Neutron Capture, Plutonium as a Power Source, and Risks of Nuclear Power Kerr Chapters – By Daniel Conlon 1

 Transmutation: changes in the makeup of the nucleus of an atom (ex: adding or removing neutrons).  Slow (thermal) Neutrons: neutrons moving at about 1.2 kms -1 (and having an energy ≈ 1 eV).  Fertile Material: able to capture neutrons to transmute into a fissionable material 2

After capturing a neutron, Uranium-238 (now Uranium-239) decays and produces Neptunium-239 which in turn decays to produce Plutonium-239. When bombarded with slow neutrons, Plutonium-239 produces Barium-147, Strontium-90 and large amounts of energy. 3

As an isotope, 235 U is about 140 times more abundant than 238 U. Both are used in breed reactors (a nuclear fission reactor that generates more fissionable material than consumed). 4

 On average, each 235 U fission will produce 2.4 neutrons. By definition, for the process to continue, one of these neutrons will be required for the next fission. Ex) If 100 fissions of 235 U take place, and 30 neutrons are lost to environmental factors, by what percentage does the fuel increase? 5

- 100 fissions n produced per fission n needed to continue reaction - 30 n lost to environment n available for 239 Pu 6 100*2.4 = 240 n produced 240 – 100 = 140 n 140 – 30 = 110 n → 110 Plutonium-239 fissions ( Pu fissions)/( U fissions) = 1.1 = 10% increase in fuel

Why go nuclear? Coal, natural gas and oil are all more efficient than nuclear power with current technology (nuclear reactors are generally about 30% efficient), so why switch to something that’s going to give less for the same cost? 7

8  This 30% is a massive amount of energy. Given how much energy is involved in the “breaking” of atoms, even less than 1/3 of the total energy involved is huge.  Comparatively produces much less “greenhouse gas” than other traditional fuel sources and less thermal pollution

 Mining Dangers: When mining Uranium, Radon-222 (a highly radioactive gas) and contaminated water may be exposed to miners and the environment.  Meltdowns: Although quite rare, a nuclear plant meltdown is extremely dangerous and far-reaching (Chernobyl – in the Ukraine - poisoned farmlands in the Northern Europe for years). 9

 Disposal: Eliminating the waste produced is a major concern. There are three basic types of nuclear waste: 1. Low-Level: Contains small amounts of short-lived radiation (clothing, equipment, etc.) 2. Intermediate-Level: Contains significantly more radiation and requires being buried in solid concrete blocks (chemical sludge, coolant and materials associated with reactor decommissioning). 3. High-Level: Extremely dangerous and radioactive materials (fuel rods, anything from inside the reactor core, etc.) – usually also hot to the touch. 10 (The most advanced method of disposing of waste currently is to lock it away in deep underground bunkers.)

 Contamination: Primary concerns include the poisoning of water supplies and irradiating the atmosphere. Obvious health risks include short-term illness, cell damage and severe cancer developing among individuals exposed to high levels of radiation. Ecosystems may be wiped out if exposed to high levels of radiation – poisoning of water suppies and genetic mutations. 11