Radioactivity Flashcards
What is an isotope?
- Is an element with the same number of protons and a different number of neutrons
How do you find the mass of a nucleus?
- Find the RFM
What is the unit for radioactive decay?
- Becquerel (Bq)
- Decays per second
What are the three types of radioactive decay?
- Alpha
- Beta
- Gamma
What are Alpha particles made from?
- A helium nucleus (4/2He)
How fast are Alpha particles emitted from the nuclei?
- 10% the speed of light
Why are Alpha particles highly ionising?
- Have a charge of 2+ therefore attract electrons
- Have a large mass therefore knock other particles out the way
What is a Beta particle and how is it emitted?
- A Beta particle is an electron emitted when a neutron in the nucleus is turned into a proton and an electron.
- The proton stays in the nucleus and the electron is emitted as a beta particle
How fast are Beta particles emitted from the nucleus?
- 50% the speed of light
Why are Beta particles weakly ionising?
- They have a charge of -1 meaning it can’t pull electrons from an atom
- They are not very massive
What is a Gamma Ray?
- A gamma ray is a high energy electromagnetic wave
How fast does a gamma ray travel?
- Speed of light in a vacuum (3*108)
List three points you should talk about when discussing the dangers of Alpha, Beta and Gamma?
- Lots of Kinetic Energy
- Ionising power
- Penetrating power
- Charge
- Mass
How ionising are gamma rays?
- Gamma rays are weakly ionising
What are Alpha, Beta and Gamma stopped by? (Penetrating power)
- Alpha particles are stopped by a few cm of air
- Beta particles are stopped by a few mm of Aluminium
- Gamma rays are stopped by a few cm of lead
Define a half-life.
- The time taken for half of the radioactive nuclei to decay
What is background radiation?
- Natural sources of radiation
State some background radiation sources.
- Radon
- Cosmic Rays
- Soil and Rocks
State some artificial radiation sources.
- Medical
- Air Travel
- Nuclear waste
- Weapons testing
How do you work out half life?
- e.g 1024/23
- If your given graph and asked to find half-life, you must find average half-life
Define Irradiation
- Exposing objects to beams of radiation
Define Contamination
- Occurs if an object has a radioactive material introduced into it
What are the differences between Irradiation and Contamination?
- Irradiation:
- Occurs when an object is exposed to a source of radiation outside the object
- Doesn’t cause the object to become radioactive
- Can be blocked from the object with suitable shielding
- Stops as soon as the source is removed
- Contamination:
- Occurs if the radioactive source is on or in the object
- A contaminated object will be radioactive for as long as the source is on or in it
- Once an object is contaminated the radiation cannot be blocked from the object
- It can be very difficult to remove all of the contamination
For a situation when you have to chose what isotope to use, what should you check?
- Alpha, Beta, Gamma
- Half-life
- Penetrating power
- Ionising power
What is Ionisation?
- Is the formation of an ion from a loss or gain of electrons
When is Alpha most harmful?
- An Alpha source is only dangerous if it can get into the body
When are Beta and Gamma most harmful?
- Beta and Gamma sources can cause harm from outside the body
How can mutations occur?
- DNA is fragile
- If ionisation occurs in DNA the strand can become damaged
- Mutations in the DNA can lead to cancer
What are the different levels of nuclear waste?
- Low level waste
- High level waste
What is low level waste?
- It contains small amounts of short lived radioactive isotopes.
What is high level waste?
- It is produced in nuclear power stations
What can happen if you are exposed to radiation?
- Radiation sickness
- Cell damage by ionising radiation
- Cell mutation which causes cancer
How do you store nuclear waste?
- Nuclear waste can be stored by burying it
- Store underwater
How do you store nuclear sources?
- In a sealed thick lead container
- In a room which is locked and away from humans
How do you reduce the risks of radiation?
- Workers wear badges to which become foggy if they detect radiation
- You don’t handle it (use tongs, gloves or robots)
- You store it in lead lined containers
How does nuclear power generation work?
- Heat is generated by nuclear fission which generates high-pressure steam which drives a turbine
- The spinning turbine drives a generator which produces electricity
State the process of nuclear fission?
- A uranium 235 nucleus absorbs neutron becoming unstable
- Fission occurs as the nucleus splits into two smaller daughter nuclei and energy is released
- With each fission more neutrons are released
- This creates a chain reaction that constantly generates heat
If a chain reaction runs out of control…
the control rods absorb all of the neutrons and moderators are used to stop the reaction
What are the control rods?
- They absorb excess neutrons reducing the rate of fission reactions and controlling heat generated
- They are made of boron
What is the moderator?
- The moderator slows down the neutrons so they are slow enough to cause fissions
What is shielding?
- The sheilding surrounds the reactor
- This prevents radiation, neutrons and fission fragments from getting out of reactor
What does fusion do?
- Fusion powers stars
- Happens in the cores of stars
What is fission?
- Heavy uranium nuclei splitting into two daughter nuclei
What is fusion?
- Light nuclei fusing (joining) together
What conditions are needed for fusion?
- Very high temperatures and pressures
- Without these the two positively charged nuclei will repel each other
State 3 ways in which nuclear fission differs from radioactive decay?
- Decay is random fission is not
- Fission produces two daughter nuclei but decay only produces one
- Decay rate can’t be altered but fission rate can
How do we detect radioactivity?
- Geiger muller tube
