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Climate Change - Renewables > Nuclear - Fission Reactors > Flashcards

Nuclear - Fission Reactors Flashcards

1
Q

Composition of naturual uranium…

A

99.28% of U238, 0.72% U235.

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2
Q

How many neutrons does spontaneous fission of a U nucleus release?

A

About 2-3 neutrons

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3
Q

Commercial reactors emply…

A

Enrichement of U235 or segregate/localise fuel within a matrix of a moderator…

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4
Q

Moderator enrichment percentages…

A

Water 2.65% or graphite 1.6%

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5
Q

Thermal Neutron

A

A neutron within thermodynamic equilibrium, moving with same kinetic energy as their surroundings

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6
Q

Neutron Multiplcation Factor(K Factor)

A

Describes ratio of neutrons produced by fission in one generation to the number of neutrons lost through absorption/leakage in the preceeding generation.

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7
Q

Cross Section

A

Measures proabbiltiuy that a prcoess will take place involved with radiant excitation intersecting a localised phenomenon

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8
Q

Mechanism of bulk moderator…

A

235 neutron emission escapes fuel element where it was created before 238 absorption, then enter fuel element as a thermal neutron.

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9
Q

Mathematic asosciation of the neutron multiplication factor…

A

Closer to one, the better, exceedingb one meaning each neuytron generation generates more neutrons, desire to equal 1.

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10
Q

K factor fluctuation…

A

With moderators and leakage of neutrons; control rods act as a controlling agent.

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11
Q

Common material for control rods…

A

Boron-carbide is resistant to environmental degradation and an excellent neutron absorber…

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12
Q

Fermis Four Factor Formula

A

This is used to determine multiplication of a nuclear chain reaction in a hypothetical infinite medium

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13
Q

What are the four FFFF?

A

Reproduction factor
Fast fission factor
Resonance Escape Probability
Thermal Utilization Factor

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14
Q

Reproduction Factor

A

Measures how many fast neutrons a thermal neutron generates when encountering a uranium nucleus

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15
Q

Fast fisssion factor

A

Generated fast neutrons initation of 238 fission likelihood before slowing down to thermal velocity.

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16
Q

Resonance Escape Probability

A

Describes likelihood a fast neutron slows to thermal velocity before being absorbed by 238

17
Q

Thermal Utilization Factor

A

Measures thermalizedd neutrons then captured by the fuel.

18
Q

Visuale a cross-section…

A

`A particle beam with velocity v impacting cross section sigma, represented as a gas of neutrons moving through a fixed density of scatteres

19
Q

What does FFFF estimate?

A

Thermal neutrons generated(n+!) by uranium absorbition of a neutron(nth generation)

20
Q

Two fates of absorbed thermal neutrons…

A

Fission initaiton or capture (238 more likely for capture whilst 235 more likely to fission

21
Q

How many neutrons does 235 fission generate?

A

2.42 fast neutrons

22
Q

Why is chance of 238 fission low?

A

High moderator concentrator.

23
Q

What does REP 235 fission depend on?

A

Fast neutrons interactions with moderator and avoiding 238 capture

24
Q

REP measures…

A

Probability thermal equilibrium is reached before capture.

25
Q

Fission Poisons

A

Materials that can capture neutrons without undergoing nuclear fission, with a large neutron-absorption cross section.

26
Q

Example of fission poison…

A

Xenon135 generated by beta decay

27
Q

Three concerns of reactor safety…

A

Reactor control and cooling
Nuclear waste
Nuclear proliferation

28
Q

Active and passive safety systems…

A

Active being control rods and coolant pumps, whilst passive without human intervntions.

29
Q

Coefficent of Void

A

The change in reactivity per percent void of core water.

30
Q

Why does water slow down neutrons?

A

H collision with KE loss in neutron with H recoil.

31
Q

Elastic Scattering

A

This is a mechanism of which fast neutrons lose their energy when interacting with atomic nuclei of low atomic number.

32
Q

What is required for neutron thermalization to occur?

A

Enough energy lost for it to match average velocity of particles in surrounding medium.

33
Q

Why is neutron thermalization important?

A

Neutrons released from fission have many MeV of energy,.

34
Q

How does Uranium form?

A

Radioactive decay of elements like thorium and potassium, with collison of beta/alpha particles with surrounding rock particles.

35
Q

What is the process of uranium formation?

A

K40 beta decay(E and Neutrino emission) forming Ca-40, becoming Ca41(neutron absorption), beta decay(antineutrino and electron emission) forming scandium-41, which beta decays forming tianium, capturing a neutron forming titanium-42.

36
Q

Why does radioactive decay occur?

A

Imbalance of forces holding nucleus together.

Climate Change - Renewables (12 decks)

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