Purpose
To demonstrate the relative penetrating power of different radioactive sources and their everyday presence using a Geiger Counter.
Procedure
- Use a Geiger counter to measure different types of radiation and their penetrating power.
- Note that samples are held by EHRS until safety training is completed. They must be locked up and properly stored.
- Show that:
- Alpha radiation is stopped by paper.
- Beta radiation is stopped by thin metal (aluminum).
- Gamma radiation requires large amounts of lead.
Present everyday devices that contain radioactive materials, such as:
- Smoke detectors (containing americium).
- Fiestaware dishes (containing uranium).
Radiation Intensity vs. Distance
I1 = d22 / I2 d12
Data
Mineral Source: UP4
| Measurement | Count Rate (cpm) |
|---|
| 3.5″ unshielded | 855 |
| 3.5″ in shoebox | 361 |
| 7″ unshielded | 155 |
| 3.5″ paper bag | 392 |
| 3.5″ glass beaker with lid | 191 |
| 3.5″ using side (gamma source) | 173 |
Fiestaware Plate
| Measurement | Count Rate (cpm) |
|---|
| 3.5″ unshielded | 666 |
| 3.5″ in shoebox | 669 |
| 7″ unshielded | – |
| 3.5″ paper bag | 537 |
| 3.5″ glass beaker with lid | – |
| 3.5″ using side (gamma source) | – |
Lantern Mantel
| Measurement | Count Rate (cpm) |
|---|
| 3.5″ unshielded | – |
| 3.5″ in shoebox | – |
| 7″ unshielded | – |
| 3.5″ paper bag | – |
| 3.5″ glass beaker with lid | – |
| 3.5″ using side (gamma source) | – |
Radioactive Item Descriptions
| Radioactive Item | Size | Isotope | Ludlum Count | Eberline Count | Bicron 50 Count | CDV-700 Count |
|---|
| Background | atomic random | – | 50 | 30 | 25 | 20 |
| #2 weak Uraninite from Arizona | >1″ | Uranium-238 | 60 | 30 | 30 | 20 |
| from Arizona #1 weak Uraninite | >1″ | Uranium-238 | 100 | 60 | 60 | 20 |
| 2% Thorium | Welding rod, red tip 1/8 x 7″ | Thorium-228 | 300 | 250 | 40 | 30 |
| Uranium Glass | 3 glass marbles 1/2″ | Uranium-238 | 450 | 250 | 100 | 40 |
| from Arizona #3 uranium ore | >1″ | Uranium-238 | 2,400 | 1,000 | 450 | 200 |
| from N. Carolina Megalodon tooth | 5″ | Uranium-238 | 2,600 | 1,200 | 320 | 200 |
| from Wyoming Schrockingerite | 1″ | Uranium-238 | 3,200 | 1,600 | 600 | 500 |
| CDV-700 Meter 700 check source | 1/4″ | Cesium-137-? | 5,000 | 2,600 | 1,800 | 1,800 |
| from Arizona Uraninite/carnotite | 5″ | Uranium-238 | 8,000 | 4,000 | 1,000 | 800 |
| Lantern mantles | 2″ x 3″ | Thorium-228 | 21,000 | 7,000 | 2,000 | 1,300 |
| Autunite crystals | 1/2″ | Uranium-238 | 22,000 | 20,000 | 3,500 | 2,800 |
| Fiestaware (red) Coffee Cup | 3″ | Uranium-238 | 32,000 | 14,000 | 3,200 | 3,000 |
| Fiestaware (red) Saucer – 6″ | 6″ | Uranium-238 | 32,000 | 14,000 | 3,000 | 3,000 |
| Fiestaware (red) Bowl 6 3/4″ | 6 3/4″ | Uranium-238 | 40,000 | 16,000 | 4,000 | 5,000 |
| Fiestaware (red) Serving plate | 14 1/4″ | Uranium-238 | 43,000 | 18,000 | 4,500 | 4,000 |
| Autunite cluster from Spokane, WA | 1/2″ | Uranium-238 | 46,000 | 22,000 | 10,000 | 8,000 |
| Smoke detector Detector sensor | 1/8″ | Americium-241 | 80,000 | 42,000 | 14,000 | 250 |
| Coffinite from Colorado | 5″ | Uranium-238 | 110,000 | 32,000 | 10,000 | 8,000 |
| Uraninite from Colorado | 7″ | Uranium-238 | 150,000 | 44,000 | 15,000 | 12,000 |
| Gummite | 1/2″ | Uranium-238 | 220,000 | 58,000 | 60,000 | 180,000 |
| Torbernite from Congo | 1″ | Uranium-238 | 330,000 | >60,000 | 50,000 | 28,000 |
Estimates of Radiation Exposures
Sources
- Nuclear Regulatory Commission Publication: NUREG 1717
Principal Radiation Exposure Pathways from Fiestaware and Uranium-Containing Tableware
- Gamma Ray Exposure
- Exposure to the body from gamma rays emitted by radionuclides.
- Exposure rates reported by Buckley et al.:
- Dinner plate surface: 0.5 to 15 mR/hr
- One meter: 0.002 to 0.3 mR/hr
- Effective dose equivalent rates at various distances:
- 1 foot: 6.5 x 10^-4 mrem/hr (10″ Plate), 3.7 x 10^-4 mrem/hr (3.5″ Cup)
- 3 feet: 7.7 x 10^-5 mrem/hr (10″ Plate), 4.1 x 10^-5 mrem/hr (3.5″ Cup)
- 6 feet: 1.9 x 10^-5 mrem/hr (10″ Plate), 1.1 x 10^-5 mrem/hr (3.5″ Cup)
- Beta Particle Exposure
- Exposure to the hands from beta particles emitted by radionuclides.
- Measured beta-gamma dose rates:
- 0.5 to 20 mrad/hr on contact.
- Annual estimated doses:
- 400 mrem to lips, 1200 mrem to fingers from daily use.
- Ingestion of Uranium
- Uranium leaching into food from ceramic glaze.
- Concentrations measured in contact with red glazed dinnerware:
- 1.8 to 8.6 ppm in acetic acid (24 hours).
- Up to 41 to 51 ppm (60 hours).
- Estimated ingestion exposure: 40 mrem per year for regular users of uranium-containing dinnerware.