This document provides an overview of nuclear power, including: - Nuclear power currently supplies about 8% of total US energy needs and 20% of electricity through 104 operating reactors. - Key terminology related to nuclear fuels, radioactive decay, and the nuclear fission process are defined. - The fission of Uranium-235 is described as releasing large amounts of energy through splitting the atom and ejecting neutrons. - Commercial nuclear reactors, including pressurized water reactors and boiling water reactors, are discussed along with the nuclear fuel cycle. - Performance metrics for US nuclear plants show high capacity factors around 90% in recent years. Operating costs are competitive with fossil fuels. - Global nuclear power policy and expansion

1. Session 10 – Nuclear Power
T. Ferguson,
University of

2. Session 10 – Nuclear Power
• Recall that nuclear supplies ~ 8 Quads to
US annually (8% of total; 20% of electricity)
• Terminology
• Fuels, reserves, wastes
• Energy Release, Efficiencies
• Costs
• Status and Policy
T. Ferguson,
University of

3. Nuclear Power
Basics
•
•
•
•
•
Nuclear vs. chemical energy
All energy derives from nuclear!
Resulting sum of
Fission: Splitting heavy atoms
products has slightly
less mass than sum
Fusion: Combining lighter atoms
of original reactants
Fissionable isotope captures neutron, yields:
–
–
–
–
Unstable isotope
Fragments with high kinetic energy
Neutrons
Beta, gamma, neutrino emissions
• Moderator
• Control Rods
T. Ferguson,
University of

4. Terminology
•
•
•
•
•
•
•
•
Nucleon
Nuclide
Radionuclide
Isotope
Alpha, Beta, Gamma Rays
Fissionable Material
Fertile Material
Enrichment
T. Ferguson,
University of

5. Radioactive Decay
Fission might be best understood by first looking at
how the most abundant, naturally occurring isotope
of Uranium, U-238, decays:
• First, elements with atomic number above Lead tend to decay
• “Decay” implies transitioning to a stable element with
smaller neutron-proton ratio
• U-238 has 146 neutrons, for an n/p of 1.587
• This neutron ratio is the highest for any natural isotope
U-238 decays by first emitting an alpha particle: 2n + 2p
• An alpha particle is identical to the Helium nucleus
• So U-238 loses 2n and 2p, reducing it to Thorium-234
• But Thorium is also unstable, and emits a
Beta particle: nuclear electron
• This, in effect, increases the proton count by 1, forcing
the release of a neutron to keep the nucleon count constant
T. Ferguson,
University of
So, Thorium-234 becomes Protactinium-234 (Z=91),
which is also unstable . . . And eventually ends at Pb

6. Radioactive Decay
Radioactive Half-life: time for half of atoms to decay
If N=number of atoms present, and
N0 = number of atoms initially, and
λ = decay rate constant,
Then N = N0 e –λt
Set N=0.5N0 to solve for T1/2
U-238 half-life is 4.5 E 9 years (age of universe)
T. Ferguson,
University of

7. Radioactive Decay
Radioactive Half-life: time for half of atoms to
decay
Radium: Discovered by Curies in 1898, T 1/2 of
1600 years, part of U-238 decay chain
Decay rate of 1 gram of Radium is basis for
unit of decay, the curie.
So, the curie is a measure of the radioactivity
of a material
T. Ferguson,
University of

8. Radioactive Decay
Derivation of curie:
If N = N0 e –λt, then λ = 0.693/T1/2.
Given T1/2 for Ra-226 = 1600 yrs,
λ = 1.375 E -11 sec-1.
To obtain the decay rate, we need the
number of atoms in one gram of Ra-226
T. Ferguson,
University of

9. Radioactive Decay
Ra-226 has atomic weight of about 226, so
1 kg-mol = 226 kg
has Avogadro’s number of atoms
(6.02 E 26), which becomes N0.
1 gram, therefore, contains 2.66 E 21 atoms,
which is N
The decay rate is λN = 3.66 E 10 disintegrations per
second
(almost 40 billion events per second)
(The curie is formally 3.7 E 10 disintegrations/s)
T. Ferguson,
University of

10. Nuclear Fission
Energy
(scattered)
(absorption &)
Uranium-235
+
Neutrons
Fission
(absorption
& capture)
Radioactive fission
products
Neutrons
(about 2.5)
Uranium-235
T. Ferguson,
University of
Process
repeats

11. Nuclear Fission
1. Neutrons are the key ingredient
Energy
Uranium-235
+
Neutrons
3. Critical: Steady rate of chain reaction
Subcritical: Decreasing reaction rate
Supercritical: Increasing reaction rate
Fission
Radioactive fission
products
2. If at least one
Neutrons of these results
(about 2.5) in a second event,
a self-sustaining
fission chain reaction
ensues
Uranium-235
T. Ferguson,
University of
Process
repeats

12. Quote of the Week
“If we have in the future an accident where the
reactors go critical, I would only pray for MiamiDade County since there is no way to evacuate
the population today compared with in 1972,
when the reactors were originally permitted," the
president Rhonda Roff of an environmental
group called "Save It Now, Glades" told AFP.
Comment from article from AFP on Florida’s electrical blackout of 2/26/08
<http://afp.google.com/article/ALeqM5hqzKZYV_FS7JoyYm90kopwwsSKBA>
T. Ferguson,
University of

13. Nuclear Fission
1. Moderator
Energy
Uranium-235
+
Neutrons
Fission
Radioactive fission
products
Neutrons
(about 2.5)
2. Neutrons:
W/O moderator: 2 MeV
With moderator: 1/40 eV
3. Neutrons start with high energy,
but are then thermalized by moderator
T. Ferguson,
University of
Uranium-235
Process
repeats

14. Thermal Nuclear Fission
vs. Fast Fission
Energy
Uranium-235
+
Neutrons
1. U-235 only natural fuel that works
with thermal neutrons
2. Probability of spontaneous fission
of U-235 very, very small (1 per
second, or 200 MeV=3.2E-11 J/s/kg)
3. Fission starts with absorption of neutron
4. Prob of absorption decreases with neutron
energy (so moderator used in
thermal reactors)
5. Fast fission reactors use other fuels able to
fission with high energy neutrons
T. Ferguson,
University of
Fission
Radioactive fission
products
Neutrons
(about 2.5)
Uranium-235
Process
repeats

15. Thermal Fission
T. Ferguson,
University of
From Wikipedia: http://upload.wikimedia.org/wikipedia/commons/7/72/Thermal_reactor_diagram.png
Accessed 2/28/08

16. Energy of Fission
• Fission of U-235 releases about 200 MeV per atom
(recall that 1 electron volt = 1.6 E -19 J,
or 200 MeV = 3.2 E -11 Joules)
• Compare to combustion of Carbon with Q=94E6 cal/kg-mol
4.1 eV per atom
• 50 million times more energy on atom-atom basis
• 2.5 million times more energy on weight basis
• Instead of 3 million tons of coal per year for 1000 MW plant,
nuclear fission would require 1.2 tons of U-235
T. Ferguson,
University of

17. PWR Fuel Assembly
Sample PWR Fuel Assembly
•Array of 14X14 rods
•179 fuel rods
•16 control rods - ganged
•1 instrumentation rod
•Assembly is 7” X 7”, 12 ft tall
Fuel: U-235 enriched from
natural concentration of
0.71% to a few %
Fission of U-238 possible
only with fast neutrons
T. Ferguson,
University of
From http://www.mnf.co.jp/pages2/pwr2.htm. Accessed 2/28/08; and instructor notes

18. The Uranium Fuel Cycle
- Sources -
T. Ferguson,
University of
Source: International Atomic Energy Agency

19. Fuel Cycle
Annual mass flows for 1000 MWe LWR
Ore
86,000 tons
Storage
(US)
Reprocessing
(UK, France)
T. Ferguson,
University of
UF6 gas
203 tons
U3O8 solid
162 tons
Spent Fuel
36 tons
Enriched UF6
53 tons
Reactor
UO2 Fuel
36 tons
Low Level Waste
50 tons
Adapted from Tester, et al, Sustainable Energy. Figure 8.6

20. Reactor Designs
Designs Currently in Operation (Generation II)
• PWR – Pressurized Water Reactor
(Westinghouse)
• BWR – Boiling Water Reactor (GE)
• GCR – Gas Cooled Reactor
• LMFBR – Liquid Metal Fast Breeder Reactor
• PHWR – Pressurized Heavy Water Reactor
• RBMK – Similar to BWR
T. Ferguson,
University of

21. New Reactor Designs
Designs Submitted in Recent Applications
(Generation III and III+):
– AP1000 (Westinghouse)
– EPR (Areva)
– ESBWR (GE)
– ABWR (GE)
– US-APWR (Mitsubishi)
1
T. Ferguson,
University of
(6 COLs)1
(3)
(5)
(1)
(1)
Combined Licenses, as of 10/21/08. Covers 25 new units

22. New Reactor Locations, US
T. Ferguson,
University of
Source: NRC

23. T. Ferguson,
University of

24. Boiling Water Reactor
Source: US NRC
T. Ferguson,
University of

25. Pressurized Water Reactor
T. Ferguson,
University of

26. Nuclear Power Performance
• Water in liquid state limited to 705 °F
• Reactors (PWR, BWR) limited to η<30%
• (70% waste heat)/(30% useful) =
2 1/3 units of waste heat per useful unit
- must be dissipated in condenser
• Fossil Fuel: η=40%, or 1.5 units
waste/useful
• Hence, difference in cooling tower size
T. Ferguson,
University of

27. Nuclear Power Performance
US Reactors Operating:
• Licensed 1968-74: 38 reactors, 6 closed
• Licensed 1975-78: 23 reactors, 3 closed
• Licensed 1979-96: 52 reactors, 0 closed
• 104 reactors in operation
• Only 1 reactor licensed since 1976 is
permanently closed (TMI-II)
T. Ferguson,
University of
Source: EIA

28. Nuclear Power Performance
US Nuclear Plant Capacity Factors
• 1980:
56%
• 1990:
66%
• 2000:
88%
• 2002:
90%
• 2007:
91.8%
• Capacity constant since 1990, but . . .
• Energy produced increased by 33%
T. Ferguson,
University of
Source: EIA

29. Costs
• Average Operating Expenses, 2001
–
–
–
–
Nuclear:
Fossil:
Hydro
Other Fossil:
1.8 cents/kWh (1/4 is fuel)
2.3 cents (3/4 is fuel)
1.0 cents (no fuel cost)
5.0 cents (80% is fuel)
• Fuel: $1787/kg UO2 (1/2007)
– For 45,000 MWd/t burn-up: 360,000 kWh/kg, or $0.005/kWh
• Capital:
$1000/kW in Czech Republic
$2500/kW in Japan
(Compare to $1000-1500 for coal, $500-1000 for gas,
and $1000-1500 for wind; 2005 numbers)
T. Ferguson,
University of
Source: EIA, Electric Power Annual 2000; Australian Uranium Association

30. Costs
Cost Projections for 2010 with 10% discount rate
(capital becomes 70% of energy cost):
USA
France
Japan
Canada
Korea
Czech Rep.
Nuclear
4.65 c/kWh
3.93
6.86
3.71
3.38
3.17
Gas
3.65
4.42
6.91
4.12
2.71
3.71
Coal
4.90
4.30
6.38
4.36
4.94
5.46
US 2003 cents/kWh; 40 year lifetime; 85% capacity factor
T. Ferguson,
University of
Source: OECD/IEA NEA 2005/Australian Uranium Association

31. Major US Nuclear Plant Operators
•
•
•
•
•
Exelon
Entergy
Duke
TVA
NMC
17,000 MW
9,000 MW
7,000 MW
6,700 MW
1,689 MW
17%
9%
7%
7%
2%
(figures are approximate)
T. Ferguson,
University of
Sources: EIA, Wikipedia.org/wiki/nuclear_management_corporation (accessed 3/10/08)

32. US Nuclear Power Policy
Energy Policy Act of 2005
– Price-Anderson Act extended to 2026 ($10B)
– Cost overrun support for up to 6 new plants
– First 6000 MW: PTC of 1.8 cents/kWh
Nuclear Power 2010 Program, of 2002
– Joint gov’t/industry effort to build adv. Plants
– 3 consortia have received grants
– Applications have been submitted
T. Ferguson,
University of
Source: DOE

33. US Nuclear Power Policy
A Renaissance?
After nearly 30 years, the first applications to
the NRC for Combined Construction and
Operating Licenses:
– 9/2007: South Texas Project: GE ABWR’s
– 11/2007: TVA in Alabama: Westinghouse
AP1000 PWR’s
– 5 18 other sites
T. Ferguson,
University of
Source: NRC

34. Global Nuclear Power Policy
•
•
•
•
•
•
•
•
•
•
•
•
Canada: will maintain current fleet
Mexico: Planning another 8 reactors
UK: Undecided
Russia: Planning another 27 reactors
China: Planning another 25
India: Planning another 15
Pakistan: Planning another 2
Japan: Planning another 12
Norway/Sweden/Finland: maybe/no/yes
Germany: Phase out by 2020
Italy: Shuttered; moratorium
Brazil: Planning another 7 reactors
T. Ferguson,
University of
Source: Wikipedia