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22 Cards in this Set
- Front
- Back
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The term "neutron generation time" is defined as the average time between..
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neutron absorbtion prodicing a fission and absorbtion or leakage of resultant neutrons
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A neutron emitted in less than 1.0 x 10-14 seconds following a nuclear fission
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Prompt Neutron
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___ are expelled with the lowest average kinetic enegy of all fission neutrons
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Delayed neutrons
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____ has an average neutron generation lifetime of 12.5 seconds
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Delayed Neutrons
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A neutron that is expelled 1.0 x 10-2 seconds after the associated fission event is a _____
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delayed neutron
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Accounts for more than 99% of fission neutrons
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Prompt Neutrons
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___ are fission neutrons that are expelled at a lower average kinetic energy than most other fission neutrons
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Delayed Neutrons
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____ are produced from the radioactive decay of certain fission fragments
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Delayed Neutrons
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it is in energy equilibrium with the moderating medium
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Thermal Neutron
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The kinetic energy of thermal neutrons in a reactor operating at full power is ____
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less than 0.1 eV
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Regarding a thermal neutron, the word "thermal" indicated that the neutron
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is at the same energy level as the surrounding atams
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A thermal neutron exists at an energy ____ the epithermal range; and its cross section for absorbtion in U-235 _____ as the neutron energy decreases
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below; increases
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A fission neutron will typically lose the most energy when it interacts with a/an ___
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hydrogen atom in a water molecule
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What will increase the amount of neutron moderation in a reactor operating at 50% power?
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Reducing feedwater inlet temperature
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____ describes the reduction of neutron energy due to scattering reactions
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Neutron moderation
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During moderation f a fission neutron, the neutron is MOST susceptible to resonance absobtion when it is a/an ____ neutron
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epithermal
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What will decrease the ability of the collant to moderate neutrons in a reactor operating at saturated conditions?
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Decreasing reactor vessel pressure
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A fast neutron will lose the greatest amount of energy during a scattering reaction in the moderator if it interacts with
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a hydrogen nucleaus
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What accounts for the majority of energy transfer from a fission neutron whule slowing down in a moderator?
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collisions with the nuclei in the moderator
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The best neutron moderator is ___ and is composed of ____ atoms
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dense , small
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The ideal moderator has a ____ macroscopic absorbtion cross section for thermal neutrons and a ____ average ligarithmic energy decrement
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small ; large
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The ideal neutron moderator as a ____ microscopic scattering cross section for thermal neutrons and a ____ density
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large ; high
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