Radioactivity + Fission and Fusion

define atomic number

number of protons (bottom number)

define mass number

number of protons + neutrons (top number)

define isotope

atoms with same number of protons but different number of neutrons

what are alpha particles, beta particles and gamma rays?

ionising radiations emitted from unstable nuclei in a random process

rank alpha particles, beta particles and gamma rays based on their ionising + penetrating powers

alpha particles = most ionising + weakly penetrating 

beta particles = moderately ionising + moderately penetrating

gamma rays = weakly ionising + most penetrating 

what stops α, β, γ?

alpha = paper

beta = aluminium

gamma = lead

what is used to detect ionising radiation?

Geiger Muller Tube

how to measure the activity?

1. place GM tube next to the source + connect it to a counter

2. measure counts in 10 seconds, repeat 5x, and do an average

3. remove the source

4. measure counts in 10 seconds, repeat 5x, and do an average

examples of sources of background radiation

• food + drink

• cosmic rays

• rocks

• nuclear accidents

what is activity and what is it measured in?

becquerels (Bq) = measurement for decays per second 

define half life

the time taken (on average) for half of the nuclei to decay

finish the sentences :

1. the half life is different for…

2. isotopes that decay faster have… 

1. different radioactive isotopes 

2. have shorter half-lives

define irradiation

an object is exposed to ionising radiation

define contamination

the transfer of the source onto/into an object

what are the dangers of ionising radiation?

• radiation can cause mutations in living organisms

• radiation can damage cells + tissue

• problems arising from disposal of radioactive waste

name risks associated with the disposal of radioactive waste

• worker/public exposure

• theft

• future discovery

• leaking into environment

how can the risk of worker/public exposure be reduced?

worker → protective clothing, rotate work via shifts, dosimeters - measures dose, tongs, robots

how can the risk of theft be reduced?

secrecy, security (people/lock)

how can the risk of future discovery be reduced?

hide well, pictograms representing injury/death

how can the risk of leaking into environment be reduces?

store waste in lead, check for leaks before disposal

uses of radioactivity when sterilising food + medical equipment 

• gamma rays

• gamma rays kills organisms on food/equipment

• gamma = best because its the most penetrating, but is weakly ionising so you need lots 

uses of radioactivity in smoke detectors 

• alpha ionises air causing electrical current smoke disrupts that, lower current

• alpha is the best ioniser

uses of radioactivity in leak detection

• put gamma emitter in pipes, use GM tube to detect leaks

• gamma = best because its the most penetrating

nuclear reactions (including fission + fusion + radioactive decay) is a source of what?

source of energy

how does ²³⁵U go through the process of fission?

• ²³⁵U nucleus absorbs slow neutron forming unstable ²³⁵U

• ²³⁶U fissions, forming 2 lighter daughter nuclei + releases a 2-3 fast neutrons

what does the process of fission (²³⁵U) produce?

• 2 lighter daughter nuclei

• small number of neutrons

how is a chain reaction set up?

• slow neutron is absorbed by ²³⁵U nucleus

• this forms unstable ²³⁶U nucleus

• ²³⁶U nucleus fissions

• this releases more neutrons

• those neutrons are absorbed by other ²³⁵U nuclei

what is the purpose of control rods and what are they made of?

• made of boron

• absorbs neutrons, allowing us to control the rate of fission

what is the purpose of a moderator and what are they made of?

• made of graphite or water

• slows down fast neutrons so they can cause fission

what is the purpose of shielding and what are they made of?

• made of steel or concrete

• stops neutron radiation from escaping the nuclear reactor

define fission

the split of an unstable nuclei

define fusion

2 lighter nuclei joined together to make a heavy nucleus, a small amount of mass is lost and converted into energy

fill in the blanks!

fusion is the ____ source for ____.

1. energy

2. stars

what is in the nucleus of an alpha particle?

2 protons + 2 neutrons

1. 4

2. 2

what is in the nucleus of a beta particle?

an electron

1. 0

2. -1

what is a gamma ray?

high electromagnetic wave

1. 0

2. 0