Nuclear power

Question 1

what is nuclear fission?

Answer 1

splitting of a large atomic nucleus into smaller nuclei.

Question 2

what happens in a nuclear reactor?

Answer 2

a slow-moving neutron is absorbed into a nucleus (typically uranium-235).

Question 3

what does the absorption of the uranium-235 nucleus with a neutron cause? (2)

Answer 3

• the nucleus to become uranium-236, which is unstable.
  -entire nucleus splits into two large fragments called ‘daughter nuclei’.

Question 4

what is the chain reaction ? (2)

Answer 4

-two or three neutrons also explode out of the fission reaction
-these can collide with other uranium nuclei to cause further fission reactions.

Question 5

what carries most of the energy from the reaction?

Answer 5

The fast moving neutrons

Question 6

what needs to happen to the neutrons before they can collide with other uranium nuclei?

Answer 6

they need to be slowed down

Question 7

what is the energy from the neutrons passed on to? why?

Answer 7

-passed on to other components in the nuclear reactor,
-which is used to heat water to drive the turbines that turn the generators.

Question 8

what is the nuclear fuel?
why is it held in rods?

Answer 8

the uranium or plutonium isotope that will split.
-so that the neutrons released will fly out and cause nuclear fission in other rods.

Question 9

what is the moderator?

Answer 9

a graphite core

Question 10

what does the graphite core do?

Answer 10

slows the neutrons down so that they are more likely to be absorbed into a nearby fuel rod.

Question 11

what do the control rods do? (2)

Answer 11

-these are raised and lowered to stop neutrons from travelling between fuel rods
-and therefore change the speed of the chain reaction.

Question 12

what is the coolant heated up by?

Answer 12

heated up by the energy released from the fission reactions

Question 13

why is there a concrete shield in the fission reactors?

Answer 13

the daughter products of the fission reaction are radioactive and can be a hazard.

Question 14

what is the basis of an atomic bomb?

Answer 14

An uncontrolled fission reaction

Question 15

what are the 6 advantages of nuclear power stations?

Answer 15

-Produces no polluting gases.
-Does not contribute to global warming.
-Very low fuel costs.
-Low fuel quantity reduces mining and transportation effects on environment.
-High technology research required benefits other industries.
-Power station has very long lifetime.

Question 16

what are the 6 disadvantages of nuclear power stations?

Answer 16

-Waste is radioactive and safe disposal is very difficult and expensive.
-Local thermal pollution from wastewater affects marine life.
-Large-scale accidents can be catastrophic.
-Public perception of nuclear power is negative.
-Costs of building and safely decommissioning are very high.
-Cannot react quickly to changes in electricity demand.

Question 17

what is nuclear fusion?

Answer 17

when two small, light nuclei join together to make one heavier nucleus.

Question 18

what do all nuclear reactions convert a small amount of their mass into?

Answer 18

energy

Question 19

what does nuclear fusion require?

Answer 19

the nucleus of positive particles

Question 20

why is fusing the nucleus of positive particles difficult?

Answer 20

As two nuclei approach each other, they will repel because they have the same charge

Question 21

which conditions are needed to complete nuclear fusion? (2)

Answer 21

-intense pressure and very high temperatures
-in order to force the nuclei together and overcome this electrostatic repulsion.