Chemical elements with unstable atomic nuclei can collapse. This so called radioactivity releases energy in form of radiation that sends out rays. This process happens stochastic and therefore irregular.
Naturally organism in the world are exposed to three different kinds of radiation:
- Cosmic radiation from outer space. The atmosphere and the magnetic fields of our earth mainly stop it.
- Terrestrial radiation from the earth.
- The absorption of potassium in the body releases also a bit of radiation from the inside.
Fission of plutonium and uranium for the production of energy also generates radioactive radiation. This radiation cannot completely be isolated from the environment even if there are tight security measures. The processing of nuclear fuel rods enormously increases the radioactive radiation of this material.
There are different categories of radioactive radiation:
- α-radiation: consists of positive charged helium nuclei - so called α-particles. It has a very small penetration because of its huge mass and big reactivity with material. Paper can absorb it. It has a range of in-between 4 and 6 cm. α-radiation from the outside it not dangerous for organic bodies.
- β-radiation: This radiation has a range of several meters. A 1 mm thick aluminum can absorb its rays, but they still can penetrate a few cm into the body and cause skin damages.
- γ-radiation: These rays are energy-rich electromagnetic waves with short wavelength. They have a very large penetration and can primly be absorbed by several mm lead. There is no specification for the range of γ-radiation. It penetrates far into organic bodies and can be damaging or destructive for cells depending on the dose.
The effects of radioactive radiation depend mainly on the time of irradiation and the sensibility of the organic body. More factors are the absorbed dose and the range of the radiation.
Radiant sources, which are absorbed by the body, cause more critical effects. So cells and DNA sequences can also be damaged or destroyed by α- and β-rays respectively.
Nuclear fission chain reaction
Radioactive material can cause a nuclear fission chain reaction, i.e. a nuclear explosion, if there is a so-called "Critical Mass". Exceeding the Critical Mass increases the neutron radiation very fast. Freely flying neutrons fission more and more uranium atoms and cause a chain reaction. Richard Feynmen calculated the Critical Mass of a uranium bomb to 50 kg of pure uranium. Uranium for a nuclear bomb is supposed to have a purity of 98%. A bomb of plutonium needs a Critical Mass of 21 kg. Different explosive mechanism can reduce the point for a Critical Mass.
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Throughout the Southwestern U.S. (Colorado, Utah, Nevada, New Mexico) there are many uranium mines. Mining uranium ore is carried out, more or less, in the same manner as any type of mining with the exception that uranium is a radioactive element. As an ore it is only mildly radioactive although special precautions, such as wearing dust masks and protective clothing, need to be taken. Uranium in its natural state cannot be used in a reactor. The type of uranium that can be used in a reactor is uranium-235. Natural uranium ore contains 99.3% uranium-238 and only 0.7% uranium-235. Uranium-235 is used for producing a fission reaction in a nuclear reactor. That is why uranium must be "enriched", to increase the relative proportion of uranium-235 from 0.7% to around 4%.
Once the uranium ore has been mined it is taken to a nearby mill where the ore is crushed and ground to dissolve the uranium oxide. This technique is used to separate out and consolidate the uranium oxide from the uranium ore. That is, to extract a concentrated percentage of the uranium oxide from the crushed uranium ore. The powdery substance which results from this process is called "yellow cake". From mine and mill, this substance is then shipped to Production Centers.
There the yellow cake is changed into uranium green salt crystals in a process of chemical transformations. This is part of the process of enrichment. Enrichment requires changing uranium oxide into uranium hexafluoride in its solid state and then changing uranium hexafloride into a gaseous state. By changing uranium oxide into the gaseous state of uranium hexafluoride, uranium-235 isotopes can be sorted out from the uranium-238 isotopes. Separating and concentrating the uranium-235 is the desired goal of enrichment. Uranium hexafluoride in its solid state is called "green salts". Tthese green salts are heated together with magnesium granules for approximately four hours at 1300 degrees Fahrenheit. Once a gaseous state is achieved, the uranium-235 is separated out.
After further processing, the uranium-235 metal, at a red hot heat of 1100 degrees Fahrenheit, is inserted into the uranium metal extrusion press. The press squeezes molten uranium-235 ingots into long tubes. This process produces the long uranium-235 metal tubes which are called "fuel rods". Once cooled these uranium-235 fuel rods are ready to be sent to reactors.
The enriched uranium in the form of fuel rods are loaded into a reactor and undergo a fission reaction by being bombarded with slow neutrons. This reaction is similar to the primary stage of a hydrogen explosion, that stage being mostly comprised of a fission reaction. As a result, there is a vast amount of heat generated, which heats water, turns turbines and provides electricity, but unique to a nuclear reactor is the by-product, plutonium-239.
The plutonium is extracted from the reactor fuel rods and concentrated into plutonium ingots or buttons. Remote control machinery extracts the plutonium from the fuel rods and transports the. The finished product, weapons grade plutonium, is shipped for final fabrication into the plutonium pits. The processes involved in transforming uranium ore into uranium-235 and finally into plutonium-239 make up the front end of the nuclear fuel cycle.
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MATERIALS: Index cards of the nuclear chain
TIME AND LOCATION: 30 minutes, circle with space in the middle for mapping the nuclear chain
The nuclear fuel cycle can simply be illustrated in several steps. The group is supposed to work out how those steps are connected and where the cycle can be found in the whole system.
Label the index cards with the several steps of the nuclear chain reaction and its waste products. You find an example for all cards in the pdf-file.
STEP 1 - BRAINSTORMING
Before you hand out the information it is important to know how much knowledge the participants may already have about the topic. Write “Uranium and the nuclear fuel cycle” on the wall, circle it and ask the participants if anything comes into their mind. Every answer relevant to the topic will be written down and connected to the circle with a stripe. If needed you can ask some questions:
Which countries do have uranium?
Is uranium dangerous?
For what is uranium used?
What is radioactivity?
STEP 2 – ILLUSTRATION
Put the prepared index cards about the steps of the nuclear chain out in front of the group and ask them to use their new knowledge to assemble the nuclear fuel cycle.
STEP 3 – EVALUTATION
In the end you can go through the whole nuclear fuel cycle once again together with the participants to make sure that everybody understood it. You can also use some pictures or videos of each step for illustration. You find them for example at www.strahlendesklima.de/.
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Since 1945 there have been more than 2000 nuclear tests on earth carried out by the eight nuclear weapon states. The United States and Russia are responsible for more than 80% of those tests.
Nuclear tests worldwide (Source: Atomwaffena-z.info)
How it all started
It was July 16 1945 as Gadget, the worldwide first nuclear, had been launched in the desert of New Mexico under the covert name Trinity. This so called nuclear big bang had an explosive force if about 21 kilotons TNT equipollent. 200 grams of TNT are sufficient to kill one human. The explosion has been covered by the US military as an explosion of an ammunition depot. It had not been confirmed as a nuclear test until the day of the bombing of Hiroshima on August 6 1945.
Nuclear tests aboveground, in the atmosphere or underwater caused immediate harms for existing and also successive generations. Those underground rooted for the release of radioactive gases to the surface by and by. In accordance with a study from the “International Physicians for the Prevention of Nuclear War” (IPPNW) the estimated number of casualties by tests aboveground raised to a total number of 430.000 until the year 2000.
Containment of further tests
Since 1992 the United States renounce self-determined more nuclear tests. Russia carried out its last test in 1990, Great Britain in 1991 respectively. France followed in 1995, China in 1996, India and Pakistan in 1998. The nuclear tests by North Korea in 2006, 2009, (2010), 2013 and 2016 are the last nuclear tests worldwide so far. In 1963 the Partial Test Ban Treaty (PTBT) was created in Moskau. It banned nuclear tests in the atmosphere, underwater or in space. It had been the forerunner for the Comprehensive Test Ban Treaty (CTBT).
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Since 1958 an agreement is negotiated which is supposed to inhibit every kind of nuclear tests or nuclear explosions for test purpose. At the same time an international monitoring system should be developed that could reveal any breach of agreement. It should further afford mutual control through for example on-site-inspections. This so called Comprehensive Test Ban Treaty (CTBT) amends the Partial Test Ban Treaty by banning every kind of nuclear test.
So far the CTBT could not entry into force, because all 44 so called Annex-II-states are required to sign and ratify it at first. Annex-II-states are those states that use nuclear power in any kind. Eight ratifications are missing currently (October 2016) the United States and China at the head.
At present the Comprehensive Test Ban Treaty Organization (CTBTO) is engaged to finish a global monitoring network. It is financed by the current treaty parties and will be used as a reliable and valid verification system as soon as the CTBT entries into force.
(Bildquellen: www.ctbto.org, 2.11.2010)
For the network there are 377 sensitive measure stations and laboratories planned which can detect nuclear explosion in the atmosphere, aboveground, underground and underwater. Current technology in the field of seismology, hydrology and radiology in the atmosphere would be used. Those facilities are part of the International Monitoring System (IMS) that is currently in testing phase. It sends the results of analyses to a central office from the CTBTO in Vienna. Those results are also shared with the parties to the treaty.
Furthermore if the CTBT entered into force, one-site-inspections would be possible in case of suspicion of nuclear testing. A group of control officers would be sent to the area of suspicion to look for more evidence for a carried out nuclear explosion. Such an inspection has already be carried out in Kazakhstan with success.
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MATERIALS: Interactive maps and information (www.ctbto.org)
TIME AND LOCATION: Very flexible from 10-30 Minutes, PC-Pool
You can find current information materials about the status of the treaty, the monitoring system and nuclear tests on the website of the CTBTO. Your group can split and take a deeper look for example into the details of every kind of measurement technology. The results of the research can be presented in front of the rest. At the CTBTO website are also movies like in case a nuclear test side would be explored or a simulation about all nuclear tests happen.
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Every day there are reports about human and technical failure in this world. Unfortunately 20.000 nuclear weapons are not excluded. There is an own definition of the understanding of accidents concerning nuclear weapons: for example unauthorized launches of nuclear capable weapon-systems, unintentional detonations or radioactive contamination.
Even though information about such accidents is rare there are plenty of examples of incorrect treatment. In the following some chosen examples:
1966: Palomares, Spain
A B-52 bomber from the United States collides with another airplane. The cargo of four nuclear bombs was dropped. Two of them were found on the ground and in the ocean respectively. The other two bombs exploded after the impact. Though there was no nuclear explosion over 1.400 tons of soil and vegetation have been contaminated.
1968: US-Airbase near Thule, Greenland
Crash of an US B-52 airplane at the coast in the Northwest of Greenland. There were four nuclear bombs on board. None of them triggered a nuclear explosion, but the conventional explosive-charges did and the components of the bombs melt down into the ground – radioactive material included. With the aid of Greenlandic and Danish workers there was a comprehensive search. After three months the US-government officially declared the end of the search. Nowadays it is known that the US military still was secretly looking for the bombs. There never has been a report about success.
1985: Heilbronn, Germany
During an exercise a Pershing-II missile suddenly caught fire and burned down under explosions. Parts of the missile flew in a distance up to 120 meters. About 250 meters away from the place of accidents there were combat-ready Pershing-II missiles with nuclear warheads deployed. Three US-soldiers dies and 16 more were badly injured because of the accident.
1989: North Cave Pool
The soviet submarine K-278 »Komsomolez« (Mike Class) with a nuclear-engine lost its bore away and sunk a few hours later. Because of burnings, injuries, suffocation and under cooling 42 crewmembers died. A core reactor and two torpedoes with nuclear warheads are still lying on the sea bottom.
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MATERIALS: newspaper, internet
TIME AND LOCATION: 30 – 45 minutes
The basic information about nuclear accidents is airy, but sufficient enough to get an impression of the treatment with the nuclear components. This method requires the participants to take a deeper look into the topic. Using the Internet as an additional source for research they are supposed to write an article in a fictional newspaper. They can choose their accident topic themselves. It may also be possible to get more information about a certain accident via the archives of newspapers in the Internet.
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