Transcript University of Minnesota Duluth Radiation Safety Annual Refresher Training Radiation Protection Division Department of Environmental Health & Safety.

University of Minnesota
Duluth
Radiation Safety
Annual Refresher Training
Radiation Protection Division
Department of Environmental Health & Safety
X-RAY DIFFRACTION
SAFETY INFORMATION
Restricted Item List
Any proposed purchase or acquisition, and
installation of x-ray equipment must be
reviewed and approved in advance by the
Radiation Safety Division/DEHS.
Caution – XRD can be hazardous
Detailed instructions on the operation, hazards,
and radiation safety features of a specific analytical
unit must be provided by the owner of the
equipment. Before starting to work on an analytical
unit, make sure you receive specific instruction on
the unit’s safe operation from the Authorized
person(s) responsible for the unit. All x-ray users
must also have radiation safety training.
Introduction
Analytical x-ray devices are important tools in
various areas of modern research. X-ray
crystallography and x-ray fluorescence
spectrometry rely on x-radiation.
But, X-ray diffraction equipment [XRD] can be very
dangerous, and operators of this equipment must
not become complacent or overconfident about the
potential danger of the x-ray beam.
X-ray Production
When high energy electrons strike an anode
in a sealed vacuum, x-rays are generated.
Anodes are often made of copper, iron or
molybdenum.
X-rays are electromagnetic radiation.
They have enough energy to cause
ionization.
Radiation Units
Roentgen R – unit of exposure, in air
for photons only. One R equals enough energy to
deposit 2.58 x 10 -4 coulombs per kg in dry air.
Rad – unit of absorbed dose. Equal to
one hundred ergs per gram
Rem – unit of dose equivalent. For x-rays,
1 rad = 1 rem
Milli – 1/1000th, as in millirem or mRem
MDH
Occupational Exposure Limits
Whole body (total effective dose equivalent)
5 rem
Individual organ or tissue
50 rem
Lens of the eye
15 rem
Skin or any extremity
50 rem
Typical X-ray Beam Intensities*
Primary beam
400,000 Rem/min, or
2.4 x 10 7 Rem/hr
Diffracted beam
80 Rem/hr
* For comparison, the annual whole body
occupational exposure limit is 5 Rem.
ALARA
ALARA means As Low As Reasonably Achievable.
Regulators recognize that it is an individual worker’s
responsibility to perform tasks on a daily basis keeping best
practices in mind, and striving to keep radiation exposure as
low as possible.
Workers are responsible for knowing all hazards and
safety practices that relate to the equipment in use.
You could be injured without knowing it
right away…
People are not able to sense radiation. Even
very large doses of radiation can not be felt.
Just because there was no sensation at the
time the dose is received, does not mean
you are safe. Serious injury can result for
radiation exposure. It is up to the individual
x-ray user to ensure that they are trained,
follow all precautions, and use all x-ray
equipment safely.
Biological Effects of Radiation
Effect
Dose,
Rem
Exposure time in
primary beam, seconds
Erythema
500-800
0.075-0.12
Epilation
350 temporary
1200 permanent
0.0525
0.180
Acute dermatitis
3000-4000
0.45-0.60
Chronic dermatitis
thousands of Rem in
many small doses over
many years
NA
small doses over a long
period of time to receive a
large dose
NA
Skin Cancer
WARNING
Very serious injuries
have resulted from the
use of XRD equipment.
Large doses of
radiation have caused
burns and permanent
injuries to workers.
Sources of Exposure
• The primary beam,
• Leakage of primary beam through cracks in
shielding,
• Penetration of primary beam through shutters,
cameras, beam stops, etc.,
• Secondary emission (fluorescence) from a sample
or shielding material,
• Diffracted rays from crystal,
• Radiation generated by rectifiers in the high voltage
power supply of older units.
Three regions of high exposure include the
primary beam, scattered radiation, and leakage
radiation.
Potential Hazards to be aware of…
•Primary Beam The primary beam is the main hazard. Exposure to the
primary beam can cause localized acute exposure. You must never
place any part of their body in the primary beam. These beams are
relatively “soft” X-rays resulting in maximal energy deposition in the skin.
Reddening of the skin can occur when skin is acutely exposed to
300 R (much less than a second). Burns may occur from longer
exposures.
•Scattered Radiation When the primary beam hits something such as a
sample or the beam stop, some of the radiation is scattered. While these
radiation fields are less intense than the primary beam, they are still
hazardous.
Scattered radiation fields can be measured with your survey meter.
•Leakage Some radiation may “leak” around the tube housing structure.
The source housing construction must be such that when all the shutters
are closed, the leakage radiation must not exceed that of radiation limits
for the general public.
Monitoring Equipment is Essential
Radiation monitoring instruments
• Instruments which are calibrated
for radiation that uniformly
exposes the active area of the
detector will give incorrect low
readings when exposed to a
beam having a smaller area. To
determine the true reading, the
measured reading must be
multiplied by f, where
f = area of detector/area of
beam
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Check instrument batteries
Have audio “on”
Begin on “fast” or “F” setting
Precise measurements may be
taken using “slow” or “S”
setting, as the needle will not
“bounce” as much
• Scales will vary with each
instrument model
Begin on X1 scale
Safety Basics
• Time – minimizing time around a radiation
source will reduce total exposure
• Distance – maximize distance from a
radiation source to reduce total exposure
See “Inverse Square Law”
• Shielding – material used to attenuate radiation and
reduce occupational exposure. For x-rays,
shielding is most often lead.
Inverse Square Law
Radiation exposure varies inversely as
the square of the distance from the source
E
∞ 1 / d2
Characteristics of XRD Beams
• Both primary and diffracted beams are generally
small and well collimated.
• Wavelengths used in crystallography are often in
the range of 0.6 to 2.5 A.
• The 1.54 A wavelength corresponds to CuKa
radiation.
Characteristic and Bremsstrahlung
radiation are present…
Engineering Controls
• Interlocks – never bypass interlocks or
other safety devices
• Warning Lights – know the beam status
whenever working with XRD
• Shielding
• Secure key or computer control
Safety Devices and Features
• All units require a clear, visible warning light that illuminates
only when the unit is producing X-rays.
• Shutter status shall be indicated clearly. Shutters must not
be able to open without a collimator or coupling device in
place.
• Safety interlocks shall not be bypassed or defeated.
• Unused ports shall be secured to prevent accidental
opening.
• Shielding or other devices must be used to prevent physical
access to open beam areas. All open beam areas must be
as small as feasible.
Examples of warning lights and labels
A label which has the following or similar words
must be in place on the x-ray source
housing:
“Caution – High Intensity X-ray Beam”
Interlocks
Safety interlocks should not be used to deactivate the x-ray beam, except in
emergencies and when testing the
interlock system.
Warning Labels continued
A label near the control panel must read
“Caution – Radiation
This unit produces radiation when energized”
Or similarly.
Warning Lights
Each port must have a readily discernible
indication of shutter status [opened or
closed]. There must be a warning light
that is illuminated when the x-ray tube is
energized. The light must be near the
x-ray tube housing or port and be in
the operator’s field of view.
Walk In Radiation Enclosure
XRD units should not be open and allow
inadvertent radiation exposure.
Older model open type units do not
meet current radiation safety standards.
Current standards require interlocked
Plexiglas® enclosures to prevent access
to the primary beam when the unit is in
operation. Enclosures can also protect
persons from leakage and scatter
radiation.
Administrative Controls
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Detailed training by PI or his/her designee
Detailed SOPs – policies and procedures
Close supervision by knowledgeable user
Authorized users only – unit security
Constant vigilance and alertness to the
dangers.
Who May Use XRD?
• Only trained, authorized persons may use,
install, maintain, or repair x-ray diffraction
equipment [XRD] at the University.
• All such persons must have
Radiation Safety Training, and should receive
radiation dosimetry device.
Dosimetry
• Requirements are in your radiation safety manual
and at www.dehs.umn.edu
• A Ring Dosimeter is required for X-ray
Diffraction Unit.
The only fee associated with the program is if badges or rings
are not returned on time.
Important Notes About Dosimetry
Due to the small cross sectional area of the
primary x-ray beam, ring
badges may not accurately record the
maximum dose received by the XRD
user.
Dosimeters should be exchanged every
quarter. Wear only your own badge/ring.
General Precautions
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Only Trained personnel shall be permitted to operate an analytical unit.
Be familiar with the procedure to be carried out.
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Never expose any part of your body to the primary beam.
Turn the X-ray beam OFF before attempting to make any changes to the
experimental set-up (except for beam alignment)
While the beam is on DO NOT attempt to handle, manipulate or adjust
any object (sample, sample holder, collimator, etc.) which is in the direct
beam path (except for beam alignment procedures).
Examine the system carefully for any system modifications or
irregularities.
Follow the operating procedures carefully. DO NOT take short cuts!
Never leave the energized system unattended in an area where access in
not controlled.
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General Precautions
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Survey the area frequently to evaluate scatter and leakage radiation
fields.
Never remove auxiliary shielding without authorization from the owner of
the analytical equipment or the Radiation Safety Officer.
Never bypass safety circuits, such as interlocks.
Report all unusual occurrences to the owner of the analytical unit for
possible corrective actions.
Only authorized, trained individuals as specified by the unit’s owner and
the Safety Office may repair, align or make modifications to the X-ray
apparatus.
Special Tasks
Only trained, authorized experts are allowed to
repair, maintain or reconfigure XRD
equipment.
Unauthorized repair or modification
Do not remove shielding, or tube housing.
Do not modify shutters, collimators or
beam stops.
Individuals may not operate an XRD unit
in a manner inconsistent with SOPs and
safe operating standards.
Problems with equipment
If there are any questions or concerns about
the functioning of an XRD unit, it must be
taken out of service immediately and
reported to the unit supervisor.
Be aware that shutter mechanisms can
fail. Warning lights can fail.
Emergencies and Accidents
• Call DEHS for all emergencies 218-726-7273.
• Get medical treatment immediately for all injuries and
exposures
• ASAP notify your supervisor and DEHS,
• Take XRD unit out of service to prevent injuries to others,
• Provide information during the incident investigation.
Transfers, relocations, donations of XRD
equipment
• ALL XRD must be registered with the DEHS/MDH prior
to its arrival.
• Contact DEHS PRIOR to any transfer, relocation, or
disposal of XRD units so that the MDH registration can
be updated.
• Donations of used XRD equipment to the University of
Minnesota will require authorization from DEHS .
Acknowledgments
Special thanks to Rigaku, and Global
Dosimetry Solutions for allowing use of
photos, images and/or other information from
their respective websites.