Chapter 15 Facilities and Equipment

Transcription

1 Chapter 15 Facilities and Equipment This chapter outlines requirements for construction of radioactive material laboratories and facilities housing radiation producing equipment. It also recommends safety equipment that should be made available by the project director. Adherence to these recommendations will be reviewed by the Radiation Safety Section (RSS) and the Radiation Safety Committee when evaluating applications for the use of radiation sources, performing radiation surveys, and conducting project reviews. Further information about obtaining an authorization to possess and use radioactive material and radiation producing equipment is found in Chapters 3, 8, 9, and 10 of this manual Maximum Permissible External Radiation Levels from Facilities The IEMA has established maximum permissible exposure limits for members of the general public that must be met by all radiation facilities. The total effective dose equivalent to individual members of the public from external sources may not exceed: 2 millirem in any one hour; and 500 millirem in any year where sources of radiation were installed before January 1, 1994, and the use of the source of radiation has not changed on or after January 1, 1994*; or 100 millirem in any year where sources of radiation were installed or where the source of radiation or its use changed on or after January 1, * Facilities designed to the 500 millirem per year limit may continue to use the 500 millirem per year effective dose equivalent for members of the general public as long as the intensity of the radiation is not increased beyond the design basis, the type of radiation use is not changed, and the type of facility use is not changed Approval of Facility Plans Prior to Construction All facilities containing sources of ionizing radiation must comply with the external exposure rate limits stated above. Some facilities will need shielding that is beyond that inherent in common building materials and standard construction methods. Facilities that usually require additional shielding include diagnostic X-ray rooms, open beam irradiators, accelerators, brachytherapy source storage rooms, and radionuclide facilities that will contain significant quantities of positron or higher energy gamma emitters such as Na-22, Sc-46, Co-60, Cs-137, Ir-192, and Ra-226. Since shielding is an integral part of all such facilities, a qualified medical physicist, health physicist, or shielding engineer must perform shielding calculations and specify any necessary construction details. In order to provide cost effective structural shielding, the proper choice of shielding materials is essential. Drywall with attached lead sheeting is readily available for construction of diagnostic x-ray installation. Bricks, cement blocks, plaster, poured concrete, steel, and other building materials may be selected for shielding depending upon the types, Page 1 of 9

2 energies and strengths of the radiation fields to be shielded. Attention to construction details is important so that shielding penetrations for essential utilities (HVAC, electrical, plumbing, etc.) will not compromise the shielding design. Further information regarding shielding design is provided in section of this manual and in several NCRP publications. 1,2,3 Before construction can begin, the RSS must review all plans and shielding calculations. The best time to begin the review of facility design is during the planning stages. This may help to avoid costly revision of architectural plans, construction plans, or revision of improperly constructed facilities. To evaluate the proposed facility, a drawing will be needed that includes the dimensions of the space, location and orientation of the source within the space, and the types and thicknesses of construction materials that have been or will be used in construction of the facility. For X-ray installations information will be needed about the maximum and average operating parameters, estimated workloads, use factors, and occupancy factors. For radioactive material facilities the radionuclides, activities, use factors, occupancy factors, and an explanation of how the sources will be used must be provided. Types of facilities that are unlikely to need additional structural shielding include dental X-ray facilities, X-ray diffraction and spectroscopy labs, labs using cabinet X-ray units, electron microscope labs, and biomedical research labs. The RSS should be consulted during the planning stages of all such facilities to confirm that additional shielding design will not be needed Radiation Protection Surveys Immediately after installation of radiation producing equipment and prior to its routine use, a radiation protection survey must be conducted by the RSS. This survey is used to determine the effectiveness of the protective features of the equipment and the adequacy of the structural and auxiliary shielding IEMA Requirements for Radiation Therapy Facilities The IEMA regulations establish the following requirements for design and survey of radiation therapy facilities Radiation Therapy Systems Operating Below 1 MeV The registrant (UIC) must consult a qualified therapeutic medical physicist in the design of any X-ray therapy facility for X-ray therapy systems operating at energies less than 1 MeV. Primary and secondary barriers (shields) are required if needed, and design information must be submitted to IEMA for all X-ray therapy systems operating above 150 kvp. A radiation survey of the new facility must be completed by a qualified medical physicist. Surveys are also required after any change in the facility or system that might produce a radiation hazard. Any deficiencies identified during surveys must be corrected before a patient may be treated. A survey report must be submitted to IEMA within 30 days after completion of the survey. Page 2 of 9

3 Particle Accelerators Operating at 1 MeV or Greater The registrant (UIC) must consult a qualified therapeutic medical physicist in the design of any particle accelerator operating at 1 MeV or greater. Primary and secondary barriers (shields) must be provided if needed and facility design information for all new accelerator facilities must be approved by the IEMA before installation. If the accelerator system is capable of producing radioactive materials in excess of the exempt quantities specified in the IEMA regulations (Part 330, Appendix B) it must also be licensed. A radiation survey of the new facility must be performed by a physicist who did not consult in the design of the facility, and who has no employment or partnership relationship with the design physicist. Surveys are also required after any change in the facility or system that might produce a radiation hazard. Any deficiencies identified during a survey must be corrected before a patient may be treated. A survey report must be submitted to IEMA within 30 days after completion of the survey Design of Radionuclide Laboratories The design of radionuclide laboratories is primarily dependent upon the types and quantities of the radioactive materials handled and the variety of work performed. Most radionuclide projects at UIC use tracer quantities, greatly simplifying laboratory design requirements Structural Shielding Walls, floors, ceilings, doors, and other permanent building features provide structural shielding. Since all building materials have some inherent shielding properties, the choice of building material can significantly affect radiation levels in adjacent areas. Masonry, concrete, and plaster construction usually, but not always, provide significant shielding for all types of radiation. Use of stud/drywall or stud/plywood systems provide adequate shielding for alpha and beta radiations but have a limited ability to shield gamma, X-ray, and neutron radiations. Structural shielding requirements for most tracer quantities are usually minimal, although structural shielding for some of the work conducted with higher energy gamma emitters must be carefully evaluated. Examples of radionuclides used at UIC that could be problematic when present in millicurie quantities are Na-22, Sc-46, Cr-51, Co-60, Sr-85, Nb-95, Tc-99m, Mo-99, Ru-106, In-111, I-131, Cs-137, Ce-141, and Ir-192. When structural shielding is not adequate to reduce radiation exposure rates to acceptable levels in adjacent area, auxiliary shielding might be needed. This may be the best or only practical solution for some shielding problems and may also be necessary to protect personnel. The National Council on Radiation Protection and Measurement (NCRP) has published several reports about proper shielding of gamma, X-ray, and neutron radiation sources (NCRP 1971, NCRP 1976, NCRP 1977). Adherence to these recommendations will usually assure adequate structural shielding in the facilities that are discussed. These publications do not provide information regarding shielding for many of the gamma emitting radionuclides commonly used in research. Page 3 of 9

4 Flooring Ease of decontamination and nonslip properties should be considered when selecting flooring materials in radionuclide labs. Porous materials are undesirable because they cannot be readily decontaminated. Wooden flooring, carpeting, and unsealed concrete are porous and are not acceptable for laboratories using unsealed radioactive material. Sealed or painted concrete is somewhat better, but these coatings will eventually wear or chip away. Asphalt, vinyl, linoleum, and rubber tiles are the usual flooring materials used at UIC. The primary advantages of tile are its long wear, chemical resistance, and ease of replacement. The cracks between the tiles, however, easily accumulate contamination. Tiled floors should be kept waxed to fill the cracks between tiles. Wide sheets of flooring, such as vinyl sheeting, provide the best surface for decontamination purposes but are difficult to repair if damaged Walls and Ceilings Walls are not likely to become contaminated unless a major incident has occurred. Walls should be smooth and easily cleanable. There should be no holes or cracks where radioactive material could accumulate or seep into other places in the building. Ceilings are very unlikely to become contaminated. Ceilings should be made of smooth easily cleaned surfaces. If the ceiling is constructed of acoustical tiles, provide a smooth easily cleaned surface under them Work Surfaces Counter tops, benches, and the floors of hoods are the most likely surfaces to become contaminated. They should be made of materials that are easy to decontaminate and that are chemically resistant such as seamless Formica, stainless steel, or fiberglass. Avoid using radioactive material on porous counter tops such as those made of wood or soapstone. If use of radioactive material must be used on porous counter tops, keep them covered with a nonporous material such as plastic backed absorbent paper or a nonporous strippable coating Plumbing Radionuclide laboratories should be equipped with at least one sink. Sinks should be made of nonporous materials to simplify decontamination. Drain lines should be in good condition and must not leak. Do not store corrosive materials under the sink as their vapors can cause severe damage to the plumbing and cabinetry Storage Areas A secure storage area must be provided within the laboratory for storage of radioactive material. Shielding of radionuclides that emit gamma rays or higher energy beta particles may be necessary to prevent radiation levels from exceeding the established limits (see Chapter 11). Refrigerators or freezers may be used to store radioactive material. Fire safety rules prohibit placing equipment or storage cabinets in hallways outside the laboratory. Contact the Environmental Health and Safety Office for further information about fire safety requirements. Page 4 of 9

5 Fume Hoods and Other Protective Enclosures Procedures used in biomedical research typically employ the use of small quantities of radioactive material that do not readily become airborne. Procedures that could cause radioactive material to become airborne include: chemical reactions that produce gaseous (e.g. sodium borohydride) or volatile products (e.g. radioiodinations) chemical synthesis using tritiated water (evaporation); use of large quantities of radioactive material or radioactive material a concentrated form; experiments using radioactive aerosols (e.g. inhalation experiments); use of solid radioactive material that is in a finely divided form (e.g. smoke, dust, powder); grinding or scraping solid radioactive material (TLC plates); and vortexing, centrifuging, or manipulating radioactive liquids with vacuum pumps or aspirators. Some of these procedures may require the use of a local ventilation system such as a fume hood or glove box to protect personnel from inhaling radioactive material. Requirements to use fume hoods and other ventilation requirements are evaluated by the RSS on a case by case basis. The type and design of ventilation systems and enclosures must be adequate for the intended uses. Requirements to use ventilated enclosures will be clearly specified in the project authorization documents Vacuum Systems Project personnel frequently use vacuum to transfer radioactive solutions. During these transfers, aerosols or liquids may be inadvertently drawn into the vacuum system. Vacuum lines, liquid traps, pump oil, pump vanes, and other components of vacuum systems can become contaminated if the system is not protected with traps and filters. Vacuum systems commonly in use are discussed below. Sink Aspirators - The use of a sink aspirator is preferred when transferring aqueous liquids because small quantities of radioactivity that are pulled into the system will flow into the sink. Periodic decontamination or replacement of the tubing and flasks used in these systems will prevent the spread of contamination. Local Vacuum Pumps - Radioactive material can collect in or on vacuum lines, the pump vanes, exhaust housing, pump oil, etc. Radioactive material may be ejected from the exhaust causing an inhalation hazard and contamination of the area. Gamma emitters may collect in sufficient quantity to present an external exposure hazard. Maintenance personnel, who may not have training or experience with radioactive contamination, will also be faced with these problems if servicing a contaminated pump. The best approach is to prevent contamination of the major components of these systems using traps and filters. Vacuum pumps that are used to transfer radioactive material must be surveyed by the RSS before being sent for service or repair. Page 5 of 9

6 House Vacuum Systems - The types of problems associated with the use of house vacuum systems are similar to those listed above for local vacuum pumps, except problems can be magnified greatly. Small quantities from several laboratories can accumulate in the system. Maintenance personnel working on the system may disturb liquid or dried contamination in the vacuum lines or pump. They may also inhale aerosols in pump exhaust or be exposed or contaminated when draining the liquid traps. Radiation levels from gamma emitters may cause a direct exposure hazard in an unrestricted area. Radiation levels, exposure, and contamination from these systems may go unnoticed by workers and Radiation Safety personnel. Local and house vacuum systems must be protected from radioactive contamination (and contamination from other foreign material) with properly placed liquid traps and filters. Figure 15.1 illustrates an acceptable trap and filter system Use of Work Space in Radioactive Material Labs Consolidate radioactive material use to occupy as small a space as is practical, but do not conduct radioactive material work in cramped quarters. Carefully consider the traffic pattern in the room. If possible, locate the areas that are most likely to become contaminated away from room entrances and major laboratory pathways. Select a storage location for the dry solid radioactive waste container that is close to the work area so the chance of contaminating the floor is minimized. Do not select a waste storage location that will cause unnecessary personnel exposure. If a convenient waste storage area is not available, move the container to the work area when necessary. Choose a sink for disposal of aqueous waste that is in close proximity to the work area. Perform work with materials that emit penetrating radiations as far away from other individuals as possible. Prevent unacceptable radiation fields in adjacent laboratories and hallways by properly selecting the work area, by using adequate shielding, and by conducting surveys at meaningful times. Page 6 of 9

7 15.7 Protective Clothing and Equipment for Radioactive Material Use The project director must supply all personnel who use radioactive materials with lab coats, laboratory gloves, shielding, and other appropriate protection equipment and properly instruct them in their use Lab Coats An adequate supply of lab coats shall be provided so that one is always available when needed. Lab coats must be kept buttoned while working with radioactive material to prevent contamination of personal clothing and they must be surveyed frequently for contamination. Do not wear a potentially contaminated lab coat outside of the laboratory unless it has been carefully checked for contamination. Do not send contaminated lab coats to the laundry. Hold them for decay in the laboratory if contaminated with short lives radionuclides, dispose of them as radioactive waste, or decontaminate them in the laboratory Gloves Always wear gloves when handling unsealed radioactive materials and potentially contaminated objects. When choosing gloves, the physical and chemical properties of the glove material must be taken into account. Improper choice of gloves may result in unnecessary contamination of the hands. Choose a glove that resists penetration by the chemical forms of the radioactive material and solvents that are present or will be used. Gloves should also be resistant to any mechanical hazards that are encountered. While disposable gloves are frequently used when working with radioactive material, the use of non disposable gloves should be considered. Non disposable gloves are generally thicker and come in a wider variety of materials, consequently they may provide improved chemical resistance, mechanical resistance, and better beta shielding. Non disposable gloves may be reused many times if they are properly decontaminated between uses. If disposable gloves are selected, wearing two pairs may also provide similar benefits. Taping the gloves to the sleeves of the lab coat is sometimes helpful in preventing contamination of wrists and sleeves. Table 15.1 lists general information regarding the chemical protection characteristics of glove materials. Before selecting the type of gloves for a particular type of work, more detailed information regarding the resistance to the particular chemicals involved should be obtained. This information is generally available from glove manufacturers and distributors. Further information is available from Fischer Scientific Safety Products Division in their Safety Products Reference Manual. Wash contaminated gloves while they are still being worn. Survey and discard them in the regular waste if free of contamination. Discard contaminated gloves in a radioactive waste container. Handling objects with contaminated gloves can spread contamination. Do not handle notebooks, telephones, door knobs, pens, or other objects while wearing contaminated gloves. Do not wear potentially contaminated gloves outside of the radionuclide laboratory unless they have been surveyed and found to be uncontaminated. Page 7 of 9

8 TABLE PROTECTION CHARACTERISTIC PROPERTIES OF GLOVE MATERIALS MATERIAL Natural Rubber (latex) Neoprene Nitrile PVC (polvinyl chloride or vinyl) CPE (chlorinated polyethylene) PVA (polyvinyl alcohol) Viton Radiation-Resistant Gloves PROPERTIES A material that is inherently elastic and resilient. May be blended or dripped in other polymers in order to achieve a combination of features. Resists acids, alkalies, salts, and ketones. A synthetic rubber developed as an oil-resistant substitute for natural rubber. Resists oil, acids, caustics, alcohols, and solvents. A synthetic rubber with superior puncture and abrasion resistance in addition to chemical protection. Also referred to as NBR or acrylo-nitrile-butadiene. Similar to neoprene. An economical substitute for latex. Resists acids and alcohols, but not petroleum products. Has increased resistance to oil, ozone, heat, and chemicals. Low permeability to gases. Resists halogenated hydrocarbons, some aromatic hydrocarbons and ketones. Not recommended for alcohols or aqueous matrix solutions. Resists oils, fuels, lubricants, most mineral acids, hydraulic fluids and aliphatic and aromatic hydrocarbons. Provides good protection from low energy beta particles, some protection from higher energy beta particles and low energy x rays. Do not use as a substitute for proper handling techniques or auxiliary shielding Other Personal Protective Equipment Other protective apparel that may be used includes protective goggles, plastic aprons, plastic sleeves, coveralls, and shoe covers. These devices are usually not needed when performing work with tracer quantities. If the use of such devices is required by the RSS, they will be specified in the project authorization documents Other Shielding Adequate shielding must be provided by the project for work and storage areas when needed. Acrylic beta shielding for work with higher energy beta emitters such as P-32 is readily available. Bench top shields, vial shields, centrifuge tube shields, test tube racks, storage boxes, waste container shields, and face shields may be obtained commercially. Lead shielding for gamma radiation is also commercially available, including lead bricks, lead sheets, lead foil, lead tubing, lead storage boxes, lead cylinders, syringe shields, lead blankets, lead glass, and lead acrylic sheets. Shielding that is not commercially available can also be fabricated. Contact the RSS for help in choosing the correct shielding for your radioactive work. Page 8 of 9

9 Handling Equipment Test tube holders, forceps, tongs, tweezers, and other devices are needed for handling containers of radionuclides that emit penetrating radiation. Even microcurie quantities of radionuclides such as P-32, Tc-99m, In-111, I-125, and Cs-137 are capable of delivering unacceptably high doses to the fingers and hands if held directly without such devices Laboratory Spill Kits While radionuclide spills are not a frequent occurrence, every laboratory must be prepared in the event one occurs. Small spills require little preparation other than knowing the correct decontamination procedure, and are usually contained and cleaned with supplies normally available in the lab. Larger spills require better planning and availability of supplies to ensure that contamination is not spread unnecessarily and exposures are minimized. Further details regarding spill kits and methods for cleaning spills can be found in Chapter 18. References 1. Protection Against Neutron Radiation, NCRP Report No. 38, 1971, National Council on Radiation Protection and Measurements, Bethesda, MD 2. Structural Shielding Design and Evaluation for Medical Use of X Rays and Gamma Rays of Energies up to 10 MeV, NCRP Report No. 49, 1976, National Council on Radiation Protection and Measurements, Bethesda, MD. 3. Radiation Protection and Design Guidelines for MeV Particle Accelerator Facilities, NCRP Report No. 51, 1977, National Council on Radiation Protection and Measurements, Bethesda, MD. Page 9 of 9