RADIOISOTOPE FUME HOOD OCCUPATIONAL RISK PREVENTION MANUAL Madrid. 3 Telstar, Josep Tapiolas, 120, Terrassa, Barcelona.

April 20, 2016 | Author: Jonah Henderson | Category: N/A
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RADIOISOTOPE FUME HOOD OCCUPATIONAL RISK PREVENTION MANUAL F. González1, C. Torres1, Dr. Cruzet2, P. Uribe2, P. Barbero2, R. Dalmau3, J. Teijeiro 1


Tecnatom, Avda. Montes de Oca, 1, 28709 San Sebastián de los Reyes, Madrid. Hospital Clínico San Carlos, Servicio de Prevención de Riesgos Laborales, c/ Prof. Martín Lagos s/n, 28040 Madrid. 3 Telstar, Josep Tapiolas, 120, 08226 Terrassa, Barcelona.

Abstract. Using radioactive substances in hospitals, laboratories, industries… has got a great importance at present. Personnel in nuclear medicine and nuclear research laboratories face with the problem of additional radiation exposure through inhalation or ingestion of airborne radioactive materials. Build-up of concentrations of radioactive materials in the air inside the laboratory may be attributed to accidental spillage of radioactive liquids or release of gaseous radioactive substances while dispensing, handling, or storing radionuclides. To ensure the removal of undesirable airborne contamination, installation of a Fume Hood may be necessary. The use of Radioisotope Fume Hoods is important to avoid radiation exposures of workers manipulating radioactive substances. Due to this, an occupational risk prevention manual about Fume Hood to prevent Ionising Radiation Risks, Physical Risks, and also Chemical and Biological Risks, has been prepared. A complete occupational risk prevention manual in this field will have to include containment and shielding functions of the Radioisotope Fume Hood, in addition to the kind of the exhaust filter. The correct use of the Fume Hood, its maintenance and the filter maintenance, the cleaning and decontamination, a good radioactive waste management, the technical features of the radioactive laboratory and the Hood location within this laboratory is of great importance.

1. Introduction. Work carried out in a laboratory can be accompanied by the formation of airborne contamination. The assessment of the significance of radioactive airborne contamination is a difficult problem due to the influence of many factors such as breathing characteristics (rate of breathing, whether the individual breathes through the nose or the mouth etc.), the size, shape and density and the chemical properties of the airborne particles (which will affect lung deposition and subsequent metabolism), and the ventilation pattern in the working area. Control is largely based on proper containment and ventilation coupled with correct working discipline Laboratory Fume Hoods are an important tool used to control exposures to radioactive airborne contamination in laboratories. A well designed Fume Hood, supply a containment and shielding functions, when properly installed and maintained, can provide a substantial degree of protection for the experimenter.

FIG. 1. Radioisotope Fume Hood.


2. Radioisotope Fume Hoods. Containment Function. The principal purpose of the different kinds of Radioisotope Fume Hoods is avoiding unnecessary radiation exposures. The containment function, that provides these facilities, avoids the internal contamination of the worker during the manipulation of the airborne radioactive material. In Nuclear Medicine and the Research laboratories scope, the used Radioisotope Fume Hoods are the Radiochemical Fume Cupboards and Biological Safety Cabinets. 2.1. Radiochemical Fume Cupboards. Radiochemical Fume Cupboards are ventilation devices where airborne radioactive materials, or radioactive dust emitters, can be handled surely. Prevent the escape of hazardous agents to the Fume Hood is the purpose of these equipments, making difficult that airborne radioactive materials make in contact with the worker, providing operator protection. This is obtained creating a depression inside the Hood using an extractor, this generate an input stream of air from the laboratory and prevent the escape of contamination protecting the worker. This air, leaves the Hood through a filtration system that captures these agents, thus avoid its escape to the environment.

Fan Filtration System Not Contaminated Air Contaminated Air

FIG. 2. Fume Cupboards AirFlow Scheme. 2.2. Biological Safety Cabinets. In this kind of Radioisotope Fume Hood, the airflow is drawn around the operator into the front grille of the cabinet, which provides personnel protection. In addition to Radioisotope Fume Cupboards, a downward laminar flow of HEPA-filtered air provides product protection by minimizing the chance of cross-contamination along the work surface of the cabinet. Because cabinet air has passed through the


exhaust filter system, it is contaminant-free ducted out of the building, providing environmental protection. Therefore, Biological Safety Cabinets provide personnel, environmental and product protection.

Clean Air Outside Air Contaminated Air

FIG. 3. Biosafety Cabinet AirFlow Scheme. To manipulate radioactive isotopes, Radioisotope Fume Cupboard will be sufficient, in which, the exhaust air speed, based on the radioisotope volatileness, can be regulated. In addition, if the sterility of the work surface is required, use Biological Safety Cabinet will be necessary. 3. Shielding Function. In addition to containment function, Radioisotope Fume Hoods should provide a shield function to avoid or limit the degree of radiation exposure, for this reason, the walls and frontal screen of the Hood must be shielded. Shielding of Fume Hood walls should be: Low and medium energy β emitters → Non necessary due to complete radiation attenuation by Hood walls. High energy β emitters → The absorption of high beta particles in the walls of the Hood, emitted by isotopes like P32, Y90… gives rise to bremsstrahlung radiation. To prevent workers irradiation by these X-Rays should be achieved: Internal walls shielded by using thick optical acrylic, like Perspex, to avoid producing significant amounts of bremsstrahlung, or, frontal sliding shielded by using leaded glass to block this kind of radiation. γ emitters → Internals walls should be shielded with lead which thickness will be proportional to gamma energy. Shielding of Frontal Sliding should be:

β emitters → Beta emissions can be effectively blocked by using 5 to 10 mm thick Perspex. γ emitters → Gamma emissions can be achieved by leaded glass shielding.


4. Filters. All Fume Hoods should be provided with an air exhaust system, which will be supplied with a filter system to retain undesirable hazardous products. The type of used filter is based on the size of particles to retain. In the case of works with radioactive material, radioactive dust or gaseous molecules could be emitted by unsealed radioactive sources. In presence of radioactive dust particles, the Fume Hood should be provided with HEPA filters, but if radioactive source is more volatile, activated charcoal filters should be introduced in the filtration system. For this reason is advisable to use a triple filtration system: antiparticles, HEPA and activated charcoal filter. 5. Construction and Coatings Materials. The constructive characteristics of the Radioactive Fume Cupboards and Biological Safety Cabinets used for handling unsealed radioactive sources will be: • Solid, resistant materials to chemical agents, and easily decontaminable. Normally, the external and internal surfaces should be made in stainless steel or plastic resins (epoxy). • The surfaces exposed to the radioactive material should be smooth, without fissures, raincoats, and free of junctions and angles, being sealed the essential junctions. In this way, the escape and accumulation of radioactive particles will be prevented, allowing easy cleaning and decontamination. • Resistant materials to the temperature, the thermal shocks and the fire. • Avoid the ignition sources using equipment equipped with electrical intrinsic safety. • For new installations or modifications of existing installations, controls for laboratory Hood services, gas, air, and water, should be located external to the Hood and within easy reach. Internal illumination should be necessary. • Shutoff valves for services, including gas, air, vacuum, and electricity shall be outside of the Hood enclosure in a location where they will be readily accessible in the event of fire in the Hood. The location of such a shutoff shall be legibly lettered in a related location on the exterior of the Hood. • Radioisotope Fume Hood exhaust fans should be connected to an emergency power system in the event of a power failure. 6. Recommendations of Use. A correct use of the Radioisotope Fume Hood is as important as a right Fume Hood election, to provide the best protection to the workers. The following are general guidelines to be followed when working in the Hood 6.1. Before Using. Before any operation is carried out in a Radioactive Fume Cupboard check that: 1. Air is flowing into the Fume Hood. Verify HEPA filter is not saturated. 2. The quantity of radioactivity being handled is suitable for its containment and shield. 3. Correct personal and environmental monitoring are available. Set up contamination monitoring equipment close the Fume Hood in such a way that gloves can be checked without touching anything outside the Hood. In addition to the recommendations considered for the use of Radioisotope Fume Cupboard, before using Biological Safety Cabinets will be necessary to make the following performances to assure sterility the work surface:


1. Ideally, the cabinet should be left running at all times. However, if it has been turned off, turn the blower switch to on and before using it, let it run at least five or ten minutes for room air to be removed from the cabinet. 2. Read the airflow meter to verify that its works properly. 3. When is equipped with a U.V. light, turn it off. 4. Clean the Hood surface with suitable product. 6.2. During the manipulation To work with radioactive material in a Fume Hood is necessary to consider: 1. As far as possible ensure that the areas in front of fume cupboards are kept clear of all obstructions. 2. Keep all materials and perform the work at least fifteen centimetres inside the sash opening. 3. Maintain the frontal lowered to avoid the irradiation risk, since it has the shield against the radiations. 4. Latex gloves must always be worn for operations within a fume cupboard. Check that laboratory coat cuffs are tucked into gloves. After any fume cupboard work and prior to touching any item outside the fume cupboard, gloves should be discarded in the fume cupboard or monitored, taking care not to contaminate the monitors. Any glove found to be contaminated should be left in the fume cupboard and disposed of in due course as radioactive waste. Gloves must not be kept in laboratory coat pockets. 5. Take care not to spread contamination from the fume cupboard. Any item to be removed from a radioactive fume cupboard must be directly monitored where possible to ensure that it is free from any loose contamination before it is allowed to come into contact with any surface outside the fume cupboard. 6. Drip trays having sufficient volume in the event of spillage should be used when handling liquids. The fume cupboard floor should also be lined with absorbent paper. 7. Keep the Fume Hood clean and tidy. All spilllages should be cleared up immediately. 8. Not use Bunsen burner, the flame could damage HEPA filter. 9. Must have receptacles in the fume cupboard correctly marked for aqueous liquid waste, organic liquid waste, and solid waste. If use 'sharps' or any broken glass, then these must be disposed of into a clearly labelled 'sharps' container. Use suitable containers for storage of radioactive and hazardous materials. Materials should be stored only for short periods of time. 10. Work with radioactive materials must be planned such that there is sufficient time to make the fume cupboard safe, tidy up, dispose of waste, and carry out personal contamination monitoring. Monitor the sill and floor area outside the fume cupboard for alpha, beta and gamma contamination by direct monitoring. In Biological Safety Cabinets, it will be necessary to consider in addition: 1. All materials should be placed as far back in the cabinet, toward the rear edge of the work surface and away from grilles of the cabinet. Avoid excessive movements in and out of the cabinet. 2. Activities that create eddy currents, opening and closing doors and windows, personnel walking near the cabinet, should be minimized as these types of activities can disrupt the air barrier. 3. All equipment that has come introduced into the cabin should be decontaminated. 4. The general workflow should be from clean to contaminated. Materials and supplies should be placed in such a way as to limit the movement of dirty items over clean ones. 5. Perform all work using a limited number of slow movements, as quick movements disrupt the air barrier. Try to minimize entering and exiting your arms from the cabinet, but if you need to, do it slowly, directly, and straight in/out.


6.3. After Using Once the work has been finished in a Radioisotope Fume Hood, will be necessary to carry out the following performances: 1. Monitoring the Hood to detect possible contamination. 2. Clean and clear up the Hood decontaminating all work surfaces. 3. Monitoring oneself to verify the absence contamination. In addition, in Biological Safety Cabinets will be necessary to consider: 1. The work surface, interior walls, and the interior surface of the frontal should be wiped with 70% ethanol 2. Keep on the cabin during at least 15 minutes. 3. Turn on, if is necessary, the ultraviolet light. 7. Cleaning and Decontamination of Fume Hoods. All containers and equipment should be surface decontaminated and removed from the Fume Hood when work is completed. At the end of the workday, the final surface decontamination of the Hood should include a wipe-down of the work surface, the hood's sides and back, and the interior of the glass. The Fume Hood should also be monitored for radioactivity and decontaminated when necessary. Workers should remove their gloves and gowns and wash their hands as the final practices. Small spills within the Fume Hood can be handled immediately by removing the contaminated absorbent paper towelling and placing it into radioactive waste containment. Any splatter onto items within the Hood, as well as the Hood interior, should be immediately wiped with a towel dampened with decontaminating solution. Gloves should be changed after the work surface is decontaminated and before placing clean absorbent towelling in the cabinet. Hands should be washed whenever gloves are changed or removed. Twenty to thirty minutes is generally considered an appropriate contact time for decontamination, but this varies with the disinfectant. Manufacturer's directions should be followed. The spilled fluid and disinfectant solution on the work surface should be absorbed with paper towels and discarded into a radioactive waste containment. 8. Conclusions. The Development of this occupational risk prevention manual to avoid radioactive exposures is important because of the lack of information about Radioisotope Fume Hoods. The use of the manual is going to provide important factors to consider when selecting a laboratory Hood ventilation system, besides to allow, to the Radiation Safety Officer, to prepare a Radioisotope Fume Hood training for workers manipulating radioactive substances. References 1. NTP 233: Cabinas de Seguridad Biológica. Técnicas Preventivas del Instituto Nacional de Seguridad e Higiene en el Trabajo. 2. Seguridad en Prácticas de Laboratorio. Servicio de Prevención de Riesgos Laborales de la Universidad Politécnica de Valencia. 3. Informe sobre Cabinas de Seguridad. Servicio de Prevención de Riesgos Laborales de la Universidad de Navarra. 4. Manual General de Protección Radiológica. Sociedad Española de Física Médica. 5. Limpieza de locales y equipos de preparación de Radiofármacos de una unidad de Radiofarmacia. Agencia Española del Medicamento. Ministerio de Sanidad y Consumo.


6. Radioactive Installation Design and Radioactive Waste Management in Biological Research Centres. Macias M.T., Sanchez A., Carnero A., Cebrian M. and Usera F. 7. Radiation Safety Manual. University of Limerick. 8. Fume Hood Program. University of New Hampshire


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