Module 7 – Irradiators and
Radiation Safety TrainingRadiation Safety Training
Dennis WidnerDennis Widner
Health Physicist – TrainingHealth Physicist – Training
• 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 SAFETYIRRADIATOR and SEALED SOURCE SAFETY
• INSPECTIONS and REQUIREMENTSINSPECTIONS and REQUIREMENTS
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
Center for Applied Isotopes
2560 Curies of Cobalt-60
Sample moves to a fixed source
Exposure to Source – 845 Rem/hr
Whole body dose limit in 21 sec
Appendage limit in 3.5 min.
Nuclear Medicine & Radiotherapy
4790 Curies of Co-60
@ 80 cm
Whole body dose limit in 2.5 sec
Appendage limit in 25 sec.
Radiation Dosimetry UnitsRadiation Dosimetry Units
Absorbed dose:Absorbed dose:
is the energy deposited by any type of ionizing radiationis the energy deposited by any type of ionizing radiation
in a volume element of mass.in a volume element of mass.
SI unit:SI unit: gray (Gy)gray (Gy)
Traditional unit:Traditional unit: radrad 1Gy = 1001Gy = 100 radrad
1 centigray (cGy) = 1 rad1 centigray (cGy) = 1 rad
Absorbed dose definition applies toAbsorbed dose definition applies to allall forms of ionizingforms of ionizing
radiation in any material.radiation in any material.
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
• 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
• 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
• manipulated the control panel to simulate monitor detection of
a safe radiation level
• 1 worker died, 1 with multiple amputations
• 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
Knowledge 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
Posting of signs and information
Proper use of radiation survey instruments
Operating procedures including disposal
• Each laboratory or
approved radiation use
must have an individual
• ALARA rules must be
posted and taught to
each radiation user
• What is “Reasonably
the following factors:
• Dose Limits, Regulations,
Social Impacts, Economic
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
• All sources of radiation must be secured againstAll sources of radiation must be secured against
theft or use by unauthorized individuals -theft or use by unauthorized individuals - CHECKCHECK
SECURITY IN YOUR LAB !!SECURITY IN YOUR LAB !!
No radioactive sources shall be abandoned !!!
You are responsible for your sources from “Cradle to Grave”
Engineering ControlsEngineering Controls
Safety SwitchesSafety Switches
• Portable and hand-heldPortable and hand-held
• Direct and immediate measurementsDirect and immediate measurements
exposure rate in milliRoentgen per hourexposure rate in milliRoentgen per hour
Survey InstrumentsSurvey Instruments
Leak testing of
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.
1. Step by step procedures for operations
2. Determination and recording of radiation doses to
persons operating the irradiator.
3. Procedures to ensure that engineering controls are not
4. Conveyance from the PI or Supervisor that if there is a
problem its ok to STOP work. Safety first !
Please Feel Free to Contact:
The Radiation Control Office
Environmental Safety Division
University of Georgia
240A Riverbend Road
Athens, Georgia 30602-8002
Radiation Safety Office
If you have any questions while reading the Radiation Safety Procedures