
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)

Subatomic 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

Amount of kinetic energy (eV) gained by an electron when accelerated through an electric potential difference of 1 volt
Electron Volt (eV)

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

A nucleus of the same element (same number of protons) with a different number of neutrons.
Isotopes

Subatomic particle that makes up an atom, has a mass of 1.00866 AMU, a neutral charge, and is located in the nucleus.
Neutron

Any particle that is part of the nucleus of an atom, neutrons and protons
Nucleon

Any atom containing a unique combination of neutrons and protons in the nucleus.
Nuclide

Subatomic particle that makes up an atom, has a mass of 1.00727 AMU, a positive charge, and is located in the nucleus.
Proton

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)

Average energy required to remove a nucleon from the nucleus.
Binding Energy (BE) Per Nucleon

The attractive or repulsive force that exist between two objects due to their electrical charge.
Electrostatic Force

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

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)

The conversion factor equating mass to energy
MassEnergy Equivalence

The strong attractive force in a nucleus between to adjacent nucleons.
Nuclear Force

The inherent ability of an atom to resist changing its atomic structure or energy level.
Nuclear Stability

The process by which an unstable nucleus spontaneously transmutes from one form to another to reach a more stable state.
Radioactive Decay

The unstable nucleus of an atom immediately following the absorption of a neutron.
Compound Nucleus

The new nucleus present after the decay event.
Daughter Nuclide

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

The probability per unit time that a decay event will occur within a radioactive sample
Decay Constant

The rate at which the atoms of a sample of radioactive material disintegrates.
Decay Rate

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

Any condition that results in an atom being electrically charged or at an energy level above its ground state energy.
Excited State Energy

Highly excited radionuclides that are the result of a fission event and generally initiate a decay chain with beta decay.
Fission Fragments

Any electron that is not electrically bound to an atom’s nucleus.
Free Electron

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

The normal energy level of an atom when it is electrically neutral and not influenced by any outside energy inputs.
Ground State Energy

The time required for a radioactive sample to decay to one half of its original value.
HalfLife

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

An atom or a group of atoms that has acquired a net electric charge by gaining or losing one or more electrons.
Ion

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

The energy required to remove one or more electrons from an atom
Ionization Energy

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

The original nucleus that decays
Parent Nuclide

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

The process by which an unstable nucleus spontaneously transmutes from one form to another to reach a more stable state.
Radioactive Decay

Any fission event that occurs independent of neutron induced fission. Generally occurs in radioisotopes with atomic numbers of 92 and above.
Spontaneous Fission

Any of the radionuclides with atomic numbers greater than 92.
Transuranic Element

A bundle of energy (photon) emitted from the electron shell of an excited atom.
XRay

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

Unit of measurement, where 1 barn is equal to 1 ´ 10‑24 square centimeters
Barn

The minimum amount of energy required for fission to occur in a specific fuel type.
Critical Energy (Ec)

A neutron born more than 1 ´ 10‑14 seconds after a fission event.
Delayed Neutron

The delayed energy released by decay of the fission fragments after reactor shutdown.
Decay

A neutron that has a kinetic energy greater than 0.1 MeV.
Fast Neutron

A fuel type that will fission due to the binding energy of an incident neutron.
Fissile Material

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

A neutron emitted as a direct result of the fission process.
Fission Neutron

Any particle created as the result of a fission event.
Fission Product

A fuel type that requires kinetic energy in addition to binding energy of an incident neutron for fission to occur.
Fissionable Material

A neutron that has a kinetic energy between 0.1 MeV and 1 eV
Intermediate Neutron

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

The average distance a neutron travels before an interaction occurs.
Mean Free Path

The probability that a given interaction will occur between a target nucleus and neutron (barns or cm2).
Microscopic Cross Section

A neutron that is emitted within 1014 seconds of a fission event and is a direct result of the fission process (fission neutron).
Prompt Neutron

A neutron that has a kinetic energy less than 1 eV.
Slow Neutron

A neutron that is produced independently of neutron induced fission.
Source Neutron

Any fission that results in the production of three fission fragments.
Ternary Fission

A neutron that is in thermal equilibrium with its surroundings.
Thermal Neutron

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

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)

The ratio of fast neutrons produced from all fission events divided by fast neutrons produced by thermal fission events.
Fast Fission Factor (e)

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 NonLeakage Probability

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

The fractional change in fission neutron population per generation, or the measure of the departure of a reactor from criticality
Reactivity

The ratio of fast neutrons produced by thermal fission events divided by the number of thermal neutrons absorbed in the fuel.
Reproduction Factor

The ratio of fast neutrons that become thermal divided by the number of fast neutrons that start to slow down.
Resonance Escape Probability

Used to describe the processes that occur during the neutron life cycle.
Six Factor Formula

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

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

The ratio of the number of thermal neutrons absorbed in the core divided by the number of fast neutrons that become thermal.
Thermal NonLeakage Factor

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

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

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

The average time between the absorption of a neutron which causes fission and the absorption of resultant neutrons
Average Neutron Generation Time

A reactivity unit related to a dollar of reactivity, where one cent is onehundredth of a dollar
Cent

The weighted average of the delayed neutron fractions for all fissile/fissionable nuclides in the reactor core
Core Average Delayed Neutron Fraction

A neutron born approximately 12.7 seconds after a fission event
Delayed Neutron

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

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

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

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 ($)

The time required for a reactor to double in power. DT is used to estimate reactor period (sec).
Doubling Time (DT)

The fraction of neutron induced fissions caused by delayed neutrons of a particular nuclide
Effective Delayed Neutron Fraction

The percentage of fissions that occur in the reactor for each particular fuel type present
Fission Fraction

The percentage of fissions that occur in the reactor for each particular fuel type present
Fission Yield

The average time required for onehalf of the atoms of a material to decay
HalfLife (T1/2)

Represents how long, on the average, a delayed neutron precursor will exist before decaying.
Mean Life

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

The initial rapid decrease in neutron population following a step insertion of negative reactivity
Prompt Drop

The initial rapid increase in neutron population following a step insertion of positive reactivity
Prompt Jump

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

The time, in seconds, required to change reactor power by a factor of e (2.718).
Reactor Period

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)

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

The reactivity coefficient that relates the change in reactivity due to a change in fuel temperature.
Doppler Coefficient or Fuel Temperature Coefficient

The reactivity coefficient that relates the change in reactivity due to a change moderator temperature
Moderator Temperature Coefficient

Discrete excitation energy levels exist within a nucleus
Resonance Energy

Reactivity coefficient that relates the change in reactivity due to a change in void fraction
Void Coefficient

The temperature decrease per unit time usually measured at the vessel skin, steam dome, and recirculation loop
Cooldown Rate

The reactor sustains a chain reaction with a stable neutron count rate and an infinite reactor period
Criticality

The heat generated in the core from the decay of fission products.
Decay Heat

The negative reactivity contributed to the core by the Doppler coefficient when the core void fraction is decreased using recirculation flow.
Doppler Defect

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

The temperature rise per unit time usually measured at the vessel skin, steam dome, and recirculation loop
Heatup Rate

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

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

The instantaneous amount of reactivity by which a reactor is subcritical or would be subcritical 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

______ scattering is the type of scattering reaction where kinetic energy raises the internal energy of the target nucleus.
Inelastic

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

Identify the 4 basic types of Radiation

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

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

What is the attractive or repulsive force that exists between two objects due to their electrical charge?
Electrostatic Force

At time t = 0, a radioactive sample contains 1x10^{10} atoms. After 31 days, the sample contains 3.6x10^{4} atoms. Determine the half life of the sample
t_{1/2}=1.7 days

When will a reactor respond to a set amount of added reactivity?
End of Life EOL

The departure from criticality can be used to describe what?
reactivity

What is the Effective Delayed Neutron Fraction B_{eff}?
The fraction of neutron induced fission caused by delayed neutrons of a particular nuclide

When a reactor has reached an equilibrium in the number of neutrons produced from one generation to another (the reactor is critical k_{eff}=1), what is the reactivity?
0

A neutron that has kinetic energy less than 1 eV is know as a ______
slow neutron

A neutron that has a kinetic energy greater than 0.1 MeV is known as a _______
Fast neutron

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

What are the two nuclides present in large amounts in the fuel of some reactors with large resonant peaks that dominate the Doppler Effect?
U^{238} Pu^{240}

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

Which electrons have the higher energy, the inner or outer electrons
Outer

The energy equivalent of the mass defect is also known as the ______
Binding Energy

The name given to the strong attractive force in the nucleus between two adjacent nucleons is known as the ____
Strong Nuclear Force

The average distance that a neutron travels before an interaction occurs is known as the ____
Mean Free Path

Given ^{A}_{Z}X define A, X, and Z
 A = Nucleons and the Atomic Mass Number
 X = The Atomic symbol
 Z = The number of protons and Atomic Number

Given an electrically neutral isotope _{92}U^{235}, how many n, p^{+} and e^{} are there?
 protons = 92
 electrons = 92
 neutrons = 143

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

Any particle that is part of the nucleus (neutrons and protons) is known as a ________
nucleon

Using the Chart of Nuclides, calculate the mass defect of Nickel58
 mass defect = (Z*hydrogen)+(AZ)(neutron)M_{atom}
 mass defect = (28*1.0078)+(5828)(1.0087)57.935348
 mass defect = 28.2184 + 30.261  57.935348
 mass defect = 0.544052 AMU

The average energy required to remove a nucleon from the nucleus is known as the ____
Binding Energy per Nucleon

Define a thermal neutron
A neutron in thermal equilibrium with its surroundings

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^{24}cm^{2})
Macroscopic cross section, microscopic cross section

Given a sample of radioactive element containing 4.8x10^{24} atoms and a halflife of 1 day, how many atoms remain after 5 days?
 4.8x10^{24}/2^{5} = 1.5 x 10^{23}


Using your chart of nuclides, name the element Xe and determine the number of stable isotopes.
Xe is Xenon and has 9 stable isotopes

The decay heat produced by a reactor shutdown from full power is initially what % of thermal rated reactor power?
~ 6% to 7%

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

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

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

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

When a reactor has a k_{eff}=1 the reactor is ______.
critical

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

A control rod withdrawal results in the k_{eff }of a reactor changing from 0.975 to 0.980, calculate how much reactivity was added to the core, in pcm (percent milli)
 ρ = k_{eff}  1 / k_{eff}
 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

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

What is the name given to the instantaneous amount of reactivity by which a reactor is subcritical 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

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

What type of neutron is more likely to cause fast fission in U^{238}?
Prompt Neutrons

What are the 3 factors that effect decay heat after a reactor is shutdown?
 Preshutdown power level
 How long the reactor has been operated
 Time since last shutdown

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

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 k_{eff} , 1

