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Energy Systems & Climate Change. Thus. 5 Nov. 2009 Ch.7: Nuclear Dr. E.J. Zita (& Cheri Lucas Jennings) [email protected] http://academic.evergreen.edu/curricular/energy/0910/home.htm. What’s happening today:. Questions? Announcements? Ch.7: Nuclear Brief Reports at 2:30

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Energy systems climate change

Energy Systems & Climate Change

Thus. 5 Nov. 2009

Ch.7: Nuclear

Dr. E.J. Zita (& Cheri Lucas Jennings)

[email protected]

http://academic.evergreen.edu/curricular/energy/0910/home.htm


What s happening today
What’s happening today:

  • Questions? Announcements?

  • Ch.7: Nuclear

  • Brief Reports at 2:30

  • 3:15 Seminar – finishing McKibben

Responses due this week to Brief Reports:




Fundamental Forces

Gravity Electromagnetism Nuclear


Unification

http://abyss.uoregon.edu/~js/cosmo/lectures/lec20.html





Isotopes

Same number of protons = same chemistry

Solve for m2




Fission→ radioactive wasteFusion is safe, but works only in stars, so far



E=Dmc2: The nuclear difference

Nuclear energy ~ 10 million x chemical energy

1 truckload Uranium/yr ~ 100 trainloads coal/wk

E=Dmc2 really only applies to mass-energy transformations (not stretched rubber bands…)



Fusion: 4H  He + Dm


Nuclear fission

Heavy, unstable nuclei can fall apart naturally.

Throwing neutrons at them can make them split faster:

Neutron-induced fission (Lise Meitner)


Discovery of fission1938 Hahn + Strassmann  Meitner + Frisch


Nuclear chain reaction:critical mass ~ 30 lb for U235 ~ 30 tonnes coal


Controlled fission reaction: Moderator keeps neutron multiplication factor = 1

Moderator slows neutrons so they can fission U. Fast neutrons can’t do the job. Removal of graphite rods stops fission.


Atomic mass

Ex.7.5 showed that using a 5 kW electric dryer (powered by a 33% efficient nuclear plant) for an hour produces

N=1.2x1018 nuclei of 239Pu (plutonium).

Mass per nucleon = mn = 1.67 x 10-27 kg

The mass of each 239Pu nucleus = m = 239 mn = _____

Total 239Pu mass produced = M = N m = ______


Nuclear reactors

  • Light-Water reactors (LWR) need enriched U235

  • (ordinary water  steam  turbine  electricity)

  • Boiling-water reactor (simple, 1/3 of LWRs)

  • Pressurized-water reactor (primary doesn’t boil)

  • Pro: Safety: loss of coolant = loss of moderator

  • Con: difficult to refuel

  • CANDU(Deuterated, or heavy water + natural U238)

  • Continuous refueling capability, easy to steal


More Nuclear reactors

Graphite moderator

Pro: continuous refueling capability

Con: loss of coolant ≠ loss of moderator

Chernobyl

HTGR (High Temperature Gas-cooled Reactor)

Pro: high safety

Con: low performance

Breeder reactors: first discuss beta decay…


Beta decay (weak force)

n  p + e- + neutrino


Breeder reactors

Rare U235 is fissile when hit with neutrons

Common U238 can transmute  Pu contributes to fission power generation in old U reactors


Breeder reactors

  • Pro:

  • * use up common U238

  • * operate at higher temperature (efficiency)

  • Con:

  • higher temperature, higher risk of nuclear accident

  • Liquid sodium coolant – flammable with air contact

  • Plutonium = potent bomb fuel

  • Critical mass ~ 5 kg (see Example 7.5)

  • Even France only uses one breeder.


Plutonium reprocessing(Union of Concerned Scientists: www.ucsusa.org)

  • Reprocessing would increase the risk of nuclear terrorism

  • Reprocessing would increase the ease of nuclear proliferation

  • Reprocessing would hurt U.S. nuclear waste management efforts

  • Reprocessing would be very expensive


Advanced reactor designs

Standard LWR: coolant = moderator

Advanced LWR: passive safety features

Standardized design – easier to build

Maximum nuclear efficiency: 36%

Advanced HTGR: pebble-bed reactor

pebbled fuel

He gas coolant  heat exchanger  turbine

Could burn Pu from old nuclear weapons

Design efficiency 50% (not yet operational)


Nuclear power plants

Pressure vessel limits Thigh and efficiency

Otherwise, much like other power plants


Radioactivity

Gamma rays: very high energy photons – zero mass (produced by excited nuclei)

Alpha particles: very high mass (Helium nuclei) can have high or low kinetic energy

If they penetrate matter, can do great damage.

Most dangerous if ingested.

Beta particles: electrons (or anti-electrons)

Can have high or low kinetic energy

Can slightly penetrate matter. (weak force)


Alpha decay

Alpha particle = helium nucleus


Radioactivity

Gamma decay

Alpha decay


C14 from cosmic rays

Cosmic rays excite N14→ decays to C14

Solar max: magnetic solar wind sweeps away cosmic rays → less *N14→ less C14

http://www.nuclearonline.org/newsletter/Oct05.htm


Lower recent C14 /C12 from fossil fuel burning

Little Ice Age: low solar magnetic activity  more cosmic rays and C14

Evidence of anthropogenic source for greenhouse gases


Nuclear policy
Nuclear Policy

  • High subsidies supported growth in industry in decades past

  • Safety regulations plus major cost and schedule overruns made nuclear start-ups increasingly diffiult

  • 1979 Three Mile Island accident “seriously damaged public confidence in nuclear power”

  • US nuclear in decline – no new plants in 30 years

  • 1986 Chernobyl near-meltdown, major irradiation of local area, contamination spreading to lesser extent throughout USSR, Europe, Asia. Undetermined # of lives lost


Radioactive decay: l=decay rate



Half-life

Solve for n and then t…


Measuring radiation

Bequerel = 1 decay per second: but what kind of decay? How much energy?

Curie = radioactivity of 1 g of 226Ra

Consider effects on biological tissue:

Rad = 0.01 J of radiation absorbed by 1 kg

Also consider what kind of particles – alpha, beta, gamma? Most useful measure:

Sv = Sievert = dose (in rad) * quality factor (QF)


Radiation quality factor (QF)

Higher QF = more dangerous radiation

TypeQF

X and gamma rays ~ 1

Beta ~ 1

Fast protons 1

Slow neutrons ~ 3

Fast neutrons up to 10

Alpha particles and up to 20

heavy ions


Chernobyl: how many deaths?

http://www.nirs.org/ch20/index.htm

http://www.nirs.org/reactorwatch/accidents/accidentshome.htm


How many accidents unreported?

http://www.iht.com/articles/2007/03/15/business/nuke.php


More nuclear policy
More Nuclear Policy

Advocates call for nuclear renaissance because:

  • Technology is well-established

  • We know it can produce high-density electric power

  • Since we are not willing to give up quality of life dependent on high-density power, nuclear and hydro are the only current options

  • Hydro is essentially fully developed in countries like the US, and has ecological costs of its own

  • Vitrification can address waste issues


Waste disposal: Yucca Mountain?

http://library.thinkquest.org/17940/texts/nuclear_waste_storage/nuclear_waste_storage.html


Waste disposal: Vitrification?

http://environment.pnl.gov/brochures/WTP.pdf

http://picturethis.pnl.gov/PictureT.nsf/All/3U2S5D?opendocument


UCS on nuclear

  • Need cheap, effective solutions to GW quickly

  • Nuclear power is not the “silver bullet”

  • Rapid major expansion of nuclear is not feasible

  • Nuclear security is a major concern

  • Research should continue, especially on nuclear waste issues


UCS: Nuclear is not the solution to GW

http://www.ucsusa.org/global_warming/solutions/nuclear-power-and-climate.html


Brief reports
Brief Reports

Please get / put homework from/on the front table

Break…

Seminar on last half of McKibben


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