Ionizing Radiation in the Lab - A Glowing Prospect
(Article #21)

IPS Program And Radiation “Treasures!”

Anyone remembering the IPS Program or Introductory Physical Science from the 1950’s will recall a series of experiments dealing with ionizing radiation. In fact, some of the radiation sample “treasures” from this era can still be found on the back shelves of chemical storerooms, cabinets and closets. So, what are these treasures and are they dangerous?

One means of learning more about these treasures or use of radioactive materials in the science laboratory, is to contact your state’s Radiation Control Officer. These officers work in effort to provide information about radiation, enforce regulations and make for a safer work environment. They are knowledgeable about professional standards, organizations, and, state and federal government regulations for protection against ionizing radiation; e.g., 10CFR part 20-34 (U.S. Nuclear Regulatory Commission); 21 CFR part 1020.40 (Food and Drug Administration – Department of Health and Human Resources); N43.2 (American National Standards Institute).

Radiation Types: The Big Four!

Ionizing radiations are the products of unstable nuclei. To become stable, the nuclei emit particles or rays. These emitted particles and rays can then affect other atoms by knocking out electrons of atoms they hit and therefore form ions. The big four radiation types are noted as follows:

1. Alpha Particles - The naked helium atom! Alpha particles are composed of two neutrons and two protons or the basic helium nucleus. These particles are the result of degradation of radio isotopes of heavy elements like uranium and radium. The penetrating power of these particles is extremely limited at best. Skin is a sufficient barrier to guard against infusion.

2. Beta Particles - The particles or electrons that originate in the nucleus of radio isotopes. Because of their relatively small size and high energy, most beta particles can penetrate skin. Low energy beta particles have difficulty penetrating skin, but do present an internal hazard. High energy beta particles can penetrate living tissue.

3. Gamma Rays - Gamma rays are not particles but photons. The rays are high energy and therefore, have high penetrating power. Lead shielding can provide protection.

4. X-rays - X-rays are similar to gamma rays. However, where gamma rays are naturally occurring in origin, X-rays are artificially generated. This is achieved by metal targets being bombarded with high-energy electrons in a vacuum. X-rays, like gamma rays are a serious hazard resulting from their penetrating power.

Enter Radiation Hazards!

Exposure to radiation can affect the body internally and externally. Internally, radiation can enter the body by inhalation, skin absorption or ingestion. External exposures are usually effected by X-rays and gamma rays.

How Much Is Too Much?

Before it can be determined how much is too much, we need to know dose rates of exposure. The dose rate is measured in rads (radiation absorbed dose) per hour. A measure of radioactivity is the Curie. One Curie is that quantity of a radioactive material that will have 37,000,000,000 transformations in one second.

To consider the biological effect, the Rem (roentgen equivalent man) is used as a unit of dose.

The Nuclear Regulatory Commission or NRC has established base dose limits for exposure to radiation. This is found in standard CFR 20. Limits include 5000mREM /year for whole body exposure and 30,000 mREM/year for skin of the whole body. If a sealed source of radiation exceeds one milliCurie, it must be registered with the government.

Handling of Radiation!

Safe handling of radiation starts with awareness through signage. A standard radiation caution sign has a yellow background and a black or magenta tri-foil symbol. This signage should be used in all radioactive materials storage areas such as cabinets, refrigerators, etc. The work area must also have signage during a laboratory operation.

The University of Illinois has developed a list called laboratory procedures or protocols in dealing with radioactive materials. At the high school level most of these procedures are appropriate but with a few alterations. Consider adopting the following protocols at the high school level when dealing with radioactive materials:

1. To prevent accidental entry of radioactive materials into the body, high standards of cleanliness and good housekeeping must be maintained in all laboratories where radioactive materials are present and/or used.

2. Visitors are not allowed without approval of chemical hygiene officer or school system safety compliance officer.

3. Wash hands and arms thoroughly before handling any object which goes to the mouth, nose, or eyes (e.g., cosmetics, foods). Keep fingernails short and clean.

4. Eating or drinking in laboratories which deal with radioactive materials is unsafe and forbidden. Refrigerators will not be used jointly for foods and radioactive materials.

5. One or more trial runs beforehand with non-radioactive materials are recommended for new procedures and new personnel to test effectiveness of procedures and equipment.

6. Do not work with radioactive materials if there is a break in the skin below the wrist.

7. Always use gloves when handling more than a few hundred counts per minute. Wear protective clothing (lab coats, masks, shoe covers) as needed.

8. Table and bench tops should be of a non-porous, chemical resistant material. Working surfaces shall be covered with absorbent paper regardless of the type of surface.

9. When work is completed each person will clean up his own work area and arrange for disposal or proper storage of all radioactive materials and equipment.

10. Laboratories shall provide special radioactive waste containers. These shall bear the words "Caution, Radioactive Waste," and a warning to janitors against handling.

Radioactive sources used in high school science laboratories should be mounted in sealed discs. These discs must never be breached or damaged. If this does happen, they must be disposed of properly as per state regulations. For relatively safe use by students, activity should be rated at 1.0 uCi or less. Because these sources are low, they are license exempt by the U.S. Nuclear Regulatory Commission (also for licensing by states). One final note – Although materials by regulation can be in non-sealed sources, it is inappropriate for high school level use, given the opportunity for contamination and exposure.

Everyday Items Containing Radioactive Treasures!

Everyday treasures such as smoke detectors, old Coleman lantern socks, Fiesta Ware, and watches with radium painted dials are radioactive sources for alpha, beta and gamma radiation. Most of these items are no longer manufactured due to the exposure/health threat to employees who made them. They can be found at tag sales and antique shops. The everyday items noted were not designed for instructional or experimental use. Therefore, they are not recommended for science laboratory use by students or teachers.

Safety Counts!

If your science curriculum calls for investigations into radiation, it would be prudent to secure radiation sources designed for student/instructor use from a commercial science supplier. In these cases they are relatively safe for limited handling in the science laboratory by students and teachers. Alternative computer simulation programs are also available and worthy of consideration.

Additional Resources:

Idaho State University Radiation Related Terms: http://www.physics.isu.edu/radinf/terms.htm

Oklahoma State University Radiation Safety Program: http://www.pp.OKstate.edu/ehs/hazmat/labman/chap4.htm

OSHA: http://www.osha.gov

University of Virginia Radiation Safety Program: http://keats.admin.virginia.edu/lsm/home.html

U.S. Nuclear Regulatory Commission: http://www.nrc.gov

Vermont Safety Website: http://www.hazard.com/

NOTE: The authors wishes to acknowledge and thank State of Connecticut Radiation Control Physicist Kevin Scott for his time and expertise in helping to review this article.

LIVE LONG AND PROSPER WITH SAFETY!

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Dr. Ken Roy
K-12 Director of Science & Safety & authorized OSHA instructor
c/o Glastonbury Public Schools
Glastonbury, CT 06033-3099
Fax 860-652-7275
E-Mail: royk@glastonburyus.org