# Shared Flashcard Set

## Details

Reactor Theory
Seabrook Reactor Theory
100
Engineering
Professional
02/27/2008

Term
 State the characteristics of the following atomic particles including relative mass, charge, and location within the atom of a Proton
Definition
 Relative Mass- Relatively LargeCharge- +1Location- Nucleus
Term
 State the characteristics of the following atomic particles including relative mass, charge, and location within the atom of an electron
Definition
 Mass extremely smallcharge -1orbital rings
Term
 State the characteristics of the following atomic particles including relative mass, charge, and location within the atom of a Neutron
Definition
 Mass equal to proton.no charge In nucleus
Term
 What is an Atomic Mass Unit
Definition
 Equal to 1/12th of a carbon 12 atom 1.666 X 10^-27 Kg
Term
 What is a Nucleon?
Definition
 Neutron and Proton
Term
 What is an isotope?
Definition
 Isotopes are any of the different forms of an element each having different atomic mass (mass number).
Term
 State the two terms that represent the method by which atoms and subatomic particles are measured.
Definition
 Atoms and their subatomic particles are measured on the atomic scale that is based on mass and energy. Energy measurements are in units of eV, as discussed previously. The unit of measure for mass is the atomic mass unit (AMU).
Term
 Describe the characteristics of the following, including relative effective distance, change with distance, and nucleons involved with  Electrostatic Force
Definition
 Electrostatic forces acts over relatively long distances and are cumulative and involve protons and electrons.
Term
 Describe the characteristics of the following, including relative effective distance, change with distance, and nucleons involved withNuclear Force.
Definition
 Act over short distances and decrease dramatically as distance increases. Nuclear forces act on adjacent nucleons.
Term
 State the role that Neutrons have regarding stability of a nucleus.
Definition
 Because of no electrostic force between protons and neutrons, the neutrons contribute binding nuclear forces to hold the neutron together. As the size of the nucleus increases, there is a point where the addition of neutrons no longer results in a balance of the repulsive and attractive forces within a nucleus.
Term
 Define Binding Energy
Definition
 Binding Energy represents the amounts of energy released when protons, neutrons, and electrons combine to form an atom.Binding energy may also be considered as the amount of energy that must be supplied to an atom to seperate the atom.
Term
 Define Binding Energy Per Nucleon
Definition
 The average energy required to remove a nucleon from the nucleus.
Term
 Define Fission
Definition
 The splitting of a nucleus.Occurs when excitation energy is sufficient in magnitude to overcome the the nuclear forces holding the nucleus together.
Term
 Define Mass Defect
Definition
 The difference between a nucleus and the sum of the sum of the masses of the individual protons and neutrons in the nucleus.
Term
 Devfine Mass-energy equivilance.
Definition
 The conversion factor equating mass to energy (931.5 MeV/AMU)
Term
 Define Nuclear Stability
Definition
 The inherent ability of an atom to resist changing its atomic structure or energy level.
Term
 State the purpose of radioactive decay
Definition
 The process by which an unstable nucleus spontaneously transmutes from one form to another to reach a more stable state.
Term
 Identify the four basic types of radiation.
Definition
 Alpha, Beta, Gama and Neutron
Term
 For each of the basic types of radiation, disscuss the following: Relative ability to penetrate substances when compared to the other three types of radiation.Size or massElectrical Charge
Definition
 Alpha Particle- Large mass with double positive charge. Low penetrating ability.Beta Particle- Positive charge and has the mass of an electron more penetration than an alpha but less than a gama.Neutrons- No charge high mass high penetration.Gamma Rays- No Mass and No charge high penetration.
Term
 [image]Explain the shape of the BE / Nucleon chart above.
Definition
 Initially the amount of energy required to remove a nucleon rises sharpely until about 60 as the binding energy increases. After that the electrostatic forces overcome the nuclear forces thereby reducing the amount of energy required to remove a nucleon.
Term
 Given an atom with multiple electron shells,compare allowed number of electrons in the outer shell to the allowed number of the inner shell.
Definition
 The number of electrons per shell increases as with the distance from the nucleus.
Term
 Given an atom with multiple electron shells, compare the energy carried by an electron in an outer shell to the energy carried by an electron in an inner shell.
Definition
 Electrons with the lowest kinetic energy reside in the innershell. Electrons with the highest energy leve reside in the outer shells.
Term
 Given and atom with multiple electron shells, describe the response of electrons in the outher shells to the ejection of an electron in an inner shell.
Definition
 If an electron in ejected from an inner shell, an electron from an outer shell will fill the vacancy.
Term
 Define Ground State Energy
Definition
 The normal energy of an atom when its electrically neutral and not influenced by any outside energy inputs.
Term
 Define excited state energy
Definition
 Any condition that results in an atom being electrically charged or at an energy level above its ground state.
Term
 Define Ion
Definition
 An atom or a group of atoms that has aquired a net electric charge by gaining or losing an one or more electrons.
Term
 Define Ionization
Definition
 Any process that results in an atom or group of atoms to have a net electric charge by gaining or losing one or more electrons.
Term
 Define Gamma Ray
Definition
 A type of electromagnetic radiation emitted from an unstable nucleus allowing the nucleus to give off energy and return to a stable ground state.
Term
 Define X-Ray
Definition
 A bundle of energy (photon) emitted from the electron shell of an excited atom
Term
Definition
 The process by which an unstable nucleus spontaneously transmutes from one form to another to reach a more stable state
Term
 Define Decay Chain
Definition
 A process involving the decay of a daughter producy of radioactive decay, which may result in transformation to another daughter product that decays. It is termed decay chain because a single decay event results in several orders of decays before reaching a stabile nuclide.
Term
 Define spontaneous fission
Definition
 Any fission that occurs independent of neutron induced fission. Generally occurs with radioisotopes with atomic numbers of 92 and above.
Term
 Define Half-life
Definition
 The time required for a radioactive sample to decay to one half of its original value.
Term
 Explain how Alpha radiation interacts with the surrounding environment and lose energy.
Definition
 An alpha particle deposits a large amount of energy in a short distance of travel due to its large mass and charge.
Term
 Explain how Beta Radiation interact with the surrounding environment and loose energy.
Definition
 Beta-minus particles interact with the electrons orbiting the nucleus of atoms, causing ionization by displacing the electrons. The Beta particle looses energy with each interaction. After the beta particle loses enough energy, it is captured in the orbital shells of an atom.
Term
 Explain how gamma radiation interacts with the surrounding environment and loses energy
Definition
 Gammas can undergo three interactions, Photoelectric effect, compton scattering, and pair production. In photoelectric a photon is absorbed and an electron is ejected. In compton scattering the photon is not fully absorbed. An electron is released and a lower energy photon is released. In pair production produces a positron-electron pair.
Term
 Explain how Alpha Decay process occurs.
Definition
 Alpha decay is the emission of an alpha particle (2 protons and 2 neutrons) from an unstable nucleus. The daughter nuclide has an atomic number 2 less than the parent nuclide and a mass number 4 less than the parent nuclide. The daughter nucleus commonly releases its excitation energy by gamma emission.
Term
 Explain how Beta Minus decay processes occur.
Definition
 Beta-Minus effectively changes a neutron into a proton and an electron which is immediately ejected from the nucleus. The daughter nuclide has its atomic number decreased by one and has the same mass number as the parent.
Term
 Explain how electron capture decay process occurs.
Definition
 In electron capture the nucleus absorbs an electron from the inermost orbit. This electron combines with a proton to form a neutron.
Term
 Explain how photon decay takes place
Definition
 When a parent nucleus emits an α or a β particle, the resulting daughter product formed may still be in an excited state.  The energy difference between the excited state and the ground state is released almost instantaneously as a gamma.
Term
 Explain how neutron emission occurs
Definition
 In reactor operations, a small fraction of the fission fragments has the necessary excitation energy to emit a neutron from the first excited daughter of the decay chain. The emission occurs shortly after the formation of the excited nucleus.
Term
 Compare elastic and inelastic scattering processes.
Definition
 Elastic scattering occurs when a neutron is deflected by a nucleus without being absorbed. Elastic scattering conserves kinetic energy.Inelastic scattering is similar to elastic scattering, except that kinetic energy is not conserved.
Term
 Compare radiative capture and fission processes
Definition
 In radiative capture, a neutron is absorbed by the target nucleus, resulting in an excited compound nucleus. Neutron induced fission is similar to radiative capture, except that sufficient energy is added to the target causing the target nucleus to split.
Term
 Explain the half life method of determining radiocative decay.
Definition
 N(T) = N0e^-(decay constant)(t)decay constant=.693/halflife
Term
 State the difference between "microscopic cross section" and "macroscopic cross section"
Definition
 Microscopic relates to the probability of an individual interaction between a neutron and a nucleus.Macroscopic relates to the probability of an event to happen within a given volume. Takes into account atomic densit and microscopic cross section.
Term
 Define Mean Free Path
Definition
 The inverse of this cross section describes how far the average neutron travels before an interaction takes place.
Term
 Define Critical Energy
Definition
 The minimum amount of energy required for fission to occur.
Term
 Define Fissile Material
Definition
 Fuel types that fission due to the neutron binding energy.
Term
 Define Fissionable Material
Definition
 Fuel types that require additional energy (above the binding energy of the neutron, in the form of neutron kinetic energy) to cause fission.
Term
 Define Fission
Definition
 The splitting of an atoms nucleus to a lower energy state.
Term
 Define Prompt Neutron
Definition
 Neutrons emitted within 10–14 seconds of the fission event that are a direct result of the fission process are defined as prompt neutrons.
Term
 Define Fast Neutron
Definition
 Fast neutrons are neutrons with a kinetic energy greater than 0.1 MeV (105 eV).
Term
 Define Intermediate Neutron
Definition
 Intermediate neutrons (also, epithermal neutrons) are neutrons with kinetic energies between 1 eV and 0.1 MeV.
Term
 Define Slow Neutron
Definition
 Neutrons having kinetic energies less than 1 eV are termed slow neutrons.
Term
 Define Thermal Neutron
Definition
 Thermal neutrons are neutrons in thermal equilibrium with their surroundings. Depending on their surroundings, thermal neutrons can be fast, intermediate, or slow.
Term
 Define Delayed Neutron
Definition
 Neutrons born more than 10–14 seconds after the fission event are defined as delayed neutrons.
Term
 Source Neutron
Definition
 Neutrons produced independently of fission are termed source neutrons. Source neutrons consist of neutrons produced by installed neutron sources and intrinsic neutron sources.Intrinsic neutron sources include neutrons produced by spontaneous fission and by alpha and gamma-neutron reactions.
Term
 Describe Neutron Induced Fission using the liquid drop model method.
Definition
 When an incident neutron strikes a target fuel nucleus and undergoes an absorption interaction, excitation of the target occurs by an amount equal to the neutron binding energy plus the neutron’s kinetic energy. The addition of this excitation energy causes the target nucleus to vibrate and deform into a dumbbell shape.If the combined binding energy and kinetic energy added by the neutron is not sufficient to overcome the nuclear forces of the target nucleus, the target nucleus returns to its original shape.If the added energy is sufficient to overcome the nuclear forces, fission is likely to occur.
Term
 Explain the reason for the shape of the Fission Product Yield Curve.
Definition
 A brief inspection of the experimental data depicted by this curve shows that one of these fission fragments is lighter (A»95) while the other is heavier (A»139).
Term
 List the components and energy breakdown resulting from the fission of U-235.
Definition
 [image]
Term
 Explain how the fission process results in heat with the reactor.
Definition
 Fission results in fragments with high kinetic energy. The kinetic energy transfers via scattering to raise the kinetic energy of the target nuclei. Thereby transferring heat.
Term
 State the meeting of the term "decay heat" and explain why it is a concern in the nuclear power plant.
Definition
 Decay heat is the heat generated from fisson fragments (daughters) and is a concern because it is there after core is shutdown.
Term
 Explain why decay heat is present following reator operation.
Definition
 Fisson fragments (daughters) radioactively decay releasing energy.
Term
 List three variables that will affect the amount of decay heat present following reactor shutdown.
Definition
 PowerTime after shutdownTime at Power
Term
 Estimate the approximate amount of decay heat that will exist one hour after a shutdown from steady stat conditions.
Definition
 Closer to 7% approx 5%1% after 2 and 3/4 hours.
Term
 Define effective multiplication factor (Keff) and discuss its relationship to the state of the reactor.
Definition
 The number of neutrons that begin one generation compared to the number of neutrons that begin the next generation. The reactor is criticallity is determined by this.
Term
 Define fast fission factor.  (E)
Definition
 Fast neutrons produced by ALL fission events/fast neutrons produced by THERMAL fission events >1
Term
 Define Fast non-leakage probability factor  Lf
Definition
 Fast neutrons that start to slowdown/fast neutrons produced from all fission events
Term
 Define resonance escape prob factor. P
Definition
 Fast neutrons that become thermal/fast neutrons that start to slowdown <1
Term
 Define thermal non-leakage prob factor. LH
Definition
 Thermal neutrons absorbed in core/fast neutrons that become thermal
Term
 Define thermal utilization factor (f)
Definition
 Thermal neutrons absorbed in fuel/thermal neutrons absorbed in core <1
Term
 Define reproduction factor. n
Definition
 Fast neutrons produced by thermal fission events/thermal neutrons absorbed in fuel >1
Term
 Define Neutron generation time.
Definition
 Time from birth of one generation of neutrons to the time of birth of the next generation
Term
 Define critical.
Definition
 Neutron pop is stable Keff=1
Term
 Define subcritical.
Definition
 Neutron pop is lowering Keff<1
Term
 Define Supercritical
Definition
 Neutron pop is increasing Keff>1
Term
 Define reactivity
Definition
 Keff-1/Keff  Departure from criticallity
Term
 State the relationship between reactivity and effective multiplication factor (Keff)
Definition
 If Keff=1 reactivity =0Keff<1 reactivity - (neg)Keff>1 reactivity - (pos)
Term
 Describe the production of delayed neutrons.
Definition
 Some fission fragments decay to a new element (Fission Daughter Product) that immediately releases neutronThese fission fragments are a called “Delayed Neutron Precursors” (DNP) The released neutron is called a “Delayed NeutronThe decay time of DNP determines how long it takes for the Delayed Neutron to be released
Term
 Explain the effect of delayed neutrons on reactor control.
Definition
 Even though the delayed neutrons constitute a very small fraction of the neutron population, they significantly increase the average neutron generation lifetime.  With a longer generation time, fewer generations occur per unit time The longer generation time makes it possible to control the fission process (i.e. reactor power)
Term
 Define reactor period
Definition
 The time in seconds for power to change by a factor of "e" (2.718)
Term
 Define Startup Rate
Definition
 The time in Minutes for for power to change one decade.
Term
 Describe the factors affecting reactor period and time.
Definition
 Prompt neutron time.Prompt neutron fractionDelayed neutron generation timeDelayed neutron fractionReactivity.
Term
 Define delayed neutron fraction.
Definition
 Fraction of all fissions neutrons in a generation that were born delayed.
Term
 Define core delayed neutron fraction.
Definition
 The average fraction of neutrons born delayed from fission of all fuels in the reactor core.
Term
 Define effective delayed neutron fraction
Definition
 Delayed neutron fraciton X importance factor.
Term
 State the reasons for the variations between delayed neutron fraction, core delayed neutron fraction, and the effective delayed neutron fraction.
Definition
 Core delayed neutron fraction takes in account the different types of fuel in the core. The effective delayed neutron fraction is the core delayed neutron fraction corrected for the lack of contribution to the fast fission factor.
Term
 Define doubling time
Definition
 The time in seconds for the neutron level to change a factor of 2.
Term
 Explain prompt critical
Definition
 When reactivity is greater than the effective delayed neutron fraction the multiplication of prompt neutrons alone will sustain the power increase.
Term
 Explain prompt jump
Definition
 The initial instantaneous increase (“jump”) in reactor power when positive reactive is added to the reactor. This increase is due to the immediate production of prompt neutrons vs. the lagging production of delayed neutrons. The prompt neutrons initially dominate the fission production and power rises very rapidly. This power increase on prompt neutrons alone is short lived due the reactor’s designed dependence on delayed neutrons
Term
 Explain prompt drop
Definition
 The quick drop in power while prompt neutron changes are outweighing the slower change in delayed neutron population. This results is a dramatic change in fission rate.
Term
 Explain why a startup neutron source may be required for a reactor.
Definition
 Without a startup neutron source, the neutron population of a subcritical reactor would decay to zero.
Term
 List four variables involved in a reactivity balance.
Definition
 (Temperature, pressure, samarium, xenon, rods, core age)
Term
 Explain how a reactivity balance may be used to predict conditions under which the reactor will become critical.
Definition
 An ECP is a mathmatical calculation that accounts for changes in the variables between shutdown and last criticality.
Term
 List three methods used to shape or flatten the core power distributions.
Definition
 reflectors, installed poisons, control rods
Term
 Describe the concept of power tilt.
Definition
 It is a non‑symmetrical variation of core power in one quadrant of the core relative to the others.
Term
 Define the concept shut down margin
Definition
 Shutdown margin is the instantaneous amount of reactivity by which a reactor is sub-critical or would be sub-critical from its present condition assuming all control rods are fully inserted except for the single rod with the highest integral worth and equilibrium xenon removed.
Term
 Identify the five changes that will occur during and after a reactor shutdown that will affect the reactivity of the core.
Definition
 ·          Control rod position·          Soluble neutron poison concentration·          Temperature of the fuel and coolant·          Xenon concentration·          Samarium concentration
Term
 Explain why decay heat is present following reactor operation.
Definition
 Decay heat is present as a result of the decay of fission fragments.
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