Nuclear

Question 1

Alpha scattering conditions

Answer 1

Same speed alpha particles (or slower will be deflected more)
Vacuum or the alpha particles will be stopped
Long half life ( so later results not lower due to decay)
Lead shield to direct particles and give a columnated beam
Thin gold foil so only scattered once

Question 2

Alpha

Answer 2

2 protons, 2 neutrons 
Range in air ≈ 100mm 
Very ionising 10^4 ions per mm in air
Stopped by paper 
Deflected in magnetic and electric fields

Question 3

Beta

Answer 3

Range in air ≈ 1 m
Stopped by ≈ 5mm aluminium
≈100 ions per mm in air
Deflected by magnetic and electric fields (more easily than alpha)

Question 4

Gamma

Answer 4

Height frequency em radiation 
Intensity = k/d ^2 - inverse square law 
Not deflected in magnetic and electric fields 
Mildly ionising 
Very penetrating 
Stopped by several cm of lead

Question 5

Sources of background radiation

Answer 5

Air, medical, ground and buildings, food and drink, cosmic rays, nuclear power, nuclear weapons, air travel

Question 6

Randomness of decay

Answer 6

Cannot predict which nucleus in a sample will decay

Cannot predict when a nucleus in a sample will decay

Question 7

Energy released per second

Answer 7

AE

Question 8

Decay equations

Answer 8

N = No e^(- lambda t) 
A = Ao e^(- lambda t) 
A = lambda N

Question 9

Half life equation

Answer 9

T1/2 = ln2/ lambda

Question 10

Uses of isotopes

Answer 10

Carbon dating
Argon dating 
Radioactive tracers 
Engine wear 
Thickness monitoring 
Power sources for remote devices

Question 11

Why electrons are suitable for radius estimation

Answer 11

Can be accelerated

Have a de Broglie wavelength of ≈ 10^-15 which is similar to the diameter of the nucleus

Question 12

Nuclear radius and atomic mass equation

Answer 12

R = ro A^1/3

ro = 1.05 fm

Question 13

Energy and mass

Answer 13

E = mc^2

Question 14

Energy transfer in beta decay

Answer 14

Energy released shared between beta particle, neutrino and nucleus
Beta particle has max Ek when neutrino has minimum
Max Ek beta particle is less than energy released due to conservation of momentum and the recoil velocity of the nucleus

Question 15

Mass defect and binding energy

Answer 15

dm = mp + mn - m nuc

BE = dm c^2

Question 16

Nuclear stability

Answer 16

Greater binding energy per nucleus = more stable

Most stable A= 50 to A=60

Question 17

Why nuclei need to collide at high speeds for fusion

Answer 17

To overcome the electrostatic repulsion between the 2 nuclei
Come close enough to interact via the strong nuclear force

Question 18

Advantages of fusion power

Answer 18

Releases more energy than fission per unit mass of fuel
Abundant fuel (deuterium in water)
Safer products of reaction ( less radioactive)

Question 19

Fuel rods

Answer 19

Enriched uranium

U-238 and 2-3% fissionable U-235

Question 20

Control rods

Answer 20

Usually boron ( has stable isotopes)
Absorb neutrons to control reaction
Keep number of neutrons in core constant
≈ 1 fission neutron per fission event goes on to induce further fission

Question 21

Moderator

Answer 21

Water or graphite (will slow the neutrons but not absorb them)
Fission neutrons need to be slowed down so that they can go on to induce further fission
Slows neutrons down via multiple collisions with the moderator molecules

Question 22

Cooling system

Answer 22

Needs to be under pressure

Prevent water evaporating (greater specific heat capacity as a liquid) or to increase the thermal capacity of CO2

Question 23

Safety features

Answer 23

Reactor core is a thick steel vessel (to withstand heat and pressure) that will absorb alpha and beta and reduce gamma and neutrons

Building has thick concrete walls to absorb gamma and neutrons

Reactor has emergency shut down system- will insert control rods fully

Fuel rods inserted and removed via remote handling

Question 24

High level waste

Answer 24

Spent fuel rods

Contain many radioactive isotopes (fission products, unused U-235)

Question 25

Disposal of high level waste

Answer 25

Removed by remote control 
Cooled in water for many months 
Vitrification (sealed in glass) 
Put in a steel capsule and steel flask 
Transported carefully 
Stores for a long time

Question 26

Intermediate level waste and disposal

Answer 26

Parts of the power station, radioactive materials with low activity, containers of radioactive materials

Sealed in drums encased in concrete
Stored in buildings with walls of reinforced concrete

Question 27

Low level waste and disposal

Answer 27

Lab equipment, protective clothing

Sealed in metal drums and buried in large trenches