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Yucca Mountain

In 1987 Congress chose a site under Yucca Mountain, a barren volcanic mountain in Nevada, as the prime candidate for the storage of nuclear waste. After a great deal of scientific and political controversy, the Energy Department decided (in Jan. 2002) to recommend this as the site for storage of waste from both military and civilian reactors. This was a recommendation to the Nuclear Regulatory Commission, to grant the Energy Dept. a license to open it for waste repository. The matter was discussed for several more years, but in 2009 the Obama administration announced its opposition to the Yucca Mountain site. Thus, at present there is no plan at all for solution of this long-term problem.






Radiation



One of the biggest examples of Radiation took place during World War II,
when The States bombed Hiroshima and Nagasaki, when the states dropped
the atomic bomb, exposing millions of people to high levels of radiation.
Millions were killed. With Yucca Mountain housing millions of nuclear waste
the potential of radiation poisoning of this caliber could be a possibility. But
what is this radiation, what kinds are there, and how do they affect us?




What Is Radiation

Radiation is the process where energy is released from one source to another sources. After being transmitted to the other source it travels in a straight line through a medium or through space; its how energy moves from something to something. Radiation comes from the sun, nuclear reactors, microwave ovens, radio antennas, X-ray machines, and power lines to name a few. Thus the energy released when a stone is dropped into the water radiates away in circular waves. Sound energy radiates from a speakers mouth to a listeners ear, light and heat energy radiates from the sun to earth. There is radiation all around us, even in the air we breathe. The radiation that is around us everyday is from naturally radioactive materials in the ground, or from cosmic rays. Radon which is a gas seeps through the Earth's crust, which is how it is present in the air we breathe. However, even though we have those that are in our environment everyday and they are not harmful, we have some that can present harm to our health and bodies. To explain them a little better first there are two different classifications of radiation, Ionizing and Non-Ionizing Radiation.

Non-Ionizing Radiation

Non-Ionizing Radiation is lower in energy. This is the lower energy radiation that comes from the electromagnetic spectrum. It is called non-ionizing radiation because it does not have enough energy to remove an electron from an atom or molecule. Examples of non-ionizing radiation includes visible light, radio waves, and microwaves.

Ionizing Radiation

Ionizing radiation is a higher form of energy. It is enough energy to remove an electron from an atom or molecule. It comes from both subatomic particles and the shorter wavelength portion of the electromagnetic specturm. Examples of Ionizing radiation is X-rays, alpha rays, beta rays, and gamma rays. Alpha, Beta, and Gamma Rays are the three rays in which we will discuss more in depth.

leftDecay
Alpha, Beta, and Gamma Rays

Alpha Rays are high speed particles. Alpha rays are also called Alpha Particles. The Alpha Particles are positively charged and are made up of two protons and two neutrons, held together by the same strong force that binds the nucleus of any atom. An alpha particle is a nucleus, its the nucleus of a Helium atom, but it doesn't have any electrons around it, plus it travels fast. Even though the Alpha Particles can move very fast they can easily be blocked. The alpha particles can be blocked by the first layer of skin, since they do not penetrate the skin deep enough. So as long as the alpha particles are external they are not hazardous.

Beta Rays on the other hand are negatively charged. Beta particles do not travel as fast as Alpha particles. They also do not travel in a straight line, but in fact travel in a random path. Since they are greater than Alpha particles they also take more to block. Beta rays or particles require a few millimeters of Aluminum or tissue to block them. There fore they are hazardous.

Gamma rays are very short wave-length electromagnetic radiation. They also have no charge. Since they have no charge they have long ranges. Gamma rays loose energy by three major routes: Photoelectric Effect, Compton Effect, and Pair Production. The Photoelectric Effect is when the gamma ray collides with and ejects an electron from an atom. Then loosing its energy in the process, its totally absorbed. The Compton Effect is when the gamma ray collides with and ejects an electron from an atom and is scatterd from the impact with reduced energy. Finally Pair Production is the complete absorbption of the gamma photon with the formation of a negatron and a positron. Gamma Rays are very hard to block and can pass through the human body. Gamma Rays are like X-rays.

Half Lives



A half life is the length of time it takes for a substance undergoing nuclear fission (nucleus of an atom splits into multiple parts)to split into two; there for decreasing its mass by half. Half lives vary based on the mass amount of the original substance. The original term for this proses was half life period, which dates back to the early 1900's; it was then shortened to half life later.

Number of
half-lives
elapsed
Fraction
remaining
Percentage
remaining
0 1/1 100
1 1/2 50
2 1/4 25
3 1/8 12.5
4 1/16 6.25
5 1/32 3.125
6 1/64 1.563
7 1/128 0.781
... ... ...
n 1/(2n) 100/(2n)


















Formulas of half life

A decay process can be described by any three of the following equations:

N_t = N_0 \left(\frac {1}{2}\right)^{t/t_{1/2}}
N_t = N_0 e^{-t/\tau} \,
N_t = N_0 e^{-\lambda t} \,


  • N0 is the initial quantity of the thing that will decay (this quantity may be measured in grams, moles, number of atoms, etc.),
  • Nt is the quantity that still remains and has not yet decayed after a time t,
  • t1 / 2 is the half-life of the decaying quantity,
  • tau|τ is a negative and non-negative numbers|positive number called the mean lifetime of the decaying quantity,
  • λ is a positive number called the decay constant of the decaying quantity.


An example of this is:

If you originally had 157 grams of carbon-14 and the half-life of carbon-14 is 5730 years, how much would there be after 2000 years?


Nt = 157(1 / 2)2000 / 5730


So there would be 123 grams left.\

Nuclear Fission

Half Life












Non-exponential decay

In exponential decay a half life is defined as the length of time it takes for a substance undergoing nuclear fission to split into tow; however, in non-exponential decay, the half life depends on the original quantity of the substance and changes over time as the quantity changes.

An example of this is water evaporating from a puddle. The half life of the H2O that is evaporating depends on the depth and size of the puddle. In one day, the puddle may evaporate down to half of its original amount; however, there is no reason to believe that by waiting a second day that the H2O will then evaporate down to a quarter of the original amount. The will probably be less than that. Thus, the half life changes as the substance decays. This is an example of the half live decreasing, but in non-exponential decay there is also examples of half lives increasing.

Isotopes




Isotopes are atoms of the same element that has different numbers of neutrons in the nucleus, which therefore have different atomic weights. For example Oxygen-16 (16O) has 8 protons, 8 neutrons, and 8 electrons. On the other hand, Oxygen-20 (20O) has 8 protons, 10 neutrons, and 8 electrons, making this an Isotope of Oxygen-16.




Stable and Unstable Isotopes

Three most frequent isotopes of carbon are carbon-12 (12C), which contains 6 protons, 6 electrons, and 6 neutrons; carbon-13 (13C), which also has 6 protons and electrons, but has 7 neutrons; and carbon-14 (14C), which also contains 6 protons and electrons, but has 8 neutrons. When there are too many or not enough neutrons compared to protons cause some isotopes, like carbon-14 to be unstable. These unstable 'radioisotopes' will decay to stable products. Other isotopes, such as 12C and 13C do not decay, because their particular combination of neutrons and protons are stable. These are referred to as stable isotopes.



Radioactive Waste

Radioactive waste typically is made up of a number of radioisotopes: which again are unstable configurations of elements that decay, emitting ionizing radiation which can be harmful to human health and to the environment. Those isotopes emit different types and levels of radiation, which last for different periods of time.



Nuclear Waste


After a reactor, and in this case power reactors, has been operated on for around 18 months it is shut down for a period of time then fuel rods are replaced. What remains of the old fuel rods is called nuclear waste. The waste is the product of lots of different nuclear process, and they contain numerous isotopes, they are usually radioactive. Uranium, Strontium, Iodine, and Cesium are the most present elements in nuclear waste.








Nuclear Power Plants



The main purpose of nuclear power plants is to basically produce electricity. On June 27, 1954, the first nuclear power plant opened in Obninsk, just outside of Moscow. Since it opened in 1954, many other countries have embrace nuclear power.





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How it works In order for nuclear fission to turn into electrical energy, the power plant must first be in control of the energy given off by the uranium. Each of these uranium rods have a diameter of a dime, and these rods are collected into a bundle. The bundles of uranium are placed under water; the water acts as a coolent. The uranium bundles are good heat sources and heat up the water, which evaporates into steam and this steam powers a turbine which spins a generator to produce power.






Chernobyl Disaster
The Chernobyl disaster occurred on the 26th of April, 1986. This disaster is considered the worst nuclear power plant accident to have ever happened. The reason why the disaster occurred was due to reactor number four in the power plant having a meltdown. the fire resulting from this meltdown sent a plume of radioactive fallout into the atmosphere and into nearby Countries. Large areas of the Ukraine, Belarus, and Russia had to be evacuated for their own safety. According to data collected after the disaster, 60% of the radioactive fallout landed over Belarus.

There were 237 people left with acute radiation sickness, and of these people, 31 dies within the first three months. The majority of these people were the workers trying to get the disaster under control. [2]

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