Nuclear Fission and Fusion Unit 8 – Part B

Nuclear Balance Delicate balance between attractive strong nuclear forces and repulsive electric forces. In all nuclei the strong nuclear forces dominate. In all nuclei the strong nuclear forces dominate. But in heavier nuclei this is lost and decay occurs But in heavier nuclei this is lost and decay occurs

Nuclear Fission Nuclear Fission: The splitting of a heavy nucleus into two lighter nuclei, accompanied by the release of a lot of energy. A neutron is shot at the nucleus and elongates the nucleus disrupting the strong nuclear force. A neutron is shot at the nucleus and elongates the nucleus disrupting the strong nuclear force. The energy released is in the form of Kinetic Energy. The energy released is in the form of Kinetic Energy.

Nuclear Fission

Chain Reaction: A self-sustaining reaction in which the products of one fission event stimulate further events.

Nuclear Fission Nuclear Fission Bomb: Critical Mass: The minimum mass of fissionable material needed in a reactor or nuclear bomb that will sustain a chain reaction. Critical Mass: The minimum mass of fissionable material needed in a reactor or nuclear bomb that will sustain a chain reaction. If a reaction occurs where there is enough space for neutrons to escape, the reaction quits. If a reaction occurs where there is enough space for neutrons to escape, the reaction quits. If a reaction occurs where the neutrons continue to collide, energy builds up, causing mass to exceed the critical mass. If a reaction occurs where the neutrons continue to collide, energy builds up, causing mass to exceed the critical mass.

Nuclear Energy Comes from Nuclear Mass Individual nucleons have the most mass in the lightest nuclei. Combined nucleons inside a nucleus have a smaller mass than individual nucleons. Combined nucleons inside a nucleus have a smaller mass than individual nucleons. The greater the mass of the nucleon, the greater amount of energy needed to pull the nucleons apart from each other. The greater the mass of the nucleon, the greater amount of energy needed to pull the nucleons apart from each other.

Nuclear Energy Comes from Nuclear Mass Carbon-12 atom – (nucleus has 6 protons and 6 neutrons). Mass exactly atomic mass units (amu) Mass exactly atomic mass units (amu) Individual Proton – amu Individual Neutron – amu 6 Protons (6x ) + 6 Neutrons (6x )= 6 Protons (6x ) + 6 Neutrons (6x )= amu amu

Nuclear Energy Comes from Nuclear Mass Remember that Energy is the ability to do work. Work = force x distance Work = force x distance A great deal of force is required to pull a nucleon out of a nucleus. Needed to overcome the attractive strong nuclear force. Needed to overcome the attractive strong nuclear force. The work done on the nucleon is energy that is added to the nucleon. Shows up as additional mass. Shows up as additional mass.

Nuclear Energy Comes from Nuclear Mass The average mass per nucleon is key to understanding the energy released. (Divide the total (Divide the total mass of a nucleus by the number of nucleons in the nucleus)

Nuclear Power Einstein’s Equation: e = mc 2. Energy = (Mass) x (Speed of light) 2 Energy = (Mass) x (Speed of light) 2 Helps us understand how energy is released in nuclear reactions. Helps us understand how energy is released in nuclear reactions. There is less mass after splitting than before. The “missing” mass is converted to energy. The “missing” mass is converted to energy.

Nuclear Fusion Nuclear Fusion: The joining together of light nuclei to form a heavier nucleus, accompanied by the release of a lot of energy. Promising future of nuclear energy because the lack of radioactive waste.

Nuclear Fusion If two small nuclei were to fuse, such as two nuclei of Hydrogen, the mass of the fused nucleus, Helium, would be less than the total mass of the two Hydrogen nuclei. The lost mass is converted into useful energy.

Nuclear Power