MIT Analytical X-Ray Safety Policies and Procedures

Transcription

1 5th Edition 2014 MIT Analytical X-Ray Safety Issued by: MIT Radiation Protection Committee

2 Contents 1.0 Program Overview Purpose Scope and Application Radiation Protection Program Services Analytical X-Ray Equipment Supervisors Responsibilities Authorized Users Responsibilities General Equipment and Safety Requirements Postings and Signage Equipment Safety Requirements Radiation Surveys User Survey Requirements RPP Survey Requirements Personnel Monitoring...6

3 1.0 Program Overview The M.I.T. Radiation Protection Committee (RPC) is responsible for the establishment and continuing review of an adequate radiation protection program at the Institute and its offcampus sites. The RPC is also responsible for the Institute s compliance with the radiation protection regulations promulgated by the state, federal, and local agencies for both ionizing and non-ionizing Radiation Producing Equipment (RPE), Radio Frequency (RF) generators, and Class 3B and 4 lasers/laser systems. These devices must be registered with the M.I.T. Radiation Protection Program (RPP). If you have any questions concerning x-ray safety, please contact: M.I.T. RPP - Building N52 Room 496 Telephone: (617) (ext ) environmental@mit.edu URL: ACKNOWLEDGMENT: Information has been incorporated into this safety guide from the following documents: ANSI-N Radiation Safety for X-Ray Diffraction and Fluorescence Analysis Equipment 105 CMR Radiation Safety Requirements for Analytical X-Ray Equipment 105 CMR Standards for Protection Against Radiation A copy of these documents are on file at the M.I.T. EHS Office, N Purpose Analytical x-ray equipment is used for X-Ray Diffraction (XRD) analysis, X-Ray Fluorescence (XRF) analysis, or direct x-ray transmission analysis of materials. These analytical x-ray systems are made up of components that use x-rays to determine elemental composition, or to examine the microstructure of materials. These analytical x-ray devices are not to be used on any live human subjects. The primary objective of this program is to keep occupational radiation exposures As Low As Reasonably Achievable (ALARA) when operating these types of equipment. This safety program establishes M.I.T. s policies and procedures for the safe operation of analytical x-ray equipment and the associated potential radiation hazards. 1 P a g e

4 3.0 Scope and Application Analytical x-ray equipment has become a major tool in research and quality control programs. Despite the advances in operating techniques and equipment design, the most common hazards are due to operator errors and equipment malfunctions. The potential exposures to the primary beam is of a major concern when evaluating potential radiation exposures. Exposures to the primary beam in a typical analytical x-ray unit may be as great as 100,000 R/min. This program applies to all Departments, Labs, and Centers (DLCs) as well as supervisors, employees, students, visiting scientists, and any personnel from other organizations whose work involves the use of analytical x-ray equipment at M.I.T. Operational procedures will be established for each x-ray unit to maintain radiation exposures ALARA with due considerations as to the feasibility and nature of the research being conducted. Written operational procedures may be required by the RPP. 4.0 Radiation Protection Program Services The M.I.T. Radiation Protection Program provides services to assist DCLs, supervisors, students and technicians in maintaining a comprehensive analytical x-ray equipment safety program. The services provided include the following: Train users on required safety procedures and practices for analytical x-ray equipment at the Institute. Maintain a current inventory of analytical x-ray equipment and authorized users. Evaluate each installation as to control of radiation exposures including recommendations for placement of radiation warning signs and/or warning devices. Perform routine annual radiation safety inspections/surveys of analytical x-ray equipment. Review and approve modifications to x-ray apparatus that affects radiation protection including: x-ray tube housing, cameras, shielding, and safety interlocks. Provide personnel monitoring badges and area monitors. Investigate any unusual radiation exposures to personnel and take remedial action if necessary. Assist in achieving compliance with all applicable federal, state, and local rules and regulations. Register x-ray units with the Massachusetts Department of Public Health as per section 105 CMR P a g e

5 5.0 Analytical X-Ray Equipment 5.1 Supervisors Responsibilities MIT Analytical X-Ray Safety 5 th Edition Provide the Radiation Protection Program with a completed RPO-81 RPE Registration Form describing the proposed use of the equipment. The RPP will review each proposed installation and operating procedure. Once reviewed, the application is presented to the RPC for ratification. Oversee all operations carried out with the equipment. Ensure all personnel under their supervision are registered with and receive general training from the RPP in the safe use of analytical x-ray equipment. Comply with the specific recommendations made by the RPP, and also the general equipment and safety requirements listed in Section 6.0. Provide specific hands-on training to the authorized users for each analytical x-ray unit. Ensure that the project has an operable survey instrument. Ensure only authorized users will enter the areas that are restricted due to the use of the analytical x-ray equipment when a radiation hazard exists. 5.2 Authorized Users Responsibilities Wear the assigned personnel monitoring badge(s) when issued, and return to RPP in a timely manner. Perform area monitoring of the x-ray unit set-up when the beam is energized using appropriate survey meter. Notify the RPP when: 1. Necessary altercations to safety devices, such as bypassing interlocks are to be performed. *Exception: generic bypassing for test purposes previously authorized by the RPP. 2. A radiation exposure of personnel has or may have occurred. 3. An existing unit is moved/transferred or beam path is altered. 4. Changes in operating parameters such as kv and ma will made beyond that which were approved previously by the RPP. 5. Changes to the approved shielding arrangement are to be made. 6. Major service will performed on the x-ray unit. 6.0 General Equipment and Safety Requirements 6.1 Postings and Signage The entrance(s) to any area that is restricted for radiation protection purposes will be posted with a sign bearing the radiation symbol and the words, CAUTION RADIATION - THIS AREA CONTAINS EQUIPMENT WHICH PRODUCES X-RAYS WHEN ENERGIZED - TO BE OPERATED ONLY BE QUALIFIED PERSONNEL. The x-ray unit switch that energizes the x-ray tube should be posted with a sign bearing the radiation symbol and the words, CAUTION RADIATION - THIS EQUIPMENT PRODUCES RADIATION WHEN ENERGIZED - TO BE OPERATED ONLY BE QUALIFIED PERSONNEL. 3 P a g e

6 6.2 Equipment Safety Requirements Unused ports on radiation source housing will be secured in a closed position in a manner which prevents casual opening. Before energizing the x-ray tube, all ports will be closed or fitted with an approved apparatus. Each x-ray unit shall have a fail-safe warning light to indicate when the x-ray tube is energized. The light will be located near the x-ray port and will be energized by the same switch that turns the beam on. The light shall either function as a fuse, or the light will be equipped with a twinbulb redundance. The analytical x-ray equipment should be placed in a separate room from other work areas whenever practical. Properly installed permanent shields should be used in preference to temporary shielding. When temporary shielding is necessary, it must be securely fastened. Set-up procedures will be carried out with the x-ray beam off or with shutters closed as much as possible. If the latter, a survey shall be performed before starting set-up. All safety devices such as interlocks, shutters, warning light, etc. should be tested weekly or upon each use (if use is less frequent) to ensure proper operation. Safety interlocks will not be routinely used to deactivate the x-ray beam. The unit will be positioned so that the primary x-ray beam is completely attenuated by the beam catcher. If this is not possible for an experimental set-up, or if the accessible scatter dose rate to personnel exceeds 2.0 mr/hr, then either the entire unit will be shielded, or entry to the room must be restricted. The room must be locked and appropriately posted with CAUTION - RADIATION AREA. Each x-ray tube housing will be constructed such that with all shutters closed, the leakage radiation measured at 5 cm from its surface does not exceed 2.5 mr/hr at any tube rating. Each generator should be checked for x-ray generation in its electronic components and, if necessary, supplied with a protection cabinet which limits the leakage radiation at a distance of 5cm from its surface to a dose rate of not more than 0.25 mr/hr. When necessary, shutter status indication (open or closed) should be provided on or adjacent to the tube housing which will automatically indicate the position of each shutter in a readily discernible manner. For OPEN BEAM x-ray equipment the following precautions apply: The unit must have visible lights that operate ONLY WHEN the primary beam is energized. This signal should be labeled with words such as X-RAY ON so that its purpose is easily identified. The analytical x-ray equipment user should be in immediate attendance at all times when the equipment is in operation unless otherwise approved by the RPP. 4 P a g e

7 When not in operation, the equipment will be secured in such a way as to be accessible to or operable by analytical x-ray equipment users only (i.e. key locks). Whenever practicable, all shutters should be provided with a shutter open indication of failsafe design. *Note: Open beam techniques should only be used after all attempts at an enclosed system have proven this to be impracticable. Particular attention should be given to viewing devices to ensure that lenses and other transparent components attenuate the radiation beam to minimal levels when alignment involves working near the open primary beam. The beam current should be reduced when a fluorescent alignment tool is used; dimming the room light will permit a significant reduction in beam current. The fluorescent alignment tool should be long enough to permit the analytical x-ray equipment user s hand to be kept a safe distance from the beam. 7.0 Radiation Surveys 7.1 User Survey Requirements Perform surveys prior to each new use of the x-ray equipment. Perform recommended weekly surveys to ensure radiation levels have not changed. Perform recommended periodic surveys on the local components to check for leakage radiation when the set-up is changed. 7.2 RPP Survey Requirements Perform surveys upon installation of the x-ray equipment and at least once a year thereafter. Perform surveys after any change in the initial arrangement, number, or type of local components in the system are med. Perform surveys after any maintenance requiring the disassembly or removal of a local component in the system. 5 P a g e

8 8.0 Personnel Monitoring The analytical x-ray equipment users shall wear whole body and/or wrist or finger badges when assigned by the RPP. The monitoring device should be worn such that the body part nearest the primary beam is monitored. Monitoring badges worn on the chest or abdomen may provide an indication as to the amount of scattered radiation dose to the whole body. Operations involving the use of analytical x-ray equipment will be planned so that the exposures are in compliance with the limits in Table I and ALARA. Table I: MIT Annual Limits for Radiation Dose Area Exposed Amount (mrems/year) Total Effective Whole Body Dose Equivalent 1 (TEDE) 5000 Skin of whole body and extremities Lens of the Eye Declared Pregnant Worker Notes: 1 Total Effective Dose Equivalent means the sum of the deep dose equivalent for external exposures and the Committed Effective Dose Equivalent for internal exposures. 2 Shallow Dose Equivalent which applies to the external exposure of the skin or an extremity, is taken as the dose equivalent at a tissue depth of centimeter averaged over an area of 1 square centimeter. 3 Declared Pregnant Worker dose equivalent limit applies to the time of the entire pregnancy. The RPO requires all preg nant workers who wish to declare their pregnancy to follow the MIT Radiation Protection Committee Policy Regarding Pregnant Employees and Staff who ar e Potentially Exposed to Ionizing Radiation. 6 P a g e