Nuclear Physics

Question 1

what is the mass defect of a nucleus

Answer 1

difference between the mass of the completely separated nucleons and the mass of the nucleus

Question 2

what is the equation for binding energy

Answer 2

mass defect x c^2

Question 3

define binding energy

Answer 3

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

Question 4

what is a thermal neutron

Answer 4

a slow / low energy neutron to increase the probability that it will be absorbed

Question 5

why is energy released in nuclear fission

Answer 5

the new smaller nuclei will have a higher binding energy per nucleon

Question 6

what is the process of nuclear fission

Answer 6

• control rods are lowered in and out to control the rate of reaction
• control rods are usually made out of boron and absorb the excess neutrons (more neutrons = quicker rate of reaction)
• coolant is used to help cool the whole reactor, must be liquid or gas so it can be pumped around the reactor
• fuel rods contain the radioactive element, usually uranium or plutonium, to undergo fission
• moderator also needed to slow down neutrons to increase chances of being absorbed
• water usually acts as moderator and coolant

Question 7

what are the environmental positives of nuclear fusion

Answer 7

• does not produce greenhouse gases
• can be adjusted to meet demand

Question 8

what are the environmental negatives of nuclear fission

Answer 8

• produces toxic waste
• needs infrastructure to store and keep the reaction cool
• toxic waste must be buried deep inside concrete vats, damaging landscapes

Question 9

what is nuclear fusion

Answer 9

two light nuclei overcome the electrostatic repulsion between them and fuse

Question 10

under what conditions is nuclear fusion possible

Answer 10

• nuclei must be moving very fast
• must have lots of energy to overcome electrostatic force of repulsion
• high pressure required

Question 11

where are conditions generally suited for fusion

Answer 11

it is only stars where the pressures and temperatures are sufficient for fusion to occur

Question 12

Energy is only released in a reaction when …

Answer 12

binding energy per nucleon increases in a reaction

Question 13

why is uranium used to produce nuclear energy

Answer 13

• it is very easy to spit apart
• found in abundance
• decays naturally