12/1/2012
RADIOACTIVITY
Nina Amini, Maria Haraldson, Julia Masselos, Sophie Mathias, Sarah Salvest and Sandhya Sridhar The Godolphin and Latymer School
INTRODUCTION What is Radioactivity? Radioactivity is the spontaneous emission of energy from unstable atoms. Unstable atoms break down or 'decay' into new atoms. They emit radioactivity from their nucleus as they decay, and are therefore said to be radioactive. The energy released in radioactivity consists of small, fast-moving particles and high-energy waves. Radioactivity is a random process that happens naturally as the isotopes decay (they continue to do this over time). Radioactivity has many uses, for example radioisotopes that are used widely in medicine, and in the production of nuclear energy as a source of energy. The discovery of radioactivity has lead to many developments and is a very important component of science today. What is the Manhattan Project? The Manhattan project was a large scientific research project, which was run in the United States during the Second World War. The outcome of this project was the development of an atomic bomb. This atomic bomb was created on July 16th 1945 and was released in Japan. Since the development of the atomic bomb the atom bomb, many scientists have discovered how to make use of the power of nuclear energy. Nuclear power plants are now much more efficient than traditional power plants. The medical field has also taken advantage of the atomic bomb. Technology used in the atomic bomb is also used for CAT scans and chemotherapy.
The Discovery of Radioactivity Wilhelm Conrad Roentgen November 8t 1895 - Wilhelm Roentgen discovered X rays. Whilst at university he was drawn to a fluorescent screen near where he was working. Roetgen thought that the fluorescence of the light was caused by invisible rays from the electrons in the ‘Hittorf -Criijes’ tube he was studying. To his surprise, the unknown rays had penetrated the opaque black paper wrapped around the tube.
Henri Becquerel In 1896, Henri Becquerel was technically the first person (along with Marie Curie) to discover radiation. He first came across it during his experiment on uranyl sulphate, which he exposed to light and placed it on photographic plates wrapped in black paper. When these photos where developed images of uranium salts appeared. Becquerel’s first thought was that the uranium had absorbed the sunlight and produced X rays. Becquerel’s assumption was proved incorrect when on he left uranium in a closed drawer on top of photographic paper without access to any sunlight. After leaving that for a few days Becquerel decided to develop the photographic paper only expecting to see faint images when in fact they appeared very clear and vivid. The uranium had emitted radiation with no help from any external sources; Becquerel had discovered radioactivity. In 1903 Becquerel received the Nobel Prize for physics.
Pierre & Marie Curie Pierre and Marie Curie decided to investigate radioactivity further. Although Becquerel discovered radioactivity Marie Curie created it. Curie noted that uranium ore was more active than the pure uranium and so concluded that the ore must contain other elements that were also radioactive. This led her to the discovery of polonium and radium; however, it took many years of processing these elements to determine their chemical properties. She was awarded the 1903 Nobel Prize for physics (joint with her husband and Henri Becquerel).
The Manhattan Project The Manhattan project was the name given to the secret US assignment that developed the first atomic bombs during the early 1940s. The project took place under the direction of General Leslie Groves of the U.S. Army Corps of Engineers. Scientists and technicians, headed by physicist Robert Oppenheimer, created two types of bombs. The Little Boy was a gun-type fission weapon constructed using the isotope uranium-235. The Fat Man bomb was an implosion-type nuclear weapon consisting of man-made plutonium-239.
World War Two Throughout the Second World War America and Japan had been engaged in battle following Japanese attempts to expand their empire. In hopes of ending and winning the war, as to spare American lives, the US decided to drop the atomic bombs on Japan under the orders of President Truman. On the 6th August 1945, the first bomb Little Boy was dropped on the city of Hiroshima, three days later the second, Fat Man, was dropped on Nagasaki. The effects were devastating; long term and short term. The explosions created winds of 800 kilometres an hour which instantly crushed people to death and in Hiroshima alone 80,000 were killed immidiately by the radiation produced, followed by a further 58,000. Several days after the Japanese surrendered. The bombings were subject to much controversy due to the sheer masses of innocent civilians that were killed. The use of the first atomic bombs marked the beginning of the Cold War, sparking the nuclear arms race between the USA and the Soviet Union. It was particularly significant in that it warned the world as to how powerful these bombs really were and the extent of the damage they could inflict. This acted as a deterrent during the Cold War due to what is known as Mutually Assured Destruction.
USES 2.Thickness Control
1.Smoke Alarms Americium-241 is used from which alpha particles are emitted which ionize the air so that it can conduct electricity. When smoke enters, it absorbs the particles and can no longer conduct electricity and the alarm sounds.
The thickness of paper can be controlled by measuring the amount of beta radiation that passes through it. It can also be used for plastic or aluminium foil.
3.Carbon Dating When alive, organisms have a known proportion of Carbon-14 in their tissues. When dead they stop taking in the Carbon14, and the amount is reduced. Using this information they can date things such as fossils.
4.Sterilising Gamma rays are used to kill bacteria and mould in food to increase its shelf life. They are also used to sterilise hospital equipment.
5.Cancer Treatment Gamma rays are used to kill cancer cells without surgery, in a process called ‘radiotherapy’. The amount of radioactivity given is crucial. Some cancers are easier to treat with radiotherapy than others.
6.Radioactive Tracers Technetium-99 is often used for medical purposes such as checking for a blocked kidney. They are also used in industry to check for leaking pipes.
DANGERS OF RADIATION Ionization and Excitation Electrons release energy along their track by interacting with the electrons of nearby molecules. Atoms near the track absorb this energy and are either excited (one of their electrons shifts to a higher energy level orbital) or ionized (one of their electrons is lost). What makes this ionization different from ionization of ordinary chemical reactions is that any electron could be lost – not necessarily one from the highest occupied energy level orbital. This makes the atoms extremely unstable radicals. UV light does not ionize skin cells when it causes sunburn – it excites them. It is important to understand the effects and mechanisms of UV light and its interaction with the skin when creating sun block.
Effect of Ionization on Cells The major affect of ionization on cells is that it causes the DNA to break on either a single strand or on both. Most single strand breaks can be repaired normally by using the intact opposite strand as a model – as the two complement each other. However, in the case of double-strand breaks, rejoining of broken ends may occur, as repair is much more difficult. These misrepairs could result in mutations, chromosome aberrations, or cell death. There are two main ways that DNA is affected by radiation exposure: 1) two separate double strand breaks in the DNA molecule whose outermost ends join together, resulting in the loss of the fragment between the two breaks, 2) the process of an enzyme digesting nucleotides of the broken ends before repairing the break by rejoining. Image of fragmentation of the DNA caused by a radioactive particle.
Exposure to Radiation Exposure to radiation, as mentioned previously, causes ionization of cells, breaking the DNA molecule into fragments which could potentially rejoin to develop mutations or cause cell death. Exposure to radiation over long periods of time also raises your risk of developing cancer. Short term exposure to radiation can cause burns or radiation sickness. Radiation sickness is a result of very large
doses of ionizing radiation. Symptoms include vomiting, fainting, hair loss, weakness, diarrhea, and reduced organ function, to name a few. Radiation exposure can also cause premature ageing and death.
THE FUTURE So having seen the more recent implications of The Manhattan Project what about the next 100 years? With high profile nuclear related accidents the public knowledge about the dangers of radioactivity is increasing. Global warming is set to continue to rise and our renewable energy options are limited. Nuclear energy looks like a good option on paper but should we look for more accepted alternatives? A recent poll by the BBC of 23 countries in 2011 showed that 30% wanted all nuclear plants to be closed, 39% said that existing plants should be used but no more should be built, 22% wanted new nuclear plants and 9% didn’t know. It seems that nuclear plants are set to stay for the moment, but what about after the next nuclear accident if there is one? The more immediate problem seems to be countries developing their own nuclear weapons. The greatest threats seem to come from North Korea and Iran. North Korea’s new “Great Leader” Kim Jong-un has only recently come to power so it remains to be seen what route North Korea will take in their nuclear programme. However a statement from the National Defence Commission stated “We declare solemnly and confidently that the foolish politicians around the world, including the puppet group in South Korea, should not expect any change from us,”. Iran has recently threatened action after more sanctions were imposed against the country over its nuclear programme. USA, EU, UN, Canada, Switzerland, Japan and Australia: all powerful countries which currently have sanctions enforced on Iran. These sanctions are wide ranging and show the impact of Iran not cooperating with the International Atomic Energy Association. Iran’s oil reserves mean it somewhat can exert control over European and North American countries.
The consequence of a Nuclear War could see much of the human populous wiped out, or most of Western Europe, certainly the theory from science and particularly chemistry has allowed us to help with our energy problem but also given humans the option of destroying life itself. In the coming years security will be key in order to prevent nuclear weapons getting into malicious hands. As we endeavour to accomplish disarmament of nuclear weapons we must also realise that it is not possible to forget knowledge, the concept of using Chemistry as a weapon will remain no matter what.
CONCLUSION Some would say that the development of weapons using radioactivity prevented World War Three between USSR and USA through mutual assured destruction. The Manhattan Project also showed the world what a group of top scientists could achieve working together with tight time constraints, it showed the world that science had the potential to advance our knowledge further than what was imaginable at that time. In a time where we all strive to be more “green” nuclear energy provides an alternative to other energy sources, even with its faults. The awareness about radioactivity has increased massively in recent years and while it has the distinct potential to destroy humanity, it also has the potential to help in a world trying to survive.
Pictures/Websites used Front - http://www.imageof.net/wallpaper/Radioactivity-Warning/ Introduction - http://www.uraniumsa.org/about/radioactivity.htm http://gk12.rice.edu/trs/science/Atom/man.htm#def Discovery - http://www.accessexcellence.org/AE/AEC/CC/images/rontgen.460.gif http://www.nobelprize.org/nobel_prizes/physics/laureates/1903/becquerel.jpg http://www.accessexcellence.org/AE/AEC/CC/images/curie.460.gif Uses - http://codered-fire.co.uk/wp-content/uploads/2011/01/smokeDetector.jpg http://www.gcsescience.com/Thickness-Control-Radioactivity.gif http://4.bp.blogspot.com/_XGFsS-NQ0cs/S7UEoNSQeqI/AAAAAAAAAAk/okqCM6JTNCY/s1600/ida-47million-year-old-fossil-01.jpg http://www.raypep.com/wp-content/uploads/2011/10/dental3.jpg http://www.dietweightloss.co.uk/images/fruit-calories.jpg http://www.nlcfn.org.uk/editorimages/radiotherapy.jpg http://images01.olx.com/ui/2/22/13/22001913_1.jpg http://www.scientificamerican.com/article.cfm?id=coal-ash-is-more-radioactive-than-nuclear-waste Dangers - http://www.encognitive.com/files/images/development-of-cancer-ionizing-radiation.gif The Future - http://news.bbcimg.co.uk/media/images/57632000/jpg/_57632805_013603124-1.jpg
