Nuclear EnergyNuclear Energy

Power PlantsPower Plants

ChernobylChernobyl

FuelFuel Uranium-235Uranium-235 an isotope of naturally occurring uranium-an isotope of naturally occurring uranium-

238238 Uranium is mined-common mineral is Uranium is mined-common mineral is

urananite.urananite. Uranium-238 is enriched so more of the Uranium-238 is enriched so more of the

isotope U-235 is present.isotope U-235 is present. Enriched from about 0.7% in naturally Enriched from about 0.7% in naturally

occurring uranium to 5% for use in occurring uranium to 5% for use in reactorsreactors

Uranium Reserves in the United Uranium Reserves in the United StatesStates

Fuel Rods in the Reactor CoreFuel Rods in the Reactor Core

The fuel rods in a reactor are about a The fuel rods in a reactor are about a finger width in diameter.finger width in diameter.

They are 12 feet longThey are 12 feet long 100 fuel rods make up a fuel rod assembly 100 fuel rods make up a fuel rod assembly

(fra)(fra) There are 100 fra in a reactor coreThere are 100 fra in a reactor core

What happens in the Reactor?

• Chain Reaction

Another view of a Chain Reaction

Chain Reactions in Fission Nuclear Chain Reactions in Fission Nuclear ReactorsReactors

Our present day Nuclear Power plants are Our present day Nuclear Power plants are fission power plantsfission power plants..

What does fission mean?What does fission mean?

The atom is split apart to produceThe atom is split apart to produceenergy.energy.

A controlled chain reaction takes place A controlled chain reaction takes place within the reactor core.within the reactor core.

Can a reactor become a Nuclear Can a reactor become a Nuclear Bomb?Bomb?

No, the uranium used in a No, the uranium used in a nuclear bomb must be nuclear bomb must be U-235 enriched to 95%.U-235 enriched to 95%.

Can a reactor sustain damage that Can a reactor sustain damage that results in the release of radiation?results in the release of radiation?

YesYes

Two examples: Three Mile Island (1979) Two examples: Three Mile Island (1979) and Chernobyl (1986)and Chernobyl (1986)

In both cases radiation was released into In both cases radiation was released into the atmosphere.the atmosphere.

Both were caused by human errorBoth were caused by human error

How is a chain reaction controlled?How is a chain reaction controlled? Control Rods-made of cadmium and Control Rods-made of cadmium and

boron.boron. They absorb neutrons to help control a They absorb neutrons to help control a

reaction.reaction.

If we drop more control rods into the reactor If we drop more control rods into the reactor core, what will happen to the reaction core, what will happen to the reaction rate?rate?

SLOW IT DOWN!SLOW IT DOWN!

What else helps to control the What else helps to control the reaction?reaction?

Water present in the reactor core slows Water present in the reactor core slows down the movement of the neutrons in the down the movement of the neutrons in the chain reaction.chain reaction.

It also absorbs heat energy.It also absorbs heat energy.

SafetySafety

Containment Domes- Containment Domes- Building that encloses Building that encloses the reactor and helps the reactor and helps to contain any to contain any radiation leaks should radiation leaks should they occur.they occur.

Four (4) foot thick wall Four (4) foot thick wall of cement.of cement.

Reactors in the United StatesReactors in the United StatesHistoryHistory

First active reactor in the Unites States to First active reactor in the Unites States to produce electricity 1957produce electricity 1957

As of 1990 there are 111 operating units As of 1990 there are 111 operating units producing about 20% of the total electricity producing about 20% of the total electricity generated in the United States.generated in the United States.

Boiling Water Reactor (BWR)Single loop

Pressurized Water Reactor (PWR)Double loop system

Minnesota Nuclear Power PlantsMinnesota Nuclear Power Plants

How many are there in MinnesotaHow many are there in Minnesota

Answer: 2Answer: 2

Where are they located?Where are they located?

Answer: Monticello and Prairie Answer: Monticello and Prairie IslandIsland

What kind of reactor are they?What kind of reactor are they?

Answer: Monticello is a BWR and Answer: Monticello is a BWR and

Prairie Island is a PWRPrairie Island is a PWR

How much power do they provide?How much power do they provide?about 40% about 40%