Nuclear Energy 1 cont..
Atomic Number = number of protons
Atomic Mass = number of protons + number of neutrons
What is Atomic Weight?
Calcium and Neon examples
Chart of Nuclides
Discovery of 40 Mg, 42,43 Al, and 44 Si in 2007
Enhanced selectivity from two-stage separator:!
1.5×10 17 48 Ca nuclei ( nat W target, E/A = 141 MeV)!
→ three 40 Mg nuclei!
Transport Beam Line!
S800 Analysis Line!
Baumann et al., Phys. Rev. C75 (2007) 064613; Nature (2007)!
Where is the Energy coming from??????
Splitting the Uranium Atom:
Uranium is the principle element used in nuclear reactors
and in certain types of atomic bombs. The specific isotope
used is 235 U. When a stray neutron strikes a 235 U nucleus,
it is at first absorbed into it. This creates 236 U. 236 U is
unstable and this causes the atom to fission.
• 235 U + 1 neutron
• 235 U + 1 neutron
2 neutrons + 92 Kr + 142 Ba + ENERGY
2 neutrons + 92 Sr + 140 Xe + ENERGY
Americium -‐241: Used in many smoke detectors for homes and business...
Cadmium -‐109: Used to analyze metal alloys for checking stock, sorCng scrap.
Calcium -‐ 47: Important aid to biomedical researchers studying the cell funcCon and
bone formaCon of mammals.
Californium -‐ 252: Used to inspect airline luggage for hidden explosives...to gauge the
moisture content of soil in the road construcCon and building industries...and to measure
the moisture of materials stored in silos.
Carbon -‐ 14: Helps in research to ensure that potenCal new drugs are metabolized withou
forming harmful by-‐products.
Cesium -‐ 137: Used to treat cancers...
Chromium -‐ 51: Used in research in red blood cell survival studies.
Cobalt -‐ 57: Used in nuclear medicine to help physicians interpret diagnosis scans of
paCents' organs, and to diagnose pernicious anemia.
Cobalt -‐ 60 : Used to sterilize surgical instruments...spices/fruits
Copper -‐ 67: cancer
very long- longer than age of earth….billions of yrs
C 5730 yrs
Half-lives are very often used to describe quantities undergoing
exponential decay—for example radioactive decay—where the half-life is
constant over the whole life of the decay.
/ 1 100
/ 2 50
/ 4 25
/ 8 12 .5
/ 16 6 .25
/ 32 3 .125
/ 64 1 .563
/ 128 0 .781
... ... ...
n 1/2 n 100(1/2 n )
A quantity is said to be subject to exponential decay
if it decreases at a rate proportional to its value. Symbolically,
this can be expressed as the following differential equation,
where N is the quantity and λ is a positive number called the
The solution to this equation is:
Here N(t) is the quantity at time t, and N 0
= N(0) is the initial
quantity, i.e. the quantity at time t = 0.
Half-‐life:Cme required for the decaying quanCty to fall to one half of its iniCal
This Cme is called the half-‐life, and oYen denoted by the symbol t 1 / 2
The half-‐life can be wriZen in terms of the decay constant, or the mean lifeCme,
Example: 14 C…..0.693/5730 yrs =1.21 x10 -‐4 /yr
or λ=ln2/t 1/2
Example: How old is an object whose 14C content is 10% of what it is in living
Fusion Energy (how the sun gets its energy)
In a fusion reaction, two light atomic nuclei fuse together to form
heavier ones, as is shown in the figure. The fusion process releases a
large amount of energy, which is the energy source of the sun and the
Proton + neutron=deuterium
Proton + 2 neutrons=tritium
D+ T= 4 He +n + 17.6 MeV
H+ 3 H= 4 He
Fusion Inside the Stars
• Fusion in the core of stars is reached when
the density and temperature are high
enough. There are different fusion cycles
that occur in different phases of the life
of a star. These different cycles make the
different elements we know. The first
fusion cycle is the fusion of hydrogen into
Helium. This is the stage that our Sun is in.
The long-term objective of
fusion research is to harness
the nuclear energy provided
by the fusion of light atoms to
help meet mankind´s future
The enormity of the nuclear binding energy can perhaps be better appreciated
by comparing it to the binding energy of an electron in an atom. The comparison
of the alpha particle binding energy with the binding energy of the electron in a
hydrogen atom is shown below. The nuclear binding energies are on the order of
a million times greater than the electron binding energies of atoms.
Nuclear Binding Energy:
Responsible for the creation of all the elements in the universe….ground rules of
Nuclei are made up of neutrons and protons but the mass of the nucleus is
always less than the masses of its constituents.
Nuclear binding energy is calculated by the change in mass or = Δmc 2
For the alpha particle Δm= 0.0304 u which gives a binding energy of 28.3 MeV.
1 u= 1 atomic mass unit
Compare with ionization energy of electrons from the atom
Nuclear binding energy = Δmc 2
For the alpha particle Δm= 0.0304 u which gives a binding energy
of 28.3 MeV.
The binding energies of nucleons are in the range of millions of electron
volts compared to a few eV for atomic electrons.
Atomic Transitions: emit a photon of a few eV
Nuclear Transitions: emit gamma rays with several MeV
galactic abundance distribution
Signatures of Nucleosynthesis
Iron, Cobalt, Copper, Zinc,Iodine
Elements are made in Stars…
How Were the Elements from
Iron to Uranium made ?
How do you decide which nuclei to measure???
Ge, 85-90 As,
Se, 93-95 Br
Cu and 78 Ni first bottle necks in n-capture flow ( 80 Zn later)
(half-lives 79 Cu: 188 ms (Kratz et al, 1991)
Ni : (predicted to be comparable)
Environmental and safety aspects of nuclear energy
Not in My Back Yucca
What are our alternatives for storing
Environmental Statement on Nuclear
Energy and Global Warming
Too expensive – power plants…
Too dangerous-‐ terrorist groups
Too polluCng-‐ radioacCve waste
ENERGY | 9/11/2011 @ 6:29PM |138,781
Is Thorium the Biggest Energy Breakthrough
Since Fire? Possibly.
So what is the big deal about thorium? In 2006, wriCng in the magazine Cosmos,
Tim Dean summarized perhaps the most opCmisCc scenario for what a Thorium-‐powered
nuclear world would be like:
What if we could build a nuclear reactor that offered no possibility of a meltdown, generated its
power inexpensively, created no weapons-‐grade by-‐products, and burnt up exisCng high-‐level
waste as well as old nuclear weapon stockpiles? And what if the waste produced by such a
reactor was radioacCve for a mere few hundred years rather than tens of thousands? It may
sound too good to be true, but such a reactor is indeed possible, and a number of teams around
the world are now working to make it a reality. What makes this incredible reactor so different
is its fuel source: thorium.
Thorium: Is It the Better Nuclear Fuel?
What is special about thorium?
(1) Weapons-grade fissionable material (uranium 233 ) is harder to retrieve safely
and clandestinely from the thorium reactor than plutonium is from the
uranium breeder reactor.
(2) Thorium produces 10 to 10,000 times less long-lived radioactive waste than
uranium or plutonium reactors.
(3) Thorium comes out of the ground as a 100% pure, usable isotope, which does
not require enrichment, whereas natural uranium contains only 0.7%
fissionable U 235 .
(4) Because thorium does not sustain chain reaction, fission stops by default if
we stop priming it, and a runaway chain reaction accident is improbable.
Lightbridge CorporaCon, a pioneering nuclear-‐energy start-‐up company based in McLean,
VA, is developing the Radkowsky Thorium Reactor in collaboraCon with Russian researchers.
In 2009, Areva, the French nuclear engineering conglomerate, recruited Lightbridge for a
project assessing the use of thorium fuel in Areva’s next-‐generaCon EPR reactor, advanced
class of 1,600+ MW nuclear reactors being built in Olkiluoto, Finland and Flamanville,
Atomic Energy of Canada Limited and a clutch of Chinese ourits began an effort in mid-‐2009
to use thorium as fuel in nuclear reactors in Qinshan, China.
Thorium is more abundant than
uranium in the Earth’s crust. The world
has an esCmated 4.4 million tons of
total known and esCmated Thorium
resources, according to the
InternaConal Atomic Energy
AssociaCon’s 2007 Red Book.
The most common source of thorium is
the rare earth phosphate mineral,
monazite. World monazite resources are
esCmated to be about 12 million tons,
two-‐thirds of which are in India. Idaho
also boasts a large vein deposit of
thorium and rare earth metals.
Here is the thorium sequence in the Rubbia reactor: A neutron is captured by
90 Th232 , which makes it 90 Th 233 .
90 Th232 + 0 n1 -> 90 Th233 
Thorium-233 spontaneously emits a beta particle (an electron from the nucleus),
leaving behind one additional proton, and one fewer neutron.
90 Th233 -> 91 Pa233 + ß 
The element with 91 protons is Protactinium (Pa). The isotope 91 PA 233 also
undergoes beta decay,
91 Pa233 -> 92 U233 + ß 
The U 233 isotope that is produced in step  is fissionable, but has fewer neutrons
than its heavier cousin, Uranium-235, and its fission releases only 2 neutrons, not 3.
92 U233 + 0 n1 -> fission fragments + 2 0 n 1 
Nuclear Energy 2
Preventing the Next Fukushima…..
Science Vol. 333 September 16, 2011 arCcle…
How do we get energy from fossil fuels?
A water turbine is a
rotary engine that
takes energy from
Boiling Water Reactor
In the boiling water reactor the same water loop serves as moderator, coolant for the core,
and steam source for the turbine.
Boiling Water Reactor
In the boiling water reactor (BWR), the water which passes over the reactor core to act as moderator and
coolant is also the steam source for the turbine. The disadvantage of this is that any fuel leak might make the
water radioacCve and that radioacCvity would reach the turbine and the rest of the loop.
A typical operaCng pressure for such reactors is about 70 atm at which pressure the water boils at about 285
C. This operaCng temperature gives a Carnot efficiency of only 42% with a pracCcal operaCng efficiency of
around 32%, somewhat less than the pressure water reactor.
Pressurized Water Reactor
In the pressurized water reactor, the water which flows through the
reactor core is isolated from the turbine.
In the pressurized water reactor (PWR), the water which passes over the reactor core
to act as moderator and coolant does not flow to the turbine, but is contained in a
pressurized primary loop. The primary loop water produces steam in the secondary loop
which drives the turbine. The obvious advantage to this is that a fuel leak in the core
would not pass any radioactive contaminants to the turbine and condenser.
Another advantage is that the PWR can operate at higher pressure and temperature,
about 160 atm and about 315 C. This provides a higher Carnot efficiency than the
BWR, but the reactor is more complicated and more costly to construct. Most of the
U.S. reactors are pressurized water reactors.
Liquid-Metal Fast-Breeder Reactor
In the LMFBR, the fission reaction produces heat to run the turbine while at the same time
breeding plutonium fuel for the reactor.
The most common breeding reaction is that of plutonium-239 from non-fissionable uranium-238. The
term "fast breeder" refers to the types of configurations which can actually produce more fissionable
fuel than they use, such as the LMFBR. This scenario is possible because the non-fissionable
uranium-238 is 140 times more abundant than the fissionable U-235 and can be efficiently converted
into Pu-239 by the neutrons from a fission chain reaction.
France has made the largest implementation of breeder reactors with its large Super-Phenix
reactor and an intermediate scale reactor (BN-600) on the Caspian Sea for electric power and
Fissionable plutonium-239 can be produced from non-fissionable uranium-238
The plutonium-239 breeder reactor is commonly called a fast breeder reactor, and the cooling
and heat transfer is done by a liquid metal. The metals which can accomplish this are sodium
and lithium, with sodium being the most abundant and most commonly used. The construction
of the fast breeder requires a higher enrichment of U-235 than a light-water reactor,
typically 15 to 30%. The reactor fuel is surrounded by a "blanket" of non-fissionable U-238.
No moderator is used in the breeder reactor since fast neutrons are more efficient in
transmuting U-238 to Pu-239. At this concentration of U-235, the cross-section for fission
with fast neutrons is sufficient to sustain the chain-reaction. Using water as coolant would
slow down the neutrons, but the use of liquid sodium avoids that moderation and provides a
very efficient heat transfer medium.
The Super-Phenix was the first large-scale breeder reactor. It was put into service
in France in 1984.
The reactor core consists of thousands of stainless steel tubes containing a mixture
of uranium and plutonium oxides, about 15-20% fissionable plutonium-239.
Surrounding the core is a region called the breeder blanket consisting of tubes
filled only with uranium oxide. The entire assembly is about 3x5 meters and is
supported in a reactor vessel in molten sodium. The energy from the nuclear fission
heats the sodium to about 500°C and it transfers that energy to a second sodium
loop which in turn heats water to produce steam for electricity production.
Such a reactor can produce about 20% more fuel than it consumes by the breeding
reaction . Enough excess fuel is produced over about 20 years to fuel another such
reactor. Optimum breeding allows about 75% of the energy of the natural uranium
to be used compared to 1% in the standard light water reactors.
Example: Spontaneous Fission of 238 U results in 140 55 Cs +92 37Rb + how
Example: What about 239 Pu?
It is not naturally occurring…..has to be made in a reactor…..