Chapter 8 Radiation Producing Machines for Non-Medical Use

Transcription

1 Chapter 8 Radiation Producing Machines for Non-Medical Use 8.1 Acquisition and Registration of Radiation Producing Equipment The Radiation Installation Act of the State of Illinois requires the registration of each location or facility where radiation machines are used and allows the blanket registration of all equipment in institutions that have a central committee with the authority to supervise radiological safety. Since the Radiation Safety Committee serves this function, IEMA has issued a single registration for all radiation producing equipment at UIC. The Radiation Safety Section (RSS) is responsible for maintaining the registration for UIC and ensuring adherence to the regulations for the use of all equipment that produces ionizing radiation. The RSS must be kept informed of all plans to acquire, store, and dispose of radiation producing equipment. Acquisition includes purchases, transfers from other departments or institutions, gifts, loans, leases, endowments, etc. In addition, information must also be provided regarding who is responsible for the use or storage of the equipment. The Purchasing Section assists the RSS by providing copies of all purchase requisitions for radiation producing machines. Purchase of machines for approved facilities will proceed normally. Purchase of machines for facilities that have not been approved may encounter significant delays, especially if the facility requires shielding to meet the standards for radiation levels in unrestricted areas. 8.2 Applying for a Radiation Producing Machine Authorization Project directors, individuals designated to be responsible for the local control of radiation safety, may be responsible for one or more radiation producing instruments. To establish a project, the RSS ensures that the facility and equipment meet existing safety standards and that the operating procedures are adequate to protect employees, ancillary personnel, and others who might receive radiation exposure. Form , Application for Authorization to Procure and Use Radiation Producing Machine(s) for Nonhuman Use, is available from the RSS. The RSS recommends that applicants become familiar with the applicable sections of this manual before completing an application form. Information to be submitted includes the qualifications of the project director, a floor plan showing the operator position and beam orientation, machine make and model, machine operating parameters, projected workload, anticipated utilization factors, shielding calculations where needed and operating and emergency procedures. If assistance is needed, applicants may make an appointment with an RSS Health Physicist to discuss the proposed project Design of Radiation Producing Machine Facilities It is very important that the RSS be notified in the early stages of planning a new or modified facility in which a radiation producing machine will be used, especially if structural shielding or shielding Page 1 of 13

2 that must be fabricated will be needed. Before the construction begins, approval of the shielding calculations and blue-prints by Radiation Safety is required. In the case of enclosed radiography, which is discussed further in section 8.10, plans must also be approved by the IEMA Review and Approval of Applications After an application is filed with the RSS, the Radiation Safety Officer (RSO) will review the submitted information, discuss the proposal with the applicant, and prepare a written evaluation. The evaluation will list the radiation producing machines being applied for, proposed use locations and safety precautions that must be followed after the authorization is granted. After the applicant reads and signs the evaluation, the application and the evaluation are provided to the Director of Radiation Protection for review and approval. Based on the type of machine(s) and the use(s) that are proposed, the application may also be referred to the Radiation Producing Machine Subcommittee or the main Radiation Safety Committee for approval. The RSS, any member of the Committee or the Subcommittee, or the applicant may make an appeal to the Committee regarding the actions taken on an application. The decision of the Radiation Safety Committee is final. Upon final approval of the application, the authorization is issued to the project director. Initial authorizations expire about one year from issuance. Renewals of authorizations are discussed in section Pre-operational Surveys Pre-operational radiation surveys will be conducted by the RSO before granting final approval to use new or modified radiation producing machines. The purpose of the survey is to measure the radiation fields around the machine and the facility, and to evaluate what exposures might be received by individuals in these areas Amendment of Authorizations It is important for the project director to keep the RSS informed regarding changes that are needed in the authorization. Authorizations must be amended for the following reasons: Addition of a new machine (apply in advance of acquisition); Modification of an existing machine or facility that could affect radiation safety (apply before modifications are made); Relocation of a machine (apply in advance of relocation); Significant change in the use of a machine that could affect radiation safety (apply before change is made); Addition or removal of project personnel (apply before change is made); and Updating of mailing addresses or telephone numbers for the project (provide prompt notification) Authorization Renewals A RSS staff member will contact the project director about four to six weeks before the expiration date of the authorization. The project authorization documents, surveys, and dosimeter reports are reviewed. Project personnel may be interviewed and an inspection of facilities, equipment, and project radiation safety records is conducted to determine the compliance status of the project. The results of the renewal inspection are discussed with the project director and renewal documents are Page 2 of 13

3 prepared. Upon approval of the renewal, a new expiration date is assigned that is based upon the type and number of machines that are authorized, complexity of the procedures being performed and the compliance status of the project. Project renewals of one to two years can be expected in most cases. Renewals of as little as 3 months may be issued in instances where numerous, repeated, or severe violations of the conditions of authorization have been identified. Projects with extremely severe or repeated violations may be referred to the Radiation Safety Committee or the Radiation Producing Machine Subcommittee to consider whether the renewal should be granted Vacations, Sabbaticals, and Leaves of Absence Project directors are responsible for compliance with the conditions of their authorizations at all times, even when they are not present to provide direct supervision. During absences, project directors should make provisions so that work continues to be conducted safely and in accordance with the conditions of the authorization. In some instances, depending upon the length of the absence, the work being conducted, and the personnel involved, it may be necessary to appoint a qualified individual to act on behalf of the project director in achieving this goal. For example, close supervision of inexperienced workers, performance of surveys at meaningful times, periodic inspection, and proper maintenance of equipment must continue. If a project director plans to be absent from the University for longer than six weeks, an Acting project director must be appointed. This individual may be a faculty member, a staff member, a post doctoral student, etc. Several weeks before the absence begins, the project director must do the following: Select a qualified individual; If the individual is not the project director of another similar project, have the individual complete form C, Training and Experience of Radiation Project Director; and Complete form , Request to Designate an Acting Project Director. Send the request and the training form, if required, to the RSS. The RSS will review the request and approve it if the selected individual is qualified. The name, address, and telephone extension of the acting project director will then be added to the RSS's database so that communication regarding the project will be with this individual during the absence Temporary Inactivation of an Authorization Projects expecting to be inactive for a period of one year or longer should be temporarily inactivated. Temporary inactivation of a project provides benefits to the project director and the RSS. Reactivation does not normally require the re-submission of application forms. Inactivation is initiated by making a written or verbal request of the RSS. A Health Physicist will contact the project director to make further arrangements. Radiation producing machines must be transferred to another project, disabled in an effective manner (see Section 8.6), or placed in storage during inactivation. To initiate reactivation, a written request is made by the project director. A Health Physicist will make arrangements for the project authorization to be reactivated. Page 3 of 13

4 8.2.8 Termination of an Authorization Authorizations should be terminated when there will be no further use of radiation producing machines. Individuals who are leaving UIC must terminate their authorization in a timely fashion. Requests to terminate an authorization should be made verbally or in writing by the project director. A Health Physicist will contact the project director to make the necessary arrangements. Projects that have been terminated cannot be reactivated without submitting new application forms. 8.3 Obtaining Radiation Producing Machines The RSS must be notified before acquiring radiation producing equipment. This includes purchases, gifts, or machines that are brought to UIC from another institution. When purchasing equipment that produces ionizing radiation, include the words "X-Ray Equipment" on the purchase requisition. The Purchasing Section has been instructed to watch for all requisitions for the purchase of radiation producing equipment. Before issuing a purchase order or initiating any bid procedures for such equipment, the purchasing agent must obtain clearance from the RSS. Permission to continue with the purchasing procedure will be granted only if the requisitioner has a current authorization for the unit being ordered or has submitted an adequate application or amendment request to the RSS for the equipment being ordered. 8.4 Fabrication of Radiation Producing Equipment Before radiation producing equipment may be fabricated, the RSS must determine that the design meets established safety standards and IEMA regulations. For instance, the design of cabinet x-ray equipment and similar devices must meet the requirements of the Food and Drug Administration, Department of Health and Human Services, Title 21, Code of Federal Regulations, Chapter 1, Subchapter J, Radiological Health, Section The IEMA also specifies safety standards for certain types of equipment. Standards promulgated by the American National Standards Institute (ANSI) and other independent agencies may also be applied. Since requirements for fabricated sources must be determined on a case by case basis, contact a Health Physicist from the RSS before such equipment is designed. Details regarding shielding, interlocks, warning lights, and other safety features are very important. Determining these details during the planning stages may save costly system redesign or retrofitting of safety devices. After a design has been approved, fabrication may proceed. 8.5 Disposal, Transfer and Accountability of Radiation Producing Machines All project directors are accountable for the radiation producing machines in their possession. Before disposing of or transferring any equipment to another person, either on or off campus, a Health Physicist from the RSS must be informed in writing. This is important because equipment may not be transferred to unauthorized recipients and the IEMA must be kept informed regarding the status of all radiation producing equipment at UIC. 8.6 Disassembly of Inactive and Stored Equipment IEMA regulations require all functional radiation producing equipment to be in full compliance with the regulations. Units that are inactive, or in storage, must be physically disabled to be exempt from this requirement. Simple disconnection of the unit from the power source may not be adequate to Page 4 of 13

5 qualify the unit as disabled. The purpose of disabling equipment in storage is to ensure that will not be used before it is inspected for operational safety and regulatory compliance. The RSS will determine the best method to disable equipment on a case-by-case basis. 8.7 Radiation Safety Requirements for Use of Analytical X-Ray Equipment The requirements in this section are primarily for x-ray diffractometers and x-ray fluorescence spectrometers, but may be applied to other equipment with similar characteristics and safety requirements Operator Training All personnel must complete one hour of radiation safety training for users of analytical x-ray equipment before operating analytical x-ray equipment. Operators must be provided with adequate "hands on" training and supervision sufficient to ensure safe operation of the equipment. The project director will ensure training and supervision are supplied. Operators must be provided with a copy of these and other applicable operating procedures before being allowed to work with the equipment Posting and Labeling Requirements A copy of the operating and emergency procedures must be posted near each analytical x-ray unit. A sign or label bearing the Caution: X Rays warning is to be posted at each entrance to areas where functional x-ray equipment is installed. A sign or label bearing the Caution: This Machine Produces X Rays when Energized warning is to be placed near any switch or control which initiates x-ray production. A sign or label bearing the Caution: High Intensity X-Ray Beam warning is to be placed immediately adjacent to each x-ray tube in such a way that it is clearly visible to any person operating, aligning, or adjusting the unit. The signs and labels mentioned above are provided by the department or the RSS Equipment and Facility Requirements A clearly visible indicator must be provided near each x-ray source that is activated whenever x rays are being produced. A clearly visible indicator (electrical or mechanical) showing the position (open or closed) of each shutter must be provided. The primary beam must be intercepted by the auxiliary apparatus, a beam trap or other auxiliary shielding under all normal operating configurations. Closed beam paths should be provided wherever practical. Page 5 of 13

6 Electrical and/or mechanical interlocks should be provided for the auxiliary apparatus that causes the primary beam to be shut off or that causes the shutters to close whenever the apparatus is not properly installed. Unused tube ports shall be closed in such a fashion that accidental opening is not possible. The RSS must be notified before new equipment is ordered, when significant equipment modifications are made, when equipment in storage is to be reactivated, or when a unit is to be moved from one laboratory to another (see Sections and 8.3). Equipment in storage must be rendered mechanically inoperable to avoid meeting the equipment requirements stated above General Operating and Emergency Procedures All operators must wear whole body dosimeter and TLD rings while using x-ray equipment. These monitoring devices must be returned to the RSS promptly at the end of each month. Prompt return of badges results in the timely detection of unusual exposures and prompt correction of any associated radiation safety problems. See Chapter 12 for further information about dosimeters and TLD rings. Qualified operators must have the approval of the project director responsible for the equipment before beginning use. Operators must follow the detailed operating procedures specified by the project director. If the procedures contained in the manufacturer's manual are inadequate or inappropriate, other written procedures shall be substituted. Before aligning cameras by eye, be certain that the x-ray tube is turned off or be certain that viewing is done only through a properly designed lead glass viewing window. Before changing samples, be certain that the beam is switched off or the shutter is closed and cannot possibly open during the procedure. To determine the status of the beam, check the kv and ma meters and all appropriate warning lights. Perform radiation safety surveys with a Geiger counter or ion chamber frequently. Ensure that exposure rates in the horizontal planes around the edges of the table are below 0.2 mr/h at all times. WARNING: Instrument readings may be a small fraction of the true exposure rate. See the discussion on the following pages. Interlocks and safety devices (shutters, indicators, shielding, warning lights, etc.) must not be defeated, blocked, or bypassed. If it is necessary to bypass interlocks for maintaining or repairing equipment (e.g., beam alignment), the work must be performed in accordance with written procedures that are approved by the RSS. Interlocks and safety devices (shutters, indicators, shielding, warning lights, etc.) on functional x- ray equipment must be tested for proper operation at least monthly. Faulty equipment shall not Page 6 of 13

7 be used until repaired. Records of these tests shall be maintained as required by the IEMA regulations on Form , Analytical X-Ray Equipment Safety Device Testing Log, available from the RSS. The x-ray tube must not be energized until all equipment and auxiliary devices are properly installed. The x-ray tube must be de-energized before making changes in the equipment arrangement. No portion of the body shall be exposed to the primary x-ray beam. Even brief exposure can cause permanent injury. Exposure to the reflected or scattered rays shall be avoided All equipment malfunctions must be reported, without delay, to the project director having responsibility for the equipment. Any suspected exposure to the primary x-ray beam must be reported immediately to the RSS. During normal working hours, call ext , to give notification. After normal working hours, call (312) to talk to a person from EHSO who will contact the RSS personnel Annual Occupational Dose Limits Table Annual Occupational Dose Limits (IEMA) OCCUPATIONAL LIMITS PART OF BODY EXPOSED Adults Minors Whole Body 5,000 mrem 500 mrem Lens of Eye 15,000 mrem 1,500 mrem Skin 50,000 mrem 5,000 mrem Extremities 50,000 mrem 5,000 mrem Other Applicable Dose Limits Embryo/Fetus, Declared Pregnancies ONLY Individual Member of the General Public 500 mrem 500 mrem Whole Body Additional information regarding dose limits, standards, and declared pregnancies can be found in Chapter 11, Maximum Permissible Dose Limits, Concentrations, and Radiation Levels of this manual. Page 7 of 13

8 8.7.6 Injuries and Localized Effects Associated with Analytical X-Ray Equipment (Excerpt from NBS Handbook 111, ANSI N43-1, Radiation Safety for X-Ray Diffraction and Fluorescence Equipment) X-ray diffraction and fluorescence analysis equipment both produce high intensity ionizing radiation that can cause severe and permanent injury if any part of the body is exposed to the primary beam even for a few seconds. In case of accidental exposure, severe burns affecting the upper extremities of the body are the most frequently reported type of injury. These are slow to heal and can lead to cancer. Amputation of one or more of the fingers is sometimes required. Exposure of the lens of the eye to large doses can result in cataracts and other opacities. At low doses the damage may not become apparent until years later. Table Localized Effects Applicable to Analytical X-Ray Injuries Location Effect Entrance Exposure Eye Skin Change in optic lens Clinically significant cataract Threshold erythema (100 kev) Threshold erythema (1000 kev) Raw moist area Ulceration, slow healing 200 Roentgens 600 Roentgens 300 Roentgens 1,000 Roentgens 1,500 Roentgens 5,000-7,000 Roentgens Page 8 of 13

9 8.7.7 Radiation Levels Emitted by Analytical X-Ray Equipment Table Danger Areas in Diffractometers and Spectrometers (Assuming Maximum Operating Parameters) Approximate Exposure Rate SOURCE OF RADIATION R/sec mr/h Inside specimen chamber of spectrometer 10 36,000,000 Inside crystal chamber of spectrometer ,000 Outside exit window of spectrometer At open port of diffraction tube or tower 2 7,200,000 At sample position of diffractometer ,000 At receiving slit of diffractometer ,800 At exit collimator of Debye-Scherrer camera with no collimator in position , Estimation and Measurement of External Radiation from Analytical X-Ray Equipment Figure 8-1 shows spectral distributions of x rays from a tube with 1 mm Be inherent filtration operated at 100 kev and with increasing thicknesses of aluminum filters. Note the two main features of the spectrum representing the two mechanisms by which x rays are produced, bremsstrahlung and electron displacement. Bremsstrahlung, or breaking radiation, is created when the electrons that are bombarding the target in the x-ray tube decelerate in the electric field close to the nucleus of the target atoms. The kinetic energy lost in this deceleration is converted into x rays, the energies of which are dependent upon the charge on the electron, which is fixed, and the strength of the electric field, which is dependent on the distance of the electron from the nucleus. The bremmstrahlung x-rays are represented by the smooth portion of the x-ray energy spectrum. Page 9 of 13

10 Kinetic energy of the electrons bombarding the x-ray tube target can also remove electrons from target atoms. The energy needed to free the electron from the shell is called the binding energy. This produces an atom with excess energy. Additional kinetic energy may also be imparted to the electron that is freed from the target atom. When the vacancy in the inner shell is filled, the binding energy is released, creating a characteristic x ray with an energy equal to the binding energy. Characteristic x rays are monoenergetic and are represented by the sharp peaks in the x-ray energy spectrum. From the spectrum, notice that as aluminum filtration is added, the lower energy x rays are preferentially filtered from the beam, increasing the average x- ray energy penetrating the filter. This is sometimes referred to as beam hardening; however, even with significant beam hardening the average x-ray energy is significantly lower than the maximum energy. A formula to approximate the exposure rate from analytical x-ray equipment, Equation 8-1, developed by Bo Lindell, was published in Health Physics, Volume 15, pp This equation provides accuracy of ±25% for tubes with tungsten targets and 1 mm beryllium windows operated at voltages between 25 and 80 kv. Other filtrations may change the exposure rate by a factor of two. Where X_ = Exposure rate in Roentgens/sec V = Voltage applied to x-ray tube in kv Z = Atomic Number of Target I = Current supplied to tube in ma r = Distance from x-ray tube focal spot in cm Measurement of the radiation fields emitted by analytical x-ray equipment can be very difficult because of the energies of radiation emitted, the intensity of the beams and the very small angles the primary beams frequently subtend. Measurement of scattered radiation can also be difficult. An important discussion regarding the properly use of geiger counters and ionization chamber survey meters to measure radiation from analytical x-ray equipment is presented in Chapter 14, Radiation Surveys. Page 10 of 13

11 8.8 Radiation Safety Requirements for Electron Microscopes Properly maintained electron microscopes do not present a significant radiation hazard to operators and other personnel in their vicinity. Electron microscopes should be registered with the RSS, and a responsible individual should be in charge of each unit with regard to radiation safety, but under normal circumstances formal approval of a radiation project director is not necessary. To register an electron microscope, submit a completed registration form, available from the RSS. Radiation surveys of electron microscopes are conducted whenever requested by the operators or personnel responsible for the equipment. To request a survey, call extension and ask to speak with a RSS staff. It is suggested that surveys be performed upon installation or relocation, and after any repair or maintenance that could increase output or reduce shielding. The person responsible for the use of an electron microscope should ensure that the following radiation safety program is followed: Operating and Emergency Procedures - Written operating and emergency procedures must be provided. These procedures should include any safety procedures that must be followed during routine use and emergency telephone numbers. The emergency call list should include the phone numbers of the project director and the telephone numbers of the RSS ( during working hours and all other hours). Maintenance Procedures - If maintenance will be performed by project personnel, written maintenance procedures must be provided that include appropriate safety procedures and warnings. Modification of the machine to increase output or reduce shielding is prohibited unless approved in writing by the RSS. The quality and functionality of replacement parts in critical areas must meet or exceed the manufacturer's original specifications. For example the materials in the column that houses the beam or target should not be changed. It is also important that leaded glass viewing windows not be replaced with ordinary glass. The written procedures should include warnings regarding avoidance of unnecessary radiation exposure and protection against high voltage hazards. Operator Training - All operators should be properly trained in operating and emergency procedures. They should also be trained in any maintenance procedures that they will perform. Posting and Labeling - A sign or sticker with the radiation symbol and the wording "Caution, This Machine Produces Radiation When Energized" should be placed near any switch or control that energizes the unit. Dosimeters - Operators of electron microscopes are not required to wear personnel monitoring devices. Maintenance personnel who perform procedures that could result in radiation exposure should obtain a badge from the RSS. See Chapter 12 for additional information. 8.9 Cabinet X-Ray Systems X-ray systems that are designed to exclude individuals are called cabinet x-ray systems. In general these units are fairly small and shielding is built directly into the cabinet. The door to these units are interlocked to prevent activation of the x-ray beam when the door is opened. Commercially available units are built to standards of the FDA. Under normal use conditions, properly designed and Page 11 of 13

12 operated cabinet systems do not present a radiation hazard to operators or others in their near vicinity. The IEMA makes the following requirements for these units: Operating and Emergency Procedures - Written operating and emergency procedures must include the following information: Security of the radiography system when not in use; Biological effects of ionizing radiation; Radiation hazards associated with the radiography system; Safety practices; Procedure for notifying proper supervisory personnel in the event of an emergency; Maintenance/repair procedures; and Use and care of personnel radiation monitoring devices (dosimeters and TLD rings). Training - Before allowing an individual to operate a cabinet x-ray system, the individual must be trained in the operating and emergency procedures and must demonstrate competence in its use. The project director is responsible for providing this training and keeping records that include the date of the training, the name of the instructor, and the name of the individuals that were trained. Use Records - Records should be maintained relative to the operating parameters and the workload of each cabinet system. This is best accomplished by maintaining equipment use logs. Equipment Requirements - All cabinet x-ray systems must comply with the FDA regulations in 21 CFR which make requirements for shielding, labeling, interlocks, beam indicators, etc. Commercially available systems should be in full compliance with these standards as purchased. Machines that are fabricated at UIC must also meet these standards. The RSS should be contacted for details well in advance of fabricating any cabinet x-ray system Enclosed Radiography Systems Enclosed radiography systems are non-portable x-ray machines with associated enclosures and controls that are designed to allow admittance of individuals. Under normal conditions of use by properly trained personnel, hazards are minimal. Improper use or use by untrained personnel could cause significant hazard to individuals who might be in or near the enclosure. Enclosed radiography systems are not usually purchased as such, they are fabricated on-site. IEMA makes the following requirements: Plans and specifications for new enclosed radiography systems or for the modification of existing systems must be submitted to the IEMA for review and approval before construction of the facility; A pre-operational survey must be conducted before any new installation is placed into operation to determine radiation exposures of all persons who may be in close proximity to the enclosure; A report must be made to IEMA regarding any alteration which increases the radiation output of the equipment or which reduces the effectiveness of protective barriers; Radiation emitted from the exterior of the system must comply with IEMA requirements as described in chapter 15; Page 12 of 13

13 Written operating and emergency procedures must be provided that include: Security of the radiography system when not in use; Biological effects of ionizing radiation; Radiation hazards associated with the radiography system; Safety practices; Procedure for notifying proper supervisory personnel in the event of an emergency; Maintenance/repair procedures; and Use and care of personnel monitoring devices (dosimeters and TLD rings). Provide a copy of and instruction in the operating and emergency procedures before allowing them to operate the system; Require individuals to demonstrate competence in the use of the unit and an understanding of the operating and emergency procedures, and to maintain records regarding compliance with these requirements; Require the use of whole body dosimeters or TLD badges for every operator, maintenance person, and individual who set-up objects for radiography in the enclosure; Conduct radiation surveys to determine that the radiation machine is "off" prior to each entry into the enclosed room; Equipment requirements include reliable interlocks at each entrance, a door fastening mechanism that can be opened at all times from inside of the room, a continuous audible and/or visible alarm within the protective enclosure that is activated at least 20 seconds immediately before the first initiation of x-ray generation, etc.; and Additional requirements may be necessary depending on equipment design, facility design, or procedures to be performed. If further information is needed, contact the RSS Other Radiation Producing Equipment Many other types of radiation producing equipment are also regulated by IEMA. Such systems include electron beam welders, electron microprobe analyzers, flash x-ray systems, electron spectroscopy for chemical analysis (ESCA) units, etc. These types of units are frequently not readily categorized with regard to the regulations, and may have special radiation safety requirements. Radiation safety requirements for these types of units will be determined on a case by case basis. Page 13 of 13