P7.7/P7.8 - Fission and Fusion reactions

Question 1

induced fission

Answer 1

-nucleus of a fissionable atom
-struck by neutron + absorbs it
-nucleus splits
-energy released
-other neutrons emitted

Question 2

spontaneous fission

Answer 2

-involves no neutrons

Question 3

Fission releases

Answer 3

• several neutrons at high speed
  -gamma radiation
  -KE in fission neutrons / fragment nuclei

Question 4

Chain reaction

Answer 4

-emits 2 neutrons
-causes other nuclei to split
-fission neutrons = more fission events

Question 5

fission neutrons produce

Answer 5

steady rate of energy in core
-chain reaction

Question 6

Fission fuel

Answer 6

-enriched uranium
-non fissionable uranium (238) and 2% fissionable U(235)

Question 7

non fissionable nuclei change into

Answer 7

heavier nuclei instead

Question 8

Reactor core

Answer 8

-contains fuel rods
control rods
water
-made up of thick steel

Question 9

Steel for core? and concrete walls

Answer 9

-withstands high temps and high pressures
-concrete prevents radiation escaping

Question 10

Fusion reaction

Answer 10

-2 smaller nuclei fuse
-1 larger nuclei
-releases energy (converted from mass)
-energy = radiation

Question 11

hen does fusion occur

Answer 11

-high temps
-high pressures
-if mass of nucleus is 55 or less

Question 12

Sun

Answer 12

-75% hydrogen
-25% helium
-made from plasma

Question 13

plasma

Answer 13

-bare nuclei
-no electrons
-fuse when collide = release energy

Question 14

2 protons fuse =

Answer 14

heavy H and other particles

Question 15

2 more protons collide with H =

Answer 15

heavier nuclei

Question 16

2 heavier nuclei of H collide =

Answer 16

4 HE
-KE and other particles emitted

Question 17

Fusion reactors

Answer 17

-plasma heated at high pressure/temp

Question 18

Why must the fusion reactor resemble conditions of the sun

Answer 18

-nuclei will repel = same charge
-conditions = faster = overcome + fuse

Question 19

how is the plasma heated in a fusion reactor

Answer 19

electric current

Question 20

magnetic field in fusion reactor

Answer 20

-prevents plasma from touching sides
-cooling off = stops reaction

Question 21

Pros of fusion

Answer 21

-fuel is available = H in sea
-Helium product = non radioactive gas (harmless)
-Energy may generate electricity

Question 22

Cons of fission

Answer 22

-fuel is only available in some places in the world
-produces nuclear waste

Question 23

Background radiation is

Answer 23

-radon gas
-travelled through ground rock
-emits alpha particles - health hazard

Question 24

why store radioactive waste undergorund

Answer 24

-prevents contamination
-radiation causes cancer

Question 25

short half life means

Answer 25

-emits lots of radiation in a short amount of time -dangerous

Question 26

Activity decreasing when storing underground

Answer 26

-hazards decrease with time