Ch 31: Fission, fusion and nuclear energy

Question 1

Natural Uranium

Answer 1

u-238 (99.3%), u-235 (0.7%), a chain reaction will not occur

Question 2

U-238

Answer 2

absorbs fast neutrons without undergoing fission, absorbs slow neutrons to a small extent

Question 3

U-235

Answer 3

absorbs fast moving neutrons and undergoes fission but is more likely to undergo fission with slow neutrons, after fission it produces fast moving neutrons

Question 4

Nuclear/fission reactor

Answer 4

A device in which uranium enriched with u-235 undergoes fission and produces energy

Question 5

Environmental impact of fission reactors

Answer 5

• mining uranium ore release radon gas which causes lung cancer
• containment of radioactive materials in reactor can be deadly in an accident, e.g. Chernobyl
• when fuel rods are spent and treated, the transport of them can lead to accidents and problems
• radioactive waste must be stored securely for a long time, which = problems for future

Question 6

Atomic/fission bomb

Answer 6

At least of fissile material of sub-critical mass are brought together, chain reaction occurs with enormous energy release, e.g. Hiroshima

Question 7

Nuclear Fission

Answer 7

the splitting up of a large nucleus into 2 smaller nuclei of roughly the same size

Question 8

Thermal neutrons

Answer 8

neutrons moving with kinetic energies = to the average kinetic energy of the surrounding atoms

Question 9

Fission fragments

Answer 9

products formed from fission

Question 10

Fissile materials

Answer 10

Materials in which fission will occur

Question 11

Critical size

Answer 11

the size of a sample in which a chain reaction will occur

Question 12

Nuclear fusion

Answer 12

the joining of 2 small nuclei to form a large nucleus

Question 13

Hydrogen bomb

Answer 13

uncontrolled fusion reaction, initial high temperatures are produces by a small fission bomb

Question 14

Advantages of fusion over fission as a power source

Answer 14

• less radioactive waste
• no possibility of uncontrolled runaway reaction
• the fuel used, deuterium, is readily available and cheap

Question 15

Disadvantages of fusion as a power source

Answer 15

a sustained controlled fusion reaction has never been achieved

Question 16

Einstein’s equivalence of mass and energy

Answer 16

E=mc^(2), mass is a form of energy and … can be converted into a different form of energy and v.v.

Question 17

Ionising radiation

Answer 17

general term for any form of radiation that will knock off outer electrons of atoms, i.e. form ions

Question 18

Factors that influence amount of harm done to the body when exposed to ionising radiations

Answer 18

• type of radiation
• activity of source producing it
• duration of exposure
• type of tissue (body part)

Question 19

Ionising radiation can cause

Answer 19

• skin burns
• cataracts, leukaemia, and other cancers
• genetic defects in children of parents exposed to radiation
• death

Question 20

Short-term effects of radiation exposure

Answer 20

vomiting, diarrhoea, fever, dehydration

Question 21

Sources of background radiation that we are all constantly exposed to

Answer 21

• outer space (cosmic rays)
• Rocks in Earth’s crust (radon gas)
• man-made radioactive materials