Topic 2: Nuclear Reactions Isotopes are important when we are looking at nuclear reactions. Recall from chemistry, isotopes are elements with same atomic numbers but different atomic masses because of different # of neutrons Protons: Neutrons: Electrons: Protons: Neutrons: Electrons:

Nuclear Reactions If the force of repulsion is greater than the nuclear force holding the p and n together, the isotope will change into another substance and release energy in the form of radiation The energy released is times more energy than chemical reactions The energy released is in the form of penetrating rays and these elements are known as radioactive

Radiation We will study three types of radiation –alpha rays –beta rays –gamma rays All of these are composed of high energy Which one of these has the highest frequency and lowest wavelength? –Check out EMR table in data booklet! A Geiger Counter is used to detect and measure intensity of ionizing radiation

Nuclear Explosions can Release Damaging Nuclear Radiation What is the name of one of the worlds greatest nuclear accidents called?

Type of Radiation Alpha Radiation Beta Radiation Made of 2 protons and 2 neutrons with a net charge of 2 + Gamma Radiation α Not very penetrating Description Penetrating Ability Symbol β A high speed electron More penetrating γ High energy photon with no mass or charge. Used to treat cancers. Most penetrating This is on page 8 of your data booklets

Atomic and mass numbers must be equal for reactants and products Ways to write nuclear reactions

Missing entity can be found by finding atomic number then finding element in data table 1.Write the nuclear equation for the alpha decay of radium-226. Practice Problem #1

Write the nuclear reaction for the beta decay of polonium-210

Write the nuclear reaction for the beta and gamma decay of cesium-144

Write the alpha and gamma decay of Americium-241

Write the equation for the alpha decay of Thorium-232 One more: write the beta decay of Radon-222

Nuclear Fission Fission Animation Nuclear fission is when a large nucleus splits into smaller nuclei/particles and releases energy A large nucleus is usually struck by a neutron and becomes unstable and splits into 2 smaller nuclei called fission products

CANDU reactor Video Great FAQ’s on CANDU reactor CANDU reactor stands for Canadian Deuterium Uranium Reactor CANDU uses energy from nuclear fission to produce electricity

Energy conversions in a nuclear reactor… Kinetic energy from fission products is used to heat water and produce steam which turns a turbine, spins a generator which creates electricity This is the same energy conversions that occur in thermal power plants! High potential energy (uranium)  Kinetic energy (of fission products)  Thermal energy (heat)  Mechanical kinetic energy (turbine and generator)  Electrical Energy

CANDU Reactor Components Fuel: The fuel used is uranium - 235, in the form of uranium Oxide pellets assembled into a fuel bundle CANDU reactors can be refueled while in operation (whereas other reactors have to be shut down Moderator: Used to sustain fission reactions by slowing down fast moving neutrons The moderator used is heavy water (Deuterium Oxide (D 2 O)) – which is a heavier isotope of water)

CANDU Reactor Components Control Rods: Control rods also help to control the rate of fission Control rods absorbs neutrons in an emergency shut down Shielding: Shielding protects against radioactive by products of chain reaction from entering the atmosphere usually made of steel or concrete

Societal Environm- ental Benefits Economical Costs Produces enormous amount of energy Uranium reserves are more plentiful than fossil fuels Nuclear plants cost considerably more money to build Benefits and Costs of Nuclear Fission Energy Risk of nuclear meltdown No gaseous emissions (CO 2 ) or particulates Lower operating costs Thermal pollution of air and water Uranium is a non-renewable resource Nuclear materials can be used in nuclear weapons Radioactivity to workers and general public Storage of spent fuel

Albert Einstein Δ E = Δ mc 2 Albert Einstein’s famous equation is… Where ΔE = energy change (J) Δm = mass change between products and reactants (kg) c = speed of light (3.00 x 10 8 m/s) This is on page 8 of your data booklets This formula says that a change in mass results in a change in energy When mass disappears it is converted into energy

Practice Problem #1 In the fission of 1 mol of beryllium-8, the mass of the products is determined to be 2.29 x kg less than the mass of the reactants. Calculate the change in energy that corresponds to with this change in mass. Identify whether this reaction is exothermic or endothermic.

Calculate the energy released by the alpha decay of radium-226 Practice Problem #2

x J/mol Practice Problem #3 Calculate the energy released by the alpha decay of polonium-210

Calculate the energy released in the following equation: x J/mol

Nuclear fusion is when 2 smaller nuclei join to form a larger nucleus which releases energy Recall: Nuclear fusion is what occurs in the sun and all stars Can we use nuclear fusion to produce energy? Not yet! We have plenty of deuterium (raw material for fusion) but we cannot contain the energy produced! Nuclear Fusion

Phase Change Chemical Reaction Type of Change Nuclear Fission Energy Released H 2 0 (g)  H 2 0 (l) Nuclear Fission Combustion of methane 40.7 kJ/mol 802 KJ/mol 1.67 x KJ/mol Comparison of Energy Change Nuclear Fusion 1.82 x 10 9 KJ/mol Nuclear Fusion