In 1939, Hahn, Strassmann, Meitner, and Frisch discovered
that neutron can split uranium.
92 → 56
Energy release 200 MeV per reaction.
∼ 70 years after it was discovered, nuclear ﬁssion is now
responsible for 1/6 the total energy produced around the world.
Mochovce power plant, Slovakia
First nuclear reactor
In 1942, Enrico Fermi and his
team built the World’s ﬁrst
nuclear ﬁssion reactor in a
squash court of University of
The atomic pile was called
Chicago Pile No. 1.
The ﬁrst man-made self-sustaining chain reactions went on for
28 minutes on 2 Dec 1942 (3:25–3:53 p.m.).
The pile consisted of uranium
pellets as fuel, and graphite
blocks as moderator.
Cadmium coated rods were
used to absorb extra neutrons,
dampening the reaction.
Chicago Pile 1
The energy of the atom’s nucleus was ﬁrst unleashed.
U-235 is ﬁssile
Fermi: U-238 is fertile → breed Pu-239 (ﬁssile) at fast n
energies → EBR-I (Experimental Breeder Reactor-I)
U-233 is also ﬁssile. Can be bred from Th-232.
First four nuclear bulbs (@ EBR-I, Idaho Falls, USA, Dec 1951)
USS Nautilus: ﬁrst nuclear submarine (1953)
Research: generate neutrons from ﬁssion. Low power level
(1–10 MW). Neutron ﬂux is in the order of 1013 n/cm2 /s.
Research reactor at TINT, in Bangkok, Thailand
Power: generate electricity from kinetic energy of ﬁssion
Power reactor in Leibstadt, Switzerland
Only 2% of African rural
people have access to
national power grid.
1.6 billion people are without access to
(IEA, World Energy Outlook 2006)
Carbon Mitigation Initiative
Collaboration between Princeton University, BP, and Ford Motor
Mission: To ﬁnd solutions to the greenhouse gas problem.
CMI’s 4 strategies
1. Increase the energy efﬁciency of our cars, homes, and
power plants while lowering our consumption by adjusting our
thermostats and driving fewer miles.
CMI’s 4 strategies
2. Capture the carbon emitted by power plants and store it
CMI’s 4 strategies
3. Halt deforestation and
soil degradation worldwide,
while reforesting more
CO2 +H2 O → C6 H12 O6 +O2
CMI’s 4 strategies
4. Produce more energy from nuclear and renewable
fuelssolar, wind, hydroelectric, and bio-fuels.
Bellville NPP, France [ c Areva]
Coming Clean: The Truth and Future of Coal in the Asia-Paciﬁc (World Wild
Fund for Nature)
“Estimated radiation doses ingested
by people living near the coal plants were
equal to or higher than doses for people
living around the nuclear facilities.”
Hvistendahl, M. (2007). Coal Ash Is More Radioactive than Nuclear
Waste. Retrieved October 14, 2009, from Scientiﬁc American Web site:
McBride, J. P. et al. (1978). Radiological Impact of Airborne Efﬂuents of
Coal and Nuclear Plants. Science, 202(4372), 1045–1050.
ash = bottom ash + ﬂy ash
ﬂy ash (U, Th) → escapes to environment
countries operating NPP’s under construction
Pakistan 2 1
China 11 21
India 18 5
S. Korea 20 6
Japan 54 1
(data: IAEA, Feb 2010)
Seoul during Korean War (1950)
At the end of WWII (1945), power generation capacity in Korea:
North 88.5%, South 11.5%. Korean War (1950–1953) put
Korea in total destruction.
First nuclear power in South Korea: 20 July 1978 (Kori-1
reactor). Today (Mar 2010) nuclear electricity is almost 40% of
Uranium is one of the most abundant elements found in the
Earth’s crust. It can be found almost everywhere in soil and
rock, in rivers and oceans.
is the only natural isotope which is ﬁssionable by thermal
World’s largest high-graded uranium deposit: McArthur River, Canada.
World’s known uranium is estimated to be about 5.5 Mt (source: OECD NEA
& IAEA, Uranium 2007: Resources, Production, and Demand)
Another important source of fuel is the nuclear weapon
stockpiles in the USA and countries of the former Soviet
Russia. These weapons contain highly enriched uranium.
Future reprocessing technology will further increase uranium
(Uranium 2005: Resources, Production and Demand, OECD/IAEA)
Samples from drilling during
( c : Cameco)
Yellowcake is the uranium compound mostly consisting of
triuranium octaoxide (U3 O8 ), and some uranium dioxide (UO2 )
and uranium trioxide (UO3 ).
Only 0.7% of natural uranium is 235 U, the ﬁssile isotope. Higher
concentration (of around 3–5%) is required in a nuclear reactor.
There are mainly two enrichment processes, both using UF6 .
1. gaseous diffusion
2. gas centrifuge
under development: laser enrichment
(photoexcitation of isotopes)
Fuel and spent fuel
Level of enrichment of reactor fuel
is much less than that of nuclear
weapon (over 85% enriched).
They serve different purposes.
Highly enriched uranium billet
UF6 is typically converted back to UO2 solid, compressed into
A typical pellet of uranium weighs about 7 grams. It can
generate energy equivalent to 3.5 barrels of oil, 480 m3 of
natural gas, or 800 kg of coal.
The uranium is encased in ceramic. The ﬁssile isotopes must
be densely packed so that the chain reaction can sustain itself.
Fuel pellets are packed inside zirconium tubes (resistant to
radiation, heat, and corrosion). The rods are bundled together
into an assembly.
For most reactors, high energy neutrons are moderated by
Kinetic energy of ﬁssion fragments heat up the water.
Converters or conversion reactors are designed to convert
material that is not ﬁssionable (but “fertile”) with thermal
neutrons to one that is.
U+n → 239
Np + β − + ν
Np − −
Pu + β − + ν
Th + n → 233
Th − −
Pa + β − + ν
Pa − →
U + β− + ν
Most power reactors use
normal water as moderator
(Nuclear Engineering International
Reactor operators must go through intensive certiﬁcation
Operators must be trained and
• reactor theory
• plant components
• design and operation
• emergency response
Each reactor type (PWR, BWR,
and others) has a different
Ranked by characteristic length: γ ∼ n > e− > hcp
Characteristic energy deposition of hcp: Bragg’s peak
Coulomb forces lead to continuous excitation and ionization of
medium. Neutrons and gamma can penetrate far due to lack of
Penetration of radiation depends on its stopping power (speciﬁc
For charged particles, S increases as velocity decreases.
Even in air, the energetic alphas can travel for only several cm.
R (cm) = 0.56E (MeV) for E < 4 MeV
R (cm) = 1.24E − 2.62 (MeV) for 4 < E < 8 MeV
For medium of mass number A,
R (mg/cm2 ) = 0.56A1/3 Rair
(Cember, H., Introduction to Health Physics, McGraw-Hill, 1996)
α’s and β’s are easy to protect against.
Just paper or plastic is ﬁne.
The concerns of radiation are mostly related to highly
penetrating radiation such as gamma rays and neutrons.
Gamma rays are electromagnetic wave. Its interaction strength
depends on the charge number (Z ) of the material.
Neutrons are neutral. Must be slowed down via direct collisions.
High-Z materials can be used to effectively shield γ-rays. Main
• Photoelectric absorption
• Compton scattering
• Pair production
Absorption coefﬁcient in Pb
H. A. Enge Introduction to nuclear physics (1966)
High-Z materials are good for shielding γ-rays.
Neutrons cross sections are very energy dependent.
Hydrogen-rich medium can be used to slow down neutrons.
Then thermal neutrons can be absorbed by materials with high
neutron capture cross section such as boron or cadmium.
Storage pool in an interim
storage facility at Oskarshamn,
(Image: SKB; Photographer:
Vitriﬁcation into borosilicate glass (mixture of SiO2 and B2 O3 ) is
used to contain high-level waste from nuclear reactors.
Pictured is the amount of high-level waste due to nuclear
electricity generation in one person’s lifetime.
A knife can cut, can decorate, can kill.
Fire can cook, can warm, can burn.
∼ 76% of electricity in France comes from nuclear (year
56 new reactors are being constructed (Feb 2010).
Generation 3+ reactors are being built around the world. They
have simpler designs, are more fuel efﬁcient, produce less
waste, and have enhanced safety.
Some of these are:
• Advanced Boiling Water Reactor (ABWR), by General
Electrics (GE) Nuclear Energy (approved May 1997)
• System 80+, by Westinghouse (May 1997). Not actively
• AP600, by Westinghouse (Dec 1999) and AP1000, by
Westinghouse (Dec 2005)
• EPR, by Areva NP
For countries without a nuclear power plant, the
ﬁrst step is the hardest step. People must have
strong determination and responsibilities.
Once an NPP is built, the country will develop
more. Everybody starts from zero.