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