Skill Sheet HM3.1.4 Atmospheric Monitoring

The Connecticut Fire Academy Skill Sheet HM3.1.4 Recruit Firefighter Program Atmospheric Monitoring Practical Skill Training Instructor Reference Materials

Radiation Survey Meters At an incident involving radioactive materials, a radiation survey meter is used to determine the type of radiation present (alpha, beta, gamma) and its level. Use meter readings and radiation safety guidelines to delineate safe and restricted zones. In addition to radiation survey meters, personal dosimeters can be used to estimate an individual’s dose of radiation; these direct read-out instruments are often the shape and size of a penlight. Consulting with a health professional trained in radiation will help determine the devices that are appropriate for a specific hazardous materials team. Instrument Operation One radiation detection device is the Geiger-Mueller tube, also known as a Geiger Counter or GM Counter. In recent years they have been replaced by newer, more accurate technology. A radiation survey instrument commonly found in fire departments today is the Ludlam Meter, named after the manufacturer. The Ludlum Survey Meter is a portable survey instrument with four linear ranges used in combination with dose rate or cpm meter dials. Four linear range multiples of x0.1, x1, x10, and x100 are used in combination with the 0-2mR/hr meter dial; 0-200 mR/hr can be read with a range multiplier. Most radiation survey instruments work on the principle that radiation causes ionization in the detecting media. The ions produced are counted and reflect the relationship between the number of ionizations and the quantity of radiation present. Many radiation meters have interchangeable detectors. While some detectors are specific to one type of radiation, others may detect alpha, beta, and gamma. Shielding can help in determining the type of radiation involved. For example, if the meter no longer detects radioactive activity when the source is covered with a sheet of paper, then the source is probably emitting alpha radiation. Calibrating Radiation survey meters are usually returned to the manufacturer for recalibration. This is because the radioactive source used for calibration may require a license to maintain. Check sources of radiation to ensure that the meter responds. Interpreting Results A gamma radiation meter usually reads in milliroentgens per hour (mR/hr) or microroentgens per hour (μR/hr). The unit mR/hr is roughly equivalent to millirem per hour (mrem/hr) for gamma radiation. These units express an exposure rate, that is, the amount of radiation to which an individual would be exposed at the point of measurement. Beta and alpha radiation are also sometimes measured in this way. Meters with a scale that reads in counts per minute (cpm) are typically used with alpha or beta detectors. These meters are generally used to monitor for contamination. Background cpm readings can be compared to readings from potentially contaminated items. If these readings are higher than the background radiation, it is likely that the item is contaminated. Measure source radiation at various distances next. Radiation activity decreases as distance from the source increases. Team members may encounter radiologic materials as a result of transportation incidents. If radiological packaging is encountered under these circumstances, it is important not to disturb the packaging. The transport index should be noted in the white box on the lower half of the label on the container. This is the maximum dose equivalent rate, expressed in mrem per hour, measured at one meter from the external surface of the container. Shipping papers can be consulted for information about the form of the radioactive source.

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Personal Dosimeters Personal dosimeters monitor the accumulated dose received by the dosimeter. Results of exposure (or non-exposure) can be documented so medical personnel can assist in evaluating radiation related illnesses. Dosimeters are available in several styles (e.g., pencil, badge, ring). Some types (pencil) can be read on the scene. Most other types are typically sent to a lab for analysis, with a report being generated. Limitations The primary disadvantage of personal dosimeters is that they indicate the dose of radiation that has already been received. Dosimeters also do not show how fast the dose is being delivered, unlike survey meters. Although personal dosimeters are fairly rugged, some can be damaged by shock, heat, light, and moisture.

Pocket Dosimeters

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Operation and Calibration of the Ludlum Model 3 Survey Meter 1.0 Applicability and Purpose A. This procedure applies to the operation and calibration of the Ludlum Model 3 Survey Meter and associated probes (e.g. GM-Pancake Detector). The Model 3, in conjunction with compatible probes, detects and measures radiation events in terms of exposure rate (mR/hr) and count rate. The procedures outlined in this text ensure that there is consistency in use between analysts, thereby providing quality data. In performing calibration procedures the technician reduces anomalies caused by instrument sensitivity, interference and fluctuations. B. This procedure may also apply to comparable survey meters and data loggers, but they may have other operational requirements. 2.0 Definitions A. Counts per minute (cpm) - number of radiation events detected by a monitoring instrument. B. Milli-Roentgen per hour (mR/hr) – exposure measure of ion pairs formed in air due to X-rays and gamma radiation. 3.0 Equipment and Reagents A. Model 3 Survey Meter B. Model 44-3 Probe C. Model 44-6 Probe D. Model 44-9 Probe, “pancake” E. Two “D” size batteries 4.0 Procedure A. The Model 3 will operate with different types of probes including any scintillation type detectors. Calibration source checks are done separately for each type of detector prior to use. Normally, probes or detectors are assigned to the meter prior to calibration. B. Battery Installation 1. The range selector in the Model 3 must be in the OFF position before beginning battery installation. 2. Open the battery lid by twisting the latch ¼ turn. The apparatus operates on two “D” size batteries, match the (+) and (-) signs according to the lid label. 3. Close the compartment by turning the latch ¼ turn clockwise. C. Battery Test and Detector Connection 1. Move the range switch to the BAT position. The meter needle should deflect to the “BAT TEST” portion of the scale range. If there is no response, recheck battery installation. 2. Detectors are connected via the detector input connector. First connect one end of the cable to the detector by pushing the connectors together and twisting clockwise ¼ turn. Then connect the cable to the instrument in the same manner. D. Testing the Instrument 1. Turn the range selector to the x100 position and turn the “AUD ON-OFF” switch to “ON”. Expose the chosen detector to a check source. The speaker in the instrument should emit clicks per counts detected. 2. If there are no radiation events detected (i.e. there are no clicks), turn the range selector to lower scales progressively until a reading is indicated. 3. The toggle labeled F-S is typically in the S position when testing the instrument. Depress the RESET button. The meter needle should go to zero. The instrument is ready for use after these steps have been completed successfully. 3 of 5 Revision: 012217 The Connecticut Fire Academy Skill Sheet HM3.1.4 Recruit Firefighter Program Atmospheric Monitoring Practical Skill Training Instructor Reference Materials

E. Calibration (normally done by outside vendor) 1. The calibration controls for this instrument are found under the calibration cover. Controls may be adjusted using a 32 cm screwdriver. 2. Calibration shall include response evaluations and adjustment for two points of each scale of the instrument. The points should be separated by at least 40% of the full-scale value and should be represented by points of approximately equal distance from the mid-point of the scale. For example, 25% and 75%, or 20% and 80% could be used. F. Exposure Rate Calibration (normally done by outside vendor) 1. Use a negative pulse generator such as the Ludlum 500 to set the proper operating voltage for the detector to be used. 2. Connect the detector to the Model 3. Place the range selector at the x100 position. 3. Expose the detector to a uniform radiation field such as 137Cs that corresponds to approximately 80% of full scale meter deflection. Adjust the x100 calibration control to obtain the correct reading for the radiation field. 4. Change the position of the detector so that the field corresponds to approximately 20% of full scale deflection. Ensure that the meter reading is within 10% of the field. 5. Repeat the process for each of the other scales (i.e. x10, x1, x0.1) 6. If the radiation field cannot calibrate two points on each scale, the pulse generator may be used to electronically calibrate the remaining points. 7. Reconnect the pulse generator to the instrument and determine the count rate conversion at a previous range calibration point. Next use that conversion rate to calibrate other points or scales. G. Count Rate Calibration (normally done by outside vendor) 1. Connect the Model 3 to a negative pulse generator such as the Ludlum Model 500 Pulser. Use the HV control to set the operating voltage of the detector to be used. 2. Adjust the pulser frequency to obtain an approximately 80% meter deflection on the X100 range. Adjust the X100 calibration control to the appropriate reading. 3. Reduce the pulser count rate by a factor of 4 to check the 20% scale deflection. The Model 3 readings should be within 10% of the actual pulse rate. 4. The above procedures must be repeated for the lower ranges. H. Calibration Source Check 1. Source checks are performed daily prior to use. 2. Place the detector at the operational distance from the NIST traceable source (normally 137Cs). 3. Compare the observed activity to the expected activity of the source based on its half-life, initial activity and measurement date (normally automatically calculated in the log).

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I. Survey measurements 1. Turn the response switch to “F” (fast) for surveys, “S” (slow) for quantitation measurements. 2. Turn on the audible alarm so the detection can be heard. 3. Starting with the x1 position, place the detector at operation distance from the surface to be measured. This distance should be about the same as the distance used for the source check (such as about 0.5 inches for a pancake probe). 4. If the meter reaches about 90% of max scale, switch to x10 or x100 as needed. 5. Begin a slow sweeping of the measurement area, generally is about 0.5 inch laterally per second. 6. If areas of interest are found, repeated measurements may be taken to define contamination zones or hotspots. 7. In screening personnel, begin with extremities and head, working the way inward towards the main body. For self- screening prior to exiting areas, begin with the fingertips, then hands before handling the main instrument that was already turned on for use. J. Maintenance 1. Keep the instrument clean and dry. When cleaning turn the instrument OFF and remove the batteries. 2. Let the instrument sit without batteries for one minute before cleaning the exterior or accessing the interior for repairs. 5.0 Quality Control and Safety Aspects A. Check the calibration sticker before use to ensure that the instrument has been calibrated. Surveying equipment is typically calibrated once a year at the factory. Record the calibration date with raw data. B. The Model 3 with pancake can differentiate between alpha and beta (generally) by adding or removing the protective plastic cover. It cannot be used to quantify gamma accurately, and cannot be used for tritium (3H), or 125I. C. Always take into account background radiation levels. Measure and record background radiation levels in the Survey Meter Log prior to doing the check source reading. D. For the check source reading, the meter is ready for use if the obtained value is within +/- 20% of the expected value. If the obtained value is not within +/- 20%, the instrument likely requires recalibration. E. Always replace the cover for the pancake probe, or close windows of other detector probes when not in use. Use extra caution to not puncture the Mylar membrane of the pancake when being used. F. During operation internal components contain live voltage. Turn the instrument OFF, remove the batteries and allow it to sit for one minute before accessing internal components. G. The connector contains voltage exceeding 1kV. Contacting it during operation may result in electric shock. 6.0 References A. Ludlum Model 3 Survey Meter, February 2013, Ludlum Measurements Inc., Sweet Water, Texas. B. Radiation Training-Survey Meter Use, Washington State University Radiation Safety Office

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