Environmental Sciences: Towards a Sustainable Future Chapter 13

Nuclear Power: Promise and Problems

INTRODUCTIONTokaimura

Tokaimura, Japan Radiation release after workers dumped

enriched Uranium into the reactors using buckets (the company had broke safety protocol and instructed them to do so). Alarms triggered, evacuation of plant and

partial evac. of town. Two of the three employees died.

Nuclear Energy in Perspective

Lesson 13.1

Nuclear Power No contribution to global

warming. Sufficient uranium to fuel

nuclear power plants into the 21st century

31 nations now have nuclear power plants.

Price-Anderson Act of 1957 Insured that companies would be

exempt from any legal liabilities with respect to the building of Nuclear facilities. General Electric, Westinghouse

constructed plants ordered by utility companies.

The United States After WWII embarked on a course to lead the

world into “nuclear age”. 1975-53 plants=9% of nation’s electricity

Another 170 plants were in various stages of planning or construction.

Many plants closed or orders canceled. By end 2005: 103 plants operating=20% of the

nations electricity. Watts Bar nuclear plant in Tennessee was the last to

come on line. February 1996. New plants expected to come online because of the

Energy Policy Act of 2005.

Nuclear Power in the United States

Nuclear Power in the United States

Nuclear Share of Electrical Power Generation

France78% currentPlan for 80%

USA20%

Regulatory Agencies (US) NRC (nuclear regulatory

agency DOE (department of energy)

Sets and enforces safety standards for the operation of plants.

Leader in Nuclear Power 433 Plants worldwide. 37 more in

the works. US peaked at 112 (current 103). 17% of world electricity supplied

by nuclear power plants. Only France and Japan remain

fully committed.

How Nuclear Power Works

Lesson 13.2

What is Nuclear Power? Objective: Controlled nuclear reaction that

produces heat. Heat energy used to boil water and produce

steam, which then drives a turbo generator. Base-load plants

Provides the energy for daily operations. Always operating unless being refueled.

Generate up to 1,400 megawatts.

Different from Fossil Fuels? Fossil fuels-materials are unchanged at

the atomic level. Nuclear-materials are changed at the

atomic level through one or two basic processes. Fission Fusion

All current plants use the fission process.

Fission: a large atom of one element is split to produce two different smaller elements, energy, and release neutrons.

Fusion: two small atoms combine to form a larger atom of a different element

Isotope: different (mass number) forms of the same element b/c of the number of neutrons in the nucleus.

Terms and Definitions

Fission The fission process of 235-U

Uranium ore mined, purified into uranium dioxide (UO2).

Enriched (separating 235-U from 238-U) When 235-U is highly enriched, spontaneous

fission of atoms can trigger a chain reaction. Process slowed and controlled to release the

heat needed (moderator used). If uncontrolled a “meltdown” can occur.

Chernobyl (Ukraine) Three mile island (Partial meltdown-Pennsylvania)

Terms and Definitions Fuel rods: rods full of U235 pellets Moderator: fluid (water) coolant that

slows down neutrons Control rods: moderate rate of the chain

reaction by absorbing neutrons LOCA: Loss of coolant accident.

Happens when a reactor vessel breaks.

Uncontrolled Fission

Fission, Fusion, or Both? Energy is released

(Both) Begins with U235

(fission) Produces radioactive byproducts

(fission) Produces free neutrons

(both)

Fission, Fusion, or Both? Splits a larger atom into smaller atoms

(fission) Fuses smaller atoms in one larger atom

(fusion) Begins with H2 and H3

(fusion) Produces helium

(fusion)

Comparing coal fired and nuclear for 1 Year.Coal fired Nuclear

Fuel needed 3 mill tons 30 tons uranium needed. 75,000 tons mined. 1 pound Uranium=burning 50 tons of coal.

CO2 Emissions?

7 million tons of CO2 released.

No CO2 released through nuclear power except while using fossil fuels to mine it

SO2 and other emissions?

300,000 tons No sulfur dioxide released

Solid wastes? 600,000 tons of ash

250 tons highly radioactive waste

Accidents limited Possibly disastrous

Hazards and Costs of Nuclear Power

Lesson 13.3

The Fission Process When fission occurs it causes Uranium

to break apart into any of some 30 different elements. (split halves)

These are unstable radioisotopes of those elements that release subatomic particles and/or high energy radiation to become stable.

Radioactive Wastes The direct and indirect products of

nuclear power. Subatomic particles Gamma rays

Biological effects occur.

Dangerous Side-effects of Radioactive Emissions Block cell division

Damage biological tissues and DNA

Death Cancer Birth defects

Terms and Definitions Radioisotopes: unstable isotopes of the

elements resulting from the fission process Radioactive emissions: subatomic particles

(neutrons) and high-energy radiation (alpha, beta and gamma rays)

Radioactive wastes: materials that become radioactive by absorbing neutrons from the fission process

Acceptable Doses Some scientists say no amount of radiation

is acceptable, others say cells have the ability to self repair and therefore there is a threshold of no biological effects occur.

Federal standards set at 1.7 mSv/yr (milliSieverts per year) except for medical x-rays.

The Average Person Although the limit is set at 1.7mSv/yr,

the average person receives 3.6 mSv/yr. Background radiation Medical/dental x-rays

No routine discharges of radiation into the atmosphere occur from nuclear power plants.

Background Radiation Sources:

Radioactive materials that occur naturally such as Uranium and Radon in Earth’s crust.

Cosmic rays from outer space.

The Real Problems Storage of wastes Disposal of wastes Potential for accident

Other Major Problems With Radioactive Wastes

Finding long-term containment sites Many radioisotopes take thousands of years to

break down (radioactive decay) Transport of highly toxic radioactive wastes

across the united states The lack of any resolution to the radioactive

waste problem Environmental racism Cost ($60 billion to 1.5 trillion)

Radioactive Decay

Half life = the time for half the amount of a radioactive isotope to decay.

Long Term Containment Nuclear nations have decided on

geologic burial for the ultimate consignment of wastes, but have yet to find a suitable site that shows no sign of volcanic, earthquake or ground water leeching.

NIMBY has also played a part.

Safety Active Safety: Operators having

the control to override and shut down machines.

Passive Safety: Engineering devices that do not allow reactors to go beyond acceptable levels of power, temperature, and radioactive emissions.

The Major Deterrent The main deterrent of building nuclear

power plants is the cost. Energy demands not as high as

originally thought. Deregulation of the electrical companies Shorter than expected life expectancies. Closing or decommissioning costs.

More Advanced Reactors

Lesson 13.4

Breeder Reactors Nonfissionable U-238 absorbs the

extra neutrons of the U-235 fission process to form Pu-239 which is fissionable. It is then purified and used as a nuclear fuel like U-235. Produces more fuel than it

consumes.

Breeder, Fusion, or Both Creates more fuel than it consumes (Br) Raw material is U238 (B) Splits atoms (Br) Fuses atoms (F) Releases energy (B) Raw material is deuterium and tritium (F) Source of unprecedented thermal pollution

(F)

The Future of Nuclear Power

Lesson 13.5

Public Opposition to Nuclear Energy General distrust of technology Skepticism of management Doubt overall safety claims about nuclear power

plants Nuclear waste disposal problems High costs of construction Prime targets for terrorism High costs of construction and unexpectedly

short operational lifetimes.

Rebirth of Nuclear power? Must haves:

Safety concerns will have to be addresses. Potential for terrorist attacks and sabotage will also

have to be addressed. Manufacturing will have to favor standard designs

and factory production of smaller reactors. Streamline framework for licensing and monitoring

reactors. Waste dilemma must be solved. Political leadership will be required to accomplish

all these developments.

George W. Bush Proposed the Nuclear Power 2010 program.

Part one: Plans to identify new sites for development Streamline regulations associated with licensing. Encourage plants that could be online by 2010.

Part two: Approve Yucca Mountain for repository.

Part three: Sign into law the Energy Policy Act of 2010 program Tax credit for the first 6,000 megawatts Insurance for companies building new reactors from the risk of

regulatory delays.

Embrittlement Occurs as neutrons from fission

bombard the reactor vessel and other hardware. Gradually the neutron bombardment causes the metals to become brittle enough that they may crack under thermal stress.