Irradiadores industriales para el proceso de irradiación.pdf

7/28/2019 Irradiadores industriales para el proceso de irradiacin.pdf

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Industrial Irradiators Electron accelerators widely used, 0.1 to 10 MeV X-rays, mostly used in medical diagnostics and

radiography; some used in radiation processing(3 to 10 MeV) Isotope sources; medical sterilization and foodirradiation Heavy ion accelerators, mostly for ion implantation Synchrotrons, mostly for resist work Nuclear reactors, for producing radioisotopes


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Radioisotope vs ElectronAccelerator Source

Electron.accelerationScanned electronI)eam

Electrical input

X-ray conversionplateElectron or X-ray beamavailable when needed,in the desired direction

60CO or 137CSphoton emission,continuous, in alldirections


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Components of an Irradiation Facility (contd)7. Shipping and Receiving Areas

They should be well separated from each other toprevent mixing of irradiated and unirradiated products8. Safety Devices and Monitors

Radiation monitors, set to shut - off the system atpredetermined dose Air conditioning - temperature fluctuations detrimental

to processing Large air f low - to maintain ozone and NOx levels low Ozone monitors - to show when it is safe to enter thetarget room


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Electron AcceleratorsAdvantagesII Various power and electron energy levels available

.. Very high dose rates

.. Generally, short processing time41 Cost increases only marginally with power41 Cost increases.with electron energy41 Can be switched off when not requiredII Can be used for electrons or X.. rays41 Directional beam (horizontal or vertical)

.. Better utilization o'f beam energy >95%availability reported


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The penetration of electrons increases with increasingelectron energy as shown by the depth/dose curves

Depth (g1cm2) The dose uniformity increases with increasing electronenergy


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The penetration of electrons increases with increasingelectron energy as shown by the depth/dose curves

Q)(f )ooQ)>-+ - 'co-Q)a:

Depth (g/cm2) The dose uniformity increases with increasing electronenergy


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The penetration of electrons increases with increasingeleclron energy as shown by the depth/dose curves

(1)CJ)oc(1)>.--o-1)a:

Depth (g/cm2) The dose uniformity increases with increasing electronenergy


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Electron Beam PenetrationTypical Depth/Dose Curve for 10 MeV Electrons

634Depth (g/cm2)

Q) 140 iC;;;;I,Vptimum Thickness of Sample~ 120 j - - ------ : :==-=--+--- Maximum Relative Dose

~ 100 := ' : : : : : : : : : : : : : : : : : Minimum Required Dose> 80 .. ' .- 60 .. ,. . .,.. .. .

..:::: 40 :: :Q) 20 :: :: Ba: 0 I:::::::::::::::':

o 1

Dose first increases with penetration and thendecreases Penetration proportional to 1/density At optimum thickness, dose uniformity is 12.5%


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ELECTRON BEAM PENETRATIONOne-Sided vs Two-Sided Irradiationfor 10 MeV Electrons By optimizing two-sided irradiation, the effectivepenetration of e- beam can be increased by a factor of >2

Dose

7 86

/ , -, "lid "til " " " '-' '-' " " " " .. " ., ::l "-'-' '"

'" '-'

140Q) 120~ 100

C 80(1) 6016Q) 40a:: 20o o

Depth (g/cm)


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..One-Sided___Two-SidedTOne-Sided

Dose Distribution in Water as a Function ofDepth(Gamma Radiation from 60Co; Saylor, 1997)1.2

0)1>; 0.8-~ 0.6-) 0.4tnoC 0.2

O + - - - - - r - - . - - - - r - - . - - ~ - - - - , - - - . . _ _ _ _ _ _ ,o 10 20 30 40 50 60 70 80Distance from 60CO Source (cm)


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Comparison ofRelative Dose vs DepthFor 60CO y-Rays and 5 MeV X-Rays

CI>tnoCCI>>.--O-I>a:

Depth in Product (em) Fpr sterilizations of typical packages of medicaldisposables


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I Radioactive Decay of 137Cs and 60Co I10090- 80 137CS~0 70-. 60....- 50>.- 40..0


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Capital Cost per kW ofElectronAccelerator .(lOMeV)300000250000

~ 200000150000- 10000050000

00 20 40 60 80 100

Power (kW)


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Cost vs Power of 10 MeV Accelerators

10000 60kW

200-+--.....- ......--......- .......---1o

1000000

5000000

-/)


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Electron ProcessingCoatings12%

H.eat-Shrmkable34%

Rubber10%Other60/0

Foam r = . : : : : : : : : : : ; ~ ~4%WireInsulation34%

-500 Accelerators Worldwide (Saunders,1988; now -1000) -150 1. - Sources Woldwide for Medical Sterilization andFood Irradiation


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Energy Spectrum of X-Rays from 5 MeVElectrons

..- 6I.l...... 5=;:J 4~~ 3a~ 2.....,!:J 1< 0---- 0 1 2 3 4 5E (MeV)

The average energy of X-rays is 1.06 MeV


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Nominal Equivalence ofElectronAccelerators and 60Co 50 kW of electron beam =3.38 MCi 60CO X-rays from 5 MeV, 200 kW electron accelerator=16 kW =1.1 MCi 60CO X-rays from 10 MeV, 50 kW electron accelerator= 10 kW =0.67 MCi of 60CO


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Types of Scanning in Low-EnergyElectron Accelerators

) 'Filament~

CURTAIN TYPE

' ' ' ' ' ' '1 \1111 I I 1 I \ I 1 I , I 1\, , I I I I I , , , 1t Il I I , \ I I 1 1,._----------...-j

,,,,,

,Product .. .,'\

Electronso . . . . - - - - - ~a: a ~ . &i l l t Ii t l Ii~ . J , " , , - - ~ , , 1 I I 1 I I I , I~ - ~ - - ~ _ ~ _ ~ __I,__ __ ~ - - ' . - - - - - - -,," '\ W."ndow I I I " I I \ \ I \ \ \/, I I t , ' I 'I I , I \ I I 1 I I

" - - -,,'" 7 1- \' - - - - - - - - - - - - ,..J.\t!!!:.:::!:::!::!::!::!::::!:::::!::::!::::!:=::;;;I I \ \, ,,, , , \1 \ \I , I I , \

1 / J I \ \I " I \_ . . . . ; . _ - ' - ..1-......,;_,,,,,,,,

SCANNING TYPE

Scanningcoil - .


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a + - - I - ~ AcceleratorTube

Direct Electron AcceleratorPrinciple OfOperation (Cleland,1992)

Low Voltage High Voltage , . . - - i : T ~ G l ~ = r r E l e c t r o n GunAC Power DC Power I-Q. , . . - - - - - - - . . . . . -Q.,-----'--1 High 1------1

Voltage' - - - - I Generator

ControlSystem,--I--L-." ~ i ! : : : t ~ E l e c t r o n Beam

~ Scan Magnet~ ~ Chamber

~ Foil WindowScanned Electron Beam


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Traveling-Wave Linear Electron Accelerator

LoadCavity ResistanceResonatorsKlystron3000 MHz

BuncherVacuum esonatorTankElectrol'l-----'1-.-I ElectronGun Beam--e!:;::: ~ ~ ~ ~ ~ ~ ~ & - ~ , ( ?~ - ~ o i lWindowatchingynchronization

r n ~ ~ ~


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Silicon Lithography1111111 hv or e -

'


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Characterization of the IrradiatorSource: e- 'Y

Determine Dose Profile0 0 -==Scan Yes Yeso Determine Nominal Dose Receivedby Product

Product Conveyor SystemYes Yes


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Conclusions Gamma irradiation would continue to be an importantcomponent of industrial radiation processing Industrial electron irradiation would continue to growfor most of the current products Areas of major growth for electron accelerators aremost likely to include environmental (water purification,sewage sludge irradiation, flue gas irradiation), viscose,and advanced composites The availability of a good variety of electronaccelerators in a wide energy ranae (0.2 to 10 MeV) is

conducive to growth of the radiation processingindustry Continued effort to increase understanding andusefulness of the technology would also help thegrowth of this industry

Irradiadores industriales para el proceso de irradiación.pdf

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