Presentation on theme: "Radiation Safety E-Training Module Radioactive Contamination Minimization and Remediation."— Presentation transcript:
Radiation Safety E-Training Module Radioactive Contamination Minimization and Remediation
Radiation Safety E-Training Module This refresher training is intended for individuals who have completed the New Radiation Worker Qualification (NRWQ) course and satisfies the annual radiation safety continuing training requirement.
Module Objectives Safe Handling of Radioactive Material Minimizing Radioactive Contamination Detection of Radioactivity Personal Protection Decontamination and Reporting
Safe Handling of Radioactive Material When working with radioactive material, users should: Prepare a radioactive materials work area in the laboratory Cover work area with absorbent paper Set up radiation shields Ensure that radioactive waste containers are available Turn on survey meter and place adjacent to work area Survey radioactive material work areas before, during, and after handling Perform swipe surveys to document removable contamination Use survey meters to identify fixed areas of contamination Perform personal contamination surveys Scan gloves frequently during experiments Monitor whole body before leaving laboratory
Sink Bench Prepare a radioactive materials work area in the laboratory Work space should be set up away from high traffic and administrative areas Area should be clean and free of clutter Volatile radioactive material must be handled in a certified fume hood Cover work area with absorbent paper Plastic backed laboratory paper is recommended to prevent seepage of liquid Designate radioactive materials handling area with identifying labels and tape Sinks must never be included in a radioactive material work area; never dispose of radioactive material down laboratory sink drains Set up radiation shields Design shielding such that radiation fields are minimized in all directions Plexiglas may be used to provide protection from beta-emitting isotopes Lead may be used to reduce radiation exposure from gamma-emitting isotopes Ensure that radioactive waste containers are available Label all containers on the top and side with radioactive symbol and isotope Segregate waste by type and isotope All sharps must be placed in a puncture resistant containers Waste Turn on survey meter and place adjacent to work area Perform battery and functionality tests prior to use Use Geiger-Müller (GM) probes to detect medium and high energy beta emissions Sodium iodide (NaI) probes are efficient at detecting low energy gamma emissions Shielding Safe Handling of Radioactive Material
Good laboratory practice will help minimize the chance of radioactive contamination. Do not consume food or drink in the laboratory Work with volatile substances in a certified fume hood Ensure familiarity with radioactive material handling procedures Limit the volume of radioactive waste stored in the laboratory
Radioactive Contamination Minimization Complete prevention of radioactive contamination during radioisotope handling is often impractical, or even impossible. Therefore, it is necessary to monitor radioactive work areas frequently to control the spread of contamination. Monitoring the movement of radioactive materials will allow you to recognize and remediate contamination in a timely manner.
Radioactive Contamination Minimization It is also important to monitor common areas and frequently touched objects, in addition to radioactive material use work areas: Common walkways Desk areas, computer keyboards, and mice Radioactive material use equipment, including pipettes and centrifuges Door knobs Light switches
Radioactive Material Detection Due to the odorless and invisible nature of radioactive material, the most challenging aspect of radioactive contamination management is determining where the contamination exists. Radioactive material will quickly and easily spread from object to object, much like dust.
Radioactive Material Detection Radioactive material contamination may be either fixed or removable. Fixed contamination: radioactive material cannot be removed with conventional cleaning methods. Removable contamination: radioactive material may be transferred from a surface with moderate pressure. It is important to consider both the type of contamination and the characteristics of the radioactive material involved when selecting a survey instrument.
Portable Survey Meters Most portable survey meters cannot detect low energy beta emissions such as H-3 and are unable to characterize contamination as fixed or removable. Portable survey meters utilize probes that have varying efficiencies based on the type of radiation detected. Geiger-Muller (GM) probe Sodium Iodide probe
Geiger-Muller (GM) Probe A Geiger-Muller (GM) probe may be shaped as either a small disc or a cylinder, and is efficient in the detection of medium to high energy beta emissions such as C-14, S-35, and P-32. The average background count rate for a GM probe at UCLA is 60 cpm.
Sodium Iodide Probe A Sodium Iodide probe is often shaped as a cylinder and is efficient in the detection of low energy gamma emissions such as I-125 and Cr-51. Due to the increased efficiency of a sodium iodide probe for low energy gamma emissions, background readings tend to be much higher than that of a GM probe due to the detection of cosmic radiation. The average background count rate for a sodium iodide probe at UCLA is 300 cpm.
Radiation Counters Radiation counters are relatively large, stationary instruments that utilize a shielded chamber to minimize background radiation and increase counting efficiency. Liquid scintillation counters Gamma counters Radiation counters allow the user to characterize radioactive contamination as either fixed or removable, but cannot identify unknown areas of fixed contamination.
Liquid Scintillation Counters (LSC) For UCLA laboratories working with low energy beta emitters, such as tritium (H-3), liquid scintillation counting is the primary method of detecting removable contamination. A small piece of filter paper is used to wipe the suspected area of contamination. This wipe sample is placed in a vial and a specialized chemical solution (liquid scintillation cocktail) is added prior to counting. When exposed to radiation, the cocktail emits visible light in direct proportion to the amount of radioactive material present on the wipe. Remember to always add liquid scintillation cocktail prior to counting your sample; the LSC is unable to detect radiation directly.
Gamma Counters For UCLA laboratories working with gamma or positron (PET) emitters, gamma counting may be used to detect removable contamination. A small piece of filter paper is used to wipe the suspected area of contamination This wipe sample is placed in a vial and counted Radiation from the sample interacts directly with the detector in the counter; a specialized chemical solution does not need to be added
Routes of Exposure Radioactive material is able to enter the body through various pathways: Ingestion: radioactive material enters the body through the mouth, leading to the gastrointestinal tract Inhalation:volatile radioactive material is transferred into the body through the respiratory system Absorption:radioactive material comes in contact with exposed skin and is absorbed into the body Injection:radioactive material is introduced into the body through a puncture wound
Personal Protective Equipment Protective measures are necessary when working with radioactive material. Utilizing personal protective equipment (PPE) along with time, distance, and shielding will ensure that exposure is kept as low as reasonably achievable (ALARA).
Personal Protective Equipment All radioactive material users are required to wear appropriate PPE during work with radioisotopes, including: Full-length pants Closed-toe shoes Laboratory coats Latex or nitrile gloves Eye protection
Personal Protection Handle all volatile radioactive compounds in a certified fume hood to protect against inhalation. Place all contaminated sharp objects, such as needles and glass pipettes, in puncture resistant containers to prevent injury and subsequent injection of radioactive material into the body.
Laboratory Accident To illustrate the importance of wearing personal protective equipment when handling radioactive material, consider the following example:
Laboratory Accident A UCLA staff research assistant was working with P-32 as part of a labeling experiment. The researcher was wearing disposable latex gloves, but because he only needed to make a single dilution from the stock vial, he decided not to put on a lab coat. During the procedure, his arm brushed up against the Plexiglas shield several times. Before leaving the laboratory for the day, the researcher decided to survey himself using a GM probe. Upon doing so, he discovered a small area of contamination on his inner forearm.
Laboratory Accident For simplicity, it is assumed that approximately 500 nCi was transferred from the shield to the inner forearm and that the contamination on the skin was confined to an area 5 mm in diameter. The dose rate per unit area is dependent upon the beta particles energy and is distributed as a function of distance from the center of the radioactive source. The half-life of the isotope must be considered, and therefore the exponential decay function has been included. The dose is calculated by first integrating over the surface of the contaminated skin. Finally, the dose rate is integrated over the exposure time of the individual. In the example, approximately 4 hours has lapsed.
Laboratory Accident In health physics it is common to use 10 cm 2 as an average area when determining radiation dose to the skin. Using this industry standard, and the given parameters, the skin dose can then be calculated: Area = 10 cm 2 Time = 4 hrs Activity = 500 nCi Diameter = 5 mm 1.32 Rem
Laboratory Accident The area of the skin directly exposed to P-32 in this example is 19.6 mm 2. ( π )(5 mm) 2 = 19.6 mm 2 The radiation dose to the portion of the skin covered with P-32 is therefore: Area = 19.6 mm 2 Time = 4 hrs Activity = 500 nCi Diameter = 5 mm 54.1 rem In 4 hours, the exposure to this area of skin surpasses the allowable annual dose of 50 rem.
Radiological Hazard Awareness Primary researchers are knowledgeable about the hazards associated with radioactive material handling and as such, take active measures to protect themselves. Therefore, these individuals do not normally become contaminated.
Radiological Hazard Awareness Peripheral laboratory workers and associated staff are often unaware of the radiological hazards present in the laboratory and do not have the same level of experience or training as radioactive material users. The authorized user or laboratory manager must provide awareness training to peripheral laboratory staff to ensure that they are familiar with the hazards in the laboratory.
Decontamination and Reporting Unfortunately, radioactive material spills do occur. It is important to be aware of the remediation procedure and to have the necessary equipment on hand at all times, before an accident happens.
Notification and Response Principal radiation workers may clean up a small radioactive materials spill, if they are comfortable doing so. In the event of a large spill, or if support is needed for a small spill, contact the Radiation Safety Division for assistance.
Notification and Response The RSD must be notified if a spill occurs in a public area (e.g. hallway, elevator, outside of a building). UCLA emergency response must be notified if a large spill occurs after normal working hours. Dial 911 from a campus phone and a Radiation Safety representative will be contacted.
Notification and Response When a radioactive material spill occurs, immediate actions must be implemented. S top the spill: place absorbent material over the spill to prevent the further spread of contamination W arn others: inform all laboratory personnel of the spill and its location; ask members of the laboratory to leave the room, if possible I solate the spill area: erect a clear barrier, including signs, to prevent laboratory staff from entering the area M inimize your exposure: keep away from the spill area unless actively decontaminating the area
Decontamination Procedure It is important to have the following items available in the event of a radioactive materials spill: Personal protective equipment: full-length pants, closed-toe shoes, booties, laboratory coat, gloves, and eye protection Detection equipment: survey meter with appropriate probe for the type of radioactive material involved and liquid scintillation counter Cleanser: household cleaner, such as 409, is usually sufficient for decontamination purposes, although specialty radionuclide removal agents are available Paper towels Clear, thick plastic bags for radioactive waste disposal
Decontamination Procedure Prior to beginning the decontamination process, ensure that the survey equipment being used is functional by checking the battery level and response. Check to make sure that the cable from the probe to the survey meter is connected securely.
Decontamination Procedure Scan all personnel for contamination, paying special attention to the soles of shoes. Begin scanning the spill area to identify the location of the contamination; scan from the outer edges of the spill area to the center of contamination. If the spill involves tritium (H-3), wipe testing must be performed as scanning will be ineffective.
Decontamination Procedure The probe must be held close to surface of the area being scanned and moved slowly to ensure sufficient response time for the detector. The RSD recommends using a distance of 1 cm from the surface of the area or object, while moving at a speed of approximately 2 cm per second.
Decontamination Procedure Spray cleaning agent onto a clean paper towel; never spray cleaner directly onto a spill. The force from the spray may spread the material. Using a very slow scooping action, work from the outside of the spill area to the center. Dispose of the contaminated paper towels as solid radioactive waste.
Decontamination Procedure Rescan and perform a wipe test of the area to determine if the contamination has been removed. Note the areas that were surveyed on a laboratory map and retain all liquid scintillation counting data. Perform personal surveys on all laboratory personnel who assisted in the clean up, including the soles of shoes.
Radioactive Material Spill Reporting After every radioactive material spill, a contamination survey of the laboratory must be completed. Survey results must be reviewed prior to release of the spill area to ensure compliance with established limits for radioactive and non-radioactive material use areas.
Radioactive Material Spill Reporting According to the NRC, a restricted, or radioactive material (RAM) use area, is defined as an area, access to which is limited by the licensee for the purpose of protecting individuals against undue risks from exposure to radiation and radioactive materials. In a RAM use area, the allowable contamination limit for beta and gamma emitting radionuclides is 2200 dpm/100 cm 2 and 220 dpm/100 cm 2 for alpha emitting radionuclides.
Radioactive Material Spill Reporting A non-restricted, or non-radioactive material use area, is defined as an area, access to which is neither limited nor controlled by the licensee. In a non-RAM use area, the allowable contamination limit for beta and gamma emitting radionuclides is 220 dpm/100 cm 2 and 22 dpm/100 cm 2 for alpha emitting radionuclides.
Radioactive Material Spill Reporting The contamination survey documentation must include: Background count rate elevated measurements Laboratory map noting the areas that were wipe tested Liquid scintillation counting data Surveyor signature Surveys must be documented and kept on file for review by outside regulatory agencies.
As Low As Reasonably Achievable In keeping with the ALARA philosophy, any areas of contamination should be cleaned to background levels when possible.
Conclusion This concludes this Radiation Safety Division refresher training module on the prevention, minimization, detection, and remediation of radioactive material contamination. The management of contamination need not be a difficult or time consuming process, but it must be done consistently and correctly in order to protect our community and environment.
Conclusion Feedback regarding this training module is welcome. Please contact the Radiation Safety Division with any questions, comments, or suggestions. Jeremy Pigeon (310)