P7 - Radioactivity Flashcards
define nuclear radiation
particles or waves emitted from an unstable nucleus
define ionising radiation
particles or waves that have enough energy to remove or “knock off” electrons from their shells. This causes atoms to become ions.
ionising - making an ion
Name 3 sources of background radiation
- Plants
- Animals
- Minerals
- Cosmic rays
- Industrial / Hospital waste
define background radiation
ionising radiation which is present in an environment
What is the difference between ionising radiation and nuclear radiation
All types of nuclear radiation are also ionising radiation, however, ionising radiation doesn’t need to be emitted from a nucleus.
Name 4 types of nuclear radiation
- Alpha α
- Beta β
- Gamma γ
- Neutron n
What is the penetrating power of each type of radiation?
in air, and what stops it
α - centimeters in air | stopped by paper
β - meter in air | stopped by aluminium
γ - kilometers in air | stopped by lead
List the properties of α radiation
- particle
- helium nucleus (2 protons 2 neutrons)
- 42He
List are the properties of β radiation
- particle
- high speed electron
- 0-1e
List are the properties of γ radiation
- wave
- no mass, no charge
short wavelength photon
When and why does gamma decay occur?
Gamma decay occurs after alpha or beta decay if the nucleus has extra energy.
What happens during beta decay?
During beta decay, a neutron (ve) turns into a proton (+ve) which emits an β particle (electron -ve)
alpha decay of
23892U
→ Th
23892U → 23490Th + 42He
beta decay of
146C
→ N
146C → 147N + 0-1e
define activity
overall rate of decay of unstable nuclei in a sample
formula activity
radioactivity module
activity = count of decays / time
Bq = count / s
Why does neutron decay occur?
Some radioactive nuclei emit a neutron n when a collision with the nucleus and an α particle occurs
What is activity measured in?
Bq - Becquerels
define half-life
The time it takes for half the nuclei in a substance to radioactivly decay
define irradiation
exposing an object to beams of radiation on its surface
define contamination
introducing a radioactive substance into an object
Is radioactive decay predictable?
No, radioactive decay is random.
Name 3 uses of radioactive decay
- Smoke detectors. Americium-241 emits α particles which are used in a circuit; α particles are stopped by smoke.
- Measuring thickness of paper. Counting how many β particles travel through paper to hit a Geiger counter.
- Irradiating food. Cobalt-60 emits γ waves which kill bacteria on food without affecting the food.
List the steps of a nuclear chain reaction
- A nucleus absorbs a neutron
- This nucleus splits into two daughter nuclei, releases 2-3 high-speed neutrons, and releases energy in the form of gamma radiation and KE
- This process repeats. This is called a chain reaction
What are fission fuel rods composed of?
enriched uranuim
3% Uranium-235 and 97% Uranium-238
Name the components in a nuclear reactor
- Moderator (water and graphite)
- Fuel rods (enriched Uranium)
- Control rods (boron)
- The coolant (water)
What does the moderator do in a nuclear reactor?
It slows down fission neutrons to help maintain the chain reaction
What do the control rods do in a nuclear reactor?
They absorb neutrons to help maintain the chain reaction
What does the coolant do in a nuclear reactor?
It transfers energy from the reactor to be converted into electrical energy. It is also used to cool the reactor.
define nuclear fusion
A reaction where 2 nuclei are joined which produces a heavier nucleus and releases energy and a neutron
define nuclear fission
A reaction where a nucleus is split which produces 2 smaller nuclei and releases energy and 2-3 neutrons
What are the pros of nuclear fusion?
- It releases a lot of energy
- It doesn’t release greenhouse gases
- It doesn’t produce radioactive waste
What are the cons of nuclear fusion?
- It requires a high-pressure and high-temperature environment
- It’s expensive
- It’s technologically difficult to achieve
What instrument can be used to detect radioactivity?
A Geiger counter consists of a Geiger-Müller tube (Geiger tube) and an electronic counter.
define Sievert (Sv)
A sievert is a unit of measurement that shows radiation dose.
Does total mass increase or decrease after fission and fusion reactions?
the total mass decreases
list:
2 use of radiation in medicine and what type of radiation used
- gamma knife to kill cancerous tumours
- gamma radioactive tracers to see inside organs (iodine)
list:
2 factors to consider for medical use of radiation
- nature of decay (α, β, γ)
- half life
