2 Chart of the Nuclides General Layout Each nuclide occupies a
square in a grid where Atomic number (Z) is plotted vertically
Number of neutrons (N) is plotted horizontally Heavily bordered
square at left side of each row gives Name Chemical symbol
Elemental Mass Thermal neutron absorptions cross section Resonance
integral
Slide 4
3 Chart of the Nuclides Nuclides on diagonal running from upper
left to lower right have same mass numbers, called isobars Colors
and shading used to indicate in chart squares used to indicate
relative magnitude of Half-lives Neutron absorption properties Four
different colors used Blue Green Yellow Orange
Slide 5
4 Chart of the Nuclides Background color of upper half of
square represents T 1/2 Background color of lower half of square
represents greater of the thermal neutron cross section or
resonance integral When nuclide is stable and thermal neutron cross
section is small or unknown, entire square is shaded grey Gray
shading also used for unstable nuclides having T 1/2 sufficiently
long (>5E8 yrs) to have survived from the time they were
formed
Slide 6
5 Chart of the Nuclides Some squares, such as 60 Co, 115 In,
and 116 In are divided Occurs when nuclide has one or more isomeric
or metastable states Has same A and Z, but different nuclear and
radioactive properties due to different energy states of the same
nucleus
Slide 7
6 Chart of the Nuclides Nuclide Properties Displayed on the
Chart Chemical Element Names and Symbols Same element names and
symbols as used on the Periodic Table of the Elements Atomic
Weights and Abundances Isotopic masses in AMUs are given for Stable
isotopes Certain long-lived, naturally occurring radioactive
isotopes Nuclides particle decay becomes a prominent mode
(>10%)
Slide 8
7 Chart of the Nuclides Isotopic Abundance Values on chart
given in atom percent Specified for 288 nuclides (266 stable and 22
radioactive) Half-lives Half-life listed below nuclide symbol and
mass number Units used pspicoseconds (1E-12 s) nsnanoseconds (1E-9
s) smicroseconds (1E-6 s) msmilliseconds (1E-3 s) sseconds mminutes
hhours ddays ayears
Slide 9
8 Chart of the Nuclides Background Color of Chart Square Upper
Half 1 day to 10 day orange >10 days to 100 days yellow >100
days to 10 years green >10 years to 5E8 years blue Background
Color of Chart Square Lower Half Refers to thermal neutron cross
section or resonance integral
Slide 10
9 Chart of the Nuclides Major Modes of Decay and Decay Energies
alpha particle - beta minus (negatron) + beta plus (positron) gamma
ray nneutron pproton ddeuteron ttriton electron capture ITisomeric
transition e - conversion electron - - double beta decay cluster
decay Ddelayed radiation
Slide 11
10 Chart of the Nuclides To understand decay schemes and
energies, look at chart square for 38 Cl - energies listed on 1 st
line in order of abundance energies listed on 2 nd line in order of
abundance Particle energies always given in MeV energies always
given in keV
Slide 12
11 Chart of the Nuclides When more than one decay mode
possible, modes listed on chart in order of abundance or intensity
Different modes of beta decay ( , +, - ) appear on separate lines
if intensity of one of the decay modes is 10% absolute intensity
with most abundant listed first.
Slide 13
12 Chart of the Nuclides When branching decay occurs by both -
and + and/or , and each decay is accompanied by emission, format
shown in 146 Pm square is used Metastable (or isomeric) state
frequently decays to ground by IT emission, followed by one or more
in cascade Internal conversion is process resulting from
interaction between nucleus and extra-nuclear electrons. Nuclear
excitation energy xfrd to orbital electron (usually K shell) and is
indicated by e -
Slide 14
13 Chart of the Nuclides Delayed emission indicated by symbol
D. When daughter product has too short of a half-life to have its
own spot on the chart or half-life is much shorter than that of the
parent nuclide, energy is listed with the parent
Slide 15
14 Chart of the Nuclides
Slide 16
15 Chart of the Nuclides
Slide 17
16 Radiation Classifications Introduction All radiation
possesses energy Inherent electromagnetic Kinetic particulate
Interaction results in some or all of energy being transferred to
surrounding medium Scattering Absorption
Slide 18
17 Radiation Classifications Ionizing or Non-Ionizing
Non-Ionizing Visible light Radio and TV Ionizing Particulate or
Photonic Particulate n Electromagnetic x
Slide 19
18 Radiation Classifications Directly or Indirectly Ionizing
Directly Ionizing Possesses charge Does not need physical contact
Indirectly Ionizing Does not have charge Needs physical
contact
Slide 20
19 Radiation Characteristics Alpha () Charge +2 Range 2-4 in.
(5 10 cm.) Shielding Paper Dead skin Hazard Internal Target Organ
Anything internal (living tissue)
Slide 21
20 Radiation Characteristics Beta ( ) Charge Negatron ( - ) -1
Positron ( + ) +1 Range Average 10 ft. Energy Specific 10 12
ft./MeV Shielding Plastic Wood Al, Cu Hazard Internal Target Organ
External eye (lens) Living tissue Low Z
Slide 22
21 Radiation Characteristics Gamma ( ) and X-Ray (x) Charge 0
Range Infinite Shielding Pb DU Hazard Internal Target Organ Living
tissue High Z
Slide 23
22 Radiation Characteristics Neutron (n) Charge 0 Range
Infinite Shielding H 2 0 Concrete Plastic Hazard Internal Target
Organ Living tissue Hydrogenous
Slide 24
23 Energy Transfer Mechanisms Ionization Removing bound e -
from electrically neutral atom or molecule by adding sufficient
energy to allow it to overcome its BE Atom has net positive charge
Creates ion pair consisting of negatively charged electron and
positively charged atom or molecule
Slide 25
24 Energy Transfer Mechanisms N N P+P+ P+P+ e-e- e-e- Ionizing
Particle Negative Ion N N Positive Ion P+P+ P+P+ e-e- e-e- e-e-
e-e-
Slide 26
25 Energy Transfer Mechanisms Excitation Process that adds
sufficient energy to e - such that it occupies higher energy state
than lowest bound energy state Electron remains bound to atom No
ions produced, atom remains neutral After excitation, excited atom
eventually loses excess energy when e - in higher energy shell
falls into lower energy vacancy Excess energy liberated as X-ray,
which may escape from the material, but usually undergoes other
absorptive processes
Slide 27
26 Energy Transfer Mechanisms N N N NN + + + + e-e- e-e- e-e-
e-e- e-e- e-e- e-e- e-e- e-e- e-e-
Slide 28
27 Energy Transfer Mechanisms Bremsstrahlung Radiative energy
loss of moving charged particle as it interacts with matter through
which it is moving Results from interaction of high-speed, charged
particle with nucleus of atom via electric force field With
negatively charged electron, attractive force slows it down,
deflecting from original path KE particle loses emitted as x-ray
Production enhanced with high-Z materials (larger coulomb forces)
and high-energy e - (more interactions occur before all energy is
lost)
Slide 29
28 Energy Transfer Mechanisms N N N NN + + + + e-e- e-e- e-e-
e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e-
Slide 30
29 Directly Ionizing Radiation Charged particles dont need
physical contact with atom to interact Coulombic forces act over a
distance to cause ionization and excitation Strength of these
forces depends on: Particle energy (speed) Particle charge Absorber
density and atomic number Coulombic forces significant over
distances > atomic dimensions For all but very low physical
density materials, KE loss for e - continuous because of Coulombic
force
Slide 31
30 Directly Ionizing Radiation Alpha Interactions Mass
approximately 8K times > electron Travels approximately 1/20 th
speed of light Because of mass, charge, and speed, has high
probability of interaction Does not require particles touchingjust
sufficiently close for Coulombic forces to interact Energy
gradually dissipated until captures two e - and becomes a He atom
from given nuclide emitted with same energy, consequently will have
approximately same range in a given material
Slide 32
31 Directly Ionizing Radiation Beta Interactions Interaction
between - or + and an orbital e - is interaction between 2 charged
particles of similar mass s of either charge lose energy in large
number of ionization and/or excitation events, similar to Due to
smaller size/charge, lower probability of interaction in given
medium; consequently, range is >> of comparable energy
Because s mass is small compared with that of nucleus Large
deflections can occur, particularly when low-energy s scattered by
high-Z elements (high positive charge on the nucleus) Consequently,
usually travels tortuous, winding path in an absorbing medium may
have Bremsstrahlung interaction resulting in X-rays
Slide 33
32 Indirectly Ionizing Radiation No charge and n No Coulomb
force field Must come sufficiently close for physical dimensions to
contact particles to interact
Slide 34
33 Indirectly Ionizing Radiation Small probability of
interacting with matter Why? Doesnt continuously lose energy by
constantly interacting with absorber May move through many atoms or
molecules before contacting electron or nucleus Probability of
interaction depends on its energy and absorbers density and atomic
number When interactions occur, produces directly ionizing
particles that cause secondary ionizations
Slide 35
34 Indirectly Ionizing Radiation Gamma absorption and x-rays
differ only in origin Name used to indicate different source s
originate in nucleus X-rays are extra-nuclear (electron cloud) Both
have 0 rest mass, 0 net electrical charge, and travel at speed of
light Both lose energy by interacting with matter via one of three
major mechanisms
Slide 36
35 Indirectly Ionizing Radiation Photoelectric Effect All
energy is lost happens or doesnt Photon imparts all its energy to
orbital e - Because pure energy, photon vanishes Probable only for
photon energies < 1 MeV Energy imparted to orbital e - in form
of KE, overcoming attractive force of nucleus, usually causing e -
to leave orbit with great velocity Most photoelectrons are
inner-shell e -
Slide 37
36 Indirectly Ionizing Radiation High-velocity e -, called
photoelectron Directly ionizing particle Typically has sufficient
energy to cause secondary ionizations Most photoelectrons are
inner-shell electrons
Slide 38
37 Indirectly Ionizing Radiation N N N NN + + + + e-e- e-e-
e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Gamma Photon (< 1 MeV)
Photoelectron
Slide 39
38 Indirectly Ionizing Radiation Compton Scattering Partial
energy loss for incoming photon Dominant interaction for most
materials for photon energies 200 keV 5 MeV Photon continues with
less energy in different direction to conserve momentum Probability
of Compton interaction with distance from nucleus most Compton
electrons are valence electrons Beam of photons may be randomized
in direction and energy, so that scattered radiation may appear
around corners and behind shields where there is no direct line of
sight to source Probability of Compton interaction with distance
from nucleus most Compton electrons are valence electrons
Slide 40
39 Indirectly Ionizing Radiation Pair Production Occurs when
all photon energy is converted to mass (occurs only in presence of
strong electric field, which can be viewed as catalyst) Strong
electric fields found near nucleus and are stronger for high-Z
materials disappears in vicinity of nucleus and - - + pair appears
Will not occur unless > 1.022 MeV Any energy > 1.022 MeV
shared between the - - + pair as KE Probability < photoelectric
and Compton interactions because photon must be close to the
nucleus
Slide 41
40 Indirectly Ionizing Radiation N N N NN + + + + e-e- e-e-
e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Gamma
Photon (E > 1.022 MeV) e+e+ e+e+ e-e- e-e- Electron Positron
0.511 MeV Photons
Slide 42
41 Indirectly Ionizing Radiation Neutron Interactions Free,
unbound n unstable and disintegrates by - emission with half-life
of 10.6 minutes Resultant decay product is p +, which eventually
combines with free e - to become H atom n interactions energy
dependent classified based on KE CategoryEnergy Range Thermal~
0.025 eV (< 0.5 eV) Intermediate0.5 eV10 keV Fast10 keV20 MeV
Relativistic> 20 MeV
Slide 43
42 Indirectly Ionizing Radiation Classifying according to KE
important from two standpoints: Interaction with the nucleus
differs with n energy Method of detecting and shielding against
various classes are different n detection relatively difficult due
to: Lack of ionization along their paths Negligible response to
externally applied electric, magnetic, or gravitational fields
Interact primarily with atomic nuclei, which are extremely
small
Slide 44
43 Indirectly Ionizing Radiation Slow Neutron Interactions
Radiative Capture Radiative capture with emission most common for
slow n Reaction often results in radioactive nuclei Process is
called neutron activation
Slide 45
44 Indirectly Ionizing Radiation Charged Particle Emission
Target atom absorbs a slow n, which its mass and internal energy
Charged particle then emitted to release excess mass and energy
Typical examples include (n,p), (n,d), and (n, ). For example
Slide 46
45 Indirectly Ionizing Radiation Fission Typically occurs
following slow n absorption by several of the very heavy elements
Nucleus splits into two smaller nuclei, called primary fission
products or fission fragments Fission fragments usually undergo
radioactive decay to form secondary fission product nuclei There
are some 30 different ways fission may take place with the
production of about 60 primary fission fragments
Slide 47
46 Indirectly Ionizing Radiation Fast Neutron Interactions
Scattering Free n continues to be free n following interaction
Dominant process for fast n Elastic Scattering Occurs when n
strikes nucleus of approx. same mass Neutron can xfer much of its
KE to that, which recoils off with energy lost by n No emitted by
nucleus Recoil nucleus can be knocked away from its e - and, being
(+) charged, can cause ionization and excitation
Slide 48
47 Indirectly Ionizing Radiation N N N N e-e- e-e- P+P+
P+P+
Slide 49
48 Indirectly Ionizing Radiation Inelastic Scattering Occurs
when n strikes large nucleus n penetrates nucleus for short period
of time Xfers energy to nucleon in nucleus Exits with small
decrease in energy Nucleus left in excited state, emitting
radiation, which can cause ionization and/or excitation
Slide 50
49 Indirectly Ionizing Radiation e-e- e-e- e-e- e-e- e-e- e-e-
e-e- e-e- N N N N
Slide 51
50 Indirectly Ionizing Radiation Reactions in Biological
Systems Fast n lose energy in soft tissue largely by repeated
scattering interactions with H nuclei Slow 0 n 1 captured in soft
tissue and release energy in one of two principal mechanisms: (2.2
MeV) and (0.66 MeV)
Slide 52
51 Radioactivity and Radioactive Decay Following a
transformation, nucleus is usually more stable than it was, but not
necessarily stable Another transformation will take place by
nucleus emitting radiation Amount of energy given off and emission
type depends on nucleus configuration immediately before
transformation As nucleus energy , nucleus disintegrates or decays
Called radioactive decay Atom before decayparent Atom after
decaydaughter Steps from parent to daughter traced to stability
called decay chain
Slide 53
52 Radioactivity and Radioactive Decay Parent-Daughter
Relationships and Equilibrium Produces daughter product and
radiation is emitted Daughter also produces radioactivity when it
decays, as does each successive daughter until stability is reached
Activity contributed by the parent vs. daughters varies based on
half-life of both parent and daughters When activity production
rate is same as product decay rate, equilibrium is said to
exist
Slide 54
53 Radioactivity and Radioactive Decay Secular Equilibrium
1/2,P >> 1/2,D (Parent half-life infinitely > daughter) As
parent activity , daughter proportionately During 10 half-lives of
the daughter, essentially no parent decay takes place during
secular equilibrium Two conditions necessary Parent must have 1/2
much longer than any other nuclide in the series Sufficiently long
period of time must have elapsed to allow for in-growth of the
decay products Rule of Thumb Secular equilibrium is reached in 6
daughter half-lives.
Slide 55
54 Radioactivity and Radioactive Decay
Slide 56
55 Radioactivity and Radioactive Decay 1/2 = 6.57 h 1/2 = 15.3
m 1/2 = 53 m
Slide 57
56 Radioactivity and Radioactive Decay Transient Equilibrium
1/2,P > 1/2,D (Parent half-life > daughter, but not
infinitely) Daughter activity decays at same approx. rate as parent
Different way of saying daughter atom formation rate = daughter
atom decay rate Same fractional decrease in parent and daughter
activities Rule of Thumb Transient equilibrium is reached in 4
daughter half-lives.
Slide 58
57 Radioactivity and Radioactive Decay
Slide 59
58 Radioactivity and Radioactive Decay Transient Transient
1/2,P > 1/2,D, but not very long 1/2 = 12.75 d 1/2 = 1.68 d
Slide 60
59 Radioactivity and Radioactive Decay No Equilibrium 1/2,P
< 1/2,D Parent activity decays at faster rate than daughter
Equilibrium is never reached
Slide 61
60 Radioactivity and Radioactive Decay
Slide 62
61 Radioactivity and Radioactive Decay 1/2 = 3.1 m 1/2 = 27 m
1/2 = 19.9 m 1/2 = 23.3 y
Slide 63
62 Decay Modes and Emissions Alpha Decay () With few
exceptions, only relatively heavy nuclides decay by emission
Essentially a helium nucleus (2 p +, 2 n) Charge of +2
Slide 64
63 Decay Modes and Emissions p n
Slide 65
64 Decay Modes and Emissions Beta (Negatron) Decay ( - ) High
n:p ratio usually - decays n changed into p n:p ratio, results in -
emission Have same mass as e - Because n has been replaced by p, Z
1, but A remains unchanged
Slide 66
65 Decay Modes and Emissions Because n has been replaced by p,
Z 1, but A remains unchanged Standard notation for - decay is: For
example, 210 Pb - decays to produce 210 Bi as follows:
Slide 67
66 Decay Modes and Emissions p n
Slide 68
67 Decay Modes and Emissions Neutrinos and
anti-neutrinosneutral particles with negligible rest mass Travel at
speed of light and are non- interacting Account for energy
distribution among + (positrons) and - (negatrons)
Slide 69
68 Decay Modes and Emissions Nuclide having low n:p ratio)
tends to decay by positron emission Positron often mistakenly
thought of as positive electron In reality, positron is
anti-particle of electron (has charge of +1) + used to designate
positrons With positron emitters, parent nucleus changes p + into n
and emits a + Because p + replaced by n, Z 1 and A remains
unchanged Neutrino also emitted during + emission
Slide 70
69 Decay Modes and Emissions Standard notation for + decay is:
For example, 57 Ni + decays to produce 57 Co as follows:
Slide 71
70 Decay Modes and Emissions p n
Slide 72
71 Decay Modes and Emissions Electron Capture (EC) For
radionuclides with low n:p ratio, another decay mode, known as EC,
can occur Nucleus captures e - (usually from K shell) Could capture
L-shell electron, but K-electron capture much more probable Decay
frequently referred to as K-capture Can result in formation of
Auger e - In lieu of characteristic X-ray being emitted Atom ejects
bound e - Auger e - are monoenergetic
Slide 73
72 Decay Modes and Emissions Transmutation resembles positron
emission Electron combines with p + to form a n, followed by
neutrino emission Electrons from higher energy levels fill
vacancies left in inner, lower-energy shells Excess energy emitted
causes cascade of characteristic X-rays
Slide 74
73 Decay Modes and Emissions Gamma Emission () Decay resulting
in transmutation generally leaves nucleus in excited state Nucleus
can reach unexcited, or ground, state by emitting Gammas are type
of electromagnetic radiationbehave as small bundles or packets of
energy, called photons, and travel at speed of light
Slide 75
74 Decay Modes and Emissions essentially the same as X-ray
usually higher energy (MeV); whereas, X-rays usually in keV range
Basic difference between and X-ray is origin originate in nucleus,
X rays originate in electron shells General decay equation slightly
different from others Most decay reactions have emissions
associated with them Some decay by particulate emission with no
emission
Slide 76
75 Decay Modes and Emissions Isomeric Transition (IT) Commonly
occurs immediately after particle emission Nucleus may remain in
excited state for measurable period of time before dropping to
ground state Nucleus that remains excited known as isomer because
it is in a metastable state Differs in energy and behavior from
other nuclei with the same Z and A Generally achieves ground state
by emitting delayed (usually > 10 9 s)
Slide 77
76 Decay Modes and Emissions Internal Conversion An alternative
isomeric mechanism to radiative transition Excited nucleus of
-emitting atom gets rid of excitation energy Tightly bound e - (K
or L) interacts with nucleus by absorbing E excitation and is
ejected Electron known as conversion electron Distinguished from -
by energy Conversion e - monoenergetic - spectrum of energies
Slide 78
77 Decay Modes and Emissions Each radionuclide, artificial or
natural, has characteristic decay pattern Several aspects
associated with pattern: Decay modes Emission types Emission
energies Decay rate
Slide 79
78 Decay Modes and Emissions All nuclei of given radionuclide
seeking stability decay in specific manner 226 Ra decays by
emission, accompanied by only decay mode open to 226 Ra Some
nuclides may decay with branching, where a choice of decay modes
exists 57 Ni, mentioned previously, decays 50% by EC (K capture)
and 50% by + emission Nuclides decay in constant manner by emission
types, and emissions from each nuclide exhibit distinct energy
picture
Slide 80
79 Decay Modes and Emissions Single Ra nucleus may disintegrate
at once or wait 1000s of years before emitting an All that can be
predicted with certainty is 1/2 of all 226 Ra nuclei present will
disintegrate in 1,622 years Called the half-life Half-lives vary
greatly for naturally occurring radioisotopes
Slide 81
80 Natural Decay Series Uranium, radium, and thorium occur in
three natural decay series, headed by uranium-238, thorium-232, and
uranium 235, respectively In nature, in secular equilibrium
Slide 82
81 Natural Decay Series Uranium-238 (Radon-222) (Radon)
Slide 83
82 Natural Decay Series Uranium-235 (Radon-219) (Actinon)
Slide 84
83 Natural Decay Series Thorium-232 (Radon-220) (Thoron)
Slide 85
84 Radioactive Decay Law Decays at a fixed rate and is not a
function of temperature, pressure, etc. Half-life defined as amount
of time it takes for activity to be reduced to 1/2 the original
value Occurs at an exponential rate
Slide 86
85 Radioactive Decay Law
Slide 87
86 Radioactive Decay Law () n or e - t Can be expressed as () n
or e - t. When calculating half-life, units of time (t) must be the
same time units as the half-life () Radioactive Decay Formula or
Decay Constant ( ) Equivalent to natural log of 2 (ln 2) divided by
half- life ( 1/2 )
