Low risk of accidents because of multiplesafety systems(except in 35 poorly designed and run reactors in former SovietUnion and Eastern Europe)

Moderate land use

Moderate landdisruption andwater pollution(without accidents)

Emits 1/6 asmuch CO2 as coal

Lowenvironmentalimpact (withoutaccidents)

Large fuelsupply

Spreads knowledge and technology for building nuclear weapons

No acceptable solution for long-term storage of radioactive wastes and decommissioning worn-out plants

Catastrophic accidents can happen (Chernobyl)

High environmental impact (with major accidents)

Low net energy yield

High cost (even with large subsidies)

Advantages Disadvantages

Fig. 14.35, p. 349

Coal

Ample supply

High net energyyield

Very high airpollution

High CO2emissions

65,000 to 200,000deaths per yearin U.S.

High land disruption fromsurface mining

High land use

Low cost (with huge subsidies)

Nuclear

Ample supplyof uranium

Low net energyyield

Low air pollution(mostly from fuelreprocessing)

Low CO2emissions(mostly from fuelreprocessing)

About 6,000deaths per year in U.S.

Much lower landdisruption fromsurface mining

Moderate land use

High cost (with huge subsidies)

Fig. 14.36, p. 349

F. Advantages of Nuclear Power:

• 1. Don’t emit air pollutants

• 2. Water pollution and land disruption are low

G. Nuclear Power Plant Safety

• 1. Very low risk of exposure to radioactivity• 2. Three Mile Island - March 29, 1979; No. 2 reactor

lost coolant water due to a series of mechanical failures and human error. Core was partially uncovered

• 3. Nuclear Regulatory Commission estimates there is a 15-45% chance of a complete core meltdown at a US reactor during the next 20 years.

• 4. US National Academy of Sciences estimates that US nuclear power plants cause 6000 premature deaths and 3700 serious genetic defects each year.

http://www.angelfire.com/extreme4/kiddofspeed/chapter1.html

Steamgenerator

Waterpumps

Crane formoving fuel rods

TurbinesTurbines

ReactorReactor

Coolingpond

Coolingpond

Reactor power output was lowered too much, making it too difficult to control.

Additional water pump to cool reactor was turned on. But with low power output and extra drain on system, water didn’t actually reach reactor.

Automatic safety devices that shut down the reactor when water and steam levels fall below normal and turbine stops were shut off because engineers didn’t want systems to “spoil” experiment.

Radiation shieldsRadiation shields

Almost all control rods were removed from the core during experiment.

Emergency cooling system was turned off to conduct an experiment.

Fig. 14.37, p. 350Chernobyl

H. Low-Level Radioactive Waste

• 1. Low-level waste gives off small amounts of ionizing radiation; must be stored for 100-500 years before decaying to levels that don’t pose an unacceptable risk to public health and safety

• 2. 1940-1970: low-level waste was put into drums and dumped into the oceans. This is still done by UK and Pakistan

• 3. Since 1970, waste is buried in commercial, government-run landfills.

• 4. Above-ground storage is proposed by a number of environmentalists.

• 5. 1990: the NRC proposed redefining low-level radioactive waste as essentially nonradioactive. That policy was never implemented (as of early 1999).

I. High-Level Radioactive Waste

• 1. Emit large amounts of ionizing radiation for a short time and small amounts for a long time. Must be stored for about 240,000

• 2. Spent fuel rods; wastes from plants that produce plutonium and tritium for nuclear weapons.

J. Possible Methods of Disposal and their Drawbacks 

• 1. Bury it deep in the ground• 2. Shoot it into space or into the sun• 3. Bury it under the Antarctic ice sheet or the Greenland

ice cap• 4. Dump it into descending subduction zones in the

deep ocean• 5. Bury it in thick deposits of muck on the deep ocean

floor• 6. Change it into harmless (or less harmful) isotopes• 7. Currently high-level waste is stored in the DOE $2

billion Waste Isolation Pilot Plant (WIPP) near Carlsbad, NM. (supposed to be put into operation in 1999)

Clay bottom

Up to 60deep trenchesdug into clay.

As many as 20flatbed trucksdeliver wastecontainers daily.

Barrels are stackedand surroundedwith sand. Coveringis mounded to aidrain runoff.

Fig. 14.38b, p. 351

What covers waste

Clay

Gravel

Sand

Compacted clay

Soil

Topsoil

Grass

Gravel

Fig. 14.38c, p. 351

Waste container

Steel wall

Steel wall

Severalsteel drumsholding waste

Lead shielding

2 meters wide2–5 meters high

Fig. 14.38a, p. 351

Storage Containers

Fuel rod

Primary canister

Overpack container sealed

Fig. 14.39c, p. 352

Underground

Buried and capped

Fig. 14.39d, p. 352

Ground Level

Unloaded from train

Lowered down shaft

Fig. 14.39a, p. 352

Personnel elevator

Air shaft

Nuclear waste shaft

2,500 ft.(760 m)deep

Fig. 14.39b, p. 352

K. Worn-Out Nuclear Plants

• 1. Walls of the reactor’s pressure vessel become brittle and thus are more likely to crack.

• 2. Corrosion of pipes and valves

3. Decommissioning a power plant (3 methods have been proposed)

• A. immediate dismantling• B. mothballing for 30-100 years• C. entombment (several thousand years)• 4. Each method involves shutting down

the plant, removing the spent fuel, draining all liquids, flushing all pipes, sending all radioactive materials to an approved waste storage site yet to be built.

Connection between Nuclear Reactors and the Spread of Nuclear Weapons

• 1. Components, materials and information to build and operate reactors can be used to produce fissionable isotopes for use in nuclear weapons.

Los Alamos Muon Detector Could Thwart Nuclear Smugglers

M. Can We Afford Nuclear Power?

• 1. Main reason utilities, the government and investors are shying away from nuclear power is the extremely high cost of making it a safe technology.

• 2. All methods of producing electricity have average costs well below the costs of nuclear power plants.

N. Breeder Reactors

• 1. Convert nonfissionable uranium-238 into fissionable plutonium-239

• 2. Safety: liquid sodium coolant could cause a runaway fission chain reaction and a nuclear explosion powerful enough to blast open the containment building.

• 3. Breeders produce plutonium fuel too slowly; it would take 1-200 years to produce enough plutonium to fuel a significant number of other breeder reactors.

O. Nuclear Fusion

• 1. D-T nuclear fusion reaction; Deuterium and Tritium fuse at about 100 million degrees

• 2. Uses more energy than it produces