24.3. Fission and Fusion http://www.ck12.org
FIGURE 24.13
A Geiger counter is used to detect radia-
tion.Radioactive tracersare radioactive atoms that are incorporated into substances so that the movement of these
substances can be tracked by a radiation detector. Tracers are used in the diagnosis of cancer and other diseases.
For example, iodine-131 is used to detect problems with a person’s thyroid. A patient first ingests a small amount of
iodine-131. About two hours later, the iodine uptake by the thyroid is determined by a radiation scan of the patient’s
throat. In a similar way, technetium-99 is used to detect brain tumors and liver disorders, and phosphorus-32 is used
to detect skin cancer.
Radioactive tracers can be used in agriculture to test the effectiveness of various fertilizers. The fertilizer is enriched
with a radioisotope, and the uptake of the fertilizer by the plant can be monitored by measuring the emitted radiation
levels. Nuclear radiation is also used to prolong the shelf life of produce by killing bacteria and insects that would
otherwise cause the food to spoil faster.
Lesson Summary
- Nuclear fission involves the splitting of large nuclei into nuclei of intermediate size. A chain reaction is
self-sustaining and is used in an uncontrolled fashion in an atomic bomb. - Nuclear power plants use controlled fission to generate electricity from the large amounts of heat produced.
- Nuclear fusion involves combining of small nuclei into larger ones, a process that releases considerably more
energy than fission. Fusion powers our sun and other stars but cannot currently be harnessed directly to
generate electricity. - Ionizing radiation is capable of doing cellular damage and is detected by a Geiger counter, scintillation counter,
or film badge. - Radiation is used for various cancer treatments, as a tracer to study other processes, and as a way to prolong
the shelf life of food.