Nuclear reactions
Nuclear fission can be a of energy. A large nucleus can split up into two smaller . When a uranium-235 nucleus absorbs a it immediately splits into daughter nuclei. Two or three are also released. The daughter nuclei and neutrons are at high speeds and so have a lot of energy.
The neutrons produced in the of uranium-235 can be absorbed by other uranium-235 . If all of the are absorbed, an nuclear chain reaction happens. This is what happens in a .
A can be controlled if only of the neutrons released is by another uranium-235 nucleus. This is the type of reaction in a – the amount of produced is regulated.
Nuclear power
In an nuclear reactor the reaction is controlled by and moderators. Control rods the extra produced in the fission of uranium-235. When the reaction needs to be down, the control rods are moved further into the . A slows down neutrons to make it that they will be absorbed by another uranium-235 .
is made into pellets that are contained in .The rods are put in the . Radioactive build up in the reactor core, along with other radioactive that are formed when fuel and other materials in the core absorb .These materials are called radioactive .
The released in fission is to a coolant. The is pumped to a heat exchanger where it is used to produce . The steam drives a , which turns a generator. The transfers energy to energy.
Fusion – our future?
Nuclear fusion occurs when nuclei combine to form ones. One fusion is the combination of nuclei to form helium. This is the source of energy for . The reaction of two of hydrogen is being investigated as an energy on Earth. The reaction produces , a neutron and a lot of .
New scientific are not accepted until they have been by the scientific community. Other review the report of the method – this is called a . They must be able to get the same as the original scientists when they carry out the .
Changing ideas
When first worked with ionising , they did not take the safety precautions that we do now. Ideas about radiation were new and they did not know about the and dangers.
As scientists worked with ionising radiation more and more, the risks and became more obvious. They touched radioactive with their hands and their skin. People who worked with ionising radiation developed . We now know that ionising radiation can the DNA inside a cell and cause a .
We now know how to the risks of damage and mutations by taking precautions. The risks are reduced by handling sources with , not sources at people and storing sources in a -lined container.
Nuclear waste
There are three types of from nuclear power stations – low, intermediate and high. -level waste is very radioactive and remains so for about 50years. -level waste is less but is so for tens of thousands of years. -level waste is slightly radioactive.
High-level waste is until it is less radioactive and has become intermediate-level waste. -level waste is stored in concrete and steel containers. Low-level waste is compacted and in special sites. Some of the options for of radioactive waste include it at sea, it into space and storing it deep .
An of nuclear power is that is does not produce when electricity is generated. Disadvantages are that it produces radioactive which has to be stored for tens of of years. Some people think that nuclear power is because of the of accidents.