Plants | Food Irradiation | Weapons
| Effects | Wastes
Nuclear power plants has been
one of the largest focuses of nuclear energy. As population
grows in our modern society, we have greater needs of electricity.
Nuclear energy is one of the best sources for producing
large quantities of electricity with very limited pollution.
After the World War II, scientists
looked for new ways to improve life utilizing applications
of nuclear energy. One of these applications is that of
food irradiation. This process is used to kill dangerous
diseases associated with foods.
The first use of food irradiation
was used during the early 60's, this technique was applied
to foods such as wheat, flour, and potatoes. As population
grew, the need for new solutions for "cleaning food"
also grew. So in the early 80's people started using food
irradiation on spices, seasonings, fruits, vegetables and
for meat such as pork to prevent trichinosis. Irradiation
has become very popular among the growing community today.
Today, over 40 nations have
accepted the use of food irradiation. These countries include
China, France, Germany, Great Britain, Israel, Japan, the
Netherlands, South Africa, and the United States among others.
process of food irradiation is to exposes food to gamma
rays from radioactive cobalt-60. Food is passed through
a small machine where irradiator (cobalt-60) is located.
The food is exposed to the radioactive material for approximate
15 to 45 minutes depending on the type of food. The food
is packaged before being introduced to the irradiator so
the food does not contact other types of bacteria after
being irradiated. When the process is completed, the rods
of cobalt-60 are retracted into a pool of water, which acts
as a radiation barrier. This process has been used not only
for food but also to sterilize medical devices, bandages,
condoms, tampons, contact lens solution, and food for astronauts.
Irradiation is used to extend
the life period of food. This is advantageous in areas where
food refrigeration is not available. The purpose of food
irradiation is to clean food in the very best way possible.
The radiation penetrates all parts of the food, killing
harmful bacteria that cause diseases, such as salmonella
in seafood, trichinosis in pork, and cholera from fish.
Even though food irradiation
deals with very dangerous materials, it does not harm the
food in any way. The one bad effect of radiating foods is
that it decreases the amount of vitamins A, B, B and E in
the food (by a very minimum amount compared to other food
containment objects). However, even with this undesirable
side effect, scientists continue to encourage the usage
of food irradiation because it saves the lives of thousands
of people each year.
Today's nuclear weapons technology
is the result of World War II. After the two famous American
bombs were dropped (Fat Man, and Little Boy) the world saw
the great powers associated with nuclear weapons. With research,
we now have new and more powerful bombs. Here we will talk
about different weapon designs.
- Fission Based
bombs utilize the concept of nuclear fission. By
splitting the nucleus, a chain reaction is started,
releasing tremendous amounts of energy.
The first atomic bombs
presented to the world were those used to end World
War II. These bombs used the basic process of fission.
The splitting of a nucleus which then causes a rapid
chain reaction in matter of seconds. Fission weapons
consist of U-235 or Pu-239 as its main fuel source.
This is because a "self sustaining" chain reaction
can start right away after the first nucleus has
been split, provided there exists a critical mass
(the minimum mass of material required to sustain
a chain reaction).
- Gun - Device
The first commonly
known gun device weapon was the bomb used on Hiroshima.
This bomb used U 235 (about 95% enriched) as a
base fuel and used the gun device method to detonate.
In a gun device, two pieces of fissionable material
(each which are less than critical mass) are powered
together to form a supercritical mass. This tube
like assembly, contains a high explosive that
blows one subcritical piece of fissionable material
located at one end towards the other end. The
two pieces bind together resulting in a critical
mass which causes the explosion to occur.
The figure to the left shows the principal
construction of a gun-type nuclear device.
- Implosion - Device
This method, although
more efficient and powerful than the gun device,
is more difficult to assemble. This bombs uses
Pu-239 as its main fuel source (although the
same process can be used with U- 235). In the
core of the assembly rests the supercritical mass
surrounded by chemical high explosives (HE). These
explosives, once detonated can produce an implosion
wave. This causes the mass to compress making
its density increase there by causing the material
to become supercritical and ready to create a
The most difficult
part of constructing this bomb is in the timing
of when to release the neutrons into the fuel
core in order to start the chain reaction. This
must be carefully calculated so that the reaction
starts at the right moment to create the blast
at the highest peak of the explosion possibilities.
The figure to the left shows the typical construction
of an implosion type bomb.
- Fusion Based
Fusion (the combining
of two nuclei) weapons are known for their power
and complexity. They are not usually called fusion
bombs but normally referred to as thermonuclear
bombs. These use heavy isotopes, but small in mass,
such as hydrogen, deuterium, and tritium. Unlike
the fission bombs, these have a two part operation.
The first part is a fission device which provides
the tremendous amount of energy required for fusion
to occur. The second phase is the fusion itself.
Although much more complex than the fission bomb
the fusion bomb is capable of releasing much more
energy there by causing more destruction and death.
When dealing with such
a destructive and powerful objects we must know how
to deal with this safely so that nothing goes wrong
unexpectedly. Nuclear weapons are difficult to build
and maintain. It would not be wise for a country which
is struggling with terrorism to have nuclear capabilities
because those weapons might end up in the wrong hands.
Because of this, we must make our weapons as safe as
Because of risks, scientists
look for ways to make nuclear weapons secure. For example,
in the bombs used on Hiroshima and Nagasaki, the scientists
knew that if the B-29 carrying the bomb crashed, it
would create chaos. Therefore they designed a method
to prevent this possible chaos. The bomb would be loaded
in the plane unassembled, and when the B-29 reach a
specified location the crew would assemble the bomb.
Today our weapons follow a similar procedure in order
to protect them from theft or mis-usage. The weapons
need a special device to function, or sometimes the
weapon can hold a key or a combination in order for
it to be used. One of these examples is the PAL system
(Permissive Action Links). These would be simple combinations
originally but now adapted into more modern systems
which allow only a certain number of tries to arm the
For protection against
accidents, our weapons today hold a special way to prevent
unwanted arming. The explosive part (as mentioned above)
can explode but leaving the core untouched and safe
because it has not made the proper connection needed
to activate itself and produce the nuclear explosion.
Everything must be calculated with precision. So there
is no mistake in the process, scientists recheck over
and over. This works as a back up along with many other
things which have been used to complicate the weapon
arming systems. And finally sophisticated radar's are
used to direct these missiles to the selected locations.
Nuclear explosions or
accidents can cause enormous amounts of damage to the
environment. First of all the radiation that is produced
can last for a very long time. When a nuclear detonation
happens, it creates a: blast, thermal pulse, x-and gamma
rays, radiation, and an electromagnetic pulse (EMP).
In an explosion, the effects can be separated into 3
parts: blast, thermal radiation, and nuclear radiation.
As soon as the weapon
is detonated the temperature rises rapidly reaching
millions of degrees (centigrade). The un-fissionable
parts of the weapon are vaporized by the heat. In addition
to the thermal energy a tremendous amount of electromagnetic
radiation is released, which is absorbed by the surrounding
area. As the temperature decreases, the heat creates
a fireball which spreads out rapidly. This highly compressed
heat forms in a matter of seconds after the detonation.
When the fireball cools down (about a minute later)
the temperature is low enough to stop giving off thermal
radiation. Then comes the mushroom cloud which is created
because the upward movement of air and the decrease
in temperature. Then after everything is cooled, small
white snow-like droplets fall from the sky spreading
radiation throughout the environment.
There are different classifications
of nuclear explosions:
- Air Bursts: Fireball
does not contact the ground, explosion cause great damage
to ground objects. Also creates maximum amount of thermal
effects. Used commonly for targeting ground units.
Fireball from an air burst in the megaton energy
range, photographed from an altitude of 12,000
feet at a distance of about 50 miles. The fireball
is partially surrounded by the condensation cloud
- Surface Bursts:These
are similar to Air Bursts but is detonated a few meters
above the ground. The fireball touches land. This explosion
concentrates more on the blast area rather than the whole
environment, which causes more damage for a small amount
In a surface burst, large quantities of earth
or water enter the fireball at an early stage
and are fused or vaporized. The image to the
right shows the formation of a dust cloud due
to a surface burst.
- Subsurface bursts:This
explosion is detonated underground, and penetrates the
ground and sometimes the underground water.
The picture to the left shows the condensation
cloud formed after a shallow underwater explosion.
You can see the effect of the shockwave on the
- High Altitude bursts:These
are used to explode at high altitudes (about 30km above
ground). The explosion can cause damage in communications
through the EMP shockwaves.
The image shows the formation of a fireball
and red luminous spherical wave formed after
the TEAK high-altitude shot.
One of the concerns about
nuclear energy and its use is the waste. Much discussion
has occurred concerning what to do with the waste. Nuclear
wastes is divide into two classes; high level wastes which
is the nuclear waste coming from the nuclear reactor, and
the low level wastes which are materials which have been
radiated (clothing etc..). These have both caused problems
around the globe and research is still going on to find
better ways to safely dispose of these materials without
harming the environment.
High Level Waste
The major concern of high
level wastes is the level of radioactivity associated with
it. Scientists have come up with various ways to safely
store high level wastes, but every question answered raises
several new questions for consideration. There have been
ideas such as sending it out in space, tossing it into the
sun, placing it on mars to mention a few. The current method
being explored is to place it deep underground in a very
deserted and geological stable area. Because it has to be
stored for a long time, the selected place must be very
stable and remote. The current site being studied is the
Yucca mountain area in Nevada.
After its complete usage from
the reactor, the uranium becomes weak, unable to produce
enough fission. The used uranium is first stored in a storage
pool at the power plant. It is then moved from the plant
and placed in a temporary dry storage area. This waste will
remain harmful for hundreds of years.
When it is finally ready to
be disposed, it must be transported to the specified location.
The transportation is a major concern and many safety levels
are used to ensure no major accidents occur during the transportation.
The waste will be put away in a very deep hole underground
where it will have very limited contact with the environment.
These materials can stay on that spot for hundreds of years,
until the radioactive level is low enough to cause no harm
to the environment.
A normal nuclear power plant
can produce about 20 tons of used fuel every year. Which
is relatively small compared to how much we save by using
nuclear energy. Fossil fuels are used by the tons every
year and though they do not produce radioactive waste, it
does far more harm to the environment through other forms
Low Level Waste
Low-level wastes can mean
different things. It is not the nuclear waste itself, but
the materials that has been in contact with radioactive
materials. These objects include protective wear for personnel,
laboratory supplies and tools, machine parts, and medical
materials . These can come from nuclear power plants, medical
centers, research labs, and other scientific locations where
they have used radioactive materials. Low-level wastes reach
safe level within 100 years or less.
In order to deal with these
objects, we must first know how much radiation it has been
contacted with, and how much time it takes for the radioactive
level of the object to reach a safe level. Not all low level
waste is the same, therefore they are divided into three
classes. Class A, which are wastes containing small amounts
of contamination, and have short half-lives. Class B and
C, contain greater amounts of contamination's and have longer
half-lives. Fortunately 95% of the low-level wastes are
qualified as Class A.
These get disposed of in many
different ways. Because of the different types, each class
can be treated differently. There are numerous ways to treat
these objects: one is to leave it in a safe area to decay
until it reaches safe levels, to compact dry wastes into
much smaller pieces and store them, to recycle the object
if it is expensive and was exposed to little radiation,
and incineration which leaves the radiation in a small amount
These low level wastes can
be stored in different places according to its contamination
type. All waste disposal locations must be located in an
isolated area, it must also ensure that no natural resources
of the area are effected. In addition it mush also avoid
any contact with water. Low-level wastes can easily be disposed
of with out problems.
Transportation casks are used to transport spent
nuclear fuel from power plants to the storage
facilities. The cask itself is weighs about 100
tons, and carries 6 tons of spent nuclear fuel.
The NRC regulates the specifications on what a
transport cask must be able to endure in the event
of an accident.
One of the most dangerous
facets of nuclear energy is in its transportation.
The concerns of the people are tremendous. As most
of us know, not all of the countries have uranium
mines, therefore they must import the uranium to be
used. The uranium is used for one of two reasons;(1)
production of nuclear energy and (2) to make nuclear
If a country wants to
produce atomic bombs, they must either process it
themselves, or order it from another country. Today
there exist few countries which have processing capabilities.
So if one country (with out processing capabilities)
desires weapons, it must import the processed uranium
(or plutonium), from another country. It all sounds
great but we have to think about how to move this
dangerous material from one country to the next. Today
there exists three transporting options, air which
is usually used for overseas, sea also used for overseas,
and road if it is a relatively close location.
The most common transportation
mode is that of air. The main concern here is that
of crashing, which could possibly release highly radioactive
materials into the environment. When an order is shipped
the shipping company must gain permission from all
countries whose air space the plane is going to cross.
In addition the material must be packaged in such
a manner to minimize spilling in case of a crash.
The same applies with the use of the sea transportation.
If one were to order and chose sea as transportation,
the ship would have to get permission from all countries
which could be effected by an accident.
For things like this
we must try to minimize all risk involved so our actions
do not affect others around us. Until a new way of
transportation arrives, we must deal with these problems
for ourselves because it is our environment in which
we are dealing with.