Lesson 3: Half- Life/ irradiation/ contamination

Question 1

What are the 2 definitions of half- life?

Answer 1

1.) The half-life of a radioactive isotope is the time it takes for the number of nuclei of the isotope in a sample to halve
2.) The time it takes for the count rate (or activity) from a sample containing the isotope to fall to half its initial level.

Question 2

Q.)

A radioactive isotope has a half life of 15 days and an initial count rate 200 counts per second. Determine the count rate after 45 days.

Answer 2

Start = 200 counts/ second
15 days = 100 counts per second
30 days = 50 counts per second
45 days = 25 counts per second

Question 3

True or False. All radioactive isotopes have the same half- life.

Answer 3

• False.
• Radioactive isotopes have a very wide range of half- life values.

Question 4

What is irradation?

Answer 4

• Irradiation is the process of exposing an object to nuclear radiaition.
• The irradiated object doesn’t become radioactive as object is in contact with radiation, not radioactive source itself.

Question 5

Give an example of irradiation.

Answer 5

• Sterilising medical equipment that can’t be heated.

Question 6

What is the major issue with ionising radiation?

Answer 6

• Ionising radiation can increase the risk of cancer in humans.

Question 7

What precautions can people who work with radioactive isotopes take?

Answer 7

• Sheilding depending on penetrating power of the radiaition.
• Monitoring: monitor the amount of radiatiation the person working with radioactive isotopes is receiving, stop them from working with RI if necessary.

Question 8

What different types of sheilding can be used for people who work with radioactive sources that emitt alpha, beta and gamma?

Answer 8

• Alpha: Wear gloves
• Beta and gamma: Lead apron/ lead walls.

Question 9

What is radioactive contamination?

Answer 9

• Radioactive contamination is the unwanted presence of materials containing radioactive atoms on other materials.
• radioactive source on you/ in you

Question 10

Why is radioactive contamination hazardous?

Answer 10

• Radioactive atoms decay and emitt ionising radiation.
• the type of radiation emitted affects the level of hazard

Question 11

What effect does each type of radiation have if it contaminates the body?

Answer 11

• Alpha radiation: very strongly ionising but stopped by cells on skin. But if inhaled/ swallowed –> HARM!!
• Beta radiation: quite ionising can penetrate into skin easily.
• Gamma radiation: weakly ionising: will pass straight in and out body.

Question 12

What type of harm does alpha radiaition lead to if swallowed or emitted?

Answer 12

• Leads to DNA of cells changing
• Eventually cancer.

Question 13

What should scientists do with the studies they make on the effect of radiation on humans?

Answer 13

• They should publish it and check it with other scientists.
• This is known as peer- review.