alpha particle: A positively charged particle emitted in the radioactive decay of certain radioactive atoms. An alpha particle is identical to the nucleus of the helium atom. *

beta particle: A negatively charged particle that is emitted by certain radioactive atoms. A beta particle is identical to the electron.*

connector: In STELLA, connectors are used to show that an item is affecting something else within the model.

converter: In STELLA, a converter is used to represent something that modifies or affects the rate of change of the stock.

decay series: This results when the product of radioactive decay is not stable. The product then undergoes radioactive decay to form another species. This process continues until a stable isotope is formed.

flow: In STELLA, the flow is used to represent stock entering or leaving its box.

gamma particle or gamma ray: Gamma radiation emitted during the radioactive decay of certain radioactive materials. *

half-life: The amount of time needed for half of the atoms in a quantity of a radioisotope to decay.*

isotope: Atoms of the same element that have equal numbers of protons but differing numbers of neutrons.*

radioactive decay: The spontaneous giving off of an alpha or beta particle or a gamma ray by a radioisotope.*

radioisotope: A naturally occurring or artificially created radioactive isotope of a chemical element.*

STELLA: This computer program allows a person to create models of systems. The program is available from High Performance Systems, Inc.

stock: A stock in STELLA is something that accumulates or depletes over time. You monitor the amount of stock. It can be compared to a warehouse where items are stored.

*These definitions were taken directly from the Unit 2 Glossary of the Department of Energy's OCRWM Education Curriculum entitled "Science, Society, and America's Nuclear Waste" educational materials. The curriculum can be found at www.rw.doe.gov/progdocs/edresource/edresource.htm. The glossary is available at www.rw.doe.gov/progdocs/edresource/unit_2_toc/37.pdf

RADIOACTIVE DECAY