Radioactivity Flashcards
1
Q
What is an isotope?
A
- Is an element with the same number of protons and a different number of neutrons
2
Q
How do you find the mass of a nucleus?
A
- Find the RFM
3
Q
What is the unit for radioactive decay?
A
- Becquerel (Bq)
- Decays per second
4
Q
What are the three types of radioactive decay?
A
- Alpha
- Beta
- Gamma
5
Q
What are Alpha particles made from?
A
- A helium nucleus (4/2He)
6
Q
How fast are Alpha particles emitted from the nuclei?
A
- 10% the speed of light
7
Q
Why are Alpha particles highly ionising?
A
- Have a charge of 2+ therefore attract electrons
- Have a large mass therefore knock other particles out the way
8
Q
What is a Beta particle and how is it emitted?
A
- 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
9
Q
How fast are Beta particles emitted from the nucleus?
A
- 50% the speed of light
10
Q
Why are Beta particles weakly ionising?
A
- They have a charge of -1 meaning it can’t pull electrons from an atom
- They are not very massive
11
Q
What is a Gamma Ray?
A
- A gamma ray is a high energy electromagnetic wave
12
Q
How fast does a gamma ray travel?
A
- Speed of light in a vacuum (3*108)
13
Q
List three points you should talk about when discussing the dangers of Alpha, Beta and Gamma?
A
- Lots of Kinetic Energy
- Ionising power
- Penetrating power
- Charge
- Mass
14
Q
How ionising are gamma rays?
A
- Gamma rays are weakly ionising
15
Q
What are Alpha, Beta and Gamma stopped by? (Penetrating power)
A
- 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
16
Q
Define a half-life.
A
- The time taken for half of the radioactive nuclei to decay
17
Q
What is background radiation?
A
- Natural sources of radiation
18
Q
State some background radiation sources.
A
- Radon
- Cosmic Rays
- Soil and Rocks
19
Q
State some artificial radiation sources.
A
- Medical
- Air Travel
- Nuclear waste
- Weapons testing
20
Q
How do you work out half life?
A
- e.g 1024/23
- If your given graph and asked to find half-life, you must find average half-life
21
Q
Define Irradiation
A
- Exposing objects to beams of radiation
22
Q
Define Contamination
A
- Occurs if an object has a radioactive material introduced into it
23
Q
What are the differences between Irradiation and Contamination?
A
- 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
24
Q
For a situation when you have to chose what isotope to use, what should you check?
A
- Alpha, Beta, Gamma
- Half-life
- Penetrating power
- Ionising power
25
What is Ionisation?
* Is the formation of an ion from a loss or gain of electrons
26
When is Alpha most harmful?
* An Alpha source is only dangerous if it can get into the body
27
When are Beta and Gamma most harmful?
* Beta and Gamma sources can cause harm from outside the body
28
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
29
What are the different levels of nuclear waste?
* Low level waste
* High level waste
30
What is low level waste?
* It contains small amounts of short lived radioactive isotopes.
31
What is high level waste?
* It is produced in nuclear power stations
32
What can happen if you are exposed to radiation?
* Radiation sickness
* Cell damage by ionising radiation
* Cell mutation which causes cancer
33
How do you store nuclear waste?
* Nuclear waste can be stored by burying it
* Store underwater
34
How do you store nuclear sources?
* In a sealed thick lead container
* In a room which is locked and away from humans
35
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
36
How does nuclear power generation work?
1. Heat is generated by nuclear fission which generates high-pressure steam which drives a turbine
2. The spinning turbine drives a generator which produces electricity
37
State the process of nuclear fission?
1. A uranium 235 nucleus absorbs neutron becoming unstable
2. Fission occurs as the nucleus splits into two smaller daughter nuclei and energy is released
3. With each fission more neutrons are released
4. This creates a chain reaction that constantly generates heat
38
If a chain reaction runs out of control...
the control rods absorb all of the neutrons and moderators are used to stop the reaction
39
What are the control rods?
* They absorb excess neutrons reducing the rate of fission reactions and controlling heat generated
* They are made of boron
40
What is the moderator?
* The moderator slows down the neutrons so they are slow enough to cause fissions
41
What is shielding?
* The sheilding surrounds the reactor
* This prevents radiation, neutrons and fission fragments from getting out of reactor
42
What does fusion do?
* Fusion powers stars
* Happens in the cores of stars
43
What is fission?
* Heavy uranium nuclei splitting into two daughter nuclei
44
What is fusion?
* Light nuclei fusing (joining) together
45
What conditions are needed for fusion?
1. Very high temperatures and pressures
2. Without these the two positively charged nuclei will repel each other
46
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
47
How do we detect radioactivity?
* Geiger muller tube
