Time Travel Research Center © 2005 Cetin BAL - GSM:+90 05366063183 - Turkey/Denizli

Benchmark I, Part I

In this part of the first benchmark, the students researched the topic of nuclear technologies in general. They specifically examined nuclear physics, the nuclear fuel cycle and reactor types, and nuclear weapon types and the effects of their use.

Nuclear Physics

To understand the basic concepts behind how nuclear weapons work, you must first understand fission, fusion, and transmutation. These three basic nuclear processes govern the way a nuclear weapon works and how it was produced.

Fission

The word fission should be a relatively familiar term to most people. Anyone who took a biology class should recall that fission is the splitting of an asexually reproductive, unicellular organism. The same goes for nuclear fission; it is simply a nuclear reaction that splits an atomic nucleus. To produce a fission reaction, a nucleus from a fissionable element needs to be bombarded by a neutron. The neutron is first absorbed into the nucleus. If we use Uranium-235 as an example: When the neutron is absorbed by the Uranium-235, it creates an unstable Uranium-236. This unstable isotope starts to fission and can divide into more than twenty different products, the key factor is that all the products masses equal 236. Fissionable isotopes are those that can undergo fission. Only certain isotopes are fissionable, if we use Uranium again as an example: Uranium-235 will undergo fission while Uranium-238 will not. Elements such as Uranium-235, Plutonium-239, and Thorium-232 are all fissionable. (1) (5)

Fusion

Fusion isn’t something that you can only read about in a science book; you feel the effects of fusion reactions everyday. Fusion occurs in stars across the universe, including our sun. These reactions provide the energy needed to sustain life on this planet. For a fusion reaction to take place, there must exist strong energies that can break the coulomb barrier between two positively charged nuclei. This causes the nuclei’s internal nuclear forces to bind together. Fusion happens most often in stars because of their dense and plasmatic environment. This is because density and temperature are the primary factors in why nucleons fuse in a fusion reaction. There are two major types of fusion reactions occurring in our own sun. But for all practical purposes we will only cover the Proton-Proton Reaction. (3)

The Proton-Proton Reaction occurs mainly in the center of our sun, the density here is about one hundred times the density of water on earth. This creates temperatures around 15 million Kelvin. Temperatures this high strip hydrogen of its electrons, creating plasma made up of free electrons and protons. This heat also provides enough energy to overcome the coulomb barrier between two hydrogen ions; forcing them to collide with each other, thus fusing the two nuclei together. When this happens, it releases among other things, a proton; this proton decays through a Beta-plus (ß+) type decay into a neutron. (4) This then forms the nucleus of deuterium, also know as a deuteron. This decay also releases an anti-electron (positron) and a neutrino. The positron will eventually collide with an electron destroying each other in the process. While the neutrino particle passes through the sun with little disruption. The newly formed deuteron (2H) may then collide with another hydrogen nucleus, forming the helium isotope 3He; and releasing a gamma ray. When two if these isotopes collide, two protons are released, creating 4He. You write out these reactions as follows: (3)
1. 1H + 1H 2H + positron (ß+) + neutrino (v)
2. 2H + 1H 3He + gamma ray (y)
3. 3He + 3He 4He + 1H + 1H

Transmutation

Transmutation is the “transformation of one element into another by one or a series of nuclear reactions” (1). Transmutation occurs when the nucleus emits an alpha or a beta particle. When the nucleus emits an alpha particle, it is reduced by two protons and two neutrons; this is because an alpha particle is made up of two protons and two neutrons. When the nucleus emits a beta particle, a neutron changes into a proton; this increases the protons in the nucleus by one, and decreases the number of neutrons by one.

When Uranium-238 absorbs a neutron, it does not undergo fission as would Uranium-235. Instead the now Uranium-239 emits a beta particle; this beta particle changes the Uranium-239 into Neptunium-239. The Neptunium-239 will then release another beta particle, creating Plutonium-239. The Plutonium is now fissionable. (2)

Bibliography:
1. The American Heritage® Dictionary of the English Language, Fourth Edition. : Houghton Mifflin Company, 2000.

2. Hewitt, Paul. Conceptual Physics. Menlo Park: Addison-Wesley, 1992.
3. Basic Fusion. Retrieved Jan. 14, 2004, from Think Quest:

4. http://library.thinkquest.org/17940/texts/ppcno_cycles/ppcno_cycles.html?tqskip1=1
About Radioactive Decay. Retrieved Jan. 14, 2004,

5. http://www.nuclides.net/Applets/about_radioactive_decay.htm
1. Basic Nuclear Fission. Retrieved Jan. 14, 2004, from Think Quest:

6. http://library.thinkquest.org/17940/texts/fission/fission.html?tqskip1=1

The Nuclear Fuel Cycle and Nuclear Reactors

In this report there will be information on the nuclear fuel cycle and each step it goes through. There will also be information about the different types of nuclear reactors: what they have in common and what they don’t.

The Nuclear Fuel Cycle is a complex process and a very distinct cycle. Uranium must be processed through a series of steps to produce an efficient energy resource, or efficient fuel, to enable the generation of electricity. To prepare uranium so it can be used in a reactor, it must endure certain steps in the front end of the cycle. The uranium goes through the processes of mining and milling, conversion, enrichment, and fuel fabrication. After it is used to produce electricity, during the back end of the cycle, it is known as ‘spent fuel’ and can undergo more steps such as storage, reprocessing, and recycling before it is eventually just waste. (3)

The first step of the nuclear fuel cycle is Mining and Milling. Uranium is usually mined at the surface from an open cut or underground mining techniques, depending on the depth where the ore is found. The mined uranium is then sent to a mill and is crushed and ground into a fine powder. After this, the ground ore is drenched in sulfuric acid to separate the good uranium from the waste. U308 is the final uranium product, which is sold from the mine. U308 is sometimes known as “yellowcake” even though it is a khaki color. Next, since the uranium needs to be in the form of a gas before it can go on to the enrichment process, the U308 is changed into the gas uranium hexafluoride (UF6) at a conversion plant. After the conversion, the gas will go on to enrichment. (3)

Most all nuclear power reactors in operation need 'enriched' uranium fuel in which the content of the U-235 isotope has been bumped up from the natural level of 0.7% to about 3.5% or a little more. The enrichment process takes away 85% of the U-238 by dividing the gaseous uranium (hexafluoride) into two streams. One stream is enriched to the required level and then goes on to the next stage of the fuel cycle which is fuel fabrication. (3)

The next step is fuel fabrication. UF6 that is enriched is moved to a fuel fabrication plant where it is made into uranium dioxide powder and compressed into pellets; these pellets can be dropped into tubes to produce fuel rods. The rods are closed and put together in clusters to make fuel elements to use in the core of the nuclear reactor. After the fuel fabrication is complete, the core of the nuclear reactor is made up of several hundred fuel assemblies. The U-238 is turned into plutonium in the reactor core, and the other half is fissioned, creating 1/3 of the reactor’s energy. Then the heat is used to produce steam to drive a turbine and an electric generator which produces about 7 billion kilowatt hours of electricity in one year. Approximately 1/3 of the spent fuel is removed about every year and replaced with fresh fuel. (3)

When the spent fuel assemblies are removed from the reactor core they are highly radioactive and give off heat. Then they are stored in special ponds located at the reactor site, to allow both their heat and radioactivity to decrease. The water in the pond acts as a barrier against radiation and gives off heat from the spent fuel. Spent fuel contains about 96% of its original uranium, 3% of spent fuel contains waste products and the last 1% is plutonium. Uranium and plutonium are separated from waste products by chopping up the fuel rods and dissolving them in acid, known as reprocessing. The covered uranium can be returned to the conversion plant for conversion to uranium hexafluoride and re-enrichment. The high level wastes are sealed into stainless steel canisters. Spent fuel rods are put in corrosion resistant metals such as copper or stainless steel. Plans for these materials are for them to be buried in stable rock structures deep underground. (3)

There are many types of reactors, they are all used for different things. Civilian reactors are used to make energy for electricity. Military reactors are used to make materials that can help produce nuclear weapons. Research reactors are used to create weapons. Research reactors can also be used for training, or nuclear physics experiments. (1)

There are also different types of nuclear reactors. One type is light water reactor (LWR). Another is the heavy water reactor (HWR). There are many differences between the two types of reactors. Light water reactors are used mainly to generate electricity whereas heavy water reactors are used in the production of plutonium. Light water reactors use water as a coolant where heavy water reactors use heavy water, also known as deuterium oxide. The light water reactors are low enriched while the heavy water reactors are not enriched. (1)

Another type of reactor is the fast breeder reactor. Like the heavy water reactor, the fast breeder reactor is used for the production of plutonium and for electricity. That is about where the similarities end between the fast breeder reactor and the light and heavy water reactors. The coolant for the fast breeder reactors is molten or liquid sodium. There is no need for a moderator in the fast breeder reactor. Plutonium dioxide as well as uranium dioxide serves as the fuel for the fast breeder reactors. The level of enrichment is in various combinations of uranium and plutonium. (1)

As with many things there are problems with nuclear reactors. People are concerned about the waste disposal of the nuclear reactor’s radioactive elements. People are also concerned that the fuel from the nuclear reactors could be diverted to produce nuclear weapons. For example a nuclear reactor that contained plutonium-239 could have the plutonium separated to form nuclear weapons. This concern is more specifically about fast breeder reactors because they produce plutonium-239 for generations of reactors that will come. (2)

After spent fuel assemblies are taken out of the nuclear reactors they are moved to “swimming pool” storage sites to be isolated from the environment. Plans to dispose of the waste have involved putting them into a glass container and burying them underground salt domes. The first site to dump the waste is planned for Yucca Mountain in Nevada. The reason they have not already dumped waste there is because of political as well as technical difficulties.

Bibliography

1. (1996). Basic Characteristics of Reactor Types. Retrieved Jan. 20, 2004, from Institute for Energy and Enviromental Research: http://www.ieer.org/reports/npd-tbl.html.

2. http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/nucprob.html.

3. Nuclear Fuel Cycle and Australia's Role in it. Retrieved Jan. 20, 2004, from URANIUM INFORMATION CENTRE Ltd.: http://www.uic.com.au/nfc.htm

Types of Nuclear Weapons

The first and most basic type of nuclear weapon is the fission bomb. A fission bomb uses an element like uranium-235 to create a nuclear explosion. It does this by a process known as induced fission. In a bomb that is working correctly the uranium is bombarded with neutrons, when U-235 captures a neutron it splits releasing more neutrons which causes fission to occur thus the process starts a “chain reaction”. This process is known as supercriticality. During this process an incredible amount of energy is released in the form of heat and gamma radiation. A pound of U-235 is equal to about 1 million gallons of gasoline, a pound of U-235 is smaller then a baseball. In order for the bomb to work it must have weapons grade uranium which is made of 90% U-235. In a fission bomb the fuel must be kept separate to prevent premature detonation. Each part of the fuel is kept in a subcritical mass. In this form it will not support fission. There are two ways to bring the subcritical masses together to form the supercritical mass needed in a nuclear weapon.

The simplest way to bring the subcritical masses together is to use a gun that fires one mass into another. The U-235 is made into a ball around the neutron generator. A small bullet of U-235 is placed at the end of a long tube with an explosive charge behind it; the ball of U-235 is placed at the other end of the tube. A barometric-pressure sensor determines the appropriate altitude for detonation. The process can be broken down like this:
1. The explosive propels the bullet down the barrel
2. The bullet strikes the ball of U-235 and penetrates into the neutron generator, which starts the fission reaction.
3. The chain reaction begins
4. The bomb explodes

This is the triggering mechanism used in the first atomic bomb “Little Boy”. It was dropped over Hiroshima on August 6th 1945. (2) It had 14.5 kiloton yield. It used about 1.5% of the U-235 before the blast carried it off. (1)

Early in the Manhattan Project scientists working on the triggering mechanism, recognized that compressing the subcritical masses together into a sphere by implosion might be a good way to make a supercritical mass. The implosion device consisted of a sphere of U-235 and P-239 (weapons grade plutonium-239) core. The core (U-235, P-239) was then surrounded by high explosives. It work like this:
5. The explosives fired, creating a shock wave.
6. The shock wave compressed the core.
7. Fission chain reaction began
8. The bomb exploded.

The implosion trigger was the type used for “Fat Man”, dropped over Nagasaki on August 9th 1945.(2) It had a 23-kiloton yield and used about 17% of its U-235 and P-239.(1)

The fission bombs worked but they weren’t very efficient. Then came the fusion bomb, also known as thermonuclear bombs. They had higher kiloton yields and greater efficiencies than fission bombs. Before they could build this bomb they had to solve some problems. The fuel for the bomb was a gas mixed with a gas, which meant that fuel would be hard to store. Tritium, one of the gases, is in short supply and does not last that long so it had to be continuously replenished. Deuterium or tritium has to be compressed at high temperatures which made it difficult to make. The way around that is to encase a fission bomb with a fusion. It works because the neutrons from fission could produce tritium from lithium, which meant that they would not have to store the tritium in the bomb. Finally, Stanislaw Ulam recognized that the heat from x-ray radiation, which is given off in a fission reaction could provide high enough temperature and pressure to initiate fusion. So in reality a fusion bomb is a bomb inside a bomb. It works like this:

9. The fission bomb implodes, giving off x-rays
10. These x-rays heat the interior of the bomb and the tamper; the shield prevents premature detonation.
11. The heat causes the tamper to burn away, exerting pressure inward against the lithium deuterate.
12. The lithium deuterate is squeezed by about 30-fold
13. The compression shock wave initiates the plutonium rod.
14. The fissioning rod gives off radiation, heat and neutrons
15. The neutrons go into the lithium deuterate and makes tritium.
16. The combination of high temperature and pressure is sufficient for the fusion reaction to occur, producing more heat, radiation and neutrons.
17. The neutrons from the fusion reaction induce fission in the U-238 pieces from the tamper and shield.
18. Fission of the tamper and shield produce even more radiation and heat, the bomb explodes.

Boosted fission weapons dramatically increase the efficiency of the weapon. They do this by introducing a small amount of material that can under go fusion. Once the fission takes place it produces the required temperatures for a fusion reaction. The fusion than accelerates the fission. The fusion only makes the fission reaction go faster and therefore increases the effectiveness of the weapon.

Enhanced radiation weapons, also called neutron bombs, are smaller tactical thermonuclear weapons which are designed to keep the blast down to a specific target. The radiation is use to eliminate ground troops even out of the blast radius. The radiation will easily penetrate armor and bunkers that are not destroyed in the blast.

Salted nuclear weapons, also known as cobalt bombs, are thermonuclear bombs that produce large amounts of long lasting radioactive fallout. This results in large scale radioactive contaminated area. The difference in the fallout of salted to unsalted nuclear weapons is that the fallout of salt-nuclear weapons stays radioactive for a much longer time, making the long term effects of this weapon much more destructive then the initial explosion. These weapons known as the dooms-day bombs could possibly kill everyone on earth. Though these weapons have been discussed, there is no proof that one has ever been built.

Bibliography:
1) How nuclear bombs work. Retrieved Jan. 11, 2004, 2)
2) http//people.howstuffworks.com/nuclear-bomb.htm
3) Nuclear weapon types. Retrieved Jan. 13, 2004, www.ausSurvivalist.com

Biological Effects of Nuclear Weapons

Biological effects from nuclear weapons are caused by the various characteristics of a nuclear explosion. Some of the effects show up immediately while effects from other causes only appear after time.

The flash from a nuclear weapon is the intense light and thermal radiation from the fireball. The closer a weapon is to the ground, the smaller the amount of energy is used in the flash. (2) The flash deposits energy on surfaces in line of sight of the explosion. The flash is so intense that if you are seven miles from a one megaton explosion you would experience 1st degree burns. If you were six miles away you would suffer 2nd degree burns, and if you are five miles away you would suffer 3rd degree burns.(1) The following table should give an idea of the amount of damage the flash can do depending on the energy deposited:

EXPOSURE (CAL CM^-2)	EFFECT
2-4	Humans suffer 1st degree burns
5-8	Humans suffer 2nd degree burns
>8	Humans suffer third degree burns
15	Rayon fabric ignites
17	Cotton dress shirt ignites
18	Draperies inside windows ignite
20	Blue jeans ignite
30	Roofing ignites (3)

The flash can also ignite simultaneous fires over a large area.

The blast is the characteristic that produces the most physical damage to structures. There are two characteristics that make up the blast. The first is a wall of pressure that expands outward from the center of the explosion. The second is the high speed winds that accompany the wall of pressure. The pressure is what blows away the walls of structures and causes the most damage. A typical two story house subjected to a 5 psi shock wave would feel the force of 180 tons on the side facing the blast.(1) The wind speed is dependent on the force of the pressure. At 2 psi there are hurricane force winds of 70 mph and people would be injured by flying debris. At 5 psi there are 160 mph winds and at 10 psi there are 300 mph winds and humans suffer lung damage. At 20 psi there are 500 mph winds and humans suffer severe lung damage and their eardrums rupture. At 100 psi humans are killed and only missile silos would survive. (3)

Prompt radiation includes any of the radiation released in the first few seconds of a nuclear explosion. Prompt radiation is ionizing radiation and causes damage at the cellular and molecular level in biological organisms. Doses of over 1000 rem almost certainly result in death within weeks due to failure of the central nervous system or digestive system. A dose of 100-1000 rem produces radiation sickness which includes injuries to blood producing tissue, if death results it will be in 1-8 weeks. Doses of <100 rem may produce genetic defects, particularly in rapidly dividing cells. Damage to cells increases the risk of cancer and damage to reproductive cells may result in genetic defects in offspring of the person. (1)

Fallout is generally an effect if the detonation is on, below, or near the surface of the earth. If the explosion is high in the atmosphere the fallout is practically zero. The explosion carries dirt, rocks, buildings, and other debris up into the fireball creating the familiar mushroom cloud as it cools and rises upward, carrying with it debris made radioactive into the atmosphere. The debris that drifts back to earth downwind of the explosion or remains in the atmosphere for decades.(1) The fallout is most intense at the location of the explosion and immediately downwind, but may be carried hundreds of miles depending on the wind and weather conditions. Biological effects due to fallout is the same as those for prompt radiation, however there are a few differences. The radiation can be inhaled or ingested because it comes from particles, causing injury to internal organs that would otherwise be unaffected by radiation. The fallout can also be distributed over a much larger area than prompt radiation. (2)

The multiple effects of nuclear weapons make them have far more health effects in the short term and long term than a like amount of conventional explosive.

Citations
1. Effects of a Nuclear Explosion. Retrieved Jan. 12, 2004, from PBS: http://www.pbs.org/wgbh/amex/bomb/sfeature/effects.html
2. Johnston, R. (2004). Nuclear Weapons Effects-- An Overview. Retrieved Jan. 12, 2004, http://johnstonsarchive.net/nuclear/effectsum.html
3. Lamb, F. (2003). Effects of Nuclear Weapons. Retrieved Jan. 12, 2004, from University of Illinois at Urbana-Champaign: http://wug.physics.uiuc.edu/courses/phys180/spring03/handouts/effs03p180.pdf

Environmental Effects

The use of nuclear technology has many effects on the environment. Nuclear weapons have been tested and we have seen the damage and destruction brought with them. The aftereffects including radioactive contaminants are also disastrous. The environment might be very contaminated with nuclear waste if the U.S hadn't designated a storage area and a waste management system.

All nuclear explosions differ in damages. Damages depend on a wide variety of things such as the weapons yield, fuel, design of device, the target, the weather, and where it explodes: whether in the air or the earth’s surface. However, the explosion will release forms of energy that are very distinct from one-another. These forms include direct thermal radiation, radiation, explosive blast, and radioactive fallout. Both types of radiation can be deadly. Detonating nuclear weapons causes several types of ionizing radiation. The damage formed from the blast is mostly caused by its shock wave. At the Trinity Test Site, one of the first plutonium fueled bombs was tested. The estimated energy generated from the blast was said to be equivalent to 15-20 thousand tons of TNT (as a conservative estimate). The effects on the environment from the blast were outrageous. One hundred miles away from the site windows shattered. The cloud which appeared after the ball of fire contained several thousands tons of dust, iron, and gaseous debris. There was also a huge amount of highly radioactive materials. The explosion created a crater with a diameter of 1200 feet. The center consisted of a shallow bowl of 130 feet in diameter and six feet in depth. Within the creator and its outer perimeter all vegetation had vanished, without a trace. (1)

There has been a lot of history on the matter of radiation whether it comes from an accidental explosion or an intentional dumping of waste into a river. Chernobyl, a nuclear power plant in Russia that exploded, sent 50 tons of radioactive dust over an area of 140,000 square miles. Radiation from the blast contaminated rivers and land. People living in the area have dealt with being exposed to radiation; some have been diagnosed with leukemia, thyroid cancer, and cardiac problems. Another explosion occurred in 1957 at the Mayak plant, again contaminating and destroying. The environment was effected because the people and animals drank from this river also agricultural plants were watered by this river. Everything in that area was contaminated. Starting from 1949 Soviet officials purposely and secretly dumped radioactive waste in the Techa River. The river was highly contaminated and people downstream drank the water from the river. (2, 3)

Protecting the environment is an important concern to most Americans. A Legislative Act in1982 established the United States nuclear waste management program. Under this policy, nuclear fuel or any high level radioactive waste had to be safely stored, transported, and disposed of. The site recommended is in Yucca Mountain, Nevada, with central surface facilities to handle the nuclear wastes, and a facility 1,000 feet below the surface for the permanent disposal of the waste. However, building a facility does not insure safe transport of the waste. For the safe travel of the waste a cast for spent fuel was created. (4)

Bibliography

1) (2000). The atom bomb. San Diego, Ca: Greenhaven Press Inc..
2) (1996). Chernobyl and the world responsibility. Online news hour,). Retrieved January 11 2004, from 3) http//: www.pbs.org/newshour/forum/chernobyl_4-26.html
3) (). Effects of a nuclear explosion. American Experience, 3. Retrieved January 12 2004, from www.pbs.org/wgbh/amex/bomb/sfeature/effects.html
http://www.pbs.org/wgbh/amex/bomb/sfeature/1mtblast.html
4)Schram, M. (Ed.). (2003). Avoiding Armageddon. , Basic Books.
, . (Ed.). (). Science, society, and America’s nuclear waste. , Department of Energy.

Hiçbir yazı/ resim izinsiz olarak kullanılamaz!! Telif hakları uyarınca bu bir suçtur..! Tüm hakları Çetin BAL' a aittir. Kaynak gösterilmek şartıyla siteden alıntı yapılabilir.

Ana Sayfa / index /Roket bilimi / E-Mail /CetinBAL/Quantum Teleportation-2

Time Travel Technology /Ziyaretçi Defteri /UFO Technology/Duyuru

Kuantum Teleportation /Kuantum Fizigi /Uçaklar(Aeroplane)

New World Order(Macro Philosophy)/Astronomy