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Nuclear Engineering > Nuclear Notes > Flashcards

Nuclear Notes Flashcards

1
Q

Sources of energy, examples, and differences.

A

Primary sources of energy (energy found in nature that has not been subjected to change)- coal -oil -gas -nuclear -hydro -renewables (solar, wind, tide)

Secondary sources of energy (man made energy produced using primary sources) – electricity – hydrogen – alcohols – oil and gas

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2
Q

Globally, what percentage of electricity is generated from nuclear. How about in the UK. Use the latest available figures respectively.

A 
France- 76.3%
Germany- 14.1%
US- 19.5%
Russia- 18.6%
UK- 18.9%
Japan- 0.5%
India- 3.5%
China- 3.0%
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3
Q

Name the top 5 countries that have relatively high proportion of electricity generated from nuclear in 2015.

A 
France- 76.3%
Ukraine- 56.5%
Slovakia- 55.9%
Hungary- 52.7%
Slovenia- 38.0%
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4
Q

Globally how many operable (not necessarily operating) nuclear reactors are there for electricity generation?

A

447

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5
Q

How many nuclear power reactors in how many plants are currently operating in the UK to produce electricity?

A

15 (19 2010)

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6
Q

Roughly, 22g enriched uranium can produce 8000 kWh of electricity in a light water reactor. To generate the same amount of electricity, how many tonnes of black coal is required, and how much greenhouse gas is produced?

A

3 tonnes of black coal are required to produce 8000 kWh of electricity and 300 kg of fly ash is produced and 8 tonnes of other gaseous emissions are produced

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7
Q

Nuclear vs natural gas power plants: which costs more to build, which produces cheaper electricity, which is more sensitive to fuel cost fluctuation?

A

Natural gas plants are more sensitive to fuel cost flcutuation
Nuclear power plants are less sensitive to fuel cost fluctuation

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8
Q

What are the three main issues of nuclear energy?

A

Cost
Safety
Waste

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9
Q

What’s the difference between “mass” and “rest mass”? How do you calculate kinetic energy of neutrons or electrons (particles having a rest mass)? What about photons (particles with no rest mass)?

A

Mass- the amount of material an object possesses
Rest mass- the mass of an object at rest
Kinetic energy of Electrons:
Kinetic energy of Neutrons:
Kinetic energy of particles with no rest mass: (h=Planck’s constant, v=frequency)

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10
Q

What determines chemistry? And what determines radioactivity?

A

Chemistry of an element is determined by the electrons in the partly filled outermost shell. An unstable atomic nuclei determines radioactivity.

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11
Q

What are alpha, beta and gamma rays? How far can they typically travel in air and in solids?

A

Alpha- fast moving helium atoms, typical range (in air)- cm, typical range (in solid)- m
Beta- fast moving electrons, typical range (in air)- m, typical range (in solid)- mm
Gamma- high energy photons, typical range (in air)- km, typical range (in solid)- cm

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12
Q

Fission vs fusion vs radioactive decay. What are they, what they have in common and what differences they have?

A

Nuclear fission- a large nucleus splits into smaller nuclei when impacted by a neutron. Energy and more neutrons are produced
Nuclear fusion- several small nuclei combine together and release energy
Radioactivity- the spontaneous breakdown of an atomic nucleus

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13
Q

What’s “fissile”, “fissionable” and “fertile”?

A

Fissile- capable of sustaining a chain reaction of nuclear fission, with neutrons of any energy
Fissionable- capable of undergoing fission
Fertile- can be converted to fissile with bombardment of neutrons in a reactor

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14
Q

Which isotope is the only naturally occurring isotope, found in significant quantities in nature, that can undergo thermal fission?

A

U-235

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15
Q

U-238 is what and what but not what (of the above three)?

A

U-238 is fissionable but not fissile (only fission with high energy neutrons) and also fertile ( can be converted into Pu-239)

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16
Q

What does “thermal” mean when it’s used to describe nuclear reaction or neutrons.

A

Slow

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17
Q

]What is the level of U-235 in natural uranium? What do you expect it to be 2bn years ago?

A

0.71% of U-235 is in natural uranium. 3.66% is the U-235 proportion 2 billion years ago

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18
Q

What’s mass defect? Roughly how much energy is released per fission of U-235, or per fusion of Deuterium and Tritium?

A

The mass defect of a nucleus represents the mass of the energy binding the nucleus, and is the difference between the mass of a nucleus and the sum of the masses of the nucleons of which it is composed.

169 MeV of kinetic energy is released per fission of U-235
17.6 MeV of kinetic energy is releaser fusion of Deuterium and Tritium

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19
Q

What does 16O(n, p)16N mean?

A

a(b,c)d (incident, emerging)

•

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20
Q

What neutron interaction is expressed by (n, n), (n, n’), (n, α), (n, p), (n, γ), (n, 3n) respectively?

A

Scattering elastic neutron interaction- (n,n)
Scattering inelastic neutron interaction- (n,n’)
Absorption reactions radiative capture- (n, γ)
Absorption reactions charged- particle reactions- (n, α), (n, p)
Absorption reactions neutron- producing reactions- (n, 2n), (n, 3n)

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21
Q

“Cross sections” are used for what purpose and for (or not for) what nuclear particles?

A 
Cross sections (1barns= 10-24 cm2) are used to quantity the extent to which neutrons interact with nuclei 
σ: proportionality constant in the collision rate expression 
σ: number of collisions with one nucleus / time / intensity 
σ/A: probability that a neutron in the beam will collide with a nucleus.
22
Q

How many neutrons are usually produced in a fission reaction? What’s the mechanism by which neutrons are “thermalised” in reactors? Where do delayed neutrons come from, what’s their proportion and significance?

A

An average number of 2 and 3 neutrons are released per fission reaction
Delayed neutrons come after the fission event and their proportion is less than 1%

23
Q

Give two main reasons why thermal neutrons are preferred for fission reaction.

A

Thermal neutrons possess more energy than non-thermal neutrons. So therefore when the thermal neutron combines with a larger atom, fission is more likely to occur.

24
Q

What’s the purpose of coolant? Give 4 examples of materials used as coolant.

A 
Coolants are used to remove from heat from the core of a reactor 
Light water (deuterium), heavy water and some gases (thermal reactors) and liquid sodium (fast reactor)
25
Q

Why water needs to be purified for use in nuclear reactors? Or why you should not use seawater or tap water in a reactor?

A

There may be impurities in the seawater or the tap water.

26
Q

• What makes a good moderator? Give 3 examples of material commonly used as moderator. If a lighter nucleus is more effective to cause neutron energy loss during an inelastic collision, why heavy water is a better moderator than light water?

A

An ideal moderator is made of light nuclei with high scattering but low absorption cross sections. 3 materials used in moderators include light water, graphite and heavy water. Neutrons are more rapidly moderated with light water; however heavy water has a higher absorption cross section than light water

27
Q

Why cladding should be thin and why it can be thin?

A

Cladding needs to be thin in order to become transparent to neutron. It can be thin since it has a low thermal expansion coefficient.

28
Q

By what mechanism control rods work, and how reactivity of a nuclear reactor is controlled? How metal structures weakens over time in a nuclear reactor?

A

Control rods work by maintaining the the desired state of fission reactions in a nuclear reactor by absorbing the neutron. Boron steel has a high a but brittle and salt-like. Steel alloy enriched with boron can get around mechanical issues. Ag-In-Cd, cadmium has a high a but it’s highly energy dependent. Most commonly used as an alloy with silver and indium

29
Q

Once U-235 is used up, it’s gone forever. True or false?

A

True

30
Q

Fast neutron breeders do not need a moderator. True or false?

A

True

31
Q

What’s meant by “multiplication factor”, “gone critical” or “achieved criticality”, and “critical mass”?

A

Multiplication factor-
K=1: critical
k>1: supercritical
k<1: subcritical

32
Q

What are the main functional components in PWR? In BRW?

A

The main functional components in a pressurised water reactor includes

  • steam generators: up to 4 producing steam at 293 celius and 5 MPa
  • pressuriser: only one to main pressure
  • cladding : zircaloy
  • control rods: on top
33
Q

State the main common features, and differences, of light water reactors?

A

Uses enriched UO2 as a fuel. It also uses water a coolant and uses graphite as a moderator.

34
Q

Main differences between light water and heavy water reactors.

A

Light water reactors use D2O and heavy water reactors use H2O

35
Q

What’s AGR?

A

Advanced gas reactor. Which is graphite moderated and uses carbon dioxide as a coolant. It is 41% efficient

36
Q

What’s Magnox?

A

A magnesium non oxidising allow used for cladding

37
Q

n a full and closed cycle, how many stages are involved and what are they? Give a brief (e.g., one sentence or key phrase) description of each stage.

A 
Mining &amp; milling
Conversion
Enrichment
Fabrication
Reactor
Storage
Reprocessing
Vitrification
Disposal
38
Q

The main differences between open and closed fuel cycles.

A

Closed fuel cycle
Reprocessing is a key
Reprocessing is pursued in the UK, Japan and France

Open fuel cycle- once through cycle
No reprocessing
Is what has happened in most cases so far due to low uranium fuel prices

39
Q

To produce 1 kg of 5% enriched uranium, how much natural uranium is required? Assuming natural uranium contains 0.7% and depleted 0.3% U-235.

A

11.8 kg of natural uranium is required to produce 1 kg of 5% enriched uranium.

40
Q

What’s “yellowcake”? How much yellowcake is needed to produce fuel for a typical 1000 MWe nuclear reactor?

A

Yellow cake is (U3O8) uranium oxide, Urania. 200 tonnes of yellowcake are required for a 1000 MWe nuclear reactor.

41
Q

What are the main benefits of fuel reprocessing?

A

Separates uranium and plutonium. It reuses MOX fuel . Recycles through UF6 cycle. Reduces waste volumes. Increases energy recovered per tonne original uranium

42
Q

What do LLW, ILW and HLW stand for? (nuclear waste)

A

LLW- Low level waste ILW- Intermediate level waste HLW- High level waste

43
Q

What’s the difference between storage and disposal? At present, only LLW is disposed of in the UK. True or false?

A

Storage is temporary and retrievable and disposal is permanent and non-retrievable

44
Q

Globally fossil fuels provide for what level of

electricity demand?

A

2/3

45
Q

Globally fossil fuels provide for what level of

primary energy demand?

A

3/4

46
Q

• Which country has the largest fleet (by number)

of nuclear reactors for electricity generation?

A

USA

47
Q

What level of contribution the nuclear is

making to the UK electricity generation?

A

-20%

48
Q

How many nuclear reactors are operating in

the UK for electricity generation?

A

15

49
Q

How much of the Earth’s internal heat is from

radioactive decay?

A

80%

50
Q

Why the cost of electricity generated using
fossil fuels is expected to increase, but that of
renewables to decrease, and nuclear remains
largely constant.

A

Fossil fuel: carbon tax, transportation cost, emission
control as well as fuel cost.
Renewables: technological advances, the economy of scale.
Nuclear: Fuel cost is relatively small.

Nuclear Engineering (1 decks)

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