27 Nuclear Energy

Question 1

energy

Answer 1

E=mc²

Question 2

the binding energy of a nucleus

Answer 2

work that must be done to separate a nucleus into its constituent of neutrons and protons
Binding energy=mc²
(MeV = mass defect)

Question 3

binding energy per nucleon

Answer 3

The average work is done per nucleon to separate a nucleus into its constituent parts. the binding energy per nucleon is greatest for ion nuclei of mass number 56 (iron).

Question 4

mass defect

Answer 4

of a nucleus is the difference between the mass of the separated nucleons

Question 5

Nuclear fission

Answer 5

The process in which a large unstable nucleus splits into two fragments which are more stable than the original nucleus

Question 6

Nuclear fusion

Answer 6

The process of making small nuclei fuse together to form a larger nucleus. The product nucleus has more binding energy per nucleon than smaller nuclei.

Question 7

chain reaction

Answer 7

a series of reactions in which each reaction cause a further reaction. in a nuclear reactor, each fission event is due to a neutron colliding with a U nucleus which splits releases two or three further neurons that can go on to produce further fission. a steady chain reaction occurs when one fission neutron on average from each fission event produces a further fission event.

Question 8

Reactor core

Answer 8

the fuel rod and the control rods together with the moderator substance are in a steel vessel through which the coolant is pumped

Question 9

control rod

Answer 9

rod made of a neutron-absorbing substance such as cadmium or boron that are moved in or out of the core of a nuclear reactor to control the rate of fission events in the reactor

Question 10

coolant

Answer 10

a fluid that is used to prevent a machine or device from becoming dangerously hot. the coolant of the nuclear reactor is pumped through the core of the reactor to transfer thermal energy from the core to a heat exchanger

Question 11

heat exchanger

Answer 11

a steel vessel containing pipes through which hot coolant in a sealed circuit is pumped, causing water passing through the steel vessel in separate pipes to turn to stream which is used to drive turbines

Question 12

moderator

Answer 12

the substance in a thermal nuclear reactor that slows the fission neutrons down so they can go on to produce further fission

Question 13

the thermal nuclear reactor

Answer 13

nuclear reactor which has a moderator in the core

Question 14

critical mass

Answer 14

minimum mass of the fissile isotope in the nuclear reactor necessary to produce a chain reaction. if the mass of the fissile isotope in the reactor is less than the critical mass, chain reaction does not occur because too many fission neutrons escape from the reactor or are absorbed without fission

Question 15

the energy released in nuclear fission

Answer 15

change of binding energy

Question 16

binding energy of a nucleus

Answer 16

the work that must be done to separate a nucleus into its constituent neutrons and protons
binding energy = mass defect x c^2

Question 17

u into MeV

Answer 17

931.3

Question 18

binding energy per nucleon

Answer 18

the average work done per nucleon to separate a nucleus into its constituents parts. the binding energy per nucleon of a nucleus = the binding energy per nucleon is greatest for iron with a mass number of 56
the binding energy curve is a graph of binding energy per nucleon against mass number A

Question 19

energy released

Answer 19

Q = Δ mc^2

Question 20

strong nuclear force

Answer 20

the strength of the strong nuclear force can be estimated by working out the force of repulsion between two protons at separation of 1fm
range of strong nuclear force 3-4 fm
diameter of the nucleus can be measured from high-energy electrons scattering experiment

Question 21

nuclear stability

Answer 21

binding energy of each nuclide is different. the binding energy per nucleon of the nucleus is the average work done per nucleon to remove all the nucleons from a nucleus it is therefore a measure of stability of a nucleus
maximum value of 56
before 50 is nuclear fusion
after 60 is nuclear fission

Question 22

induce fission

Answer 22

fission of a nucleus occurs when a nucleus splits into two approximately equal fragments. this happens when the uranium is bombarded with neutrons.
the plutonium isotope is only other isotope formed by bombarding nuclei of the uranium isotope with nueutrons

(thermal neutrons)

Question 23

energy released in fission events

Answer 23

when a fission event occurs because the fragments repel each other with sufficient force to overcome the strong force trying to hold them together. the fragment nuclei and fission neutrons therefore gain kinetic energy

Question 24

nuclear fusion

Answer 24

fusion takes place when two nuclei combine to form a bigger nucleus. the binding energy curve show that if two light nuclei are combined, the individual nucleons become more tightly bound together. the binding energy per nucleon of the product nucleus is greater than of the initial nuclei.
have to combined collide at high speed. this is necessary to overcome the electrostatic repulsion between the two nuclei so they can become close enough to interact through the strong force

Question 25

solar energy

Answer 25

produce as a result of fusion reactions inside the sun. at high temperatures are stopped of their electrons (plasma). the nuclei of the plasma mover at very high speeds because of the enormous temperature
when two nuclei collide, they fuse together because they overcome the electrostatic repulsion due to their charge and approach each other closely enough to interact through the strong nuclear force.

Question 26

inside a nuclear reactor

Answer 26

a termal bucear reactor in a bucales power satino contains fuel rods spaced evenly in a steel vessel known as the reactor core. the reactor core also contains controversial; rods and a coolant as well as fuel rods and is connected by means of steel pipes to a heat exchanger. a pump is used to force the coolant through the reactor core and through the heat exchanger where it is used to raise stream to drive the turbines that turn the electricity generators in the power station

Question 27

control rods

Answer 27

absorb neutrons
depth of the control rods in the core is automatically adjusted to keep the number of neutrons on the core constant so that exactly one fission neutron per fission event on average
if the control rods are pushed in further, they absorb more neutrons

Question 28

safely features

Answer 28

• reactor core is thick steel vessel that can with stand high pressure and temperature (absorbs b radiation)
• very thick concrete walls to absorb neutrons and gamma radiation
• emergency shut-down system designed to insert the control rod fully into the core to stop fission completely
• seal fuel rods are inserted and removed from the reactor by means of remote handling devices

Question 29

radioactive waste

Answer 29

three different levels
disposal of any form of radioactive waste must be in accordance with legal regulations ab day approved disposal companies to ensure that the radioactive waste is stored safely in secure containers until its activity is insignificant

Question 30

high-level radioactive waste

Answer 30

spent fuel rods from a nuclear power station contains many different radioactive isotopes
must be removed by remote control and stored underwater in cooling ponds for up to a year because they continue to realise heat due to radioactive decay
radioactive waste is stored in seal containers in deep trenches at Stellafeild (cumbria).
the waste has to be stored for centuries as it contains long-lived radioactive isotopes which must be prevented from contaminating food and water supplies

Question 31

intermediate-level waste

Answer 31

radioactive materials with low activity and containers of radioactive materials are sealed in drums that are encased in concrete and stored in specially constructed buildings with walls of reinforced concrete

Question 32

low-level waste

Answer 32

such as laboratory equipment and protective clothing is sealed in metal drums and buried in large trenches