the Physics Education Technology Project
the National Science Foundation
This resource simulates a nuclear chain reaction, as users fire a neutron gun to induce fission in a radioactive isotope. It initiates with a single Uranium-235 nucleus alongside a graph displaying potential energy. Fire away and watch the nucleus split into two daughter nuclei. Next, start a chain reaction by using multiple U-235 nuclei, or prevent one by introducing non-radioactive isotopes. Switch the tab to "Nuclear Reactor" and adjust control rods to manage the reaction.
Editor's Note: For secondary learners, we recommend using this simulation after completing the PhET Simulation "Isotopes and Atomic Mass". Students will have a clearer understanding of the atomic symbols and factors that affect stability of an atomic nucleus. See Related Materials for a link to a printable student guide appropriate for grades 8-12.
This item is part of a larger collection of simulations developed by the Physics Education Technology project (PhET).
Please note that this resource requires
Java Applet Plug-in.
6-8: 3C/M5. New technologies increase some risks and decrease others. Some of the same technologies that have improved the length and quality of life for many people have also brought new risks.
9-12: 3C/H3. In deciding on proposals to introduce new technologies or curtail existing ones, some key questions arise concerning possible alternatives, who benefits and who suffers, financial and social costs, possible risks, resources used (human, material, or energy), and waste disposal.
9-12: 3C/H5. Human inventiveness has brought new risks as well as improvements to human existence.
4. The Physical Setting
4D. The Structure of Matter
6-8: 4D/M1a. All matter is made up of atoms, which are far too small to see directly through a microscope.
9-12: 4D/H1. Atoms are made of a positively charged nucleus surrounded by negatively charged electrons. The nucleus is a tiny fraction of the volume of an atom but makes up almost all of its mass. The nucleus is composed of protons and neutrons which have roughly the same mass but differ in that protons are positively charged while neutrons have no electric charge.
9-12: 4D/H2. The number of protons in the nucleus determines what an atom's electron configuration can be and so defines the element. An atom's electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. Atoms form bonds to other atoms by transferring or sharing electrons.
9-12: 4D/H3. Although neutrons have little effect on how an atom interacts with other atoms, the number of neutrons does affect the mass and stability of the nucleus. Isotopes of the same element have the same number of protons (and therefore of electrons) but differ in the number of neutrons.
9-12: 4D/H4. The nucleus of radioactive isotopes is unstable and spontaneously decays, emitting particles and/or wavelike radiation. It cannot be predicted exactly when, if ever, an unstable nucleus will decay, but a large group of identical nuclei decay at a predictable rate. This predictability of decay rate allows radioactivity to be used for estimating the age of materials that contain radioactive substances.
11. Common Themes
6-8: 11B/M1. Models are often used to think about processes that happen too slowly, too quickly, or on too small a scale to observe directly. They are also used for processes that are too vast, too complex, or too dangerous to study.
6-8: 11B/M4. Simulations are often useful in modeling events and processes.
6-8: 11D/M3. Natural phenomena often involve sizes, durations, and speeds that are extremely small or extremely large. These phenomena may be difficult to appreciate because they involve magnitudes far outside human experience.
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