CHAPTER 25 Nuclear Chemistry III. Fission & Fusion (p ) III. Fission & Fusion (p ) I IV III II

A. F ission  Nuclear Reactions produce exponentially more energy than chemical reactions. (nuclear bomb vs. dynamite chemical bombs)  Fission is splitting a nucleus into two or more smaller nuclei  1 g of 235 U = 3 tons of coal

A. F ission  chain reaction - self-propagating reaction  critical mass - mass required to sustain a chain reaction  Super-critical is when chain rxn goes too fast… MELTDOWN

B. Fusion  combining of two nuclei to form one nucleus of larger mass  thermonuclear reaction – requires temp of 40,000,000 K to sustain  1 g of fusion fuel = 20 tons of coal  occurs naturally in stars

C. Fission vs. Fusion  235 U is limited  danger of meltdown  toxic waste  thermal pollution  Heavy hydrogen fuel is abundant  no danger of meltdown  no toxic waste  not yet sustainable FISSIONFISSION FUSIONFUSION

CHAPTER 25 Nuclear Chemistry IV. Applications I IV III II

A. Nuclear Power  Fission Reactors Cooling Tower

A. Nuclear Power  Fission Reactors

A. Nuclear Power  Fusion Reactors (not yet sustainable)

A. Nuclear Power  Fusion Reactors (not yet sustainable) Tokamak Fusion Test Reactor Princeton University National Spherical Torus Experiment

B. Synthetic Elements  Transuranium Elements  elements with atomic #s above 92  synthetically produced in nuclear reactors and accelerators  most decay very rapidly

C. Radioactive Dating  half-life measurements of radioactive elements are used to determine the age of an object  decay rate and amount of radioactive material remaining indicate the age  EX: 14 C – can date ages of up to 40,000 years 238 U and 40 K - over 300,000 years old

PET Scan  Positron Emission Topography  Inject or swallow a sugar with a radioactive tag that emits positron, which are measured by a scanner

D. Nuclear Medicine  Radioisotope Tracers (bonded to sugars, proteins, or medicines)  absorbed by specific organs and used to diagnose diseases  Radiation Treatment  larger doses are used to kill cancerous cells in targeted organs  internal or external radiation source Radiation treatment using  -rays from cobalt-60.

E. Nuclear Weapons  Atomic Bomb  chemical explosion is used to form a critical mass of 235 U or 239 Pu  fission develops into an uncontrolled chain reaction  Hydrogen Bomb  chemical explosion  fission  fusion  fusion increases the fission rate  more powerful than the atomic bomb

F. Others  Food Irradiation   radiation is used to kill bacteria  Radioactive Tracers  explore chemical pathways  trace water flow  study plant growth, photosynthesis  Consumer Products  ionizing smoke detectors Am