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 Energy research

Understanding the science

Nuclear fission and radiation protection are topics which can appear daunting if you do not understand the science behind them. In this section the more basic aspects of nuclear physics are explained to give an overview of nuclear science and technology.

1 - Nuclear basics

A small dose of basic nuclear physics link 1

Atoms – the basic building blocks of matter – are made up of a nucleus of protons and neutrons which is surrounded by electrons. Inside the nucleus, opposing forces (repulsive and attractive) act on the protons and neutrons. These forces vary in strength with the mass of neutrons and protons and the distance between them. A nucleus, when formed by bringing neutrons and protons together, is governed by the binding energy. The change in binding energy is exploited in the processes of nuclear fusion (fusing light atoms together) and nuclear fission (splitting heavy atoms), leading to the release of nuclear energy.

2 - Nuclear fission

2.1 Uncovering the mysteries of nuclear fission link 2

When a heavy atom such as uranium splits (or fissions) either spontaneously or on impact with another particle such as a neutron, energy is released. This process is known as nuclear fission. Typically, besides the main lighter atoms, fission produces two or three free neutrons, one of which can go on to cause further fission, leading to a chain reaction. The energy (or heat) thus released can be harnessed by steam turbines to produce electricity.

2.2 The physics of fission reactors link 3

Inside a nuclear reactor, the chain reaction is maintained in a safe and controlled manner. The neutrons produced during the fission reaction are too fast to be able to cause more fission of uranium-235 (U-235). They are therefore slowed down by a material (often water or graphite) called the moderator. If there are too many neutrons in the system, and the reaction needs to be slowed down, control rods, made of neutron-absorbing materials such as cadmium or boron, are inserted into the system.

2.3 Various types of fission reactors link 4

Although the basic components of reactors are the same, variations in layout, fuel type, coolant, and moderator mean that there are many different types of fission reactor in operation around the world today. These basic designs are constantly being changed and improved on, as researchers seek to make nuclear power safer and more efficient. In addition to this, radical new designs are being developed which are based on entirely new concepts.

3 - Radiation protection

3.1 Understanding radiation link 5

Radiation is ubiquitous in the environment and arises naturally from radioactive materials in the Earth's crust and from cosmic sources. Mankind has always been subjected to natural radiation and has learnt to make use of the benefits of manmade radiation. Indeed, radiation has become an invaluable tool in the modern world. It helps us to diagnose and cure human diseases, is used extensively for the purposes of sterilisation, enables the efficient control of many industrial processes, and is widely utilised in non-destructive testing.

However, we know that radiation can also have a detrimental impact on health and we must therefore protect ourselves from unnecessary exposure to ionising radiation irrespective of whether its origins are natural or artificial.

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