Geologic Resources: Nonrenewable Mineral and Energy Resources

Geologic Resources: Nonrenewable Mineral and Energy Resources

Chapters 14 & 15

G. Tyler Miller’sLiving in the Environment

Chapters 14 & 15

G. Tyler Miller’sLiving in the Environment

NUCLEAR POWERNUCLEAR POWER

• President Dwight Eisenhower, 1953, “Atoms for Peace”speech.– Nuclear-powered electrical generators

would provide power “too cheap to meter.”• Between 1970 and 1974, American utilities

ordered 140 new reactors for power plants.

Nuclear PowerNuclear Power

• After 1975, only 13 orders were placed for new nuclear reactors, and all of those were subsequently cancelled.– In all, 100 of 140 reactors on order in 1975

were cancelled.• Construction costs, declining demand for

electrical power, safety fears• Electricity from nuclear power plants was

about half the price of coal in 1970, but twice as much in 1990.

How Do Nuclear Reactors WorkHow Do Nuclear Reactors Work

• Most commonly used fuel is U235, a naturally occurring radioactive isotope of uranium.

• Occurs naturally at 0.7% of uranium, but must be enriched to about of 3%.

• Formed in cylindrical pellets (1.5 cm long) and stacked in hollow metal rods (4 m long).– About 100 rods and bundled together to make a

fuel assembly.– Thousands of fuel assemblies bundled in reactor

core.

How Do Nuclear Reactors WorkHow Do Nuclear Reactors Work

• When struck by neutrons, radioactive uranium atoms undergo nuclear fission (splitting) releasing energy and more neutrons.– Triggers nuclear chain reaction.

Nuclear FissionNuclear Fission

How Do Nuclear Reactors WorkHow Do Nuclear Reactors Work

• Reaction is moderated in a power plant by neutron-absorbing solution (Moderator).– In addition, Control Rods composed of

neutron-absorbing material are inserted into spaces between fuel assemblies to control reaction rate.• Cadmium or boron

– Water or other coolant is circulated between the fuel rods to remove excess heat.

PWRPWR

Periodic removaland storage of

radioactive wastesand spent fuel assemblies

Periodic removaland storage of

radioactive liquid wastes

Pump

Steam

Small amounts of radioactive gases

Water

Black

Turbine Generator

Waste heat Electrical power

Hot water output

Condenser

Cool water input

Pump

Pump Wasteheat

Useful energy25 to 30%

WasteheatWater source

(river, lake, ocean)

Heatexchanger

Containment shell

Uranium fuel input(reactor core)

Emergency corecooling system

Controlrods

Moderator

Pressurevessel

Shielding

Coolantpassage

CoolantCoolant

Hot coolantHot coolant

RADIOACTIVE WASTE MANAGEMENTRADIOACTIVE WASTE MANAGEMENT

• Until 1970, the US, Britain, France, and Japan disposed of radioactive waste in the ocean.

• Production of 1,000 tons of uranium fuel typically generates 100,000 tons of tailings and 3.5 million liters of liquid waste.– Now approximately 200 million tons of

radioactive waste in piles around mines and processing plants in the US.

Radioactive Waste ManagementRadioactive Waste Management

• About 100,000 tons of low-level waste (clothing) and about 15,000 tons of high-level (spent-fuel) waste in the US.– For past 20 years, spent fuel assemblies

have been stored in deep water-filled pools at the power plants. (Designed to be “temporary”.)• Many internal pools are now filled and a

number plants are storing nuclear waste in metal dry casks outside.

Radioactive Waste ManagementRadioactive Waste Management

• US Department of Energy announced plans to build a high-level waste repository near Yucca Mountain Nevada in 1987.– Facility may cost

between $10 and 35 billion, and will not open until at least 2015.

Decommissioning Old Nuclear PlantsDecommissioning Old Nuclear Plants

• Most plants are designed for a 30 year operating life.– Only a few plants have thus far been

decommissioned.– General estimates are costs will be 2-10

times more than original construction costs.

CHANGING FORTUNESCHANGING FORTUNES

• Public opinion has fluctuated over the years.– When Chernobyl exploded in 1985, less

than one-third of Americans favored nuclear power.• Now, half of all Americans support nuclear-

energy.

• Currently, 103 nuclear reactors produce about 20% of all electricity consumed in the US.

NUCLEAR FUSIONNUCLEAR FUSION• Nuclear Fusion - Energy released when two

smaller atomic nuclei fuse into one large nucleus. (Sun)

– Duterium and tritium, two heavy isotopes of H

– Temperatures must be raised to 100,000,000o C and pressure must reach several billion atmospheres.

– Advantages:• Production of few radioactive wastes• Elimination of products that could be made into bombs• Fuel supply that is larger and less hazardous than

uranium.

NUCLEAR FUSIONNUCLEAR FUSION

Despite 50 years and $25 billion, fusion reactors have never produced more energy than they consume!

Nuclear EnergyNuclear Energy Fission

reactors Fission

reactors

Uranium-235 Uranium-235

Potentially dangerous

Potentially dangerous

Radioactive wastes

Radioactive wastes

Refer to Introductory Essay p. 338Refer to Introductory Essay p. 338

Fig. 15-35 p. 366Fig. 15-35 p. 366

Dealing with Nuclear WasteDealing with Nuclear Waste

• Low-level wasteLow-level waste• High-level wasteHigh-level waste• Underground Underground

burialburial• Disposal in spaceDisposal in space• Burial in ice sheetsBurial in ice sheets• Dumping into Dumping into

subduction zonessubduction zones• Burial in ocean mudBurial in ocean mud• Conversion into Conversion into

harmless materialsharmless materials

Fig. 15-40p. 370

Nuclear AlternativesNuclear Alternatives

Breeder nuclear fission reactors

Breeder nuclear fission reactors

Nuclear fusion

Nuclear fusion New reactor designs

New reactor designsStorage Containers

Fuel rod

Primary canister

Overpackcontainersealed

Underground

Buried and capped

Ground Level

Unloaded from train

Lowered down shaft

Personnal elevatorAir shaft

Nuclear waste shaft

Fig. 15-42p. 376