Worldwide Commercial Energy Production

Nuclear Power Countries

Nuclear Energy Use (textbook)Nuclear Energy Use (textbook)439 reactors worldwide = 16% electricity

France = 77% electricity; Japan+ Korea = 39%) investing increasingly;

U.S. = no new U.S. power plants ordered since 1978; 40% of 105 commercial nuclear power expected to be retired by 2015 & all by 2030;

© Brooks/Cole Publishing Company / ITP

Locations of Facilities

Source: http://www.pbs.org/wgbh/amex/three/maps/index.html

PART 3: NUCLEAR POWER

• Nuclear power now produces only 7% of the U.S. energy supply.

• Construction costs and safety concerns have made nuclear power much less attractive than expected.

• Between 1970-1974, American utilities ordered 140 new reactors, but 100 were subsequently canceled.

• WWPSS – Washington Water Power + Supply System canceled 9 reactors in Washington State after cost overruns and bankruptcy in 1980’s

• Major Accidents –• 1979 - Three Mile Island• 1986 - Chernobyl

Nuclear Fuel Cycle

Source: http://www.sonic.net/~kerry/uranium.html

Pressurized Water Reactors

are 70% of reactors

• Water circulating through the core absorbs heat from fuel rods. The hot water is pumped to a steam generator where it heats a secondary loop which drives a high-speed turbine making electricity.

• Both reactor vessel and steam generator are housed in a special containment building of reinforced concrete.

Nuclear fission occurs in the core of a nuclear reactor

Reactor Design

How Do Nuclear Reactors Work

• The common fuel for nuclear reactors is U235

that occurs naturally (0.7%) as a radioactive isotope of uranium.

• U235 is enriched to 3% concentration as it is processed into cylindrical pellets (1.5 cm long). The pellets are stacked in hollow metal rods (4 m long).

• 100 rods are bundled together into a fuel assembly. Thousands of these fuel

assemblies are bundled in the reactor core.

How Do Nuclear Reactors Work

• When struck by neutrons, radioactive uranium atoms undergo nuclear fission, releasing energy and more neutrons. This result triggers a nuclear chain reaction.

• This reaction is moderated in a power plant by neutron-absorbing solution .

• Control Rods composed of neutron-absorbing material are inserted into spaces between fuel assemblies to control reaction rate.

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

Three Mile Isle

Three Mile IslandThree Mile IslandMarch 29, 1979, number 2 reactor near Harrisburg, Pennsylvania lost coolant & core suffered partial meltdown;

50,000 people evacuated & another 50,000 fled area;

unknown amounts of radioactive materials released;

partial cleanup & damages cost $1.2 billion so far;

released radiation increased cancer rates.

© Brooks/Cole Publishing Company / ITP

March 28, 1979, 4:00 am

• Secondary cooling loop stops pumping. • Rising temperatures caused emergency valve

to open to release pressure, but indicator light malfunctioned

• Due to loss of steam, water level drops, water overheats and burns out pump

• Reactor core overheats and begins to melt (a “meltdown”)

Chernobyl

Chernobyl. In an experiment, technicians let the power of reactor 4 fall, and on April 26, 1986 the result was rapid power levels rising inside the core— melting fuel and causing a reactor containment breach—in addition to an internal hydrogen explosion. The top of the reactor blew off and spewed radioactive material into the atmosphere for 10 days.

ChernobylChernobylApril 26, 1986, reactor explosion (Ukraine) flung radioactive debris into atmosphere.

health ministry reported 3,576 deaths; Greenpeace ~32,000 deaths;

about 400,000 people were forced to leave their homes;

~160,000 sq km (62,00 sq mi) contaminated;

> half million people exposed to dangerous levels of radioactivity;

cost of incident > $358 billion.© Brooks/Cole Publishing Company / ITP

Decline of Nuclear Power

• The public began growing fearful of possible meltdowns, especially after the disaster at Three Mile Island

• Nearly 2/3 of all orders for new plants were cancelled in the late 1970’s

• No new plants having been built in the past twenty-five years

Energy Policy Act of 2005

• Signed by president BUSH in August 2005

• Government would cover cost overruns due to delays, up to $500 million each for the first two new nuclear reactors, and up to $250 million for the next four reactors