x ray diffraction safety information
TRANSCRIPT
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X-RAY DIFFRACTION
SAFETY INFORMATION
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Restricted Item List
Any proposed purchase or acquisition, and
installation of x-ray equipment must be
reviewed and approved in advance by the
Tufts Radiation Safety/EHS.
Radiation symbols inform persons of
radiation producing
equipment or RAM
use.
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Caution XRD can be hazardous
Detailed instructions on the operation, hazards, andradiation safety features of a specific analytical unit
must be provided by the owner of the equipment.Before starting to work on an analytical unit, makesure you receive specific instruction on the units
safe operation from the Tufts person responsible forthe unit. All x-ray users must have attended
Tufts radiation safety training, but that is NOT a
substitute for unit specific operation and safety
training.
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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.
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X-ray Production
When high energy electrons strike ananode in a sealed vacuum, x-rays aregenerated. Anodes are often made of
copper, iron or molybdenum.
X-rays are electromagnetic radiation.
They have enough energy to causeionization.
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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
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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. Radio-isotope users at Tufts generally receive
< 100 mRem/yr.
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MA DPH Occupation Exposure
Limits
Area: Annualdose limit, Rem:
Whole body,
lens of eye,
head, trunk 5
Hands, arms, 50
skin of whole
body
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ALARA
ALARA stands for as low as reasonably
achievable. Regulators recognize that it
is an individual workers responsibility to performtasks 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.
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Biological Effects of Radiation
Effect Dose, Exposure time inRem primary beam, seconds
Erythema 300-600 0.075-0.12
Epilation 350 temporary 0.05251200 permanent 0.180
Acute dermatitis 3000-4000 0.45-0.60
Chronic dermatitis thousands of Rem in
many small doses over NA
many years
Skin Cancer small doses over a long ???
period of time
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GENERAL RADIATION
INFORMATION
IONIZING RADIATION CAN CAUSE
CHEMICAL CHANGES IN BIOLOGICAL
TISSUE. THESE CAN LEAD TO CELL
DEATH, CELL TRANSFORMATION, AND
DAMAGE WHICH CAN NOT BE
REPAIRED.
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WARNING
Very serious injuries
have resulted from
the use of XRDequipment. Large
doses of radiation
have caused painful
burns and permanentinjuries to workers.
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You could be injured without
initially knowing it -
People are not able to sense radiation. Even
very large doses of radiation can not be felt. Justbecause 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 thatthey are trained, follow all precautions, and use
all x-ray equipment safely.
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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 sampleor shielding material,
Diffracted rays from crystal,
Radiation generated by rectifiers in the highvoltage power supply of older units.
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Sealed Tube/Microfocus Systems:
What are the danger areas?
1. Primary Beam 2. Scattered
Radiation
3. Leakage
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Three regions of high exposure include the
primary beam, scattered radiation, and leakage
radiation.
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1.Primary Beam The critical radiation exposure problem with analyticalX-ray equipment is the primary beam. Exposure to the primary beam can
cause localized acute exposure. Consequently, the analytical operator
must never intentionally place any part of their body in the primary beam.Typically, these beams are relatively soft X-rays resulting in maximal
energy deposition in epithelial tissues. Erythema or reddening of the skin
can occur when skin is acutely exposed to 300-600 R (much less than a
second). Radiation burns may occur from longer exposures.
2.Scattered Radiation When the primary beam intersects a materialsuch as a sample or elements of the X-ray unit including the beam stop,
some of the radiation is scattered out of the primary beam. While these
radiation fields are considerable less intense than the primary beam, they
still represent a potential hazard. Scattered radiation fields can be
measured by the analytical operators with a survey meter.
3.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.
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Monitoring Equipment is Essential
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Radiation monitoring instruments
Instruments which arecalibrated for radiation thatuniformly exposes the activearea of the detector will give
incorrect low readings whenexposed to a beam having asmaller area. To determinethe true reading, the measuredreading must be multiplied by f,where
f = area of detector/area ofbeam
Check instrument batteries
Have audio on
Begin on fast or F setting
Precise measurements may betaken using slow or S
setting, as the needle will not
bounce as much
Scales will vary with each
instrument modelBegin on X1 scale
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Safety Basics
Time minimizing time around a radiation
source will reduce total exposure
Distance maximize distance from aradiation source to reduce total exposure
See Inverse Square Law
Shielding material used to attenuate radiationand reduce occupational exposure. For x-rays,
shielding is most often lead.
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Inverse Square Law
Radiation exposure varies inversely as
the square of the distance from the source
E 1 / d 2
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DETAILED INSTRUCTION ON THE SAFE USEOF XRD MUST BE PROVIDED BY THESUPERVISING PI AND/OR HIS/HER DESIGNEE.THIS INSTRUCTION MUST INCLUDE
DEMONSTRATION OF ALL SAFETYFEATURES OF ALL SPECIFIC EQUIPMENT TOBE USED. BEFORE BEGINNING USE OF ANYXRAY EQUIPMENT, BE SURE YOUUNDERSTAND ALL OF THE TRAINING. IF
PROBLEMS OR QUESTIONS ARISE, STOPWORK AND CONSULT YOUR SUPERVISORAND THE EQUIPMENT OWNER/SUPERVISOR.
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Characteristics of XRD Beams
Both primary and diffracted beams are
generally small and well collimated.
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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.
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Characteristic and Bremsstrahlung
radiation are present
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Safety Devices and Features
All units require a clear, visible warning light whatilluminates only when the unit is producing X-rays.
Shutter status shall be indicated clearly. Shutters must notbe 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 accidentalopening.
Shielding or other devices must be used to preventphysical access to open beam areas. All open beamareas must be as small as feasible.
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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
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Interlocks
Safety interlocks should not be used to de-
activate the x-ray beam, except in
emergencies and when testing the
interlock system.
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Warning Labels continued
A label which has the following or similar
words must be on the control panel of
each XRD unit near the switch used to
energize the unit:
Caution Radiation
This unit produced radiation when
energized
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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 inthe operators field of view.
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XRD units should not be open and allow
inadvertent radiation exposure.
Older model open type units do not
meet current radiation safety standards.
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Current standards require interlocked
Plexiglas enclosures to prevent access
to the primary beam when the unit is in
operation. Enclosures can also protectpersons from leakage and scatter
radiation.
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Administrative Controls
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.
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Who May Use XRD?
Only trained, authorized persons may use,
install, maintain, or repair x-ray diffraction
equipment [XRD] at Tufts University.
All such persons should attend the Tufts
Radiation Safety Training, and should
receive radiation dosimetry devices.
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General Precautions
Only Trained personnel shall be permitted to operate an analytical unit.
Be familiar with the procedure to be carried out.
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
Survey the area frequently to evaluate scatter and leakage radiationfields.
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 units owner and
the Safety Office may repair, align or make modifications to the X-ray
apparatus.
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Special Tasks
Only trained, authorized experts are allowed
to repair, maintain or reconfigure XRD
equipment.
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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.
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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
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Emergencies and Accidents
Call Tufts Police for all emergencies 6-6911
Get medical treatment immediately for
all injuries and exposures - at TMC
[or the nearest hospital for Grafton or Medford.]
ASAP notify your supervisor and EHS,
Take XRD unit out of service to preventinjuries to others,
Provide information during the incident
investigation.
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Radiation Badges
Anyone at TuftsUniversity who uses x-raydiffraction equipment andmost other types of x-ray
equipment should wearradiation monitoringbadges. Contact HealthPhysics at 636-6168to make arrangements to
obtain monitoring badges.In Medford, contact EHS
at 636-3450.
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Important Notes About Dosimetry
Due to the small cross sectional area of the
primary x-ray beam, whole body and 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.
T f l ti d ti f
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Transfers, relocations, donations of
XRD equipment
ALL XRD must be registered with the MADPH -RCP prior to its arrival/use at Tufts.
Contact EHS PRIOR to any transfer,relocation, donation or disposal of XRDunits so that the MA DPH registration can
be handled.Donations of used XRD equipment willrequire a signed waiver from the recipient.
Additi l I f ti
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Additional Information or
AssistanceFor emergencies call Tufts Police at 6-6911.
In Boston, contact Environmental Health & Safety at 636-3450, 636-3615 {Main Office #}, or using the RSOs
cell phone at 617 308-3781.
In Grafton and Medford, call Tufts Environmental Healthand Safety as above during normal business hours.
After hours, contact Campus Police who can summonassistance for you.
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Acknowledgments
Special thanks to Rigaku, and Global
Dosimetry Solutions for allowing use of
photos, images and/or other information
from their respective websites.