overview of chapter 12 introduction to nuclear power atoms and radioactivity nuclear fission pros...

Introduction to Nuclear Power Atoms and radioactivity

Nuclear FissionPros and Cons of Nuclear Energy

Cost of Nuclear Power

Safety Issues at Power Plants Three Mile Island & Chernobyl Nuclear Weapons

Radioactive WasteFuture of Nuclear Power

Nuclear energy

Nuclear fission ______________ of an atomic nucleus into two smaller fragments,

accompanied by the release of a large amount of energyNuclear fusion

_______________ of two lightweight atomic nuclei into a single, heavier nucleus, accompanied by the release of a large amount of energy

Nuclear reactions produce __________________ times more energy per atom than is available from a chemical bond between 2 atoms

Nucleus Comprised of protons (+)

and neutrons (neutral)

Electrons (-) orbit around ________________

Neutral atoms Same # of ________________ and

________________

Atomic mass

Atomic number Each element has its own atomic number

Isotope Usually an atom has an equal number of neutrons and protons If the number of neutrons is greater than the number of protons =

isotope Examples…

Unstable isotope

Radioactive Decay Emission of ______________________________________ particles or rays from

unstable atomic nuclei

Example Uranium (U-235) decays over time to lead (Pb-207)

Each isotope decays based on its own half-life What is half-life??

Varies greatly in time

Nuclear Fuel Cycle Processes involved in

producing the fuel used in nuclear reactors and in disposing of radioactive (nuclear) wastes

Uranium ore – mineral fuel used in conventional nuclear power plants __________________________

resource Ore contains 3 isotopes:

U238 (99.28%), U235 (.71%) and U234 (less than 0.01%)

U235 composes less than 1% of ore – uranium must be refined to concentration to ~3%

In nuclear reactor fission occurs… U-235 is bombarded with

neutrons The nucleus absorbs ____________ It becomes unstable and splits

into 2 smaller atoms 2-3 neutrons are emitted and

bombard another U-235 atom

Fission releases ______________________ , which transforms water to steam Steam used to generate electricity

Be able to elaborate on imageSafety?

BNF- A type of nuclear fission in which non-fissionable U-238 is converted into fissionable Pu-239

What is different?Concerns…US performed first

breeder reactor experiments but abandoned nuclear reactor development in 1977 by President Carter

Europe, reactors that use mixed oxide fuel (_______________) Can be used to

generate ___________________

Pros _____________________ of an immediate environmental

impact compared to fossil fuels Carbon-free

source of electricity- no ______________________________ emitted

May be able to generate H-fuel

Cons Generates _______________________ waste Many steps require fossil fuels (mining and

disposal)

Cost is very ___________________20% of US electricity is from Nuclear Energy

Affordable due to government subsidies

Expensive to build nuclear power plants _______________________ cost-recovery time

Fixing technical and safety issues in existing plants is _______________________

True costs of nuclear energy are _________________ always obvious in utility bills

In US, no nuclear power plants have been ordered since 1976 for 2 reasons:

Nuclear Power and Electrical Power Deregulation Prior to late 1990s During late 1990s – state governments __________________

the electricity market Early 2000s – amid widely publicized electricity

shortages in several states, the market price of electricity soared and nuclear power became more attractive economically

US concerned about our reliance on _________________________________________

Supports of nuclear energy – it would ______________ our dependence use nuclear power Not as convincing as sounds – oil generates only _________

of electricity in USTechnological advance could change nuclear

power’s potential contribution in the future

Meltdown

Probability of meltdown or other accident is ______Public perception is that nuclear power is not

safe… why?Sites of major accidents:

Three Mile Island – US Chernobyl (Ukraine) – global Japan!!

1979- most serious reactor accident in US50% meltdown of reactor core

Containment building kept radiation from escaping

Elevated public apprehension of nuclear energy Led to ___________________________ of many new plants in US

1986- worst accident in history

1 or 2 explosions destroyed the ______________________________ Large amounts of radiation

escaped into ___________________Spread across large

portions of Europe

Radiation spread was ___________________

Radiation fallout was dumped unevenly

Death toll is 10,000-100,000

Health issues

___________ countries use nuclear energy to create electricity

These countries have access to spent fuel needed to make nuclear weapons

Safe storage and handling of these weapons is a ________________________

Special concerns of international safety Russia

What has the US done?

Low-level radioactive waste Radioactive solids, liquids, or

gasses that give off ________________________________________________________________________________

High-level radioactive waste Radioactive solids, liquids, or

gasses that give off ________________________________________________________________________________

Fuel rods – must be stored for _________________ of years

Long term solution to waste As of 2004, site must meet EPA million year standard

(compared to previous 10,000 year standard) Possibilities:

Deep geologic burial –Yucca Mountain

U235 may split in several ways – forms smaller atoms which are ___________________________ The smaller atoms have very short half lives

Safe storage of fission products – concern because _________________ produces larger amounts of these materials Compared to amount with extremely longer half lives

Health concerns exist - mimic essential nutrients, concentrate in the body continue to decay w/ harmful effects Sr90 – chemically similar to Ca; incorporated into bone and teeth Cs137 – replaces potassium in body, accumulates in muscle tissue I131 – concentrates in thyroid gland

_____________________ storage solutions In nuclear plant facility (require high security)

Under water storage Above ground concrete and steel casks

Need approved ______________________ options soon.

70,000 tons of high-level radioactive waste

_______________________ issues have been identified

High level ___________ waste

Licensed to operate for 40 years Several have received 20-year extensions

Power plants ________________ be abandoned when they are shut down

Three solutions Decommissioning (dismantling)

Fuel= isotopes of hydrogen (deuterium and tritium)

Way of the future?? Produces ________________ high-level waste Fuel is _____________________________ (plenty of it!)

Problems It takes very high temperatures (millions of degrees) to

make atoms fuse Confining the __________________________ after it is formed

Scientists have yet to be able to create _______________________ from fusion

Nuclear and utility executives have developed a plan that addresses the safety and economic issues associated with nuclear power Building a series of “new generation” nuclear reactors

New design: Pebble bed modular reactor (PBMR) – uses small ceramic encased balls

of uranium instead of fuel rods 2007 – Bush called for 30 new commercial nuclear power plants

to be built between 2015 and 2025 2011 – Obama support continuing to explore nuclear power in

US Globally:

16 of 25 nuclear power plants currently under construction are in Asia 2004 – France announced intention to replace aging nuclear reactors

with new ones