University of MinnesotaDuluth

Radiation SafetyAnnual Refresher Training

Radiation Protection DivisionDepartment 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, Exposure time in

Rem primary beam, seconds

Erythema 500-800 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 inmany small doses over NAmany years

Skin Cancer small doses over a longperiod of time to receive a NAlarge dose

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.

•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.

Potential Hazards to be aware of…

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

• 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 / d 2

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 de-activate 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

• 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• 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.

General Precautions

• 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.