atomic physics - using radioactive isotopes

Question 1

when does irradiation occur

Answer 1

when there is exposure to ionising radiation from the radioactive source

Question 2

when does contamination occur

Answer 2

when the radioactive source itself is spread (e.g. by an explosion)

Question 3

does contamination or irradiation cause greater problems and why

Answer 3

contamination causes greater problems as decontamination may be very difficult - even impossible - and very time-consuming and costly

Question 4

what is the harm of ionising radiation

Answer 4

it damages molecules that make up the cells of living tissue –> this is common but random and cells can repair over time
repeated damage can however kill cells or make them mutate and some kinds of cancers can be a result of this and they may divide uncontrollably

Question 5

danger of alpha, beta, and gamma particles

Answer 5

alpha - are of little danger unless ingested (cells may be damaged if exposure is prolonged)
e.g. radon gas (alpha emitter) is in the air and can be breathed in. it is also in cigarette smoke.

beta and gamma - can penetrate the body but have lower ionising power (damage depends on their path before entering the body)

Question 6

radioactive medical tracers

Answer 6

a radioactive substance (like technetium-99) is injected into the bloodstream or taken orally

the substance emits gamma rays and gradually works its way around the body then a gamma camera scans the body, detecting radiation and forming an image

in this way, the radioactive isotope can be followed as it flows through a particular organ in the body

Question 7

what are musts for the isotope flowing through the body in radioactive medical tracers

Answer 7

• must be a source of gamma ray so the gamma camera can detect it
• must be low-ionising radiation that can still penetrate the body
• half life must be long enough to do tests but short enough to ensure radiation levels don’t stay high for too long

Question 8

radiotherapy

Answer 8

a gamma knife - highly focused beam of gamma rays pointed at a target - are used to destroy cancer cells so that they are unable to reproduce

care must be taken to aim the gamma rays carefully at the target to not damage any other organs