Dr. Catherine Hurt Middlecamp, Nelson Institute for Environmental Studies, University of Wisconsin-Madison
Humans are born lacking a “radioactive sense.” Although they can feel the heat of infrared radiation and see the colors of a rainbow, they are unable to detect the presence of nuclear radiation unless they employ some sort of detector.
In posing the question, “What’s radioactive in this room?” this activity immediately helps students recognize the limits of their perception. Common radioactive substances in their world neither tick nor glow! The activity also launches a conversation including terms such as radiation, radioactive, and radioisotope. To write or speak about nuclear issues, students need these terms, which tend to be easily confused.
At the start of this activity, students name some of the items present in their classroom: furniture, lights, portable electrical devices, air, people. Next, they take their best guess as to whether any of these items are radioactive and, if so, how strongly. Finally, they employ a hand-held detector to confirm or disprove their guesses. The discussion that ensues readily connects to real-world issues of nuclear power, nuclear medicine, nuclear waste, and nuclear weapons.
Courses Into Which This Activity Could Fit
- Introductory (general) chemistry or physics
- Topics: radioactivity, radiation, nuclear decay, half-life
- Environmental science/studies
- Topics: energy, nuclear energy, nuclear fuel cycle, environmental justice
- General education
- Citizen controversies
- Literature of the nuclear age
- Cancer: causes and cures
- The legacy of Marie Curie
- Special topics courses
- Nuclear medicine
- Nuclear power
- Nuclear weapons, fallout
- Nuclear waste
Most people—including students—are inherently curious about radioactive substances. Do these glow or tick? Are they dangerous? How would a person know one if he or she saw one? This Pearl builds on this curiosity.
The activity proceeds in stages. Each has the potential to generate class or small-group discussion. First, students prepare a list of items found in their classroom or laboratory. They also could use a list prepared by the instructor ahead of time. In either case, the list should include items such as cell phones, laptop computers, fluorescent lights, electrical outlets, the walls, the air in the room, and the people.
Next, students categorize these items as to their radioactivity. To do this, students must either base their response on prior knowledge or guess. The categories can be set either ahead of time by the instructor or in the moment by the students themselves. One possible set is weakly radioactive, moderately radioactive, strongly radioactive, or not radioactive (“stable”).
Students then discuss their categorizations. Options include:
- Students first working individually and later pooling their knowledge (or ignorance) of radioactive substances in small groups
- Students using clickers to submit their responses
- The instructor leading a discussion with the whole class
As part of the discussion, the instructor can introduce the use of a Geiger counter and test the item in question.
Scientific Concepts Addressed and Related Civic Issues
Since people are born lacking a “radioactive sense,” they can feel the heat of infrared radiation on their skin and see the colors of the rainbow that make up visible light, but they are unable to detect nuclear radiation. If an alpha or beta particle passes them by, they are blind to it. The same thing applies for a gamma ray.
Were this otherwise, human history would have taken a different course. In the 1950s, the inhabitants of upstate New York could have seen the fallout from atmospheric nuclear weapons testing as it came down in the rain. In 1986, it would have been no secret where the chunks of the Chernobyl reactor landed in the surrounding countryside. Each new leak from the nuclear power plant at Fukushima in 2011 would have lit up the landscape.
For students to know what is radioactive in their surroundings—and therefore have a solid basis from which to assess risk and safety in the presence of nuclear radiation in the world around them—they need either prior knowledge or a means to detect this radiation. In the process of learning about radioactive substances in their world, students are likely to start asking some helpful questions: Which radioactive substances are commonly found in our surroundings? How did they get there? How much radiation do they emit? What types of radiation do they emit? Is this radiation dangerous, beneficial, both, or neither?
Larger civic issues relating to nuclear energy, waste, accidents, weapons, and medicine all require students to raise and seek answers to questions such as these. For example, a course on nuclear energy needs to include a discussion of the uranium fuel cycle and the types of radioactive waste. Similarly, a course on nuclear medicine must include the radioisotopes used for diagnosis and treatment. Which radioactive substances are involved, and in what amounts? What are the risks and what are the benefits?
Prior knowledge required
No prior knowledge is required. Although people tend to be familiar with terms such as radioactivity and nuclear radiation, in the author’s experience, most college students (including chemistry, physics, and biology majors) have little knowledge of the specifics. For example, some will have heard of a Geiger counter, others will not have, and fewer still will know what a Geiger counter can and cannot detect.
- Hand-held Geiger counter (widely available online)
- A radioactive item that will cause the Geiger counter to beep. Possibilities include a uranium ore rock, yellow-green uranium glass beads (from a bead store), an orange Fiestaware plate manufactured between 1936 and 1943, or an americium source removed from a smoke detector.
- Data sheet, if desired
Context and Concepts for Instructors
- The term radiation is likely to confuse everybody, including instructors.
“Radiation” can refer to either electromagnetic radiation or nuclear radiation.
- The type of radiation sometimes must be deciphered from its context. Compare, for example, “avoid exposure to the Sun’s radiation” with “nearby residents were exposed to harmful radiation.” The former refers to the ultraviolet radiation from the Sun that reaches the surface of the Earth (electromagnetic radiation); the latter most likely refers to the release of a nuclear isotope (nuclear radiation). These are two very different things!
- One type of radiation fits in both categories but is given two different names: X-rays (electromagnetic radiation) and gamma rays (nuclear radiation). The former is generated by a machine, and the latter comes from the nucleus of a radioactive substance.
- The term radiation is misused by many people, including those in the media: “Fukushima leaked harmful radiation.” Actually, radioisotopes were released from the nuclear reactor. These emitted the nuclear radiation. Radiation is not something that “leaks,” although a liquid containing one or more radioisotopes can leak from a vessel. Instructors can determine the extent to which they wish to delve into the details of terms such nuclear radiation, ionizing radiation, and electromagnetic radiation in this activity, depending on the focus of the course and students’ interests.
- Students, like all people, cannot detect radioactive substances with their senses.
As a result, the only way that a student would know that something is radioactive would be from their prior knowledge. For example, some students may correctly recall that the air they breathe contains a tiny amount of radon. Some may know that their bodies contain tiny amounts of K-40 and even tinier amounts of C-14. If there is a smoke detector in the room, they may know that it most likely contains americium.
- Students, like most of us, have misconceptions about what things are radioactive.
Students may (link #2) suspect or believe that cell phones, computer monitors, fluorescent lights, and microwave ovens are radioactive. None of these, however, emit nuclear radiation unless they have been contaminated with a radioisotope.
- Classrooms contain numerous radioisotopes, but most in trace amounts. The Geiger counter is not able to detect these.
Radioisotopes naturally present in our world include C-14, K-40, and all isotopes of radon and uranium. These all contribute to background radiation and are present in tiny amounts.
Radioisotopes that contribute to background radiation from anthropogenic sources include americium and plutonium, both from the testing of nuclear weapons. With a few exceptions, such as areas contaminated by weapons production, these radioisotopes are present in only tiny amounts as well.
It is handy to bring in a known radioactive source so that students can see the Geiger counter’s response and compare it to the counter’s response to background radiation. Sources might include green depression-era glassware, Fiestaware, or a uranium-containing rock, all of which contain U-238 and its radioactive decay products. The Geiger counter will also register background radiation, including radon and cosmic rays.
What students will be able to do
Depending on how the instructor employs this activity, students may learn to:
- List key points about radioactive substances in our world, including:
- Radioactive substances are naturally present in our world.
- Radioactive substances also are present because humans have produced them.
- Radioactive substances emit nuclear radiation. Non-radioactive substances don’t.
- Most of our world is not radioactive (this is a good thing).
- Whether radiation is naturally occurring or anthropogenic, we cannot detect it with our senses.
- Use the terms radiation and radioactive accurately in speaking and writing.
- Apply what they know about radioactive substances in their classroom to the presence or absence of radioactive substances in another place.
- Understand that in the case of a nuclear spill, citizens in the area are “blind” to the nuclear radiation just as the students were in the classroom.
- Be able to compare the radioactivity of what is naturally present in their classroom with what is unnaturally present elsewhere.
- Recognize that wherever conversations are held about radioisotopes, the language is likely to be inaccurate and confusing.
- Raise and answer questions about a social/civic issue relating to nuclear substances, such as nuclear power, nuclear medicine, nuclear waste, and nuclear weapons.
Ways that this activity enriches the engagement of citizens with social and civic problems having underlying scientific issues
This activity connects to the following SENCER ideals:
- Extract from the immediate issues the larger, common lessons about scientific processes and methods.
This activity starts with the immediate question of what is radioactive in the room. From this vantage point, the knowledge students gain can be extrapolated to larger common issues of radioactive substances in our world.
- SENCER, by focusing on contested issues, encourages student engagement with “multidisciplinary trouble” and with civic questions that require attention now. By doing so, SENCER hopes to help students overcome both unfounded fears and unquestioning awe of science.
Radioactive substances and fear usually go hand-in-hand. There are reasons to be afraid of radiation! But in some cases, the benefits outweigh the risks. All of the issues that connect to radioactive substances are contested: nuclear power, nuclear waste, nuclear weapons, and even nuclear medicine.
The College Board’s Enduring Understandings That Connect Most Closely
As an interdisciplinary topic, radioactivity connects to enduring understandings in chemistry and physics, launching a larger discussion about the elements in our world, which of them are radioactive, and how the three types of nuclear radiation (alpha, beta, and gamma particles) originate in the nucleus.
Big Idea 1: The chemical elements are fundamental building materials of matter, and all matter can be understood in terms of arrangements of atoms. These atoms retain their identity in chemical reactions.
Enduring Understanding 1.A: All matter is made of atoms. There are a limited number of types of atoms; these are the elements.
Enduring Understanding 1.B: The atoms of each element have unique structures arising from interactions between electrons and nuclei.
Catherine Middlecamp, “Nuclear Unclear,” Science Education and Civic Engagement: The Next Level, Richard Sheardy and William David Burns, Eds. Symposium Series 1121, American Chemical Society, Washington, DC, 2012.
This activity was first used in a SENCER model course, as described in these two publications:
Catherine Middlecamp and Omie Baldwin, Environmental Chemistry & Ethnicity, SENCER Model Series, 2004. http://serc.carleton.edu/sencer/uranium_american_indians/index.html
Catherine Hurt Middlecamp, Anne Kathleen Bentley, Margaret Phillips and Omie Baldwin, Chemistry, Society and Civic Engagement, Part II: Environmental Chemistry & Ethnicity. J. Chem. Educ. 83, 1308–1312 (2006).