Nuclear Sciences Defs Only

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ereim
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Nuclear Sciences Defs Only
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2010-09-16 14:05:34
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  1. A unit of measurement equal to 1/12 the mass of a Carbon 12 atom (1.6605402 x 10–24 grams).
    Atomic Mass Unit (AMU)
  2. Sub-atomic particle that makes up an atom, has a mass of 0.00055 AMU, a negative charge, and is located outside the nucleus in probability shells (orbits).
    Electron
  3. Amount of kinetic energy (eV) gained by an electron when accelerated through an electric potential difference of 1 volt
    Electron Volt (eV)
  4. A basic substance that cannot be broken down into any simpler substance after it is isolated from a compound, but can be combined with other elements to form compounds.
    Element
  5. A nucleus of the same element (same number of protons) with a different number of neutrons.
    Isotopes
  6. Sub-atomic particle that makes up an atom, has a mass of 1.00866 AMU, a neutral charge, and is located in the nucleus.
    Neutron
  7. Any particle that is part of the nucleus of an atom, neutrons and protons
    Nucleon
  8. Any atom containing a unique combination of neutrons and protons in the nucleus.
    Nuclide
  9. Sub-atomic particle that makes up an atom, has a mass of 1.00727 AMU, a positive charge, and is located in the nucleus.
    Proton
  10. The energy equivalent of the mass defect (MeV). Represents the amount of energy that is released when an atom is formed from its component protons and neutrons. Also, represents the amount of energy that must be supplied to the atom to completely separate it into its individual protons and neutrons.
    Binding Energy (BE)
  11. Average energy required to remove a nucleon from the nucleus.
    Binding Energy (BE) Per Nucleon
  12. The attractive or repulsive force that exist between two objects due to their electrical charge.
    Electrostatic Force
  13. The splitting of an atoms nucleus resulting from an energy input (excitation energy) into the nucleus greater than the nuclear forces holding the nucleus together.
    Fission
  14. The difference in mass between a nucleus and the sum of the masses of the individual protons and neutrons in the nucleus (AMU).
    Mass Defect (Dm)
  15. The conversion factor equating mass to energy
    Mass-Energy Equivalence
  16. The strong attractive force in a nucleus between to adjacent nucleons.
    Nuclear Force
  17. The inherent ability of an atom to resist changing its atomic structure or energy level.
    Nuclear Stability
  18. The process by which an unstable nucleus spontaneously transmutes from one form to another to reach a more stable state.
    Radioactive Decay
  19. The unstable nucleus of an atom immediately following the absorption of a neutron.
    Compound Nucleus
  20. The new nucleus present after the decay event.
    Daughter Nuclide
  21. A process involving the decay of a daughter product of radioactive decay, which may result in transformation to another daughter product that decays, etc.
    Decay Chain
  22. The probability per unit time that a decay event will occur within a radioactive sample
    Decay Constant
  23. The rate at which the atoms of a sample of radioactive material disintegrates.
    Decay Rate
  24. The interaction between a neutron and nucleus of an atom resulting in the neutron transforming some of its kinetic energy to the nucleus with all kinetic energy shared between the neutron and nucleus and total KE conserved.
    Elastic Scattering
  25. Any condition that results in an atom being electrically charged or at an energy level above its ground state energy.
    Excited State Energy
  26. Highly excited radionuclides that are the result of a fission event and generally initiate a decay chain with beta decay.
    Fission Fragments
  27. Any electron that is not electrically bound to an atom’s nucleus.
    Free Electron
  28. A type of electromagnetic radiation emitted from an unstable nucleus allowing the nucleus to give off energy and return to a stable ground state
    Gamma Ray
  29. The normal energy level of an atom when it is electrically neutral and not influenced by any outside energy inputs.
    Ground State Energy
  30. The time required for a radioactive sample to decay to one half of its original value.
    Half-Life
  31. The interaction between a neutron and nucleus of an atom resulting in some of the kinetic energy being transferred from the neutron to the nucleus and causing excitation of the nucleus such that it returns to ground state by gamma emission. KE is not conserved.
    Inelastic Scattering
  32. An atom or a group of atoms that has acquired a net electric charge by gaining or losing one or more electrons.
    Ion
  33. Any process that causes an atom or group of atoms to have a net electric charge resulting from losing or gaining one or more electrons
    Ionization
  34. The energy required to remove one or more electrons from an atom
    Ionization Energy
  35. The interaction between a neutron and nucleus resulting in capture of the neutron with enough energy to cause the resulting excited nucleus to split into two fission fragments and the release of neutrons and radiation.
    Neutron Induced Fission
  36. The original nucleus that decays
    Parent Nuclide
  37. The interaction between a neutron and nucleus resulting in capture of the neutron and excitation of the nucleus such that it returns to ground state by gamma emission.
    Radiative Capture
  38. The process by which an unstable nucleus spontaneously transmutes from one form to another to reach a more stable state.
    Radioactive Decay
  39. Any fission event that occurs independent of neutron induced fission. Generally occurs in radioisotopes with atomic numbers of 92 and above.
    Spontaneous Fission
  40. Any of the radionuclides with atomic numbers greater than 92.
    Transuranic Element
  41. A bundle of energy (photon) emitted from the electron shell of an excited atom.
    X-Ray
  42. The number of atoms of a given isotope in a unit volume. Atomic density uses the symbol “N” as a designation, and the units are atoms per cubic centimeter.
    Atomic Density
  43. Unit of measurement, where 1 barn is equal to 1 ´ 10‑24 square centimeters
    Barn
  44. The minimum amount of energy required for fission to occur in a specific fuel type.
    Critical Energy (Ec)
  45. A neutron born more than 1 ´ 10‑14 seconds after a fission event.
    Delayed Neutron
  46. The delayed energy released by decay of the fission fragments after reactor shutdown.
    Decay
  47. A neutron that has a kinetic energy greater than 0.1 MeV.
    Fast Neutron
  48. A fuel type that will fission due to the binding energy of an incident neutron.
    Fissile Material
  49. A neutron reaction in which an incident neutron is absorbed by a target nucleus, resulting in the splitting of the target nucleus into two new atoms, some neutrons, and gamma rays.
    Fission
  50. A neutron emitted as a direct result of the fission process.
    Fission Neutron
  51. Any particle created as the result of a fission event.
    Fission Product
  52. A fuel type that requires kinetic energy in addition to binding energy of an incident neutron for fission to occur.
    Fissionable Material
  53. A neutron that has a kinetic energy between 0.1 MeV and 1 eV
    Intermediate Neutron
  54. A measure of the probability that a given interaction will occur between a single target nucleus and an incident neutron. The effective area presented by the target nucleus to the incident neutron, for a particular reaction.
    Macroscopic Cross Section
  55. The average distance a neutron travels before an interaction occurs.
    Mean Free Path
  56. The probability that a given interaction will occur between a target nucleus and neutron (barns or cm2).
    Microscopic Cross Section
  57. A neutron that is emitted within 10-14 seconds of a fission event and is a direct result of the fission process (fission neutron).
    Prompt Neutron
  58. A neutron that has a kinetic energy less than 1 eV.
    Slow Neutron
  59. A neutron that is produced independently of neutron induced fission.
    Source Neutron
  60. Any fission that results in the production of three fission fragments.
    Ternary Fission
  61. A neutron that is in thermal equilibrium with its surroundings.
    Thermal Neutron
  62. The condition of the reactor where the number of neutrons produced by fission in one generation equals the number of neutrons produced by fission in the previous generation (keff = 1) (r = 0).
    Critical
  63. The factor by which the number of neutrons produced by fission in one generation must be multiplied to determine the number of neutrons produced by fission in the next generation.
    Effective Multiplication Factor (keff)
  64. The ratio of fast neutrons produced from all fission events divided by fast neutrons produced by thermal fission events.
    Fast Fission Factor (e)
  65. The ratio of the number of fast neutrons that start to slow down divided by the number of fast neutrons produced from all fissions.
    Fast Non-Leakage Probability
  66. The time from the birth of one generation of neutrons to the time of the birth of the next generation of neutrons.
    Neutron Generation Time
  67. The fractional change in fission neutron population per generation, or the measure of the departure of a reactor from criticality
    Reactivity
  68. The ratio of fast neutrons produced by thermal fission events divided by the number of thermal neutrons absorbed in the fuel.
    Reproduction Factor
  69. The ratio of fast neutrons that become thermal divided by the number of fast neutrons that start to slow down.
    Resonance Escape Probability
  70. Used to describe the processes that occur during the neutron life cycle.
    Six Factor Formula
  71. The condition in which the number of neutrons produced by fission in one generation is less than the number of neutrons produced by fission in the previous generation (keff < 1) (negative r).
    Subcritical
  72. The condition in which the number of neutrons produced by fission in one generation is greater than the number of neutrons produced by fission in the previous generation (keff > 1) (positive r).
    Supercritical
  73. The ratio of the number of thermal neutrons absorbed in the core divided by the number of fast neutrons that become thermal.
    Thermal Non-Leakage Factor
  74. The ratio of the number of thermal neutrons absorbed in fuel divided by the number of thermal neutrons absorbed in the core.
    Thermal Utilization Factor
  75. The weighted average of the decay constants for the six groups of delayed neutron precursors in the reactor core (sec–1).
    Average Delayed Neutron Precursor Decay Constant
  76. The weighted average of the effective delayed neutron fraction for all fissile nuclides in the reactor core. equals the number of fissions caused by delayed neutrons divided by the total number of fissions caused by fission neutrons.
    Average Effective Delayed Neutron Fraction
  77. The average time between the absorption of a neutron which causes fission and the absorption of resultant neutrons
    Average Neutron Generation Time
  78. A reactivity unit related to a dollar of reactivity, where one cent is one-hundredth of a dollar
    Cent
  79. The weighted average of the delayed neutron fractions for all fissile/fissionable nuclides in the reactor core
    Core Average Delayed Neutron Fraction
  80. A neutron born approximately 12.7 seconds after a fission event
    Delayed Neutron
  81. The fraction of neutrons born delayed from fission of a particular nuclide. b equals the number of neutrons born delayed divided by the total number of neutrons born from fission of a particular nuclide.
    Delayed Neutron Fraction
  82. The total time from the fission event to absorption of a delayed neutron born from a delayed neutron precursor resulting from that fission event. » 12.7 seconds
    Delayed Neutron Lifetime
  83. The decay constant for a delayed neutron precursor. It is the probability that a nucleus will decay per unit time (sec–1).
    Delayed Neutron Precursor Decay Constant
  84. A unit of reactivity where one dollar of reactivity is equivalent to the effective delayed neutron fraction . If the reactivity of the core is one dollar, the reactor is prompt critical
    Dollar ($)
  85. The time required for a reactor to double in power. DT is used to estimate reactor period (sec).
    Doubling Time (DT)
  86. The fraction of neutron induced fissions caused by delayed neutrons of a particular nuclide
    Effective Delayed Neutron Fraction
  87. The percentage of fissions that occur in the reactor for each particular fuel type present
    Fission Fraction
  88. The percentage of fissions that occur in the reactor for each particular fuel type present
    Fission Yield
  89. The average time required for one-half of the atoms of a material to decay
    Half-Life (T1/2)
  90. Represents how long, on the average, a delayed neutron precursor will exist before decaying.
    Mean Life
  91. The condition of the reactor reaching criticality on prompt neutrons alone. It will occur when positive reactivity added
    is equal to, or greater than, the average effective delayed neutron fraction
    Prompt Critical
  92. The initial rapid decrease in neutron population following a step insertion of negative reactivity
    Prompt Drop
  93. The initial rapid increase in neutron population following a step insertion of positive reactivity
    Prompt Jump
  94. The total time from the fission event to absorption of a prompt neutron born from that fission event. » 1 ´ 10–4 sec
    Prompt Neutron Lifetime
  95. The time, in seconds, required to change reactor power by a factor of e (2.718).
    Reactor Period
  96. The time (in minutes) required to change reactor power by a factor of 10. Expressed as DPM (decades per minute). It is a measure of the rate of change of reactor power in DPM
    Startup Rate (SUR)
  97. The widening and flattening effect on resonance capture probability peaks for epithermal neutrons due to increased kinetic energy of target atoms resulting from increased fuel temperature.
    Doppler Broadening
  98. The reactivity coefficient that relates the change in reactivity due to a change in fuel temperature.
    Doppler Coefficient or Fuel Temperature Coefficient
  99. The reactivity coefficient that relates the change in reactivity due to a change moderator temperature
    Moderator Temperature Coefficient
  100. Discrete excitation energy levels exist within a nucleus
    Resonance Energy
  101. Reactivity coefficient that relates the change in reactivity due to a change in void fraction
    Void Coefficient
  102. The temperature decrease per unit time usually measured at the vessel skin, steam dome, and recirculation loop
    Cooldown Rate
  103. The reactor sustains a chain reaction with a stable neutron count rate and an infinite reactor period
    Criticality
  104. The heat generated in the core from the decay of fission products.
    Decay Heat
  105. The negative reactivity contributed to the core by the Doppler coefficient when the core void fraction is decreased using recirculation flow.
    Doppler Defect
  106. An estimate, made by the reactor engineers that determines on what rod pattern what rod, and what rod position the reactor is expected to go critical
    Estimated Critical Position
  107. The temperature rise per unit time usually measured at the vessel skin, steam dome, and recirculation loop
    Heatup Rate
  108. The point during a reactor startup where heat production from fission exceeds ambient heat losses. A further increase
    in power will raise the temperature of fuel and moderator
    Point of Adding Heat
  109. A plot using the inverse count ratio (ICR) following reactivity change events to obtain a conservative estimate of critical rod position. May also be used during fuel loading to monitor for inadvertent criticality. This is sometimes also referred to as an inverse count ratio plot or an inverse count rate ratio plot.
    1/M Plot
  110. 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
    Shutdown Margin
  111. ______ scattering is the type of scattering reaction where kinetic energy raises the internal energy of the target nucleus.
    Inelastic
  112. Any process that causes an atom or group of atoms to have a net electric charge resulting from losing or gaining one or more electrons can be referred to as:
    Ionization
  113. Identify the 4 basic types of Radiation
    • Alpha
    • Beta
    • Gamma
    • Neutron
  114. The difference in mass between a nucleus and the sum of the masses of individual protons and neutrons in the nucleus is called the _______
    Mass Defect
  115. The splitting of an atom's nucleus resulting from an energy input (excitation energy) into the nucleus greater than the nuclear force holding the nucleus together is called ______
    fission
  116. What is the attractive or repulsive force that exists between two objects due to their electrical charge?
    Electrostatic Force
  117. At time t = 0, a radioactive sample contains 1x1010 atoms. After 31 days, the sample contains 3.6x104 atoms. Determine the half life of the sample
    t1/2=1.7 days
  118. When will a reactor respond to a set amount of added reactivity?
    End of Life EOL
  119. The departure from criticality can be used to describe what?
    reactivity
  120. What is the Effective Delayed Neutron Fraction Beff?
    The fraction of neutron induced fission caused by delayed neutrons of a particular nuclide
  121. When a reactor has reached an equilibrium in the number of neutrons produced from one generation to another (the reactor is critical keff=1), what is the reactivity?
    0
  122. A neutron that has kinetic energy less than 1 eV is know as a ______
    slow neutron
  123. A neutron that has a kinetic energy greater than 0.1 MeV is known as a _______
    Fast neutron
  124. A fuel type that requires kinetic energy in addition to binding energy of an incident neutron for fission to occur is known as a _____ material
    fissionable
  125. What are the two nuclides present in large amounts in the fuel of some reactors with large resonant peaks that dominate the Doppler Effect?
    U238 Pu240
  126. The time in minutes required to change the reactor power by a factor of 10, expressed in DPM, which is a measure of the rate of change of reactor power is known as the _____
    Start Up Rate SUR
  127. Which electrons have the higher energy, the inner or outer electrons
    Outer
  128. The energy equivalent of the mass defect is also known as the ______
    Binding Energy
  129. The name given to the strong attractive force in the nucleus between two adjacent nucleons is known as the ____
    Strong Nuclear Force
  130. The average distance that a neutron travels before an interaction occurs is known as the ____
    Mean Free Path
  131. Given AZX define A, X, and Z
    • A = Nucleons and the Atomic Mass Number
    • X = The Atomic symbol
    • Z = The number of protons and Atomic Number
  132. Given an electrically neutral isotope 92U235, how many n, p+ and e- are there?
    • protons = 92
    • electrons = 92
    • neutrons = 143
  133. Any fission event that occurs independent of neutron induced fission is known as _______.
    Generally, this occurs in radioisotopes with very large atomic numbers.
    spontaneous fission
  134. Any particle that is part of the nucleus (neutrons and protons) is known as a ________
    nucleon
  135. Using the Chart of Nuclides, calculate the mass defect of Nickel-58
    • mass defect = (Z*hydrogen)+(A-Z)(neutron)-Matom
    • mass defect = (28*1.0078)+(58-28)(1.0087)-57.935348
    • mass defect = 28.2184 + 30.261 - 57.935348
    • mass defect = 0.544052 AMU
  136. The average energy required to remove a nucleon from the nucleus is known as the ____
    Binding Energy per Nucleon
  137. Define a thermal neutron
    A neutron in thermal equilibrium with its surroundings
  138. The probability of an incident neutron interacting with a target nucleus per unit length of travel of the incident neutron (∑) and in units or cm-1 is known as the __________, while the measure of the probability that a given interaction will occur between a single target nucleus and an incident neutron is known as the _______ and is represented as (σ). This is defined as the effective area presented by the target nucleus to the incident neutron for a particular reaction (units of barns = 1 x 10-24cm2)
    Macroscopic cross section, microscopic cross section
  139. Given a sample of radioactive element containing 4.8x1024 atoms and a half-life of 1 day, how many atoms remain after 5 days?
    • 4.8x1024/25 = 1.5 x 1023
  140. Using your chart of nuclides, name the element Xe and determine the number of stable isotopes.
    Xe is Xenon and has 9 stable isotopes
  141. The decay heat produced by a reactor shutdown from full power is initially what % of thermal rated reactor power?
    ~ 6% to 7%
  142. Any fission that results in the production of 3 fission fragments is known as a ______. This is not as common as a regular fission where the nucleus splits into two masses of _____ sizes.
    Ternary fission, unequal
  143. The process where a high energy gamma (>1.02MeV) interacts with the electric field and is converted to mass (electrons and positrons) is known as ______. Mid energy reactions with a photon, where some energy is transferred to the electron, the electron is knocked out and the gamma is scattered is known as ______. The low energy photon reaction, where the total energy of the γ is absorbed by the electron and the electron is ejected is known as ______
    pair production, compton scattering, photoelectric effect
  144. What is the cutoff for the time in which a prompt neutron is produced? What is the average time for the production of a delayed neutron?
    • Prompt < 1x10-14 seconds
    • Delayed 12.7 second
  145. In the 6 factor formula, the factor f represents which factor. expressed as
    f=thermal neutrons absorbed in fuel / thermal neutrons absorbed in core
    Thermal Utilization Factor
  146. When a reactor has a keff=1 the reactor is ______.
    critical
  147. The ratio of fast neutrons that become thermal, divided by the number of fast neutrons that start to slow down is known as the _______, and is expressed as
    p=fast neutrons that become thermal/fast neutrons that start to slow down
    Resonance escape probability
  148. A control rod withdrawal results in the keff of a reactor changing from 0.975 to 0.980, calculate how much reactivity was added to the core, in pcm (percent milli)
    • ρ = keff - 1 / keff
    • 1 pcm = 1x10-5 Δk/k
    • ρ = 0.975 - 1 / 0.975 = -0.025641026
    • ρ = 0.980 -1 / 0.980 = -0.020408163
    • Δρ = 0.005232863
    • 523.2863 pcm
  149. What is the widening and flattening effect on resonance capture probability peaks for epithermal neutrons due to increased kinetic energy of target atoms resulting from increased fuel temperature?
    Doppler broadening
  150. What is the name given to the instantaneous amount of reactivity by which a reactor is sub-critical or would be from its present condition assuming all control rods are fully inserted except for the single rod with the highest integral worth and equilibrium Xe removed?
    Shutdown Margin
  151. What is the condition where the reactor period is reduced to the prompt neutron component? It is associated with rapid increase in neutron power.
    Prompt Critical
  152. What type of neutron is more likely to cause fast fission in U238?
    Prompt Neutrons
  153. What are the 3 factors that effect decay heat after a reactor is shutdown?
    • Pre-shutdown power level
    • How long the reactor has been operated
    • Time since last shutdown
  154. The condition in which the number of neutrons produced by fission in one generation is greater than the number of neutrons produced by fission in the previous generation is known as ______.
    Supercritical
  155. The factor by which the number of neutrons produced by fission in one generation must be multiplied by to determine the number of neutrons produced by fission in the next generation is know as the _______. In order to have a critical reactor this value must be _______, meaning that the reactor is able to sustain a chain reaction.
    Effective Multiplication Factor keff , 1

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