Module 6 Particles And Medical Physics 6

Front 1

Einstein's mass - energy equation

Back 1

ΔE=mc^2

Front 2

Energy is conserved in radioactive decay, therefore...?

Back 2

The mass of the daughter nucleus and α particle in α decay is less than that of the original nucleus, because energy is released. The same is true for β decay.

Front 3

Minimum energy of two gamma Photons produced in an annihilation reaction

Back 3

1. Δm=me+mp, as all mass is converted to energy, so Δm=2m.

2. E=(2m)c^2.

3. Therefore the minimum energy is 2mc^2.

Front 4

Pair production

Back 4

The production of a particle-antiparticle pair from a single photon.

Front 5

Minimum energy of a photon in pair production

Back 5

1. Minimum energy of a electron is mc^2.

2. Minimum energy of the photon is double that.

Front 6

Mass in atomic units

Back 6

1u=1.66×10^-27kg

Front 7

Mass defect

Back 7

Mass difference between particles joined in a nucleus and the mass of the particles added together when they are separate.

Front 8

Binding energy

Back 8

Minimum energy required to completely separate a nucleus into its constituent protons and neutrons.

Front 9

Binding energy equation

Back 9

Binding energy=mass defect of nucleus×c^2

Front 10

Graph of binding energy per nucleon helps us understand 3 processes

Back 10

1. Radioactive decay

2. Fission

3. Fusion

Front 11

For nuclei with A<56, binding energy per nucleon?

Back 11

Increases as A increases.

Front 12

For nuclei with A>56, binding energy per nucleon?

Back 12

Decreases as A increases.

Front 13

Iron is the?

Back 13

Most stable isotope in nature. It has the highest binding energy per nucleon.

Front 14

Helium-4, carbon-12, and oxygen-16 have...?

Back 14

Abnormally high binding energy per nucleon.

Front 15

In the fusion process

Back 15

Two nucleons join to produce a nucleus which has a much higher binding energy than the initial nuclei, therefore releasing energy.

Front 16

In the fission process

Back 16

An atom with a high A splits into two lower A nuclei. Energy is released because the two nuclei produced have a higher binding energy than the parent nucleus.

Front 17

Fuel used for induced fission

Back 17

1. Uranium is the most common fuel used in reactors.

2. U-235 is only 0.7% of the mined uranium, 99.3% is U-238.

3. U-235 is good at absorbing thermal neutrons, causing them to undergo fission.

4. U-238 usually just captures these neutrons instead of undergoing fission.

Front 18

Thermal neutrons

Back 18

Mean kinetic energy is similar to the thermal energy of particles in the reactor core.

Front 19

When the U-235 absorbes a proton...

Back 19

It becomes U-236, which is highly unstable, splitting to produce two daughter nuclei and three protons.

Daughter nuclei can be Barium-141 and Krypton-92.

Front 20

Difference in binding energies after the fission reaction is...?

Back 20

Equal to the energy released in the reaction.

Front 21

Key components of a fission reactor

Back 21

1. Fuel rods are placed within a steel-concrete vessel; the reactor core.

2. Coolant removes the thermal energy from the fission reactions.

3. Fuel rods are surrounded by the moderator.

4. Control rods can be moved in and out of the core.

Hint 21

Front 22

Fuel rods

Back 22

Consists of enriched uranium, mainly U-238, and 2-3% U-235.

Front 23

Moderator

Back 23

1. Slows down the neutrons in the reaction.

2. Must be cheap and readily available.

3. Must not absorb the neutrons.

4. Thermal neutrons have a mean kinetic energy if about 3/2kT, and a root mean square speed of a few kms^-1.

5. Fast neutrons just bounce off U-235 nuclei with negligible energy loss, however when they collide elastically with protons or carbon nuclei, they transfer significant kinetic energy and slow down.

6. This makes water and carbon good candidates for the moderator.

7. Some reactors use water as the coolant and the moderator.

Front 24

Control rods

Back 24

1. Made of a material which readily absorbs neutrons.

2. Often made of cadmium or boron.

3. Control rod position is monitored to ensure an average of one neutron survives per fission reaction.

4. To slow down or stop the reaction, the rods can be pushed in further.

Front 25

Environmental impact

Back 25

1. U-238 nuclei absorb some of the faster protons and quickly decay into plutonium-239.

2. Has a half-life of 24 thousand years.

3. High-level waste, such as fuel rods, has to be buried deep underground for many centuries.

4. They must be safe from leaking into our water supplies. The burial ground must be geologically stable, and safe from attack.

Front 26

How to make fusion occur

Back 26

Must bring nuclei within 10^-15m of each other, because the strong nuclear force is attractive at that range, and overcomes electrostatic repulsion.

Front 27

Proton - proton cycle

Back 27

p+p➡Deuterium+e+ν

Deuterium+p➡helium-3

Helium-3+helium-3➡helium-4+2protons

Front 28

Fusion on earth is...?

Back 28

Not possible, requires very high temperatures for a very long time, which we do not have the technology to achieve.