Radioactivity is a natural process where a nucleus is broken into several parts. During that process, some energy is released into the surrounding environment. A nuclear reactor will use that energy to power a turbine which will create either electricity or a torque. The classic view is that one neutron will hit an unstable nucleus, which will break into two stable parts and will also emit at the same time a few more neutrons. In nuclear reactors, the usual fuel is the uranium 235, which can undergo a fission reaction. However, most of the uranium you can find by mining it is the uranium 238, which is not fissile. It can absorb one neutron and then can form, by nuclear reactions, the plutonium 239. Another reaction that the uranium 235 can undergo is the alpha decay, producing the thorium 231. This reaction is spontaneous. The relation used for expressing its radioactivity is: N(t) = 2Noe 11/12 In this equation, No is the initial amount of nuclear material, and t₁/2 is the half-life of the element. The half-life of uranium 235 is 703.8 million years, and its current abundance is 0.7204%. It has a mass of 235,043 93 g/mol. The energy emitted by this decay is 4.679 MeV. 1) What was the abundance of the uranium 235 when the Earth formed, 4.55 billion years ago? 2) What is the total energy emitted by the uranium 235 since the Earth formation? 3) What is the mass of pure uranium 235 you would need in order to observe one alpha decay per second? 4) The uranium 235 decay chain finish at the lead. If you do assume that the thorium created by the alpha decay will change instantaneously into lead, how much lead would you obtain after 2 billion years from a block of 1 ton of uranium 235, and 1 ton of natural uranium?

Radioactivity is a natural process where a nucleus is broken into several parts. During that process, some energy is released into the surrounding environment. A nuclear reactor will use that energy to power a turbine which will create either electricity or a torque. The classic view is that one neutron will hit an unstable nucleus, which will break into two stable parts and will also emit at the same time a few more neutrons. In nuclear reactors, the usual fuel is the uranium 235, which can undergo a fission reaction. However, most of the uranium you can find by mining it is the uranium 238, which is not fissile. It can absorb one neutron and then can form, by nuclear reactions, the plutonium 239. Another reaction that the uranium 235 can undergo is the alpha decay, producing the thorium 231. This reaction is spontaneous. The relation used for expressing its radioactivity is: N(t) = 2Noe 11/12 In this equation, No is the initial amount of nuclear material, and t₁/2 is the half-life of the element. The half-life of uranium 235 is 703.8 million years, and its current abundance is 0.7204%. It has a mass of 235,043 93 g/mol. The energy emitted by this decay is 4.679 MeV. 1) What was the abundance of the uranium 235 when the Earth formed, 4.55 billion years ago? 2) What is the total energy emitted by the uranium 235 since the Earth formation? 3) What is the mass of pure uranium 235 you would need in order to observe one alpha decay per second? 4) The uranium 235 decay chain finish at the lead. If you do assume that the thorium created by the alpha decay will change instantaneously into lead, how much lead would you obtain after 2 billion years from a block of 1 ton of uranium 235, and 1 ton of natural uranium?