2- Chapter 18 - Radiation

Question 1

What is absorbed dose?

Answer 1

The energy deposited per Kg of tissue.

measured in grays.

Question 2

Effective dose(absorbed dose) =

Answer 2

absorbed dose (in grays) x quality factor

measured in Sieverts/Sv

Question 3

what is quality factor?

Answer 3

used to calculate effective dose, and its based off the type of radiation and type of tissue effected.

Question 4

What stops beta radiation?

Answer 4

small thickness of metal

Question 5

what stops alpha radiation

Answer 5

skin, few cm of air

Question 6

Fraction absorbed equation

Answer 6

I/I₀ = e^-μX

(I=intensity, μ = absorbtion coefficent, X = thickness)

Question 7

Half thickness absorbed (X_1/2)=

Answer 7

ln2/μ

Question 8

What is conserved in neuclear decay?

Answer 8

• Energy/mass (through E=mc²)
• Momentum
• Proton number
• Charge
• Neucleon Number

Question 9

What is mass defect?

Answer 9

The difference in mass between bound and unbound neucleons.

Mass in neucleus - Mass of individual protons

Question 10

What is binding energy?

Answer 10

The energy needed to bind neuclons into the neucleus.

Mass defect (in kg) used in E=Δmc²

^{(is negative)}

Question 11

Binding energy per neucleon

Answer 11

Binding energy divided by number of neuclons

Question 12

whats the neuclear valley

Answer 12

plot mass number against binding energy per neucleon, forms a valley around iron.

Question 13

What causes mass defect?

Answer 13

the mass is less as its been converted to potential energy in the nucleus.

Question 14

Relationship between binding energy per neuclon and stability?

Answer 14

more negative BEPN means its more stable as more energy is needed to seperate neuclus.

Question 15

What happenes to proton and neuton number as you go down the periodic table and why

Answer 15

there starts to be more neclouns per proton the further you go down. As the neutral neutons will dilute the protons and reduce the repulsion so PE and BE is lower. They also provide futher nuclear attration.

Question 16

Binding energy per unit mass=

Answer 16

Binding energy/Mass defect =931MeV

Question 17

What can cause a neucleous to becoms unstable, and the decay it causes. (4 things)

Answer 17

• Too many neutrons - β^- decay
• Too Few neutrons - β⁺ decay
• Too many nucleons - Alpha Decay
• Too much energy - Gamma Decay

Question 18

Example Equation for β^- decay and what happens.

Answer 18

Neutron converts to a proton and electron - Anti neutrino is also created to conserver momentum.

Question 19

Example Equation for β⁺ decay and what happens.

Answer 19

proton converts to a neuton and positron - neutrino is also created to conserver momentum.

Question 20

risk=

Answer 20

probability x consequence

Question 21

how does fission split a nucleus?

Answer 21

Neutron can set the nucleus ocilating, into a dumbbell like shape which can split into two smaller nuclei.

The two smaller ones have less energy so are more stable.

Question 22

rough order of energy per particl in fission

Answer 22

1 MeV per particle

Question 23

Chain reaction principle?

Answer 23

One neutron is fired at a nucleus, which splits into two spaller nucli and 2-3 more neutrons which can split more neucli.

Question 24

What is critical mass?

Answer 24

Reaction is at a steady rate, one new fission follows each fision.

Question 25

super critical and sub critical mas?

Answer 25

Super - more then one new fissions per fission

Sub - more neutrons esape, the reaction eventually stops.

Question 26

Design of a steam presurised water reactor

Answer 26

Question 27

What does the moderator do?

Answer 27

Slows the neutrons down which greatly increases the chance of their capture by a U-235 nucleus

Question 28

What are the control rods for?

Answer 28

making sure the reactor doesnt go super critical by absorbing varying amounts of neutrons

Question 29

What does the coolant do?

Answer 29

carry away energy

Question 30

Fusion in the sun

Answer 30

Question 31

Fusion on earth

Answer 31

Question 32

What happens to the neutrons that dont cause a fission?

Answer 32

absorbed in moderator/U-238 or escape.