Introduction

Radioactivity is a natural phenomenon and natural sources of radiation are features of the environment. Radiation and radioactive substances have many beneficial applications, ranging from power generation to uses in medicine, industry and agriculture. The radiation risks to workers, patients, the public and the environment that may arise from these applications have to be assessed and, if necessary, controlled. Therefore activities such as the medical uses of radiation, the operation of nuclear installations, the production, transport and use of radioactive material, and the management of radioactive waste must be subject to standards of safety. The prime responsibility for safety must rest with the person or organization responsible for these activities.

 

What is radiation?

Radiation is energy in motion in the form of waves or streams of particles. There are many kinds of radiation all around us. Sound and visible light are familiar forms of radiation. Other types include ultraviolet radiation, which produces a suntan, infrared radiation, which is a form of heat energy, and radio and television signals. When most people hear the word radiation, they often think of atomic energy, nuclear power, and radioactivity. The energy in this kind of radiation can cause changes in atoms, creating electrically charged atoms which we call ions. Radiation which produces ions is called ionising radiation. All life has evolved in an environment filled with ionising radiation. However, unlike heat and light, ionising radiation is invisible to our senses. You can’t feel, see, hear, taste, or smell it. Before 1895 we didn’t even know it existed.

What is ionising radiation and where does it come from??

Ionising radiation is produced by radioactive materials when they decay. The radiation is spontaneously emitted from the atoms in the form of particles or waves of energy. The main types of ionising radiation are alpha and beta particles, gamma and X-rays and neutrons. All types of ionising radiation can cause physical damage to living cells, which may result in injury to living tissues and organs, and cancers, and cause genetic damage to present and future generations.

Alpha Radiation Alpha particles consist of two protons and two neutrons, and carry a positive charge. Alpha particles are barely able to penetrate skin and can be stopped completely by a sheet of paper.			Beat Radiation Beta radiation consists of fast moving electrons ejected from the nucleus of an atom. More penetrating than alpha radiation, beta radiation is stopped by a book or human tissue.
X-Rays X-rays are a form of radiation produced mainly by artificial means rather than by naturally occurring radioactive substances.			Gamma Radiation Gamma radiation is a very penetrating type of radiation. It is usually emitted immediately after the ejection of an alpha or beta particle from the nucleus of an atom. It can pass through the human body, but is almost completely absorbed by denser materials such as concrete or lead.
			Neutrons Less common, neutron radiation occurs when neutrons are ejected from the nucleus by nuclear fission and other processes.

What are the natural sources of ionising radiation?

The nuclear chain reaction is an example of nuclear fission. Ionising radiation is a natural part of the world. You receive small amounts of radiation from uranium and other radioactive elements which are found everywhere in rocks and soil. As these naturally occurring radioactive materials decay and change, some of them produce a radioactive gas called radon, which is present in small amounts in the air we breathe.

How do you measure ionising radiation?

Ionising radiation can only be detected and measured using special types of instruments and detectors. Many types of instruments have been developed to measure the different types of ionising radiation, e.g. the Geiger counter, neutron, alpha, beta and gamma counters. Ionising radiation is measured in units referred to as “Sieverts”. For example, on average each individual receives about three millisieverts (mSv) per year from natural background radiation sources.

What are the artificial sources of radiation?

The production of radiation by artificial means began in 1895 when X-rays were discovered. In the following two decades many of the naturally occurring radioactive elements were identified. Scientists devised theories to explain the structure of atoms and the forces at work inside them. Putting these theories to work, they discovered ways to create and control artificial sources of radiation. In 1942, the first nuclear reactor went into service in the United States and five years later, Canadian scientists started up Canada’s first reactor at Chalk River, Ontario. With the means to produce radiation artificially, scientists inherited a responsibility to control its use and to understand its effects. Those first pioneers of radiation knew little about the harm it could cause, but they soon realized that ionising radiation could have damaging effects upon living organisms.

What are the biological effects of radiation?

When ionising radiation penetrates living tissues the chemical structure of living cells can change. If enough radiation is absorbed, cells may be altered or destroyed. Living tissue has a great ability to repair itself, but in some cases these cellular changes can develop into cancer. They could also cause genetic damage or birth defects. These effects are most likely when a person is exposed to high or moderate levels of radiation. However, exposure to a large amount of radiation would be unusual and unlikely. Even exposure to moderate levels occurs only under the rarest of circumstances.

What are radiation protection principles for the environment?

People who work in areas with radioactive materials, such as uranium mines, reactors, or radiology units at hospitals, have a greater need for protection. Three primary means are used to protect them from radiation: time, distance, and shielding.

Time The shorter the period of exposure to radiation, the less radiation will be absorbed. When possible, people who work in radiation areas must reduce the time that they spend near radioactive sources.		Distance The intensity of ionising radiation, like the radiation of visible light, rapidly decreases with distance. By increasing the distance from a radioactive source, the amount of exposure is reduced.		Shielding People working with or near radiation sources are protected by barriers which include shielding of lead, concrete, and other heavy materials. Protective clothing provides protection against some types of radiation. People who work near radioactive materials routinely wear devices called dosimeters. These devices monitor and record ionising radiation doses to guard against the possibility of over exposures.

What to do when there is an imminent radiation hazard?

Why take iodine tablets?

In an accident, a lot of radioactive iodine may be released into the air. Most of the inhaled iodine is stored in the thyroid gland. Hence the thyroid gland receives a considerably high radiation dose. The radiation emitted by radioactive iodine may cause tumours or hypofunction in the thyroid gland. The accumulation of radioactive iodine in the thyroid gland can be efficiently reduced by taking a iodine tablet at the right moment. Non-radioactive potassium iodine saturates the thyroid gland. Consequently, radioactive iodine cannot be absorbed in the thyroid gland. Radioactive iodine is passed from the body with urine. The tablet should be taken 1 – 6 hours before the radioactive cloud is transferred to the area. One iodine dose provides protection for about 24 hours.

What is radioactive material and where does it come from?

Radioactive materials contain elements whose atoms are unstable (changeable) and emit energy in the form of ionising radiation. There are two sources of radioactive materials, those that are naturally occurring (i.e. they are freely found in nature in solids, water, air and all living organisms) and those that are man made (e.g. fuel for nuclear reactors, spent fuel from nuclear reactors and radioactive sources for medical, scientific and industrial use.

Radiation Protection

It has long been recognized that large doses of ionizing radiation can damage human tissues. Over the years, as more was learned, scientists became increasingly concerned about the potentially damaging effects of exposure to large doses of radiation. The need to regulate exposure to radiation prompted the formation of a number of expert bodies to consider what needs to be done.