Nuclear energy

Summary of period 1

Parts of the atom

Mass (A.M.U) Charge

Proton 1 +1

Neutron 1 0

Electron 1/1830 -1

• Add/subtract a proton: creates a different atom• Add/subtract a neutron: creates a different isotope• Add/subtract an electron: changes oxidation state / creates ion

Isotopes

U23592

Mass number (protons + neutrons)

Atomic number (number of protons)

Element symbol

•The isotope of uranium above has 92 protons It has 143 neutrons

•U-238 has 92p and 146n

Isotopes of hydrogen

3 forms of hydrogen: Protium, deuterium, tritium

Differ only in the number of neutrons they have

Diagram from Microsoft Encarta

Fission and Fusion

Typical output of chemical reaction ~ 10 eV per atom

Output of nuclear fission reaction ~ 3.2 MeV per atom

Output of nuclear fusion reaction ~ 200 MeV per atom

The energy outputs of nuclear rxns are massive compared to the output of a chemical reaction, like burning HC fuels

Possible advantages: Lower mass of fuel needed Less atmospheric emissions

Fusion & Fission

Fusion: collision of two nuclei to make a new nucleus, e.g. two deuterium atoms fuse to make a helium-3 nucleus, emission of a neutron and released energy

Fission: neutron collides with large, unstable nucleus causing it to break into smaller fragments. In ex. Shown, two neutrons emitted which may collide with two more U-235 nuclei – chain reaction

Illustration from Microsoft Encarta

Fusion & Fission

Fusion reactions – usu. Small stable nuclei Fission reactions – usu. Large, unstable nuclei

Natural abundance of U-235 is very low (~ 0.7%) Not enough to ensure stray neutrons collide with them

and give a sustained nuclear reaction (critical mass)

Fuel enrichment is required

(next period – the nuclear fuel cycle)

The pressurized water reactor

Make sure you can label this or a similar diagram Be able to describe the operation of the reactor

Why are PWR’s generally located by a lake, river or the sea?

Location, location , location…

The nuclear pwr station need not damage local ecology

The San Onofre reactor

Cooling

Volumes of steam are released after work has been done on the turbines.

Is this efficient use of all that energy?

The reactor core

The long object is a boron control rod that is being removed for maintenance

The turbine floor

These are the turbines that turn the generator

to make electricity

Next Period

The Nuclear Debate

Arguments forArguments against