Name Title Affiliation Measuring Radiation

Caring for your CD V700 Note that ANS provides vintage Geiger counters that have been donated to the Society. The CD V-700 (often written as "CDV-700") is a Geiger counter manufactured by several companies under contract to United States federal civil defense agencies in the 1950s and 1960s.  Tens of thousands of the counters were distributed to state civil defense agencies.

Getting acquainted Probe with Geiger-Müller tube Range Switch Meter Point out the different parts of the unit. Wikipedia has a thorough article about the Geiger counters, their cases and various parts. Note that the check source on the side of the case is radioactive, and the inside of the unit contains high-voltage electronics. Meter Navigating Nuclear Science

Geiger-Müller tube Check source Demonstrate how to use the probe. Closed, the probe will detect gamma radiation. Open, it will detect beta and gamma radiation. The CDV counters will not measure alpha radiation. Install batteries, open and close the probe, and put it back in its holder. NOTE: Remind teachers/students that the probe should always be stored in the closed position. This protects the delicate Geiger Müller tube in the probe. Also, note that batteries should be removed after every use. If the batteries degrade, the Geiger counter will be ruined. Note that the check source on the side of the case is radioactive, and the inside of the unit contains high-voltage electronics. Check source Navigating Nuclear Science

How a Geiger-Müller tube works Describe how the detector works: The GM tube is a hollow cylinder filled with a gas at low pressure. The tube has a thin window made of mica at one end. There is a central electrode inside the GM tube. A high voltage supply is connected across the casing of the tube and the central electrode. When beta or gamma radiation enters the tube, it produces ions in the gas, making it charged. The power supply creates an electric potential in the tube. A current is produced in the tube for a short time. The current produces a voltage pulse. Each voltage pulse corresponds to one ionizing radiation entering the GM tube. The voltage pulse is amplified and counted. NOTE: ANS supplies headphones with the CDVs it distributes for teacher workshops. Instructions for attaching a speaker are available at: http://nuclearconnect.org/in-the-classroom/connecting-a-speaker-to-your-geiger-counter Navigating Nuclear Science

Describe the units measured. The top scale is mr/hr millirem per hour or millirad per hour. The Geiger counter measures beta and gamma radiation, so the millirem and millirad measurements are the same. See slide 10 for further information. This measurement is a dose rate for beta and gamma. The bottom scale is C/M counts per minute, telling us how many times in a minute the counter is detecting radiation. This measurement is an indication of how much activity is in the area   The CDVs distributed by ANS have not been calibrated. The meter should only be used as a reference point and for comparative measurements. When beginning to use the unit, place the range switch to x100 and hold a radioactive source, such as a lantern mantle, near the open probe. If the meter needle doesn’t move, place the range switch to x10. Only place the range switch at x1 if there is no reading at x10. Beginning at x1 can overwhelm the unit and it may not recover.

Measurement terms R = radioactivity E = exposure A = absorbed dose number of nuclei that decay in a given time used for comparing elements E = exposure the amount of radiation in the air A = absorbed dose the amount of radiation absorbed by tissue D = dose equivalent amount of radiation absorbed + the medical effects of that type of radiation Be aware that this topic is extremely confusing for lay people. There are four different but interrelated units for measuring radioactivity, exposure, absorbed dose, and dose equivalent. These can be remembered by the mnemonic R-E-A-D Navigating Nuclear Science

Units of radioactivity Activity: the number of emissions of radiation per unit time Becquerel (Bq) = 1 disintegration per second (dps) international unit Curie (Ci) = 37,000,000,000 dps Picocurie (pCi) = 0.037 dps or 2.2 dpm U.S. unit Radioactivity refers to the amount of ionizing radiation released by a material. Whether it emits alpha or beta particles, gamma rays, x-rays, or neutrons, a quantity of radioactive material is expressed in terms of its radioactivity (or simply its activity), which represents how many atoms in the material decay in a given time period. The units of measure for radioactivity are the curie (Ci) and becquerel (Bq). Radioactivity refers to the amount of ionizing radiation released by a material. Whether it emits alpha or beta particles, gamma rays, x-rays, or neutrons, a quantity of radioactive material is expressed in terms of its radioactivity (or simply its activity). This represents how many atoms in the material decay in a given time period. The units of measurement for radioactivity are the curie (Ci, U.S. unit) and becquerel. Becquerels are the international unit used to measure radioactivity. One becquerel is the amount of a radioactive material that will undergo one transformation per second. Becquerels are not used to measure radiation dose or radiation exposure. The U.S. unit is the Curie (Ci).  Note that becquerel are very small units, so measurements in becquerel seem very high. Just like 100 pennies seems much bigger to young children than 1 dollar. Navigating Nuclear Science

Units of exposure and absorbed dose Roentgen (R) unit of exposure amount of ionization in the air caused by radioactive decay mR = milliRoentgen Radiation absorbed dose (rad) energy deposited in material, such as human tissue U.S. unit Gray (Gy) is international unit 1 Gy = 100 rad Exposure describes the amount of radiation traveling through the air. Many types of radiation monitors measure exposure. The units for exposure are the roentgen (R, U.S. unit) and coulomb/kilogram (C/kg, international unit).   Absorbed dose describes the amount of radiation absorbed by an object or person. The unit for absorbed dose is the rad, the U.S. unit used to measure absorbed radiation dose (the amount of radiation absorbed by an object or person). The international equivalent is the Gray (Gy). One hundred rads are equal to 1 Gray.    ​ Navigating Nuclear Science

Dose equivalent or effective dose equivalent Roentgen equivalent man (REM) rad x quality factor (Q) Q = 1 for beta and gamma Q = 20 for alpha Q = 10 for neutron International unit is sievert (Sv) 100 rem = 1Sv Dose equivalent or Effective Dose describes the amount of radiation absorbed by a person, adjusted to account for the type of radiation received and the effect on particular organs. The U.S. unit used for effective dose is rem. The international unit is sieverts (Sv). It is also called biological dose. The dose in rem equals the dose in rad multiplied by the quality factor (Q). For beta and gamma radiation, the quality factor is taken as one, that is, rem equals rad. For alpha radiation, the quality factor is taken as 20. For neutrons, Q is typically taken as 10. Rem is essentially a measure of the potential for biological damage. Question attendees about why alpha radiation has a much higher Q

Chart comparing US and International units Chart comparing US and International units. Shows that rad is related to Gray and rem is related to Sievert. Note that US units are on the left.

For example: radioactivity Comparative chart. Have attendees calculate how radioactive they are. Have them convert Bq to curie

Equivalent dose Comparison of some common medical diagnostics

Measuring Radiation in the classroom Have teachers install batteries then test their Geigers, using something like a thorium lantern mantle. Show the professional development video featuring ANS member Candace Davison describing the Navigating Nuclear: Energizing Our World™ Measuring Radiation lesson and how to use it. With an internet connection, the image links to the training video. It is only 5 minutes long, and you may choose to show it. The lesson can also be found on the NavigatingNuclear.com website. https://www.navigatingnuclear.com/#/classroom-resources Navigating Nuclear Science