Presentation on theme: "Radiation Safety E-Training Module"— Presentation transcript:
1Radiation Safety E-Training Module Radioactive Contamination Minimization and Remediation
2Radiation 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.
3Module Objectives Safe Handling of Radioactive Material Minimizing Radioactive ContaminationDetection of RadioactivityPersonal ProtectionDecontamination and Reporting
4Safe Handling of Radioactive Material When working with radioactive material, users should:Prepare a radioactive materials work area in the laboratoryCover work area with absorbent paperSet up radiation shieldsEnsure that radioactive waste containers are availableTurn on survey meter and place adjacent to work areaSurvey radioactive material work areas before, during, and after handlingPerform swipe surveys to document removable contaminationUse survey meters to identify fixed areas of contaminationPerform personal contamination surveysScan gloves frequently during experimentsMonitor whole body before leaving laboratory
5Safe Handling of Radioactive Material Cover work area with absorbent paperPlastic backed laboratory paper is recommended to prevent seepage of liquidDesignate radioactive materials handling area with identifying labels and tapeSinks must never be included in a radioactive material work area; never dispose of radioactive material down laboratory sink drainsPrepare a radioactive materials work area in the laboratoryWork space should be set up away from high traffic and administrative areasArea should be clean and free of clutterVolatile radioactive material must be handled in a certified fume hoodTurn on survey meter and place adjacent to work areaPerform battery and functionality tests prior to useUse Geiger-Müller (GM) probes to detect medium and high energy beta emissionsSodium iodide (NaI) probes are efficient at detecting low energy gamma emissionsEnsure that radioactive waste containers are availableLabel all containers on the top and side with radioactive symbol and isotopeSegregate waste by type and isotopeAll sharps must be placed in a puncture resistant containersSet up radiation shieldsDesign shielding such that radiation fields are minimized in all directionsPlexiglas may be used to provide protection from beta-emitting isotopesLead may be used to reduce radiation exposure from gamma-emitting isotopesSinkBenchShieldingWaste
6Safe Handling of Radioactive Material Good laboratory practice will help minimize the chance of radioactive contamination.Do not consume food or drink in the laboratoryWork with volatile substances in a certified fume hoodEnsure familiarity with radioactive material handling proceduresLimit the volume of radioactive waste stored in the laboratory
7Radioactive 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.
8Radioactive Contamination Minimization It is also important to monitor common areas and frequently touched objects, in addition to radioactive material use work areas:Common walkwaysDesk areas, computer keyboards, and miceRadioactive material use equipment, including pipettes and centrifugesDoor knobsLight switches
9Radioactive 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.
10Radioactive 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.
11Portable Survey Meters Portable survey meters utilize probes that have varying efficiencies based on the type of radiation detected.Geiger-Muller (GM) probeSodium Iodide probeMost portable survey meters cannot detect low energy beta emissions such as H-3 and are unable to characterize contamination as fixed or removable.
12Geiger-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.
13Sodium Iodide ProbeA 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.
14Radiation CountersRadiation counters are relatively large, stationary instruments that utilize a shielded chamber to minimize background radiation and increase counting efficiency.Liquid scintillation countersGamma countersRadiation counters allow the user to characterize radioactive contamination as either fixed or removable, but cannot identify unknown areas of fixed contamination.
15Liquid 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.
16Gamma CountersFor 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 contaminationThis wipe sample is placed in a vial and countedRadiation from the sample interacts directly with the detector in the counter; a specialized chemical solution does not need to be added
17Routes of ExposureRadioactive material is able to enter the body through various pathways:Ingestion: radioactive material enters the body through the mouth, leading to the gastrointestinal tractInhalation: volatile radioactive material is transferred into the body through the respiratory systemAbsorption: radioactive material comes in contact with exposed skin and is absorbed into the bodyInjection: radioactive material is introduced into the body through a puncture wound
18Personal 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).
19Personal Protective Equipment All radioactive material users are required to wear appropriate PPE during work with radioisotopes, including:Full-length pantsClosed-toe shoesLaboratory coatsLatex or nitrile glovesEye protection
20Personal ProtectionHandle 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.
21Laboratory AccidentTo illustrate the importance of wearing personal protective equipment when handling radioactive material, consider the following example:
22Laboratory AccidentA 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.
23Laboratory AccidentFor 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 particle’s 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.
24Laboratory Accident 1.32 Rem In health physics it is common to use 10 cm2 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 cm2Time = 4 hrsActivity = 500 nCiDiameter = 5 mm1.32 Rem
25Laboratory Accident 54.1 rem The area of the skin directly exposed to P-32 in this example is 19.6 mm2.(π)(5 mm)2 = 19.6 mm2The radiation dose to the portion of the skin covered with P-32 is therefore:Area = 19.6 mm2Time = 4 hrsActivity = 500 nCiDiameter = 5 mm54.1 remIn 4 hours, the exposure to this area of skin surpasses the allowable annual dose of 50 rem.
26Radiological 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.
27Radiological 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.
28Decontamination 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.
29Notification 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.
30Notification 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.
31Notification and Response When a radioactive material spill occurs, immediate actions must be implemented.Stop the spill: place absorbent material over the spill to prevent the further spread of contaminationWarn others: inform all laboratory personnel of the spill and its location; ask members of the laboratory to leave the room, if possibleIsolate the spill area: erect a clear barrier, including signs, to prevent laboratory staff from entering the areaMinimize your exposure: keep away from the spill area unless actively decontaminating the area
32Decontamination 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 protectionDetection equipment: survey meter with appropriate probe for the type of radioactive material involved and liquid scintillation counterCleanser: household cleaner, such as 409, is usually sufficient for decontamination purposes, although specialty radionuclide removal agents are availablePaper towelsClear, thick plastic bags for radioactive waste disposal
33Decontamination 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.
34Decontamination 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.
35Decontamination 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.
36Decontamination 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.
37Decontamination 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.
38Radioactive 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.
39Radioactive 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 cm2 and 220 dpm/100 cm2 for alpha emitting radionuclides.
40Radioactive 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 cm2 and 22 dpm/100 cm2 for alpha emitting radionuclides.
41Radioactive Material Spill Reporting The contamination survey documentation must include:Background count rate elevated measurementsLaboratory map noting the areas that were wipe testedLiquid scintillation counting dataSurveyor signatureSurveys must be documented and kept on file for review by outside regulatory agencies.
42As Low As Reasonably Achievable In keeping with the ALARA philosophy, any areas of contamination should be cleaned to background levels when possible.
43ConclusionThis 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.
44ConclusionFeedback regarding this training module is welcome. Please contact the Radiation Safety Division with any questions, comments, or suggestions.Jeremy Pigeon(310)