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TEACHING GUIDES


Nordic Sagas: Radioactive Reindeer


In April 1986, the world's worst nuclear disaster occurred at the Chernobyl power plant in the Ukraine. Fallout carried by wind and rain contaminated Lapland over 1,000 miles to the northwest, where the Sami people live. Reindeer are central to Sami culture and the economy, so the first reports of radioactive contamination in reindeer were devastating to hear. Monitoring people and reindeer is a constant reminder of the long-term consequences of Chernobyl.

Curriculum Links
Related Frontiers Show and Activity
Activity 1: After Chernobyl
Activity 2: Figuring Out Half-Life



CURRICULUM LINKS


CHEMISTRY

half-life, nuclear chemistry, radioactivity
EARTH
SCIENCE


radon, tundra ecosystem
FOOD
SCIENCE


irradiation
LIFE
SCIENCE


food chains, lichen

MEDICINE


nuclear medicine
SOCIAL
STUDIES


Lapland, Scandinavia, tundra

TECHNOLOGY


nuclear power




RELATED FRONTIERS SHOW AND ACTIVITY

Life's Big Questions (Show 501): How Did Earth Get Animals? (Activity: Get a Half-Life)





ACTIVITY 1: AFTER CHERNOBYL

On April 26, 1986, a nuclear power reactor in the Ukraine (then part of the U.S.S.R.), became the site of the world's worst nuclear reactor accident. It happened when the cooling system in one of the reactors at the Chernobyl power plant failed during a test to see how the reactor would function in a power outage. The core overheated, causing an explosion and fire. Tons of nuclear fuel and other radioactive materials were released into the atmosphere. Scientists continue to assess the long-term effects on health and the environment.

Just two days after the accident, scientists in Sweden detected radioactivity in their air. Fallout carried by wind and rain contaminated large areas of Eastern Europe and Scandinavia, more than 1,000 miles (1,600 km) to the northwest. Tons of fresh produce and dairy products had to be destroyed in affected regions.

For the Sami people living in Lapland, the accident had multiple effects. Reindeer, their primary food source and export product, were contaminated by Cs-137, a radioactive isotope with a half-life of about 30 years. Lichen, which acts like a sponge to absorb nutrients from the air and rain, absorbed Cs-137 from the atmosphere. Because lichen is the principal food eaten by reindeer in the winter months, scientists knew the reindeer would also be contaminated from eating the radioactive lichen.

The first reports after Chernobyl suggested that the reindeer meat could not be consumed for 40 years (estimates based on the half-life of Cs-137). Fortunately for the Sami, whose entire culture is built around reindeer, Cs-137 has since fallen to more acceptable levels. Soil in Scandinavia and other areas absorbed Cs-137 after the accident and is still contaminated. This activity will demonstrate how soil absorbs radioactivity. Like all radioactive fallout, Cs-137 is invisible and can be detected only by monitors like Geiger counters. Use your imagination to simulate fallout in the form of "rain."

OBJECTIVE

Simple modeling of Cs-137 absorption by soil and lichen.

MATERIALS
  • clear plastic water or soda bottle(s) (1 L, 1.5 L or 2 L)
  • knife for cutting the bottle
  • 100 to 300 ml of rich, organic soil
  • floral foam ("Oasis") or sponge
  • food coloring
  • water
  • optional: watering can
  • optional activity: play sand, fine net (fish net will do)
NOTE: Any size plastic bottle will work. Ideally, soil should be organic, from the ground. You don't need much. If you don't have access to a good soil sample, make a mix of gardening soil and peat moss. Regular potting soil alone is too fine for this purpose. Floral foam for fresh flower arrangements is sold at craft stores or supermarket flower departments. The amount and variety of supplies will depend on whether this is done as a demo or a student activity.


PROCEDURE
  1. Cut off the tops of the soda bottles about one-third of the way down. Turn the top of the bottle upside-down and fit into its bottom portion.

  2. Prepare setup as shown using soil. Keep the cap on the bottle to keep the soil from dribbling out until you are ready to pour the water.

  3. Cut pieces of floral foam or a sponge to represent the lichen and place a piece on top of the soil in the bottle.

  4. Mix the "radioactive rain" by filling a beaker with 100 ml of water and adding ten or more drops of food coloring. Stir.

  5. Remove the bottle cap and slowly pour the radioactive rain over the soil sample. If you have a watering can, the effect will be more realistic.

  6. Observe: What happens to the lichen? What happens to the soil?
QUESTIONS
  1. What do your observations tell you about how soil absorbs Cs-137 (and other radioactive isotopes)?

  2. What impact would Cs-137 have on plants growing in the soil? What about other radioactive isotopes falling on soil or grass, which are then consumed by other animals in the food chain?

  3. What do you think would be the impact of Cs-137 on areas of tundra with permafrost?
EXTENSIONS
You can make this simple activity into a more scientific experiment by using some other kinds of soils and making comparisons. Use beach or desert sand, clay or soil from different areas. Remember to measure how much water you pour on each sample and how long it takes to percolate through. For finer soil and sand, you will need to attach a screen to the top of the bottle so the sand does not fall out. Fish net works well for this purpose.

REAL-LIFE CONNECTION
Radon is a natural product of the decay of radioactive minerals that contain uranium-238. Radon from minerals in the earth can seep through cracks in basement floors. This invisible gas is denser than air, so it collects in lower levels of houses. Radon can be found in many parts of the U.S., but is more prevalent in a geological belt in the Northeast. The radioactive particles in radon cling to dust, which lodges in the lungs. If inhaled, radon is considered a health hazard. Testing is mandatory in many states when homes are sold. Has your home been tested? Kits are available at hardware stores.



ACTIVITY 2: FIGURING OUT HALF-LIFE

Cesium-137, or Cs-137, is a radioisotope of cesium with a half-life of 30.14 years. Cs-137 is released into the atmosphere in two ways: nuclear bomb explosions and nuclear power plant leaks or accidents. Cs-137 is also used to treat cancer.

Half-life of radioactive matter is the time it takes for one-half of the atoms in a sample to decay. If Cs-137 has a half-life of 30 years, then in 30 years, one-half of the original sample will decay. One-half will remain. Then, in another 30 years, one-half of the remaining sample (or one-fourth of the original sample) will decay, leaving one-fourth of the original sample. Half of what remains will decay at each half-life.

Some radioactive isotopes have a half-life of a few seconds; others, tens of thousands of years. When people have nuclear tests for thyroid or heart functions, radioactive isotopes with short half-lives of a few hours are used as tracers.

HERE'S AN EXAMPLE OF A HALF-LIFE PROBLEM

A 24g radioactive sample has a half-life of five days.

Fill in the blanks on the chart at right.

What remains of the sample after five days? After 25 days?






 

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