Presentation on theme: "RADIOACTIVITY. Pierre Curie was already a famous scientist before he married Marie Sklodowska in 1895. This famous couple did not only find true love,"— Presentation transcript:
Pierre Curie was already a famous scientist before he married Marie Sklodowska in 1895. This famous couple did not only find true love, they also discovered radium and polonium. For their groundbreaking research in radioactivity, the couple were awarded the 1903 Nobel Prize in physics. It was Marie Curie who coined the term "radioactivity", and in her honor, the 1910 Radiology Congress chose the curie as the basic unit of radioactivity. Pierre died from being run over by a horse drawn wagon, but Marie continued their research, and was eventually awarded a second Nobel Prize, the 1911 prize for Chemistry. She died in 1934, suffering from pernicious anemia which had undoubtedly been the result of years of radiation exposure.
RADIOACTIVITY ? The atoms making up matter are generally stable, but some of them are spontaneously transformed by emitting radiations which release energy. This is called radioactivity.
There are three types of radiations corresponding to three types of radioactivity. alpha radioactivity corresponds to the emission of a helium nucleus, a particularly stable structure consisting of two protons and two neutrons, called an a particle. beta radioactivity corresponds to the transformation, in the nucleus: - either of a neutron into a proton, beta - radioactivity, characterised by the emission of an electron e- - or of a proton into a neutron, beta + radioactivity, characterised by the emission of an anti-electron or positron e+. It only appears in artificial radioactive nuclei produced by nuclear reactions. gamma radioactivity, unlike the other two, is not related to a transmutation of the nucleus. It results in the emission, by the nucleus, of an electromagnetic radiation, like visible light or X-rays, but more energetic. gamma radioactivity can occur by itself or together with alpha or beta radioactivity
When we talk about the alpha decay then it means that a twice positive charged heliumion (helium atomic nucleus) is emited from the atomic nucleus. Then we find two protons ans two neutrons less in this atomic nucleus, so it is lighter. The alpha radiation is the most dangerous of the three types of radiation, but a sheet of paper is enough to protect oneself. The skin protects us also from alpha radiation
There are two types of the beta decay. The one is the beta minus decay and the other is the beta plus decay. When we talk about the beta minus decay a neutron decays into a proton, an electron and an antineutrino. The electron and the antineutrino are emited. The radioactive particle is the electron. The number of nucleons do not change, but we have got one proton more than before the decay. 2 or 3 cm of wood are enough to protect oneself.
When we talk about the beta plus decay a proton decays into a neutron, a positron (the antiparticle of the electron) and a neutrino. The positron and the neutrino are emited. The radioactive particle is the positron
When we talk about the gamma decay high-energy electromagnetic waves are emited from the atomic nucleus. This waves are photons, which have got a higher frequency and less wave long than light. A gamma decay can happen after an alpha decay or a beta decay, because the atomic nucleus is very energitic.
RADIATION AND ITS CHARGE ALPHA BETA – BETA+ GAMMA X-RAYS +2 +1 0
RADIATION PENETRATION Radiation is absorbed by the material through which it passes. During radioactive decay the alpha or beta particles, and the gamma rays that are given off can all penetrate matter, although alpha- particles can be stopped by a piece of paper or the human skin, whereas beta-particles require a few millimetres of metal to absorb them. Gamma-rays, on the other hand, are very penetrating and require lead shields or a metre of concrete to stop them. The dose of radiation received is the amount of energy absorbed per unit mass of matter. Exposure to ionizing radiation can be harmful as the radiation can cause cancers in the living population and genetic changes that may produce heritable defects in future generations
Alpha particles can usually be stopped by a very thin barrier. Radioisotopes emitting alpha particles are usually not hazardous outside the body, but they can cause damage if ingested. Betas (streams of electrons) can pass through a hand, but are usually stopped by a modest barrier such as a few millimeters of aluminum, or even a layer of clothing. As with alphas, beta particles are more hazardous if inhaled or ingested. Gammas can be very penetrating and can pass through thick barriers. Several feet of concrete would be needed to stop some of the more energetic gammas. A natural gamma source found in the environment (and in the human body) is 40 K, an isotope of potassium. Neutrons are also very penetrating. Some elements, like hydrogen, capture and scatter neutrons. Water is commonly used as a neutron radiation shield.
THE HALF LIFE of a radioisotope is the time that it takes for half the atoms in the sample to decay. Although we cannot predict when a particular nucleus will decay, no matter how many atoms there are, the halving of the number always takes the same time
A decay chain Uranium-238 has a half life of 4½ million years and emits alpha- particles. It decays to produce thorium-234 which has a half life of 24 days and produces beta-particles, to protactinium-234 with a half life of 7 hours emitting beta-particles, to uranium-234 with a half life of a quarter of a million years which decays by emitting alpha-particles... and so on until it finally creates the stable isotope lead-206.
CARBON DATING The rate at which 14 C decays is absolutely constant. Given any set of 14 C atoms, half of them will decay in 5730 years. Since this rate is slow relative to the movement of carbon through food chains (from plants to animals to bacteria) all carbon in biomass at earth's surface contains atmospheric levels of 14 C. However, as soon as any carbon drops out of the cycle of biological processes - for example, through burial in mud or soil - the abundance of 14 C begins to decline. After 5730 years only half remains. After another 5730 years only a quarter remains. This process, which continues until no 14 C remains, is the basis of carbon dating
NUCLEAR ENERGY FISSION Splitting the Uranium Atom: U ranium is the principle element used in nuclear reactors and in certain types of atomic bombs. The specific isotope used is 235 U. When a stray neutron strikes a 235 U nucleus, it is at first absorbed into it. This creates 236 U. 236 U is unstable and this causes the atom to fission
In a nuclear reactor, however, the last thing you (and the rest of the world) want is all your atoms splitting at once. But the reactor core needs to be slightly supercritical so that plant operators can raise and lower the temperature of the reactor. The control rods give the operators a way to absorb free neutrons so operators can maintain the reactor at a critical level.To turn nuclear fission into electrical energy, the first step for nuclear power plant operators is to be able to control the energy given off by the enriched uranium and allow it to heat water into steam