Description of the Experience
The principle of a nuclear reaction is already known to the students. Here it is applied to uranium, specifically to the uranium isotope 235. The core is very heavy because it contains, in a negligible area, 235 parts. The reaction is such that the core of uranium is bombarded with neutrons. The result of this collision creates two new elements -barium and krypton, and an additional three quick neutrons. Each of these neutrons starts the same response and the whole reaction is implemented as an immediate downfall of a huge avalanche. The ongoing phenomena are a sound wave, shock wave, an extremely high temperature and light radiation.
This reaction was used in a bomb that was dropped down in 1945 on Hirosima. The principle of the bomb is quite a primitive one. There are two smaller quantities of uranium placed inside of the bomb. They are separated by a mechanical barrier and then these two pieces of uranium are connected together at a particular place over the earth's surface. This way there is a sufficient amount of fissile material to make the bomb explode. The most dangerous phenomenon is the emergence of a radioactive radiation, which can not be registered by a man.
Today the topic does not relate to the secondary school students. If they even know there was the World War II. they still do not have an idea how long time ago it was. You can only bring it closer to them by a description of the whole project. I tell them why the American scientists were involved in this project and why they then informed the U.S. President about the so called secret weapon that Hitler was talking about. First nuclear experiment was carried out with a bomb in New Mexico. Its results shocked the participants that were present, everything made of metal evaporated. The original target of the real nuclear bomb test was the Japanese city of Kokura, but the weather did not allow dropping the bomb there. The substitute target was Hirosima. Since then in Japan it is often said to have “luck from Kokura". The aircraft, which was carrying this bomb, was named after the pilot's mother, Enola Gay. Neither the pilot, nor his colleague on the plane knew what they carried and what effect it will have. The bomb immediately killed 170,000 people. Those who were near ground zero literally evaporated. Others were continuously carried to the hospital where the doctors were baffled because they did not know what has happened and what could be the cause of such huge disaster. The only thing that they could provide was antibiotics. The consequences of this explosion are still reflected in the present, because there was a genetic damage to the Japanese population.
The moral question of this terrible event is dubious. Students are being heard of different opinions because the Japanese government also had a large share on the event. The students are shocked by the photographs of this event. At least for the moment they realize that in the world there is something else then their cell phones, computers and fast cars.
Exactly the same reaction as in a nuclear bomb is carried out in a nuclear reactor. The difference is that it is maintained at the desired level in order to prevent the explosion. For us the most well known catastrophe of this kind is the Chernobyl, where there was a crash in 1986 but this is already a subject for another class.
Experience with this lesson I evaluate positively.
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Date: 2014.10.16
Posted by Silviana Ivanova (Bulgaria)
Very good lesson of the colleague Fabianova! The example used for fission of uranium is very strong and no one can remain calm to the plight of people affected by radioactive emissions. In the subject of the atomic nucleus, I touch on this topic emphasizing a closer problem for Bulgaria- the Chernobyl accident.
