X-Ray Diffraction Safety at UIC

1. X-Ray Diffraction Safety at UIC Allan Jackimek, RSO Konstantin Povod, CHP

2. 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 person responsible for the unit.

3. 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.

4. 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.

5. Radiation Units Roentgen (R) – unit of exposure in air for photons only. 1R = 2.58 x 10 -4 C/kg in dry air. Gray (Gy), rad – units of absorbed dose. 1Gy = 1Joule/1kg 1Gy = 100 rad Sievert (Sv), rem – units of equivalent dose. 1Sv = 100 rem For X-rays, 1 rem = 1 rad and 1R delivers 0.96 rad to tissue Milli – 1/1,000th, as in millirem or mrem

6. 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 dose limit is 5 rem, extremities dose limit is 50 rem.

7. Biological Effects of Radiation Effect Dose, rad Exposure time in primary beam, s Erythema 500-800 0.075-0.12 Epilation 350 temporary 0.0525 1200 permanent 0.180 Acute dermatitis 3000-4000 0.45-0.60 Chronic dermatitis thousands of rads in many small doses over NA many years Skin Cancer small doses over a long period of time to receive a NA large dose

8. WARNING! Very serious injuries have resulted from the use of XRD equipment. Large doses of radiation have caused burns and permanent injuries to workers.

9. 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

10. Analytical Unit Types Open-Beam: an analytical x-ray system in which an individual could accidentally place some part of his body in the primary beam path during normal operation.

11. Analytical Unit Types Closed-Beam: an analytical system in which all possible X-ray paths (primary and diffracted) are completely enclosed so that no part of a human body can be exposed to the beam during normal operation.

12. Analytical Unit Types Cabinet: an X-ray system with the x-ray tube installed in an enclosure which, independent of existing architectural structures except the floor on which it may be placed, is intended to contain at least that portion of a material being irradiated, provide radiation attenuation, and exclude personnel from its interior during generation of x-radiation. The cabinet units are the safest of the analytical unit types because they prevent exposure to the primary beam by including numerous safety interlocks. The cabinet units also have built-in shielding within the unit to prevent excess exposures to the users

13. Characteristics of XRD Units • Units usually operate at low X-ray energies (<50 kVp), but can also be operated at higher X-ray energies (>50 kVp). • The currents for analytical units can range from less than 1 mA to greater than 200 mA. • This will produce a wide range of x-ray energies depending on the specific operating conditions of the unit.

14. Sealed Tube/Microfocus Systems:What are the danger areas? 3. Leakage 2. Scattered Radiation 1. Primary Beam

15. Three regions of high exposure 1. Primary Beam The critical radiation exposure problem with analytical X-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 rad (much less than a second). Radiation burns may occur from longer exposures.

16. Three regions of high exposure 2. Scattered Radiation When the primary beam intersects a material such 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 present a potential hazard. Scattered radiation fields can be measured by the analytical operators with a survey meter.

17. Three regions of high exposure 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 (100 mrem year).

18. Monitoring Equipment is Essential

19. Factors Affecting Radiation Dose Radiation Dose is inversely proportional to the square of the distance from the source. Distance INcreases x2 -> Dose DEcreases x4 Distance INcreases x3 -> Dose DEcreases x9 Shielding is used to attenuate radiation and reduce occupational exposure. For x-rays, shielding is most often lead. • Time. • Distance. • Shielding. Radiation Dose is directly proportional to the exposure time

20. Important! Detailed instruction on the safe use of XRD must be provided by your supervisor and/or his/her designee. This instruction must include demonstration of all safety features of all specific equipment to be used. Before beginning use of any X-ray equipment, be sure you understand all of the training. If problems or questions arise, stop work and consult with your supervisor, equipment owner or Radiation Safety.

21. 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 Å. • The 1.54 Å wavelength corresponds to Cu Kα radiation.

22. Safety Devices and Features • All units require a clear, visible warning light what illuminates 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.

23. 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

24. 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” • 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”

25. 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.

26. XRD units should not be open and allow inadvertent radiation exposure

27. 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

28. Administrative Controls • Detailed training by PI or his/her designee • Detailed SOPs – policies and procedures • Close supervision by a knowledgeable user • Authorized users only – unit security • Constant vigilance and alertness to the dangers

29. Who May Use XRD? • Only trained, authorized persons may use, install, maintain, or repair X-ray diffraction equipment (XRD) at UIC. • All such persons must receive XRD Initial Training, and should receive radiation dosimetry devices.

30. General Rules • 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!

31. General Rules cont. • Never leave the energized system unattended in an area where access in not controlled. • Survey the area frequently to evaluate scatter and leakage radiation fields. • Never remove auxiliary shielding without authorization from the owner of the analytical equipment and 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 Radiation Safety Office may repair, align or make modifications to the X-ray apparatus.

32. Special Tasks Only trained, authorized experts are allowed to repair, maintain or reconfigure XRD equipment

33. 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.

34. 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 your supervisor. Be aware: • Shutter mechanisms can fail! • Warning lights can fail!

35. Emergencies and Accidents Get medical treatment immediately for all injuries and exposures - at UIC Employee Health Services ASAP notify your supervisor and Radiation Safety at 312-996-7429 (312-996-7233 after hours) Take XRD unit out of service to prevent injuries to others! Provide information during the incident investigation.

36. Radiation Badges • Anyone at UIC who uses X-ray diffraction equipment should wear radiation monitoring badges. Contact Radiation Safety at 6-7429 to make arrangements to obtain monitoring badges. Forms are also available online at www.uic.edu/depts/envh

37. 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 month. • Wear only your own badge/ring.

38. Transfers, relocations, donations of XRD equipment • ALL XRD must be registered with the UIC Radiation Safety prior to its arrival/use. • Contact Radiation Safety PRIOR to any transfer, relocation, donation or disposal of XRD units so that the IEMA registrations can be corrected. • Donations of used XRD equipment will require a signed waiver from the recipient.

39. Questions?