance, shielding and time, and dose equals dose rate times time.
Three questions to ask
There is no one right wording. Listen for the idea.
- What is the difference between irradiation and contamination?
- Why is alpha harmless outside the body but harmful inside it?
- How do distance, shielding and time each lower a dose?
After the chapter, the learner can
- Compare contamination and irradiation
- Explain how distance, shielding and time reduce a dose
What they copy into their notebook
Irradiation: a source outside, it stops when you leave. Contamination: radioactive material on or in you, it goes with you. Alpha is worst inside, gamma worst outside. Lower a dose by distance, shielding and time. dose = rate × time.