Uses and dangers of radioactivity

Question 1

what is irradiation?

Answer 1

Exposing objects to beams of radiation

Question 2

why is irradiation safe for sterilisation?

Answer 2

it does not cause the irradiated object to become radioactive.

Question 3

how are gamma beams controlled so that healthy cells are not damaged? (2)

Answer 3

-beams are aimed at the tumour from many different directions to maximise the dose on the tumour
-but to minimise the dose on the surrounding soft tissue.

Question 4

how are the long term effects of irradiation reduced in medical applications? (3)

Answer 4

-nature of decay (alpha, beta or gamma)
-half life
-toxicity

Question 5

what does the half life have to be? (2)

Answer 5

-long enough for the isotope to produce useful measurements,
-short enough for the radioactive sources to decay to safe levels soon after use

Question 6

what would happen if the half-life was too long? (2)

Answer 6

-If the half-life chosen is too long, the damaging effects of the radiation would last for too long
-and the dose received would continue to rise.

Question 7

what are the advantages of irradiation? (2)

Answer 7

-Sterilisation can be done without high temperatures.
-It can be used to kill bacteria on things that would melt.

Question 8

what are the disadvantages of irradiation? (2)

Answer 8

-It may not kill all bacteria on an object.
-It can be very harmful - standing in the environment where objects are being treated by irradiation could expose people’s cells to damage and mutation.

Question 9

what us contamination?

Answer 9

object has a radioactive material introduced into it.

Question 10

In medical applications that involve injecting radioactive sources, how do we ensure that contamination does not cause any long term effects? (2)

Answer 10

-have very short half-life -so after a couple of days there will hardly be any radioactive material left in a person’s body
-are not poisonous

Question 11

why is half-life crucial to predicting the reactivity of radioactive substances? (2)

Answer 11

-it cannot be predicted when a particular nucleus
will decay
-but half-life enables the activity of a very large number of nuclei to be predicted during the decay process

Question 12

how do PET scanners work? (3)

Answer 12

-use a positron emitter as the contamination tracer.
-positrons emitted will react with electrons in the patient’s body
-and produce gamma rays which can be detected outside the body

Question 13

why are tracers difficult to maintain? (2)

Answer 13

-have very short half-lives,
-need to be manufactured in the hospital and injected into the patient’s blood soon after manufacture.

Question 14

how do we use Contamination to check for leaks?

Answer 14

Water supplies can be contaminated with a gamma-emitting radioactive isotope to find leaks in pipes.

Question 15

how do we identify the leak using contamination? (4)

Answer 15

-Where there is a leak, contaminated water seeps into the ground,
-this causes a build-up of gamma emissions in that area.
-The build-up of gamma emissions can be found using a Geiger-Muller tube,
-this makes it easier to decide where to dig to find the leak.

Question 16

what must the isotopes used for checking leaks be? (3)

Answer 16

-be a gamma emitter
-have a half-life of at least several days to allow the emissions to build up in the soil
-not be poisonous to humans as it will form part of the water supply

Question 17

advantages of contamination: (3)

Answer 17

-Radioactive isotopes can be used as medical and industrial tracers
-Use of isotopes with a short half-life means exposure can be limited
-Imaging processes can replace some invasive surgical procedures

Question 18

disadvantages of contamination: (3)

Answer 18

-Radioactive isotopes may not go where they are wanted
-It can be difficult to ensure that the contamination is fully removed so small amounts of radioisotope may still be left behind
-Exposure to radioactive materials can potentially damage healthy cells

Question 19

does the object become radioactive with irradiation and contamination? (2)

Answer 19

irradiation: Doesn’t cause the object to become radioactive
contamination: A contaminated object will be radioactive for as long as the source is on or in it

Question 20

can irradiation and contamination be blocked? (2)

Answer 20

-irradiation: Can be blocked with suitable shielding
-contamination: Once an object is contaminated, the radiation cannot be blocked

Question 21

can an object be cleared of radiation with irradiation and contamination? (2)

Answer 21

-irradiation: Stops as soon as the source is removed
-contamination: It can be very difficult to remove all of the contamination

Question 22

why are alpha particles used in smoke alarms?

Answer 22

they are easily absorbed

Question 23

why is radiation used to gauge the thickness of a material? (2)

Answer 23

-it is absorbed as it passes through materials
-thickness is measured by measuring the amount of radiation that passes through

Question 24

state the effects of radiation on the eyes and thyroid: (2)

Answer 24

Eyes: High doses can cause cataracts
Thyroid: Radioactive iodine can build up and cause cancer

Question 25

state the effects of radiation on the Lungs and Reproductive organs: (2)

Answer 25

Lungs: Breathing in radioisotopes can damage DNA
Reproductive organs: High doses can cause sterility or mutations

Question 26

state the effects of radiation on the skin and bone marrow: (2)

Answer 26

Skin: Radiation can burn skin or cause cancer
Bone marrow: Radiation can cause leukaemia and other diseases of the blood

Question 27

state 4 ways to reduce the risk of using radioactive sources:

Answer 27

-wear protective clothing to prevent the body becoming contaminated should radioactive isotopes leak out
-wear face masks to avoid breathing in materials
-limit exposure time - so less time is spent around radioactive materials
-handle radioactive materials with tongs in order to keep a safer distance from sources

Question 28

what is background radiation?

Answer 28

low level, naturally occurring radiation

Question 29

which unit to measure radiation dose? what does it measure damage from? (the cause)

Answer 29

-Sievert (Sv)
-absorption of 1 joule of energy in each kilogram of body mass