Nuclear Radiation

Question 1

Why are beta and gamma used as medical tracers

Answer 1

They can penetrate the skin and other body tissues

Question 2

What happens to a tracer

Answer 2

It penetrates the body tissues and can be detected externally to monitor its progress

Question 3

What does the radioactive source in a tracer need to have

Answer 3

A short half-life so that you can use less of the radioactive source, but still detect it

Question 4

Why are alpha particles not useful for medical tracers

Answer 4

They would be stopped by the body’s tissues

They are very ionising which is dangerous

Question 5

what does the nucleus contain?

Answer 5

protons and neutrons

Question 6

what is the atomic number?

Answer 6

the number of protons in the nucleus

Question 7

what is the mass number?

Answer 7

the total number of protons and neutrons in the nucleus

Question 8

what are isotopes?

Answer 8

atoms with different numbers of neutrons but the same number of protons

Question 9

what are the common isotopes?

Answer 9

carbon-14 and carbon -12

Question 10

what kind of process is radioactive decay?

Answer 10

random, it is not affected by conditions such as temperature

Question 11

where does background radiation come from?

Answer 11

• Earth
• space
• living things
• human activity (eg. nuclear waste)

Question 12

how is ionisation caused?

Answer 12

-nuclear radiation bashes into atoms and knocks electrons off them

Question 13

what is the pattern for ionisation?

Answer 13

the further along the radiation can penetrate before hitting an atom and getting stopped, the less damage it will do along the way

Question 14

how can ionising radiation be detected?

Answer 14

with photographic film or a Geiger-Muller detector

Question 15

what are alpha particles made up of?

Answer 15

• 2 protons and 2 neutrons
• they are big and slow moving
• they are strongly ionising

Question 16

alpha particles are stopped…

Answer 16

quickly

Question 17

alpha particles are…

Answer 17

deflected by electric and magnetic fields

Question 18

what happens to the atomic number when an alpha particle is emitted from the nucleus?

Answer 18

it decreases by 2

Question 19

what happens to the mass number when an alpha particle is emitted from the nucleus?

Answer 19

it decreases by 4

Question 20

what is a beta particle?

Answer 20

an electron

Question 21

how is a beta particle formed?

Answer 21

a neutron turns into a proton and an electron

Question 22

what happens to the atomic number when a beta particle is emitted?

Answer 22

it increases by 1

Question 23

what happens to the mass number when a beta particle is emitted?

Answer 23

it stays the same

Question 24

beta particles are…

Answer 24

moderately penetrating and moderately ionising

Question 25

beta particles are...(2)

Answer 25

deflected by electric and magnetic fields

Question 26

what are gamma rays?

Answer 26

- very short wavelength electromagnetic spectrum waves - they have no mass - they are energy

Question 27

gamma rays are...

Answer 27

- weakly ionising - they have no charge - they are always emitted after an alpha or beta particle has been emitted - they are not deflected by electric or magnetic fields

Question 28

what are alpha particles blocked by?

Answer 28

- paper - skin - a few cm of air

Question 29

what are beta particles blocked by?

Answer 29

-thin metal (eg aluminium)

Question 30

what are gamma rays blocked by?

Answer 30

- thin lead | - very thick concrete

Question 31

half-life definition

Answer 31

the time taken for half of the radioactive atoms now present to decay

Question 32

half-life definition 2

Answer 32

the time taken for the activity (or count rate) to fall by half

Question 33

what is radioactivity measured in?

Answer 33

becquerels

Question 34

what is radioactivity measured in?

Answer 34

becquerels

Question 35

what are gamma rays used for?

Answer 35

industrial tracers

Question 36

how do industrial tracers work?

Answer 36

- squirt the gamma rays into the pipe - go along the outside with a detector - if there is a crack in the pipe, the detector will show extra-high radiation at that point

Question 37

why cant alpha and beta particles be used for industrial tracers?

Answer 37

they would be too easily blocked

Question 38

what do you need to know to work out the age of a sample?

Answer 38

- the amount of radioactive isotope left in the sample | - the half-life of the sample

Question 39

what does uranium eventually decay to become?

Answer 39

lead

Question 40

a clue to a rock's age is...

Answer 40

the relative proportions of uranium and lead isotopes

Question 41

how to calculate how old something is using carbon-14

Answer 41

- compare the activity of a sample to living tissue | - this lets you estimate how many half-lives have passed

Question 42

is alpha radiation dangerous?

Answer 42

yes, once it gets inside the body

Question 43

why is alpha radiation dangerous?

Answer 43

- it collides with molecules in your cells - these collisions cause ionisation - lower dosages can cause mutations in cells, which causes them to divide uncontrollably. This can cause cancer - higher doses tend to kill cells completely, which causes radiation sickness.

Question 44

how is radiation used to treat cancer?

Answer 44

- using radiotherapy - this involves a high dose of gamma rays, carefully directed at the tumour, while minimising the damage to the rest of the body

Question 45

how can you protect yourself from radioactive materials?

Answer 45

- avoid skin contact - keep the source pointed away from the body and avoid looking at it - store radioactive sources in a sealed lead box whenever they're not being used

Question 46

what do people regularly working with radioactivity need to do?

Answer 46

- wear lead aprons - stand behind lead screens during procedures - wear full protective suits - use remote controlled robot arms - avoid inhaling/touching the radioactive samples

Question 47

what do people regularly working with radioactivity need to do?

Answer 47

- wear lead aprons - stand behind lead screens during procedures - wear full protective suits - use remote controlled robot arms - avoid inhaling/touching the radioactive samples

Question 48

nuclear fission

Answer 48

the splitting of an atom, which releases energy

Question 49

the fuel that is split up in a nuclear reactor

Answer 49

uranium-235

Question 50

what is the 'fuel' that is split up in a nuclear reactor?

Answer 50

uranium-235

Question 51

what happens when a uranium-235 nucleus splits up?

Answer 51

it spits out a number of neutrons

Question 52

what does uranium-235 make when it splits in two?

Answer 52

two new daughter nuclei

Question 53

what are the daughter nuclei?

Answer 53

- they are lighter than uranium - they are radioactive because they have the 'wrong' number of neutrons in them - this produces huge amounts of radioactive waste

Question 54

what does a moderator do?

Answer 54

it slows down neutrons so that theu can successfully collide with uranium nuclei and sustain the chain reaction

Question 55

what are control rods often made of?

Answer 55

boron

Question 56

what do control rods do?

Answer 56

they limit the rate of fission by absorbing excess neutrons

Question 57

how is the heat from the reactor carried away?

Answer 57

a gas, typically carbon dioxide, is pumped through the reactor

Question 58

what does the gas do after it has carried away the heat from the reactor?

Answer 58

- it is passed through a heat exchanger, where it gives its energy to water - this water is heated and turned into steam, which turns a turbine, which turns a generator, which produces electricity