Activity Overview: While nuclear materials are part of the earth’s crust and have been for millions of years, the modern history of harnessing nuclear energy for power generation is relatively short. Nuclear fission was first discovered in 1939, and the first controlled nuclear chain reaction took place in Chicago as part of the wartime Manhattan Project in 1942. Three years later, the first nuclear weapon was tested in New Mexico. In 1948, nuclear reactors first generated electricity at a power plant in Idaho.
The most common fuel for nuclear reactors worldwide is uranium-235 (235U), an isotope of uranium. Other fuels such as thorium can also be used, but uranium became the conventional source of most production for a variety of historical, geopolitical, and technical reasons. The key physical aspect of controlled fission is the chain reaction that begins when a neutron splits a uranium atom. Splitting the atom emits more neutrons, which then split other atoms. During the fission process, some mass is lost, which is converted into thermal energy, as described by E=mc2. That heat can be used to make steam to spin a turbine and generate electricity.
As an instructor, you may want to ensure your students have a firm knowledge of the role of protons, neutrons, electrons, and the function of the strong force before undertaking this activity. Further, students should be able to define and identify isotopes.
Time: 1 hour
Describe and illustrate the process of nuclear fission in the context of its role in energy production.
Students should use the description above and their knowledge of subatomic particles and forces to construct an illustration of and description of the process of nuclear fission.
Chapter 17: Nuclear Energy from Energy 101: Energy Technology & Policy contains a detailed description of the process of nuclear fission within the broader context of the energy industry. Consider assigning a reading and allowing students to synthesize the information from that chapter into their illustrations and descriptions.
The BBC has produced a more straightforward explanation of the particulars of the process of nuclear fission and fusion. This site contains illustrations of the process, which can be used as an example against which to evaluate students work.
Students should clearly articulate that nuclear fission is the process of using a high-energy neutron to split the nucleus of an atom into smaller atoms which releases more high-energy subatomic particles, which in turn repeat the process. Excellent work will recognize the introduction of a neutron to the atomic nucleus as the creation of an unstable isotope, which immediately breaks down releasing energy and subatomic particles.
Applying this knowledge to the energy industry, students should identify the preferred stable isotope, uranium-235, and the unstable isotope created, uranium-236. Excellent work will contextualize the process of fission as occurring within the nuclear reactor core, where high-energy neutrons released from the initial reaction interact with other uranium-235 atoms in a chain reaction. The reactor core also contains the facilities to absorb the energy released from the reaction into steam generation for a traditional steam turbine.
During the process of nuclear fission with the uranium-235 isotope, 0.1 percent of the uranium's mass is "lost."¹ We know based on the law of conservation of mass that matter can neither be created nor destroyed, so where did this mass go? Thanks to Einstein's special relativity and his famous formula, physics has an answer for the intrinsic relationship between mass and energy. The 0.1% of uranium is converted to energy according to the principles of E=mc2.
In this second activity, reveal to students that physicists weighed all the daughter nuclei and free neutrons from the illustration they created in the first activity and reported that 0.1% of the initial mass was converted during the process of nuclear fission. Have them use Einstein's mass-energy equivalence to calculate how much energy was produced from the fission of 1 gram (g) of uranium-235. (This amount is arbitrary and should not be perceived as the actual amount of fuel used in controlled nuclear reactions.)
0.1% of 1 g uranium is 0.001 g or 0.000001 kg or 1 x 10⁻⁶ kg
J = kg m² s⁻²
E = energy measured in joules (J)
m = mass measured in kilograms (kg)
c = the speed of light in meters per second (3 x 108 m/s)
E = mc2
E = (1 x 10-6 kg) x (3 x 108 m/s)2
E = (1 x 10-6 kg) x 9 x 1016 m2/s2
E = 1 x 9 x 1010 kg;m2/s-2
E = 9 x 1010 J
The BBC Bitesize GCSE review pages provide a succinct explanation with illustrations of the process of fission and fusion.
Chemistry Matters from Georgia Public Broadcasting features a lesson on nuclear fission and the different types of radiation. Although formally aligned with the Georgia Standards of Excellence, this material also addresses the TEKS listed on this page.
Portions of this activity have been reprinted from Energy 101: Energy Technology & Policy Chapter 17: Nuclear Energy.
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