Module 7 – Irradiators and Sealed Sources
Radiation Safety TrainingRadiation Safety Training
InstructorDennis WidnerDennis Widner
Health Physicist – TrainingHealth Physicist – Training
542-0526542-0526
• TYPES OF SEALED SOURCESTYPES OF SEALED SOURCES
• TYPES OF IRRADIATORSTYPES OF IRRADIATORS
• IRRADIATOR AND SEALED SOURCE ACCIDENTSIRRADIATOR AND SEALED SOURCE ACCIDENTS
• IRRADIATOR and SEALED SOURCE SAFETY IRRADIATOR and SEALED SOURCE SAFETY PROGRAMPROGRAM
• INSPECTIONS and REQUIREMENTSINSPECTIONS and REQUIREMENTS
OUTLINEOUTLINE
TYPES OF SEALED SOURCES
Campus Sealed SourcesCampus Sealed SourcesCesium-137Used for Meter Calibrations
Button Source
Cabinet X-Ray Machine
Rod Source
LSC Stds(mixed)
LSCInstruments
StaticEliminators
GCECDs
IrradiatorsGC ECDs
Sealed Sources come in all shapesrods, disks, pellets, BBs, pencils
TYPES OF IRRADIATORS
Irradiators are large self-shielded devices housing several
hundreds to thousands of Curies of a high-energy gamma or
beta emitter. The shielding, which is integral to the device is
required for operation.
There are 2 major types of Irradiators
1. Self-contained – primary beam is completely shielded
during use and storage conditions.
2. Non-self-contained or Panoramic – primary beam is not contained. Only when source is in storage is it shielded. Collimators are used to focus the beam.
Irradiators have numerous safety features such interlocks, position indicators, and radiation monitors prevent entry into the
chamber while the unit is on.
There are 2 major types of Source Geometries
1. Radioactive source is in a fixed position(sample chamber moves to the source)
2. Radioactive source is a moving type (source moves to the sample chamber)
Nordion's cobalt-60 irradiator is a maze of concrete walls, with an intricate system of alarms, locks and other safety features.
The Gray*Star irradiation unit is small enough to fit inside a food plant. The unit generates radiation using Cs-137.
Food Irradiators
Other Irradiators
UGA Irradiators
Center for Applied Isotopes(CAIS)
2560 Curies of Cobalt-60
Sample moves to a fixed source
Exposure to Source – 845 Rem/hr
Whole body dose limit in 21 secAppendage limit in 3.5 min.
Veterinary SchoolNuclear Medicine & Radiotherapy
UGA Irradiators
4790 Curies of Co-60
7200 Rem/hr@ 80 cm
Whole body dose limit in 2.5 secAppendage limit in 25 sec.
IRRADIATOR AND SEALED SOURCEACCIDENTS
Radiation Dosimetry UnitsRadiation Dosimetry UnitsAbsorbed dose:Absorbed dose:
is the energy deposited by any type of ionizing is the energy deposited by any type of ionizing radiation in a volume element of mass.radiation in a volume element of mass.
SI unit:SI unit: gray (Gy)gray (Gy)
Traditional unit:Traditional unit: radrad 1Gy = 100 1Gy = 100 radrad 1 centigray (cGy) = 1 rad1 centigray (cGy) = 1 rad
Absorbed dose definition applies to Absorbed dose definition applies to allall forms of forms of ionizing radiation in any material.ionizing radiation in any material.
RADRAD
Of all the radioactive material we can use, sealed sources and irradiator operations pose the greatest
potential of exposure when mishandled.
Hundreds to thousands of Curies of a gamma emitter !
Typical high level sealed sources in irradiators primarily consist of
Co-60 and Cs-137
Because of their high energy gamma rays
Maryland 1991
• no personnel dosimeters or survey meters• flashing warning signals ignored• padlock missing from gate• 2 of 3 photocells inoperative (1 switched off)• pressure mat removed• deliberately passed beneath only working
photocell• safety procedures & interlocks routinely
bypassed• fingers of both hands amputated
Photon burns to the fingers
• operating procedures not in local language• didn’t follow procedures• malfunctioning “source down” indicator• disconnected radiation alarm• used ‘established trick’ to simulate radiation monitor test• did not check portable radiation monitor (inoperative)• died 36 days later
• operators had only received informal on-the-job training
• facility poorly maintained• safety systems failed and were not replaced• irregular maintenance• operator manipulated ‘source down’ microswitch to
induce a green light• manipulated the control panel to simulate monitor
detection of a safe radiation level• 1 worker died, 1 with multiple amputations
Norway 1982
• flawed design • one switch failure caused false
reading• 2 procedures violated
– didn’t note fixed radiation monitor– didn’t use portable instruments
• died 13 days later
Radiation overdose from angioplasty
QECC Data on Sealed Source Accidents
IRRADIATOR and SEALED SOURCE SAFETY PROGRAMS
Program FundamentalsKnowledge of the radiation levels, equivalent dose and radiation exposure.
Potential hazards associated with exposure to ionizing radiation
Precautions to minimize risks
Appropriate responses to abnormal operations
Control of access to Irradiator units
Personnel monitoring
Posting of signs and information
Proper use of radiation survey instruments
Operating procedures including disposal
Training
ALARA Requirements
• Each laboratory or approved radiation use must have an individual ALARA program
• ALARA rules must be posted and taught to each radiation user
• What is “Reasonably Achievable?” Consider the following factors:• Dose Limits, Regulations,
Social Impacts, Economic Impacts
Find this posting in your lab
AND READ IT !!AND READ IT !!
Your authorization requires you to train your personnel
Document all training !
Radioactive Materials Security• .03(10) lists SECURITY requirements
• Recent incidents in this country and other states have prompted the NRC to increase security requirements
• All sources of radiation must be secured All sources of radiation must be secured against theft or use by unauthorized against theft or use by unauthorized individuals -individuals - CHECK SECURITY IN YOUR CHECK SECURITY IN YOUR LAB !!LAB !!
No radioactive sources shall be abandoned !!!You are responsible for your sources from “Cradle to Grave”
Engineering ControlsEngineering Controls
VentilationVentilationAccess Control
Safety SwitchesSafety Switches
• Portable and hand-heldPortable and hand-held• Direct and immediate Direct and immediate
measurementsmeasurementsMeasure:Measure:
exposure rate in milliRoentgen per hourexposure rate in milliRoentgen per hourmR/hrmR/hr
Survey InstrumentsSurvey Instruments
INSPECTIONS and REQUIREMENTS
Rule .03(6)
Leak testing of sealed sources
in your lab
Sealed SourcesSealed Sources
Every 6 Months!!!
Wipe Testing Options
1. Engage the services of a consultant or commercial facility to take samples, evaluate the samples and report back to you.
2. Use a commercial leak-test kit. You take the sample and send the sample to the kit supplier, who reports the results back to you. This is our preferred method.
3. You perform the entire leak-test sequence, including taking the sample and measurement.
Inspections
1. Step by step procedures for operations2. Determination and recording of radiation doses to
persons operating the irradiator.3. Procedures to ensure that engineering controls are not
over- ridden.4. Conveyance from the PI or Supervisor that if there is a
problem its ok to STOP work. Safety first !
Questions ???
Please Feel Free to Contact:
The Radiation Control OfficeEnvironmental Safety DivisionUniversity of Georgia240A Riverbend RoadAthens, Georgia 30602-8002
Radiation Safety Office
If you have any questions while reading the Radiation Safety Procedures
542-5801