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January 25, 2012

What's Cool About Nuclear Science –

and Why Our Country Needs Nuclear Energy

Presented by: Mark T. Peters and Justin Thomas

What's Cool About Nuclear Science – and Why Our Country Needs Nuclear Energy

Mark T. Peters Justin ThomasDeputy Laboratory Director for Programs Principal Nuclear Engineer

Argonne National LaboratoryNational Nuclear Science WeekJanuary 25, 2012

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What’s cool about nuclear science?

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Why does our country need nuclear energy?

How will our future energy demands be met?

Today: 15 terawatts(TW) Future: 30 TW (2030) to 50 TW (2100)

Nuclear energy: Best U.S. source of sustainable, reliable, affordable, plentiful

electricity

Nuclear energy is the most widely used source of carbon-free electricity in the

United States

Energy Information Administration, 2006 Annual Energy Review

Wind: 2.3%Geothermal: 1.3%Solar: <0.05%

Wind: 2.3%Geothermal: 1.3%Solar: <0.05%

Nuclear energy provides lowest-cost baseload energy

Despite benefits of nuclear energy, concerns remain

Challenge of nuclear waste management remains

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There is still adventure in nuclear energy

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What’s under the hood?

Nuclear Fission Chain Reaction

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Nuclear Fuel

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Nuclear Electric Generation

Source: http://www.nrc.gov/reading-rm/basic-ref/students/animated-pwr.html

Heat sink

U.S. nuclear plants produce electricity for 1.72 cents per kilowatt-hour, compared to 2.37 cents for coal and 6.75 cents for natural gas.

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Nuclear Power Plant

Coal Power Plant

How much fuel?

One metric ton (1000 kg) of nuclear fuel: 50 Giga-Watt-days of thermal energy 400 million kW-hours of electrical energy

According to the Energy Information Agency, average U.S. household electricity usage in 2008 was 920 kW-hours per month

How much fuel is required to power one family’s home for a month? About 2 grams

Mass of nuclear fuel required to generate enough electricity for an American family’s home for a month

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Most of Used Fuel (a.k.a. “Nuclear Waste”) Is Still Useful

About 965 kg of fissionable material remains

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Current Reactors Are “Once-Through”

Uranium ore is mined from the ground

Natural uranium is only 0.7% U-235. Enrichment increases the U-235 content to 4-5%.

Enriched uranium goes to fuel fabrication to make UO2 ceramic pellets.

After generating power in a reactor (4–6 years) used fuel may be disposed of in a geologic repository.

Conventional Power Plant

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Fast Reactors Can Recycle Fuel

Reduces need for mining Conserves valuable resources Enables reliable fuel services Reduces repository burden Reduces long-term toxicity

Conventional Power Plant

Fast Reactor

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Recycling Nuclear Fuel Reduces Its Toxicity

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10 100 1000 10000 100000

Storage Time, years

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No Recycling (The waste includes uranium & plutonium.)

Recycling Uranium & Plutonium Back to Reactors

Radiotoxicity of Uranium Ore

(What was taken from the Earth)

With recycling, used fuel becomes less toxic than what was removed from the ground in ~200 years.

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Nuclear Power Plants Have Many Protections against Accidents

Containment building– Steel, reinforced concrete, or a

combination– Missile protection, confines any

radioactive release Automated shutdown systems Emergency core cooling systems Redundancy and diversity in design Defense in depth Passive Safety

– Relies on natural forces (e.g. gravity), rather than electrical pumps

– Relies less on intervention by plant operators

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Passive Safety?

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Small Modular Reactors (SMRs)

Financing: Lower absolute overnight capital cost for low power plant

Fitness for small electricity grids, reduced design complexity, reduced impact of human factors and, perhaps, reduced infrastructure and staff requirements

– May be a good choice for developing countries An option of incremental capacity increase Move generation closer to where electricity

is needed Option of operation without on-site refueling

– Attractive for nonproliferation regime Potential for enhanced safety

Pressurization Volume

Steam generator coils

Reactor coolant pumps

Control Rod Drive Mechanisms

Core

DHRS heat exchangers

mPower SystemBabcock & Wilcox125 MWe capacity(example)

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Modeling and Simulations

Nuclear reactor design relies heavily upon computer simulation to predict how a reactor will respond to adverse conditions

– What will the reactor do when the power goes out?– What would happen if we increased the power a little?

How do we know that a computer model is realistic?– Compare models to experiment– Compare results from competing computer models

Example: Physics of fluid flow and heat transfer– Heat generated by nuclear fission must be removed by a cooling fluid (water), which

then performs work on a turbine to convert the energy to electricity– Just above the core, this cooling fluid mixes in a large tank (or plenum)

• Need to reduce any “hot spots” where a small area could have a higher than average temperature

• Hot spots could damage the materials over a long time

The MAX experimental facility takes high-resolution measurements that can be compared to our simulation codes’ results for this problem

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MAX Experimental Facility

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Code Simulations of the MAX facility

Comparison of results from two simulation codes (Nek5000 and STAR-CCM+)

Velocity Predictions by the Nek5000 code

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Major Difference in Jet Behavior for Minor Design Change

MAX1

MAX2

Simulation Results:

– Small perturbation yields big change in jet behavior

– Unstable jet, with low-frequency (20 – 30 s) oscillations

– Visualization shows change due to jet / cross-flow interaction

– MAX2 results NOT predicted by steady RANS (URANS ok)

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For more info…

Nuclear energy learning resources: – http://students.ne.anl.gov/schools/ – For students at or below high school level and their teachers. Resources that will help

you find information on how nuclear reactors work, what makes certain materials radioactive, the importance of nuclear energy in the 21st century, and many other nuclear energy topics.

Argonne’s Nuclear Engineering Division– http://students.ne.anl.gov/outreach/ – http://www.facebook.com/NuclearEngineeringAtArgonne – neoutreach@anl.gov

Student programs in nuclear energy at Argonne– http://students.ne.anl.gov/students/ – Find out about the programs Argonne has for students just graduating from high school

or in college.

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Questions from the audience.

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