Nuclear - Fission Reactors

Question 1

Composition of naturual uranium…

Answer 1

99.28% of U238, 0.72% U235.

Question 2

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

Answer 2

About 2-3 neutrons

Question 3

Commercial reactors emply…

Answer 3

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

Question 4

Moderator enrichment percentages…

Answer 4

Water 2.65% or graphite 1.6%

Question 5

Thermal Neutron

Answer 5

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

Question 6

Neutron Multiplcation Factor(K Factor)

Answer 6

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

Question 7

Cross Section

Answer 7

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

Question 8

Mechanism of bulk moderator…

Answer 8

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

Question 9

Mathematic asosciation of the neutron multiplication factor…

Answer 9

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

Question 10

K factor fluctuation…

Answer 10

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

Question 11

Common material for control rods…

Answer 11

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

Question 12

Fermis Four Factor Formula

Answer 12

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

Question 13

What are the four FFFF?

Answer 13

Reproduction factor
Fast fission factor
Resonance Escape Probability
Thermal Utilization Factor

Question 14

Reproduction Factor

Answer 14

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

Question 15

Fast fisssion factor

Answer 15

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

Question 16

Resonance Escape Probability

Answer 16

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

Question 17

Thermal Utilization Factor

Answer 17

Measures thermalizedd neutrons then captured by the fuel.

Question 18

Visuale a cross-section…

Answer 18

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

Question 19

What does FFFF estimate?

Answer 19

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

Question 20

Two fates of absorbed thermal neutrons…

Answer 20

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

Question 21

How many neutrons does 235 fission generate?

Answer 21

2.42 fast neutrons

Question 22

Why is chance of 238 fission low?

Answer 22

High moderator concentrator.

Question 23

What does REP 235 fission depend on?

Answer 23

Fast neutrons interactions with moderator and avoiding 238 capture

Question 24

REP measures…

Answer 24

Probability thermal equilibrium is reached before capture.

Question 25

Fission Poisons

Answer 25

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

Question 26

Example of fission poison...

Answer 26

Xenon135 generated by beta decay

Question 27

Three concerns of reactor safety...

Answer 27

Reactor control and cooling Nuclear waste Nuclear proliferation

Question 28

Active and passive safety systems...

Answer 28

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

Question 29

Coefficent of Void

Answer 29

The change in reactivity per percent void of core water.

Question 30

Why does water slow down neutrons?

Answer 30

H collision with KE loss in neutron with H recoil.

Question 31

Elastic Scattering

Answer 31

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

Question 32

What is required for neutron thermalization to occur?

Answer 32

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

Question 33

Why is neutron thermalization important?

Answer 33

Neutrons released from fission have many MeV of energy,.

Question 34

How does Uranium form?

Answer 34

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

Question 35

What is the process of uranium formation?

Answer 35

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.

Question 36

Why does radioactive decay occur?

Answer 36

Imbalance of forces holding nucleus together.