Whats Radiation

Radiation



What is radiation?
What types of radiation are associated with nuclear energy?
What are the sources of radiation?
How is radiation exposure measured?
What are the effects of radiation?
Why do we need radioactive materials?
What controls are there on radiation created by industries?
What safety measures are in place for those who work around radioactive materials?
What is radiation?


All matter is composed of atoms and many atoms are unstable. In fact, over half of the elements in the periodic table including uranium, are in a constant process of rearranging themselves. This is not something that humanity can control.
When the nucleus of an atom attempts to become more stable, it releases energy, known as radiation. Once this happens the original atom changes into a new atom. In some instances, a new element is formed and in other cases, a new form of the original element, called an isotope, appears. The spontaneous change in the nucleus of an unstable atom that results in the emission of radiation is called radioactivity and this process of change is often referred to as the decay of atoms.
Radioactive decay is described in half-lives. The time required for 50% of a given radioactive material to disintegrate (or decay) and become a new element or isotope (i.e. lose one-half of its original level of radioactivity) is known as a half-life. In other words, after one half-life only half of the original material is still around, and after two half-lives only 25% of the original material is still in existence. The half-lives of various substances differ widely, from small fractions of a second to billions of years.
Radiation is energy in the form of sub-atomic particles (protons, neutrons and electrons) or electromagnetic waves. When radiation has enough energy to remove the electrons of atoms with which it interacts, it causes the atoms to become charged, or ionized, and it is called ionizing radiation. Ionizing radiation occurs in several forms - as alpha particles, beta particles or neutrons, or in the form of electromagnetic radiation (gamma rays and X-rays). However, people routinely encounter electromagnetic radiation that is not ionizing. It makes up our visible light, radio and television signals, emanates from our computer screens and heats our food in microwave ovens. Yet, because of their low energy, all of these examples are classified as non-ionizing radiation.
What types of radiation are associated with nuclear energy?


The types of radiation associated with nuclear energy are alpha particles, beta particles, gamma rays and neutron radiation. Each type can interact with matter, including the human body, but all can be effectively stopped by different types of material.
Alpha particles consist of two protons and two neutrons, identical to the nucleus of a helium atom. A sheet of paper or a person's surface layer of skin will stop them. Alpha particles are only considered hazardous to a person's health if they are ingested or inhaled and thus come into contact with sensitive cells such as in the lungs, liver and bones.
A source of alpha particles is radon gas, a colourless and odourless gas formed from the radioactive decay of radium which in turn is one of the products of the uranium decay chain. It is not radon itself that is a health concern, but the radioactive products into which it decays. Radon, being a gas, is simply the vehicle by which members of the uranium decay chain can enter the lungs. Outside the body, radon is not a concern since the alpha particles it emits cannot penetrate the skin.
Beta particles are electrons emitted from the nuclei of many fission products. They can travel a few feet in air but can usually be stopped by clothing or a few centimeters of wood. They are considered hazardous mainly if ingested or inhaled, but can cause radiation damage to the skin if the exposure is large enough.
Neutrons which are contained in the nucleus of an atom can be expelled during fission. They interact weakly with matter and are very penetrating - not easy to stop. Neutron radiation typically occurs inside nuclear reactors but water and concrete provide effective shielding.
Gamma rays are a form of electromagnetic radiation (like light, radio, and television) that come from the nucleus of a radioactive atom. They penetrate matter easily and are best stopped by water or thick layers of lead or concrete. Gamma radiation is hazardous to people inside and outside of the body.
Beta particles, neutrons and gamma rays are produced during the fission process. First, when a uranium nucleus captures a neutron and fissions, electrons, gamma rays, and neutrons are emitted instantaneously. Second, the new fragments formed from the fission of a uranium nucleus emit radiation. Most of this radiation consists of electrons and gamma rays. Third, during fission ordinary materials can absorb neutrons and subsequently emit radiation. Many materials can be made radioactive by exposing them to neutrons. For example, the iron used in the structural supports inside reactors becomes radioactive. Most radioactive materials made this way will emit electrons and gamma rays, but some will emit neutrons.

Alpha and beta particles, neutrons and gamma rays are types of radiation associated with nuclear energy.



What are the sources of radiation?


Radiation is all around us and we are exposed to some form of it every day of our lives. Most natural substances contain radioactive material - soil and rocks, rivers and oceans, food and drinks, our own bodies. A typical backyard, with dimensions of 10 metres by 10 metres and a soil depth of one metre, contains approximately 300 grams of uranium. A typical backyard is therefore slightly radioactive. While uranium emits radiation it is not the only source.
More than 85% of all radiation to which people are exposed occurs naturally, but radiation is also created by our own activities. Take for example the X-rays generated for medical uses. These represent about 12% of the radiation to which we are regularly exposed. Radiation from the nuclear industry is less than 1% of all radiation. A person living at the boundary of a nuclear power plant would receive less radiation each year from living there than received from a single round-trip flight from Vancouver to Halifax.
How is radiation exposure measured?


The principal result of radiation passing through something such as human tissue is the transfer of energy. Radiation loses energy as it interacts with matter and the matter gains this energy. So the unit used to measure radiation is based on the amount of energy absorbed. Radiation exposure, also referred to as dose, is measured in grays (Gy).
Some types of ionizing radiation are more damaging than others. For example, alpha particles tend to deposit lots of energy over very short distances and therefore cause significant damage if they travel through sensitive biological tissue. Neutrons on the other hand, interact very infrequently with atoms but when they do, the effects can be significant. For these significant reasons, different types of radiation are given different weighting factors. These factors are used to relate their physically deposited energy to the biological significance of the damage they cause.
The unit used to measure this biological significance is the sievert (Sv). The sievert is equal to the amount of energy deposited in grays, multiplied by the relevant weighting factor. The higher the factor, the greater the reckoned damage. For alpha particles the factor is 20; for neutrons it is in the 5 - 20 range varying with their energy; for gamma rays and beta particles, the factor is 1.
When estimating damage, several factors are to be taken into consideration such as exposure to the whole body or only a part, and if so, which part. Different tissues (e.g. lungs, liver, bones) have different sensitivities to radiation damage. For example, the most biologically significant radiation emitted by uranium are alpha particles. These cannot even penetrate a person's skin, so exposure to uranium dust on the skin is generally not hazardous. But if the same dust is inhaled and ends up next to sensitive lung tissue it can be damaging to the cells exposed.

Radiation is an invaluable method of diagnosing injuries and diseases, which it can also cure as well. For example, radiation therapy for cancer helps save many lives. This patient is receiving radiation. (Photo courtesy of the Nuclear Energy Institute)


What are the effects of radiation?


Exposure to radiation and the effects of exposure continue to be subject to controversy. The effects of radiation depend on the dose, which is the amount of radiation a person's body absorbs. Low doses such as those received from the environment, normal work activity exposures, exposures to manufactured products containing radioactive materials — like smoke detectors, and medical procedures like X-rays, have no noticeable effects. Predicting the long-term effects of low radiation exposures is therefore difficult. Most people exposed to low doses do not suffer any harm — just as not everyone who rides in a car will be in an accident, not everyone who is exposed to radiation will develop cancer. However, because there is not enough scientific evidence to conclude what the long-term risks of exposure to low levels of radiation may be, a conservative assumption is that all exposures to radiation may pose some risk.
Studies of animals and humans exposed to high levels of radiation indicate that high doses of radiation can increase the rate of cancer and genetic damage in the body and can have an immediate effect. This may include reddening of the skin, nausea, or even death (at very high doses).
The ability of very high doses of radiation to kill cells is used in cancer treatment. These doses are directed at the cancerous tumour to try and destroy the cancer cells, while every effort is made to leave the normal body tissues around it undamaged.

Nuclear medicine techniques are used to conduct millions of procedures and laboratory tests each year. At least 80% of all new drugs are tested with radioactive materials to help prove that they are safe and effective. Radiation is used to sterilize medical supplies such as syringes, sutures, and clothing worn by health-care workers.


Why do we need radioactive materials?


Radiation and radioactive materials affect our lives in some way every day. Over 400 reactors worldwide use radioactive uranium as the fuel to generate electricity.
Radiation is also used to check for flaws when manufacturing jet engines, to toughen rubber in radial tires, to eliminate static in photocopiers and to scan luggage at airports. Radioactive materials are used in industry to verify the quality of steel, in the production of coated paper, in highway construction to test the density of road surfaces, to test the strength of welds on pipes and in museums to authenticate paintings and art objects.
In agriculture, radioactive materials are used to develop hardier crops, to control insect pests, and to study such things as plant absorption of fertilizer to optimize the rate of application and avoid unnecessary pollution of soil and the water table. Radioactive materials are also used in consumer products such as smoke detectors to improve their performance.
What controls are there on radiation created by industries?


Most countries have their own regulations concerning radiation protection. Many of these regulations are based on the recommendations of the International Commission on Radiological Protection (ICRP), an independent non-profit organization established to provide recommendations and guidance on all aspects of protection against ionizing radiation. The ICRP's main recommendations are that all exposures shall be kept as low as reasonably achievable, with social and economic factors considered, and that dose limits to individuals shall not exceed specific values over specified periods of time.
In Canada, radiation protection is regulated by the Canadian Nuclear Safety Commission (CNSC) which is a federal agency answerable to the Canadian parliament. The CNSC exercises control through a regulatory system that establishes the health, safety, security, and environmental standards for the handling and use of nuclear substances. The CNSC licenses only those activities that can meet and maintain those strict standards.
The use or disposal of radioactive material in Canada must be licensed, and the facilities where radioactive substances are handled are regulated and inspected. This applies to hospitals and clinics using radioisotopes in diagnosis or cancer treatment, uranium mines and refineries, oil companies using radioactive materials for exploration and nuclear power plants.

Underground monitors such as this one at Cameco's McArthur River mine continually check the level of radon and display results like a traffic light. The green light indicates the area is safe.


What safety measures are in place for those who work around radioactive materials?


Radiation has been studied extensively, is easily measured and can be safely controlled. People who work in areas where radiation is a concern wear radiation measuring devices to monitor exposure levels. In work areas such as certain areas in underground uranium mines, various monitoring and warning systems are in place.
Wherever there are concerns about radioactivity, every effort is made to minimize exposure. A person's radiation exposure can be reduced by:
Distance - putting a greater distance between the person and the source of radiation
Shielding - placing something that will absorb the radiation between the person and the source
Time - reducing the amount of time the person is exposed
Cameco utilizes all three of these factors to ensure safety at our uranium mining, milling and processing operations. As well, work areas are continuously monitored for radiati