radiographic testing ndt
TRANSCRIPT
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Radiographic Testing
Compiled for ASNT by
Bahman ZoofanThe Ohio State University
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Level I
Radiographic Testing
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Lesson 1
Introduction to
Radioraphic Testin
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Radioraphy
!" In radioraphy# test ob$ects are
e%posed to &'rays# amma rays
or neutrons# and an imae isproduced"
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Radioraphy
(" Radioraphy is used to test a
variety of products# such as
castins# forins and )eldments" Itis also used heavily in the
aerospace industry for the detection
of crac*s in airframe structures#
detection of )ater in honeycombstructures and detection of forein
ob$ects"
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Advantaes of Radioraphic Testin
!" Radioraphy can be used on most
materials"
(" Radioraphy provides a permanentrecord of the test ob$ect"
+" Radioraphy reveals discontinuities
)ithin a material"
," Radioraphy discloses fabrication errors
and often indicates the need for
corrective action"
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-imitations of Radioraphic Testin
!" The radiorapher must have
access to both sides of the test
ob$ect"(" .lanar discontinuities that are
not parallel to the radiation beam
are difficult to detect"
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-imitations of Radioraphic Testin
+" Radioraphy is an e%pensive
testin method"
," /ilm radioraphy is timeconsumin"
0" Some surface discontinuities or
shallo) discontinuities may bedifficult# if not impossible# to
detect"
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Test Ob$ective
The ob$ective of radioraphic testin
is to ensure product reliability"
.erformin the actual radioraphictest is only part of the procedure"
The test results must then be
interpreted to acceptance standards
by 1ualified personnel# and anevaluation of the results must be
made"
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Safety Considerations
Radiation can cause damae to the
cells of livin tissue# so it is
essential that personnel be a)areand protected" Compliance )ith
state and federal safety reulations
is mandatory"
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2ualification
!" It is important that personnel
responsible for radioraphic
testin have ade1uate trainin#education and e%perience"
(" 3uidelines are for the
1ualification and certification ofnondestructive testin personnel"
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2ualification
+" ASNT has published uidelines
for trainin and 1ualifyin
nondestructive testin 4N5T6personnel" These uidelines are
*no)n as Recommended
Practice No. SNT-TC-1A:
Personnel Qualification andCertification in Nondestructive
Testing.
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2ualification
," Recommended Practice No.
SNT-TC-1Adescribes the
*no)lede and capabilities ofN5T personnel in terms of
certification levels"
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2ualification
0" .er SNT-TC-1A# there are three basic levelsof 1ualification applied to N5T personnel7
a" -evel I"
b" -evel II"
c" -evel III"
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Certification
!" The formal certification of a person
in N5T to a -evel I# -evel II and
-evel III is a )ritten testimony thatthe individual has been properly
1ualified"
(" Certification is meant to document
the actual 1ualification of the
individual in a specific N5T method"
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Certification
+" .roper 1ualification and
certification are e%tremely
important in modernmanufacturin# fabrication and
inservice inspection due to the
impact on the health and safety
of the public"
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Lesson 2
Radioraphic Testin .rinciples
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.enetration and
5ifferential Absorption!" &'rays and amma rays have
the ability to penetrate materials#
includin materials that do nottransmit liht"
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.enetration and
5ifferential Absorption(" 5ependin on the thic*ness and
density of the material# and the
intensity of the source bein used#the amount of radiation that is
transmitted throuh the test ob$ect
)ill vary"
+" The radiation transmitted throuhthe test ob$ect produces the
radioraphic imae"
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.enetration and
5ifferential Absorption," The follo)in fiure illustrates
the partial absorption
characteristics of radiation"Thic*er portions of the test ob$ect
or dense inclusions )ill appear
lihter because of more
absorption of the radiation"
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.enetration and
5ifferential Absorption
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3eometric 8%posure .rinciples
!" A radioraph is a shado) picture of
a test ob$ect placed bet)een the
film9detector and the &'ray oramma radiation source"
(" If the film9detector is placed too far
from the test ob$ect# the imae )illbe enlared"
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3eometric 8%posure .rinciples
+" If the test ob$ect is too close to
the source# the imae )ill be
reatly enlared# resultin in theloss of resolution"
," The deree of enlarement )ill
vary accordin to the relativedistances of the test ob$ect from
the film9detector"
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3eometric 8%posure .rinciples
0" As sho)n in the follo)in fiure#
the imae enlarement Df 9D:is
e1ual to the ratio df 9d:"
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3eometric 8%posure .rinciples
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/ilm95etector Imae Sharpness
!" The sharpness of a radioraphic imae isdetermined by7
a" The si;e of the radiationsource"
b" The ratio of the ob$ect'to'film9detector distance"
c" The source'to'ob$ectdistance"
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/ilm95etector Imae Sharpness
(" The unsharpness or fu;;iness
around an imae is called
geometric unsharness4enum!ra6# as sho)n in the
follo)in fiure"
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/ilm95etector Imae Sharpness
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/ilm95etector Imae Sharpness
+" To minimi;e the eometric
unsharpness 4"g6 around the
imae# the test ob$ect should beplaced as close to the film9detector
as possible"
,"
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/ilm95etector Imae Sharpness
0" 3eometric unsharpness can be
calculated usin the follo)in
formula7"g= #d$D
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/ilm95etector Imae Sharpness
a" "grepresents the eometric
unsharpness 4in millimeters or
inches6"b" #is the source si;e 4the
ma%imum pro$ected dimension
of the radiation source# oreffective focal spot si;e6"
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/ilm95etector Imae Sharpness
c" Dis the distance from the
source of the radiation to the
ob$ect bein radioraphed"d" dis the distance from the
source side of the test ob$ect
to the film9detector"
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/ilm95etector Imae Sharpness
>" Optimum eometric unsharpness of
the imae is obtained )hen7
a" The radiation source is small"b" The distance from the source
to the test ob$ect is relatively
lare"c" The distance from the test
ob$ect to the film9detector plane
is small"
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Imae 5istortion
T)o possible causes of radioraphic imaedistortion are7
!" The test ob$ect and thefilm9detector plane are not
parallel"
(" The radiation beam is not
directed perpendicular to the
film9detector plane"
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&'Radiation and 3amma Radiation
!" &'rays and amma rays are part
of the electromanetic spectrum"
(" These rays have hih eneryand short )avelenths"
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&'Rays
The conditions re1uired to enerate&'rays are7
!" A source of electrons"(" A suitable taret for electrons to
stri*e"
+" A means of speedin theelectrons in the desired direction"
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&'Rays
Characteristic X-rays7 ?hen an
electron from a hiher enery level
interacts )ith an electron in a lo)erenery orbit of an atom# then
characteristic &'rays may be
enerated"
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&'Rays
Continuous radiation:The
enerated &'rays have a
continuous enery spectrum andare not entirely dependent on the
disturbed atom@s characteristics"
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&'Rays
Bremsstrahlung radiation7 This is
a 3erman name for bra*in or
continuous radiation"
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&'Rays
Ke !"ilo-electron volts#7 This unit
corresponds to the amount of
*inetic enery that an electron)ould ain )hen movin bet)een
t)o points that differ in voltae by
! *"
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&'Rays
$e !1 %%% %%% electron volts#7
This unit corresponds to the
amount of *inetic enery anelectron ains )hen movin
bet)een t)o points that differ in
voltae by !
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8lectron Source
!" ?hen a suitable material is heated#
some of its chared neative
particles 4electrons6 become aitatedand escape the material as free
electrons"
(" Cathode7 In an &'ray tube# a coil of
)ire or filament 4*no)n as thecathode6 serves as the electron
source"
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8lectron Taret
/or industrial radioraphy
applications# a solid material of hih
atomic number# usually tunsten# isused as the taret in the tube
anode"
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8lectron Acceleration
!" By placin a positive chare on
the anode of an &'ray tube and a
neative chare on the cathode#free electrons are accelerated
from the cathode to the anode"
(" The electron path should occur in
a vacuum"
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Radiation Intensity
!" The number of &'rays created by
electrons stri*in the taret is
one measure of the intensity ofthe radiation"
(" Intensity depends on the number
of electrons available at the
cathode of the &'ray tube"
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Radiation Intensity
+" eepin the other factors constant#
an increase in the current throuh
the tube filament )ill increase thecathode temperature# causin
emission of more electrons and
conse1uently increasin the
intensity of the &'ray beam"
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Radiation Intensity
," Similarly# thouh to a lesser
deree# an increase in the
applied tube voltae )illincrease the beam intensity"
0" The output ratin of an &'ray
tube is e%pressed in volts 4* or
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Inverse S1uare -a)
!" The intensity of an &'ray beam varies
inversely )ith the s1uare of the
distance from the radiation source# as
sho)n in the follo)in formula7
I!9I( = 5((95!(
(" This relationship is *no)n as the
inverse s%uare la&')here I!and I(arethe received radiation intensities at
distances 5!and 5("
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&'Ray 2uality Characteristics
!" The spectrum of continuous
&'rays covers a )ide band of
)avelenths# as sho)n in thefollo)in fiure"
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&'Ray 2uality Characteristics
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&'Ray 2uality Characteristics
(" An increase in applied voltae in
an &'ray tube increases the
intensity 41uality6 of &'rays" Thisproduces hiher enery rays )ith
reater penetratin po)er"
+" &'rays )ith hiher enery4shorter )avelenths6 are called
hard (-ra)s"
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&'Ray 2uality Characteristics
," &'rays )ith lo)er enery 4loner
)avelenths6 are called soft
(-ra)s"0" ariation in tube current chanes
the intensity of the beam# but the
spectrum of )avelenths
produced remains unchaned#
as seen in the follo)in fiure"
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&'Ray 2uality Characteristics
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&'Ray 2uality Characteristics
>" 8ffects of chanes in *ilovoltae
and tube current on the produced
&'rays are summari;ed in thefollo)in table"
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8ffects of ilovoltae and Amperae
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Interaction ?ith
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Interaction ?ith
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.hotoelectric Absorption
!" In photoelectric absorption# )hen
&'rays 4photons6 )ith relatively lo)
enery pass throuh matter# thephoton enery may be transferred
to an orbital electron" 4See the
follo)in fiure"6
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.hotoelectric Absorption
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.hotoelectric Absorption
(" .art of the enery is e%pended in
e$ectin the electron from its
orbit# and the remainder ivesvelocity to the electron"
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.hotoelectric Absorption
+" This phenomenon usually ta*es
place )ith lo) enery photons of
:"0
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Compton 8ffect
!" ?hen hiher enery photons 4:"! to
+
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Compton 8ffect
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Compton 8ffect
(" This process is repeated#
proressively )ea*enin the
photon# until the photoelectriceffect completely absorbs the last
photon"
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.air .roduction
.air production occurs only )ith
hiher enery photons of !":(
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.air .roduction
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Scatter Radiation
!" The ma$or components of scatter
radiation are the lo) enery rays
represented by photons )ea*enedin the Compton process"
(" Scatter radiation is lo)'level enery
content of random direction"
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Internal Scatter
!" Internal scatter is the scatterin
that occurs in the ob$ect bein
radioraphed" 4See the follo)infiure"6
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Internal Scatter
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Internal Scatter
(" Internal scatter affects imae
definition by blurrin the imae
outline"+" Buildupoccurs )hen scatter in
the for)ard direction causes an
increase in radiation passin
throuh matter"
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Sidescatter
!" Sidescatter is the scatterin from
)alls of ob$ects in the vicinity of
the test ob$ect or from portions ofthe test ob$ect that causes rays to
enter the sides of the test ob$ect"
(" Sidescatter obscures the imae
outline $ust as internal scatterdoes"
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Bac*scatter
!" Bac*scatter is the scatterin of
rays from surfaces or from
ob$ects beneath or behind thetest ob$ect" 4See the follo)in
fiure"6
(" Bac*scatter also obscures the
test ob$ect imae"
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Bac*scatter
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3amma Rays
!" 3amma rays are produced by
the disinteration of the nuclei of
a radioactive isotope"(" Isotopes are varieties of the
same chemical element havin
different atomic )eihts"
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3amma Rays
+" The )avelenth and intensity of
amma )aves are determined by
the source isotope characteristicsand cannot be controlled or
chaned"
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Natural Isotope Sources
!" Some heavy natural elements
disinterate because of their
inherent instability"(" Radium is the best *no)n and
most used natural radioactive
source"
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Natural Isotope Sources
+" Natural radioactive sources
release enery in the form of7
a" 3amma rays"b" &lpha particles7 .ositively
chared particles havin
mass and chare e1ual in
manitude of a helium nuclei"
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Natural Isotope Sources
c"Beta particles7 Neativelychared particles havin thesame chare and mass of theelectron"
," The penetratin po)er of alpha
and beta particles is relatively
neliible"
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Artificial Sources
!" There are t)o )ays of
manufacturin radioactive
isotopes# or so'calledradioisotoes7
a" By usin the by'product of
nuclear fission in atomic
reactors# such as cesium'!+4Cs'!+6"
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Artificial Sources
b" By bombardin certainelements )ith neutrons toma*e them unstable" 8%amples
include7
i" Cobalt'>: 4Co'>:6"
ii" Thulium'!: 4Tm'!:6"
iii" Selenium'0 4Se'06"iv" Iridium'!D( 4Ir'!D(6"
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Artificial Sources
(" These artificial isotopes emit
amma rays# as )ell as alpha
and beta particles"
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3amma Ray Intensity
!" The activity of a amma ray
source determines the intensity
of its radiation"(" The measure of activity is the
curie# )hich is +" & !:!:
bec1uerel 4B16 or disinterations
per second"
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Specific Activity
!" Specific activity is defined as the
deree of concentration of
radioactive material )ithin aamma ray source"
(" Specific activity is e%pressed in
terms of curies per ram or
curies per cubic centimeter"
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Specific Activity
+" Specific activity is an important
measure of radioisotopes
because the smaller the source#the sharper the radioraphic
imae that can be produced 4as
sho)n in the follo)in fiure6"
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Specific Activity
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Ealf -ife
!" The lenth of time re1uired for
the activity of a radioisotope to
decay to one half of its initialintensity is called its half life"
(" The half life of a radioisotope is a
basic characteristic and depends
on the particular isotope of a
iven element"
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Ealf -ife
+" 5ated decay curves 4similar to
the one sho)n in the ne%t slide6
are supplied by source suppliersfor each particular radioisotope
and should be used by
radioraphers to determine the
e%act source intensity"
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5ated 5ecay Curve
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3amma Ray 2uality Characteristics
!" Radiation from a amma ray
source consists of rays )hose
)avelenths and enery are
determined by the nature of the
source"
(" 8ach of the commonly used
radioisotopes has a specificapplication because of the fi%ed
amma enery characteristics"
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3amma Ray 2uality Characteristics
+" The table on the ne%t slide lists the
most common radioisotopes for
radioraphy and their e1uivalentenery"
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Common Radioisotopes
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3amma Ray 2uality Characteristics
," 3amma rays and &'rays have
identical propaation
characteristics# and both conform
to the inverse s1uare la)"
0" The mechanism of interaction of
amma rays )ith matter is
identical to those discussed for &'rays"
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Lesson '
81uipment
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&'Ray 81uipment
There are three basic re1uirementsfor the eneration of &'rays7
!" A source of free electrons"(" A means of rapidly acceleratin
the beam of electrons"
+" A suitable taret material to stop
the electrons"
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.ortable &'Ray Units
In field radioraphy 4inspection of
pipelines# brides# vessels and
ships6# portable &'ray units are veryimportant" The characteristics of
these tubes are7
!" -iht)eiht"
(" Compact"
+" Usually air'cooled"
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&'Ray Tube
!" The main components of &'raye1uipment are the follo)in7
a" Tu(e7 8nclosed in a hih'vacuum envelope of heat'
resistant lass or ceramic"
b" Cathode7 To produce free
electrons"
c" &node7 Taret )hich the
electrons stri*e"
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&'Ray Tube
(" Associated )ith the tube are the
follo)in parts7
a" 81uipment that heats thefilament# accelerates and
controls the resultant free
electrons"
b" 81uipment to remove the heat
enerated by the &'rays"
c" Shieldin of the e1uipment"
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&'Ray Tube
+" There are many varieties in the
si;e and shape of &'ray tubes"
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Tube 8nvelope
!" A tube envelope is constructed oflass or ceramic that has7
a" A hih meltin point"
b" Sufficient strenth"
(" /or the follo)in reasons# a
hih'vacuum environment for
the tube element is necessary"
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Tube 8nvelope
a" .revents o%idation of the
electrode material"
b" .ermits ready passae of theelectron beam )ithout ioni;ation
of as )ithin the tube"
c" .rovides electrical insulation
bet)een the electrodes"
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Cathode
The cathode of an &'ray tubeconsists of7
!" )ocusing cup7 /unctions as anelectrostatic lens"
(" )ilament7 A coil of tunsten )irethat produces a cloud of electrons
by flo)in an electrical currentthrouh it"
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/ilament Eeatin
!" A small flo) of current throuh the
filament is enouh to heat it to a
temperature that causes electron
emission"(" A chane in the number of emitted
electrons varies )ith the current flo)
throuh the filament"
+" The tube current# measured inmilliamperes 4mA6# controls the
intensity of &'rays"
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Anode
!" The anode of an &'ray tube is
usually made of copper"
(" Copper and tunsten are themost common anode materials"
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Anode
+" A dense taret material is
re1uired to ensure a ma%imum
number of collisions"
,"
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/ocal Spot
!" The imae sharpness is partly
determined by the si;e of the
focal spot"
(" The electron beam is focused so
that it bombards a rectanular
area of the taret"
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/ocal Spot
+" The pro$ected area of the
electron beam is the effective
focal spot 4as seen in the
follo)in slide6"
," The si;e to )hich the focal spot
can be reduced is limited by the
heat enerated in taretbombardment"
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8ffective /ocal Spot
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-inear Accelerators
There are t)o types of linear
accelerators7
!" Standin )ave linear acceleratorfor enery up to (::
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&'Ray Beam Confiuration
!" Once the &'rays are created#
they cannot be focused or
other)ise directed"
(" The direction of useful
&'radiation is determined by the
positionin of the taret and the
lead shieldin"
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Acceleratin .otential
!" The applied potential bet)een the
cathode and anode determines the
penetratin effect of the produced &'
ray"
(" The hiher the voltae# the reater
the electron velocity alon )ith
shorter )avelenths and morepenetratin po)er for the enerated
&'rays"
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Iron Core Transformers
!" The ma$ority of &'ray e1uipment
for industrial radioraphy 4up to
,:: *6 use iron core
transformers"
(" Their basic limitations are their
si;e and )eiht"
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Eeat 5issipation
!" &'ray eneration is a very
inefficient process as most of the
electron enery is e%pended in
producin heat"
(" Eeat dissipation in the &'ray tube
is accomplished by a flo) of oil#
as or )ater"
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Eeat 5issipation
+" 8fficiency of an &'ray tube
coolin system is the main factor
in determinin the duty cycle of
the tube"
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81uipment Shieldin
!" To prevent un)anted radiation#
lead is used to shield the &'ray
tube"
(" Shieldin desin varies )ith
different &'ray tubes# but in all
cases# it serves to absorb that
portion of the radiation that is nottravelin in the desired direction"
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Control .anel
!" The control panel of an &'ray
system is desined to permit a
radiorapher to set the desired
e%posure parameters"
(" The control panel also provides
critical indications for tube
performance# such as the flo) ofoil or )ater in the coolin system"
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3amma Ray 81uipment
!" Eandlin and storae of amma ray
sources are e%tremely important
since they cannot be shut off"
(" The United States Nuclear
Reulatory Commission 4NRC6 and
various state aencies recommend
safety standards for propertransportation# storae and handlin
of radioisotopes"
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3amma Ray Sources
!" There are t)o types of amma
ray sources7
a" Natural isotopes"
b" Artificial isotopes"
("
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Radium
!" Radium is a natural radioactive
substance havin a half life of
about !>:: years"
("
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Radium
+" Because of its lo) specific
activity and its lon half life#
radium is rarely used in industrial
radioraphy"
f
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Artificial Radioisotopes
!" The artificial radioisotopes usedin industrial radioraphy forain purposes are7
a" Cobalt'>: 4Co'>:6"b" Iridium'!D( 4Ir'!D(6"
c" Selenium'0 4Se'06"
d" Thulium'!: 4Tm'!:6"e" Cesium'!+ 4Cs'!+6"
A ifi i l R di i
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Artificial Radioisotopes
(" The follo)in table ives a
summary of the main
characteristics of the most used
isotopes"
R di i t Ch t i ti
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Radioisotope Characteristics
I t C
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Isotope Cameras
!" The e1uipment to accomplish
safe handlin and storae of
radioisotopes is called a camera
or e+osure device"
(" These cameras are self'
contained units# meanin no
e%ternal po)er supply isre1uired"
I t C
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Isotope Cameras
+" The e%posure devices contain
self'loc*in mechanisms
ensurin safety in accordance
)ith ANSI and ISO re1uirements#
in addition to NRC and IA8A
re1uirements"
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Lesson *
Radioraphic /ilm
I t d ti
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Introduction
!" Radioraphic film consists of7
a" Base7 A thin# transparent plastic
sheet"
b" +mulsion coat7 A coat of an
emulsion of elatin about
:"::! in" 4:"::+ cm6 thic* on
one or both sides" The emulsioncoat contains very fine rains of
silver bromide 4ABr6"
I t d ti
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Introduction
("Latent !hidden# image7
8%posure of radiation on the film
that cannot be detected until
chemical processin occurs"
+"isi(le image7 Imae on the film
after developed by chemical
processin"
U f l f R di h
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Usefulness of Radioraphs
!" )ilm density7 5eree of
dar*enin on the developed film"
(" Radiographic contrast75ifference bet)een t)o film
areas" The dar*er area 4hiher
density6 has received more
radiation compared to the areaof liht density"
U f l f R di h
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Usefulness of Radioraphs
+" ,einition7 Sharpness of any
chane in film density"
," Contrast and definition areimportant for a successful
interpretation of radioraphs"
R di hi C t t
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Radioraphic Contrast
!" The film density Dis a loarithmic
value defined as7
D= lo!:4,-$,6)here 4,-6 is the intensity of the
incident liht to vie) the film# and ,
is the intensity of the transmitted
liht throuh the film" The hiher
the number# the dar*er the film"
R di hi C t t
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Radioraphic Contrast
(" If the intensity of liht is !:::
units and the film allo)s only one
unit of that intensity to pass
throuh# the film density based
on the previous e1uation )ill be7
D= lo!:4!:::9!6 = +
Radioraphic Contrast
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Radioraphic Contrast
+" Radioraphic contrast 4as sho)n
in the follo)in fiure6 is defined
as the difference in the film
density bet)een t)o selected
areas of the e%posed and
developed film"
Radioraphic Contrast
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Radioraphic Contrast
Radioraphic Contrast
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Radioraphic Contrast
," Eiher contrast is better for film
interpretation"
0" Radioraphic contrast is acombination of7
a" Sub$ect contrast"
b" /ilm contrast"
Radioraphic Contrast
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Radioraphic Contrast
>" Radioraphic contrast depends on7
a" Applied radiation enery
4penetratin 1uality6"b" Contrast characteristics of the
film"
c" Amount of e%posure 4the productof radiation intensity and
e%posure time6"
Radioraphic Contrast
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Radioraphic Contrast
d" /ilm screen"
e" /ilm processin"
f" Scattered radiation"
Sub$ect Contrast
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Sub$ect Contrast
!" Sub$ect contrast is the relative
radiation intensities passin
throuh any t)o selected
portions of material" Sub$ect
contrast depends on the
follo)in factors7
Sub$ect Contrast
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Sub$ect Contrast
a" Type and shape of the test
ob$ect"
b" 8nery of the applied eneryradiation 4)avelenth# type of
source6"
c" Scattered radiation"
Sub$ect Contrast
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Sub$ect Contrast
(" Sub$ect contrast decreases as
the )avelenth of the incident
radiation decreases"
Sub$ect Contrast
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Sub$ect Contrast
+" Eiher sub$ect contrast can beachieved by7
a" -arer thic*ness variation"
b" Use of different &'ray oramma ray eneries"
c"
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/ilm Contrast
!" #ilm contrastis the ability of film
to detect and record different
radiation e%posures as
differences in film density"
/ilm Contrast
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/ilm Contrast
(" The relationship bet)een the
amount of e%posure and the
resultin film density is
e%pressed in the form of film
characteristic curves and is
determined by the follo)in
factors7
/ilm Contrast
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/ilm Contrast
a" /ilm rain si;e"
b" Chemistry of the filmprocessin chemical"
c" Concentration of theprocessin chemicals"
d" 5evelopment time"
e" 5evelopment temperature"f" Aitation in the developer
solution"
/ilm Characteristic Curves
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/ilm Characteristic Curves
!" The fiure follo)in the ne%t slide
sho)s a film characteristic curve"
a" The vertical a%is is the
resultin film density"
b" The hori;ontal a%is is
e%pressed in a loarithm ofrelative e%posure"
/ilm Characteristic Curves
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/ilm Characteristic Curves
c" The minimum point of the curve
on the vertical a%is is called fog
densit)"
d" Based on this curve# as the
e%posure increases# film contrast
increases"
/ilm Characteristic Curves
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/ilm Characteristic Curves
/ilm Characteristic Curves
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/ilm Characteristic Curves
(" A film characteristic curve hast)o different sections7
a" A tail of lo)er densities"
b" A straihter portion 4)ith a
hiher slope on the curve6"
/ilm Characteristic Curves
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/ilm Characteristic Curves
+" Eih radioraphic contrast is
achieved )ith densities alon the
straiht portion of a characteristic
curve" This is the reason that films
should al)ays be e%posed for a
density of at least !"0"
/ilm Characteristic Curves
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/ilm Characteristic Curves
,"
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/ilm Speed
!" /ilm speed is an important
consideration in determinin the
proper e%posure time to obtain the
desired film density"
(" The ne%t fiure illustrates films
)ith hih# medium and lo)
speeds"
/ilm Speed
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/ilm Speed
/ilm Speed
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/ilm Speed
+" no)in film speed is important
)hen selectin film for each
particular radioraphic testin
tas*"
3raininess
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3raininess
!" 3raininess is the visible evidence of
the roupin into clumps of the
silver particles that form the imae
on the radioraphic film"
(" The follo)in fiure sho)s the
effect of rain variation on the
imae definition"
3raininess
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3raininess
3raininess
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3raininess
+" The deree of raininess of an
e%posed film depends on the
follo)in factors7
a" 3rain si;e"
b" The 1uality of the radiation"
c" /ilm processin conditions"
d" Type of film screens"
/ilm Selection /actors
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/ilm Selection /actors
!" ?hen not other)ise specified by
the customer or overnin
standards# the selection of film is
made by the radiorapher"
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/ilm Selection /actors
a" Need for certain contrast anddefinition 1uality"
b" Thic*ness and density of the
test ob$ect"c" The type of indication or
discontinuity normallyassociated )ith the ob$ect"
d" Si;e of an acceptableindication"
/ilm Selection /actors
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/ilm Selection /actors
e" Accessibility# location and
confiuration of the test ob$ect"
f" Customer re1uirements"
/ilm Selection /actors
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/ilm Selection /actors
(" In film selection# remember that7
a" /ilm contrast# film speed and
raininess are interrelated"
b" /aster films need shorter
e%posure time but usually
have larer rains and poor
resolution9sensitivity"
/ilm Selection /actors
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/ilm Selection /actors
c" Slo)er films need loner
e%posure time but have finer
rain and ood
resolution9sensitivity"
/ilm Selection /actors
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/ilm Selection /actors
d" /ilm manufacturers@
recommendations for film
selection are a useful tool in
selectin the proper film for aiven application"
/ilm .rocessin
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/ilm .rocessin
!" /ilm processin ma*es the latent
imae visible"
(" The follo)in eneral
precautions must be observed
durin film processin7
/ilm Selection /actors
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Se ec o ac o s
a" /ollo) manufacturer
recommendations for
chemical concentrations#
temperature and processintime"
b" Use e1uipment# tan*s# trays
and holders that can)ithstand the chemical action"
/ilm Selection /actors
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c" 8nsure tan*s are clean"
d" Use recommended safelihts#
and chec* them reularly"
e"
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The arranement of a tan*
processin 4manual processin6 unit
is sho)n in the ne%t slide"
Tan* .rocessin
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Tan* .rocessin
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!" The tan*s for processin solutions
and )ash )ater should be deep
enouh for the film to be
submered"(" The chemicals in the tan*s must
be stirred and the temperature
must be chec*ed )ith a calibratedthermometer before turnin off the
ambient liht"
Tan* .rocessin
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+" All re1uired e1uipment should be
arraned before turnin off the
ambient liht"
," All unnecessary materials shouldbe *ept a)ay from the
processin area"
Tan* .rocessin
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0" Test the safelihts and arrane
them for easy vie)in" /ollo)
the standard recommendations
for reular chec*in"
>" -oc* the door to the dar*room to
prevent accidental e%posure to
ambient liht"
Tan* .rocessin
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" To load the film inside the haners#
rasp it by its edes or corner to
avoid finerprints# bendin#
)rin*lin or crimpin durinhandlin"
F" eep the loadin area completely
dry"
D" /ollo) the tan* processin
procedures"
Tan* .rocessin .rocedures
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There are five separate steps in
tan* processin7
!" 5evelopin"
(" Stop bath"
+" /i%in"
," ?ashin"0" 5ryin"
5evelopin
-
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p
5evelopin is the chemical process
of reducin silver bromide particles
in the e%posed area of the film
emulsion to metallic silver"
5evelopin
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p
!" /ollo) the manufacturers@
recommendations for developin
temperature and time"
(" Aitate the film durin developin
to obtain a uniform development
and to avoid any air bubbles from
attachin to the film"
5evelopin
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p
+" Use strips of e%posed radioraphs
to control the developer activity as
a method of reular 1uality control
chec*in"," /ollo) the manufacturers@
recommendations to replenish the
solution"
Stop Bath
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The stop bath# a solution of acetic
acid and )ater# serves to remove
the residual developer solution from
the film"
!" Runnin uncontaminated )ater
for at least ( min" can be used
as an alternative to the stopbath"
Stop Bath
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("
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!" /i%er# an acidic solution# has t)o functions on thefilm7
a" It dissolves and removes the
silver bromide from theundeveloped portions of the film
)ithout affectin the developed
portion"b" It hardens the emulsion elatin"
/i%in
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(" The minimum time re1uired for
fi%in is t)ice the amount of time
necessary to clean the film"
+" /i%in time should not e%ceed
!0 min"
," Improper fi%in shortens the
archival lenth of the film"
/i%in
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0" /ilm should be aitated in fi%in
solution at ('min" intervals"
>" The replacement of fi%in
solution should be determined by
chec*in the acidity of the
solution"
?ashin
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After fi%in# )ashin is necessary to
remove the fi%er from the emulsion"
!" 8ach film is )ashed for a period of
time e1ual to t)ice the fi%in"
(" Eypo clearin aent may be used
to speed up film )ashin"
?ashin
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+" Best results for )ashin are
obtained )ith a )ater temperature
bet)een >0 and : G/ 4!F"+ and
(!"! GC6"
," To avoid any )atermar*s# film is
immersed in a )ettin aent that
also aids in reducin the dryintime"
5ryin
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The final stae of film processin is
dryin"
Automatic /ilm .rocessin
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Automatic film processin systems
are used )henever the volume of
)or* ma*es them economical"
Automatic /ilm .rocessin
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!" The entire processin cycle is
completed in less than !0 min"
(" Automatic film processin units
consistently produce radioraphs
of much hiher 1uality than those
obtained usin a manual process"
Automatic /ilm .rocessin
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+" -oadin the film inside the unit
should be done in a dar*
environment"
," .roperly maintainin the system
is the *ey for hih performance
of an automatic system"
5ar*room /acilities and 81uipment
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Some re1uirements that must besatisfied in the desin and
construction of a dar*room7
!" It must be lihted )ith suitable andtested safelihts"
(" It must be protected aainst
ambient liht from outside sources"
+" The )alls and ceilin must be
painted )ith lihtly colored#
semiloss paint"
5ar*room /acilities and 81uipment
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," 5ar*room floors are usually
covered )ith chemical resistant#
)aterproof and slip'proof
materials"
0" Cleanliness is of reat
importance durin the entire film
processin procedure"
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Lesson .
Safety
Introduction
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!" Radioraphers are cautioned to
be a)are of the latest effective
safety reulations"
(" Radiation safety practices are
based on the effects of radiation
on the human body and
characteristics of radiation"
Introduction
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+" .ersonnel protection is
dependent upon detection
devices# as )ell as the proper
use of time# distance andshieldin"
Introduction
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," Areement States are states that
observe the reulations coverin
use# handlin and transportation of
radioactive materials approved bythe Nuclear Reulatory
Commission 4NRC6"
Introduction
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0" All of the safety reulations are
desined to limit e%posure to the
radiorapher and to provide
protection to the eneral public"
Introduction
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>" The radiorapher# )ho is
employed by a licensee of NRC
or )ho is employed by a
licensee of an areement state#must have *no)lede of# and
comply )ith# all applicable
reulations"
Units of Radiation
5ose
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5ose
-
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5ose
-
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!" The roenten 4R6 or sievert 4Sv6 is
the physical unit of measure of the
ioni;ation of air by &'radiation or
amma radiation"
Roenten 4R6
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(" Roenten 4R6 is defined as the
1uantity of radiation that )ill
produce one electrostatic unit
4esu6 of chare in one cubiccentimeter of air at standard
temperature and pressure 4ST.6"
Roenten 4R6
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+" ! R of radiation e1uals absorption
by ioni;ation of about F+ er 4unit
of )or* or enery in physics6 of
radiation enery per ram of air"
," /or practical purposes# mR is
often used# )hich is7
! mR = !9!::: R"
Radiation Absorbed 5ose 4rad6
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!" Radiation absorbed dose 4rad6 is
the unit of measurement of
radiation absorption by humans"
(" It represents an absorption of
!:: er of enery per ram of
irradiated tissue"
Radiation Absorbed 5ose 4rad6
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+" ?hereas the roenten applies
only to &'rays and amma rays#
rad applies to any type of
radiation"
," /or &'ray and amma radiation#
e%posure to ! R results in ! rad"
Radiation Absorbed 5ose 4rad6
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0" The unit gra)43y6 has been
introduced as7 !:: rad = ! 3y"
2uality /actor
-
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!" 2uality factor ta*es into account
the bioloical effect of different
radiations on the human body"
2uality /actor
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(" 2uality factor values are
determined by the National
Committee on Radiation
.rotection" They are summari;edin the follo)in table"
2uality /actor
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Roenten 81uivalent
-
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!" Roenten e1uivalent mammal
4rem6 represents the radiation
absorbed dose 4rad6 multiplied
by the 1uality factor of the type ofradiation"
(" Radiation safety levels are
established in terms of roentene1uivalent mammal 4rem6"
Roenten 81uivalent
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+" Since the 1uality factor of
&'radiation and amma radiation
is !# then7
! rad = ! rem"
International System of Units
4SI6
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4 6
!" The Nuclear Reulatory
Commission# state reulations
and radioraphers in the U"S"
often still use the old 8nlishunits7 curie# roenten# rem and
rad"
International System of Units
4SI6
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4 6
(" 5ifferent orani;ations# such as thefollo)in# support the replacementof older units )ith SI units7
a" The National Institute of
Standards H Technoloy 4NIST6"
b" The American National
Standards Institute 4ANSI6"
c" The American Society for Testin
and
-
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4 6
d" The Institute of 8lectrical and
8lectronics 8nineers 4I8886"
e" The International Orani;ation for
Standardi;ation 4ISO6"
f" The American Society for
Nondestructive Testin 4ASNT6"
Bec1uerel Replaces Curie
-
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!" Curie 4Ci6 is the oriinal unit for
radioactivity# )hich is defined as7
+" & !:!:disinterations per
second"(" In SI# the unit for radioactivity is
the bec1uerel 4B16# )hich is !
disinteration per second"
Bec1uerel Replaces Curie
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+" ! Ci = + 3B1 4iabec1uerel6#
)here ia = !:D"
Coulomb per iloram
Replaces Roenten
-
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!" Coulomb 4C6 is the unit of
electrical chare# )here7
! C = ! ampere & ! s
(" ! R = (0F microcoulombs per
*iloram of air 4(0F CJ*K!of
air6"
3ray 43y6 Replaces Rad
-
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In the SI system# the unit of
radiation dose is the ray 43y6# and
! 3y = !:: rad"
Sievert 4Sv6 Replaces Rem
-
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In the SI system# the unit of
radiation absorbed by the human
body is the Sievert 4Sv6# and
! Sv = !:: rem"
-
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!" .ermissible dose is defined by
NIST as the dose of radiation that
is not e%pected to cause
appreciable bodily in$ury to aperson"
-
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(" The follo)in restrictions for the
ma%imum annual permissible
dose limits for classified )or*ers
should be observed7a" Total effective dose e1uivalent
bein e1ual to 0 rem 4:":0 Sv6"
-
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Or
b" The sum of the deep dose and
the committed dose
e1uivalent to any individualoran or tissue other than the
lens of the eye bein e1ual to
0: rem 4:"0 Sv6"
-
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c" The ma%imum dose absorbed
by the lens of the eye bein
!0 rem 4:"!0 Sv6"
d" A shallo) dose e1uivalent of0: rem 4:"0 Sv6 to the s*in of
the )hole body or to the s*in
of any e%tremity"
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+" The ma%imum annual radiation
dose is limited to 0 rem 4:":0 Sv6"
," The absorbed dose shouldn@t
e%ceed :"0 rem 40 mSv6 durin anentire prenancy"
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0" 5ose limits to the eneral public
shall not e%ceed :"::( rem or
( mrem 4:":( mSv6 per hour or
e%ceed :"0 rem or 0:: mrem40 mSv6 annually"
.rotection Aainst Radiation
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Safe radioraphic techni1ues and
radioraphic installation desin are
achievable by applyin these
principles7!" Time7 eep the time close to a
radiation source as lo) as
possible"
.rotection Aainst Radiation
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(" ,istance7 eep the distance
from a radiation source as hih
as possible"
+" /hielding7 eep ade1uateshieldin for the radiation source"
Allo)able ?or*in Time
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!" The amount of absorbed radiation
by the human body is directly
proportional to the time that the
body is e%posed to radiation"8%ample7 ( rem 4:"( mSv6 in
>: s = !: mrem 4! mSv6 in 0 min"
Allo)able ?or*in Time
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(" Allo)able )or*in time for )or*in
)ith amma sources is calculated
by measurin radiation intensity
and substitutin it in the follo)ine1uation7
allo&a!le &oring time in hr$&ee
/ermissi!le e+osure in Ci$&9
e+osure rate in Ci$h
?or*in 5istance
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!" The reater the distance from a
radiation source# the lo)er the
radiation intensity"
?or*in 5istance
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(" The inverse s1uare la) is used
to calculate radiation intensities
at various distances from a
radiation source7,1$,0= D00$D10
)here ,1and ,0are intensities at
distances D1and D0#respectively"
?or*in 5istance
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+" The same principles hold for
&'radiation" The intensity at a
*no)n distance )ith
predetermined current andvoltae settin 4usually iven by
the &'ray tube@s manufacturer6
can be determined by applyin
the inverse s1uare la)"
?or*in 5istance
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," Radiation intensity at any point is
the sum of the primary radiation
and the secondary 4scattered6
radiation at that point"
Shieldin
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!"
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(" Shieldin cannot stop all of the
enery of &'radiation or amma
radiationL therefore# it is practical
to measure shieldin efficiency interms of half value layers"
Shieldin
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+" Ealf value layer 4E-6 is that
amount of shieldin that )ill stop
half of the radiation of a iven
intensity"
Shieldin
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," Similarly# shieldin efficiency is
often measured in tenth value
layers" A tenth value layer is that
amount of shieldin that )ill stopnine tenths of the radiation of a
iven intensity" 4See the
follo)in tables"6
&'Ray Ealf alue -ayers
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3amma Ray Ealf andTenth alue -ayers
8%posure Area
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!" The e%posure area should consist
of a room )ith concrete or bloc*
)alls# lined )ith lead or other
suitable shieldin materials"(" An e%posure area can be an
enclosed shieldin cabinet lare
enouh for the test ob$ects and
)ith reliable safety features"
8%posure Area
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+" Controls should be located
outside the e%posure area"
," In field radioraphy# a safe
distance in relation to e%posuremust be secured by7
a" 3uard rails or ropes"
b" -eible radiation )arnin sins"c" Sufficient shieldin"
8%posure Area
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0" Only monitored radioraphers arepermitted in the radiation area"
>" eepin a safe distance from the
radiation source is the simplest andmost effective safety consideration
in field radioraphy"
Radiation .rotective Construction
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!" -ead and concrete are the most
common materials used to protect
aainst radiation"
(" Shieldin measurements areusually e%pressed in terms of
thic*ness"
Radiation .rotective Construction
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+" 8nsurin a lea*'proof shieldin is
very important"
," Sheets of lead must be
overlapped# and nails and scre)s
in the )alls must be covered )ith
ade1uate lead"
Radiation .rotective Construction
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0" .ipes# conduits and air ducts
passin throuh the )alls of the
shieldin must be completely
shielded" 4See the follo)infiure"6
Radiation .rotective Construction
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Radiation .rotective Construction
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>" The thic*ness of lead is dependent on t)o factors7
a" 8nery of the radiation source"
b" Occupancy of the surroundinareas"
" Other than lead# structural
materials such as concrete andbric* are often used as shieldin
materials"
Radiation .rotective Construction
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F" At voltaes reater than ,:: *#concrete is used as shieldin because7
a" Installin very thic* lead can bedifficult"
b" Thic* sheets of lead are cost'
prohibitive"
Radiation .rotective Construction
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c" Concrete is the best
alternative material because of
its property of radiation
protection and its simplicity ofconstruction"
3amma Ray Re1uirements
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!" Special radiation protection is
re1uired for amma radiation
based on t)o factors7
a" 3amma radiation cannot beshut off"
b" 3amma radiation has
considerable penetratin ability"
3amma Ray Re1uirements
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(" A combination of shieldin and
distance is usually used durin
amma radioraphy"
+" Specially labeled storaecontainers are necessary to
store amma sources )hen not
in use"
3amma Ray Re1uirements
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," After every use# readins )ith
survey meters are ta*en to ensure
the source is safely stored"
0" Special pro$ectors 4calledigs6 orisotope cameras containin heavy
shieldin made of lead or depleted
uranium should be used forhandlin radioisotope sources"
Nuclear Reulatory Commission
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!" The NRC reulates handlin#
storae and use of radioisotopes"
(" The ne%t t)o slides sho) NRC
/orm', and NRC /orm'0# used tomonitor the occupational dose
history"
Nuclear Reulatory Commission
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Nuclear Reulatory Commission
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Occupational Radiation
8%posure -imits
-i it ti i di id l d
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-imitations on individual dosae
reater than those listed in the table
after the ne%t slide may be permitted
)ith the follo)in conditions7!" The dose for the )hole body does
not e%ceed 0 rem 4:":0 Sv6 durin
any calendar year"
Occupational Radiation
8%posure -imits
( Th i di id l@ l t d
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(" The individual@s accumulated
occupational dose has been
recorded on NRC /orm', and
the individual has sined theform"
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-evels of Radiation in
Unrestricted Areas
Th f ll i t bl h th
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The follo)in table sho)s the
e%posure limits in an unrestricted
area"
8%posure -imits in Unrestricted
Areas
8 ti 8 li it illi
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8%posure time 8%posure limit millirem4millisievert6
! hour
! calendar year
( 4:":(6
!:: 4!6
.ersonnel
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There are different personnel
monitorin devices re1uired for use
by radioraphers and their assistants
durin radioraphic operations7
.ersonnel
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!" /ilm bades"
(" Thermoluminescent dosimeters
4T-5s6"
+" Optically stimulatedluminescence bades 4OS-6"
.ersonnel
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," 5irect readin dosimeters"
0" .oc*et dosimeters"
>" 8lectronic personal dosimeters"
The last t)o types should be
capable of measurin e%posures
from : to (:: mR 4: to ( mSv6"
Caution Sins# -abels and Sinals
! The radiation symbol 4as
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!" The radiation symbol 4asillustrated on the ne%t slide6 should
be placed7
a" In e%posure areas"b" On containers for transportin
and storin radioactive
materials"
Caution Sins# -abels and Sinals
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Caution Sins# -abels and Sinals
( The )ords caution or danger also
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(" The )ords cautionor dangeralsomust appear"
+" The )ords radioactive material
should be mar*ed on containers ofradioactive materials and in the
areas housin such containers"
Caution Sins# -abels and Sinals
, 8%posure devices should be
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," 8%posure devices should belabeled )ith a radiation symbol
and the phrase Danger
radioactive material do nothandle" Company information
and a (,'hr" phone number must
be mentioned on the sin"
8%posure 5evices and
Storae Containers
Based on the radiation reulations7
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Based on the radiation reulations7
!" 8%posure devices must have the
name of the company or
laboratory and the location of theoffice placed in a noticeable site
on the device"
(" All of the labels# sins# etc"# shallbe leible"
Radiation Survey
Instrumentation Re1uirements
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!" Radioraphers should have
operable and calibrated radiation
survey meters"
(" 8ach e%posure device shall be
accompanied by a survey meter"
+" The meters shall have a rane of
( mR 4:":( mSv6 per hour throuh! R 4:"! Sv6 per hour"
Radiation Surveys
! Operable and calibrated radiation
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!" Operable and calibrated radiation
survey instrumentation should be
available at an e%posure area"
Radiation Surveys
( ?hen )or*in )ith radioisotopes
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(" ?hen )or*in )ith radioisotopes#
a radioactive survey shall be made
around the camera to ensure the
source has been returned to itsshielded condition" This is *no)n
as a 234 s&ee"
Radiation Surveys
+ Before storin each sealed
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+" Before storin each sealed
source# a radiation survey shall
be made to ensure that the
source is in its shielded position"," All these readins shall be
recorded on a radiation report
survey"
5etection and
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There are different instruments that
measure radiation based on the
ioni;ation produced in a as" These
instruments fall into t)o cateories7!" Instruments that measure total
dose e%posure"
(" Instruments that measure doserate 4radiation intensity6"
Instruments that
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a" .oc*et dosimeters"
b" .ersonal electronic
dosimeters"
c" /ilm bades andthermoluminescent dosimeters
4T-5s6"
d" Optically stimulatedluminescence 4OS-6 bades"
Instruments that
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Instruments that measure dose rateare called surve) meters" Theseinclude7
!" Ioni;ation chambers"(" 3eier'mueller counters"
.oc*et 5osimeters
The poc*et dosimeter is a small
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The poc*et dosimeter is a smalldevice# about the si;e of a fountain
pen" 4See the follo)in fiure"6
.oc*et 5osimeters
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.oc*et 5osimeters
! The operation is based on t)o
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!" The operation is based on t)omain principles7
a" Radiation causes ioni;ation in a
as"b" Similar electrical chares repel
each other"(" The dosimeter should be properly
chared 4the indicator on ;eroscale6 before usin"
.oc*et 5osimeters
+ .oc*et dosimeters are desined
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+" .oc*et dosimeters are desined)ith a sensitivity that permits
them to be scaled in doses from
: to (:: mR 4: to ( mSv6"," .oc*et dosimeters must be
calibrated annually# per NRC
reulation# and the date should
be labeled on them"
.ersonal 8lectronic 5osimeters
! .ersonal electronic dosimeters
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!" .ersonal electronic dosimeters4or electron dosimeters67
a" Are easy to use"
b" Are sensitive"
c" Eave numerous functions that
can be enabled or disabled"
.ersonal 8lectronic 5osimeters
( 8lectronic dosimeters provide
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(" 8lectronic dosimeters providedose# dose rate and set point
chec*s# and usually operate )ith
an AA battery"+" The set points can be preset to
definitive alarm points"
," The poc*et'si;ed monitorsprovide three'diit diital display"
.ersonal 8lectronic 5osimeters
0 The enery response of the
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0" The enery response of thepoc*et'si;ed monitor for amma
rays and &'rays is ,: *e to
!"(
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!" /ilm bades 4sho)n on the ne%tslide6 consist of a small film
holder e1uipped )ith thin lead or
cadmium filters"(" Bades are desined to be )orn
by individuals only )hen )or*in
in a radiation area"
/ilm Bades and
Thermoluminescent 5osimeters
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/ilm Bades and
Thermoluminescent 5osimeters
+" After a period of time# the film is
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+" After a period of time# the film isremoved and developed by standard
techni1ues"
," Both devices record total radiation
received and serve to chec* each
other"
0" Thermoluminescent dosimeters
4T-5s6 contain a special crystal oflithium fluoride that stores the enery"
/ilm Bades and
Thermoluminescent 5osimeters
> The T-5 is sent to a lab )here
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>" The T-5 is sent to a lab )herethe crystals are processed to
e%tract the amount of absorbed
enery"" Compared to film bades# T-5s
are not as sensitive to heat#
moisture or rouh handlin# but
they are more e%pensive"
Optically Stimulated
-uminescence 4OS-6 Bades
!" OS- bades measure beta 4b6#
-
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!" OS- bades measure beta 4b6#amma# neutron and
&'radiation e%posures"
(" The OS- is a thin strip ofspecially formulated aluminum
o%ide crystalline material"
Optically Stimulated
-uminescence 4OS-6 Bades
+" OS- bades detect eneries
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+" OS- bades detect eneriesfrom 0 *e to ,:
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!" Ioni;ation chambers measurethe radiation intensity 4dose rate6
in milliroenten per hour or
millisievert per hour"(" Ioni;ation chambers typically
attain an accuracy of M!0#
e%cept in lo)'intensity radiation
areas"
Ioni;ation Chambers
+" In areas of lo)'intensity
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+" In areas of lo) intensityradiation# radiation intensity
measurements are usually made
)ith eier'mueller counters"," Ioni;ation chambers should be
calibrated annually"
3eier'
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ysensitive radiation detection
devices"
(" 3eier'mueller counters aretypically accurate to M(: for the
1uantity of radiation to )hich they
are calibrated"
+" They should be calibrated annually"
Area Alarm Systems
!" These systems consist of one or
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ese syste s co s st o o e omore sensin elements# usually
ioni;ation chambers# )hose
output is fed to a central alarmmeter"
Area Alarm Systems
(" The meter can be preset so that
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pan audible alarm is sounded and
a visual indication is displayed
)hen permissible radiation levelsare e%ceeded"
8lectrical Safety
!" Because &'ray machines use
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yhih'voltae circuits# the
radiorapher must comply )ith
safe electrical procedures"(" This is more serious specifically
for portable &'ray e1uipment#
)hich re1uires certain electrical
precautions"
8lectrical Safety
+" 5urin operation or service of
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p&'ray e1uipment# the follo)in
precautions# applicable to both
permanent and portableinstallations# should be observed
carefully"
8lectrical Safety
a" 5o not turn po)er on until
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psetup for e%posure is
completed"
b" 8nsure that roundininstructions are complied )ith"
8lectrical Safety
c" Reularly chec* po)er cables
-
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y pfor sins of )ear# and replace
them )hen necessary"
d" Avoid handlin po)er cables)hen the po)er is on" The
machine@s operational *ey
should be removed )hen not in
use"
8lectrical Safety
e" If po)er cables must be handled
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p)ith the po)er on# use safety
e1uipment such as rubber
loves# rubber mats andinsulated hih'voltae stic*s"
f" Be sure that )ater and moisture
are not in close contact )ith
po)er cables"
8lectrical Safety
" 8nsure that capacitors are
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pcompletely dischared before
chec*in an electronic circuit"