Radioactivity and radioisotopes

1. Radioactivity and radioisotopes • Exam type questions • Why is radiation harmful?

2. Exam type question • The half-life of Radon gas 222Rn is 3.30 x 105 s. • Calculate: • the number of Rn-222 in 10-5 kg of gas (1u = 1.66 x 10-27 kg) Show answer • the decay constant l Show answer • the initial activity. Show answer • Counting experiments were conducted on the above sample of radon gas over a three hour period. Calculate: • the activity after three hours Show answer • the percentage change in activity over this period • Show answer

3. Answer to 1.a • - Mass of one Rn-222 atom in kg: • m(Rn) = 222 x 1.66 x 10-27 kg = 369 x 10-27 kg

4. Answer to 1.b

5. Answer to 1.c

6. Answer to 2.a

7. Answer to 2.b

8. Why is radiation harmful? • Radiation causes damage to living cells by ionizing their molecules. Ionizing means that the radiation knocks electrons off the molecules of the cells, leaving positively charged atoms and molecules in the organism  THIS IS DANGEROUS, because these damaged cells can die or reproduce uncontrollably causing cancer. • Long exposure to radiation, or large amounts of radiation can cause serious damage. • Radioactive gases and dust are the most dangerous, because they are very easily taken into the body, but the most difficult to get rid off. Once the radioactive source is inside it stays there and it causes problems, because it ionizes many molecules.

9. Protection from radiation a-sources Point away from the body Use tongs to handle Wear full protective suits to avoid inhaling radioactive particles b-sources Point away from the body Use robot arms in highly radioactive areas Use tongs to handle Wear lead-lined suits to stop beta particles from entering the body g-sources Point away from the body Use tongs to handle Wear lead-lined suits to stop gamma-rays from entering the body Operate under lead/concrete barriers and thick lead screens