The book is intended to meet the requirements of a wide range of readers who are involved, either directly or indirectly, with ionizing radiation, including doctors, dentists, research workers, nuclear plant designers and operators. In particular the authors believe that the work is suitable for the health physics monitors and technicians who are concerned with the day-to-day control of radiation hazards in nuclear power stations, research establishments, hospitals and in industry.
In the UK, the generally accepted standard of training in this type of work is that set by the City and Guilds of London Institute courses in Radiation Safety Practice which are held in various centers. The chapters of the book dealing with the general aspects of health physics are aimed a this standard.
Later chapters dealing with particular aspects of the subject are more detailed. In the second half of the book there are individual chapters on the more specialized topics of nuclear reactor health physics, problems associated with X-rays and radiography, health physics in medicine, the disposal of radioactive waste and radiological emergencies.
Chapters are also presented on legislation and on the organization of health physics. Country of publication.
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- Introduction to Radiation Safety.
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Introduction to radiation safety and monitoring.
Through further experimentation including non-phosphorescent uranium, he instead came to recognize that it was the material itself that gave off the rays. Although it was Henri Becquerel that discovered the phenomenon, it was his doctoral student, Marie Curie, who named it: radioactivity. She would go on to do much more pioneering work with radioactive materials, including the discovery of additional radioactive elements: thorium, polonium, and radium.
She was awarded the Nobel Prize twice, once alongside Henri Becquerel and her husband Pierre in Physics for their work with radioactivity, and again years later in Chemistry for her discovery of radium and polonium. She also conducted pioneering work in radiology, developing and deploying mobile X-ray machines for the battlefields of World War I. Free radicals may form compounds, such as hydrogen peroxide, which may initiate harmful chemical reactions within the cells. As a result of these chemical changes, cells may undergo a variety of structural changes which lead to altered function or cell death.
Exposure of Living Tissue to Non-ionizing Radiation A quick note of caution about non-ionizing radiation is probably also appropriate here. Non-ionizing radiation behaves exactly like ionizing radiation, but differs in that it has a much greater wavelength and, therefore, less energy. Although this non-ionizing radiation does not have the energy to create ion pairs, some of these waves can cause personal injury. Anyone who has received a sunburn knows that ultraviolet light can damage skin cells. Non-ionizing radiation sources include lasers, high-intensity sources of ultraviolet light, microwave transmitters and other devices that produce high intensity radio-frequency radiation.
Radiosensitivity is the relative susceptibility of cells, tissues, organs, organisms, or other substances to the injurious action of radiation. In general, it has been found that cell radiosensitivity is directly proportional to the rate of cell division and inversely proportional to the degree of cell differentiation. In short, this means that actively dividing cells or those not fully mature are most at risk from radiation. The most radio-sensitive cells are those which:.
Reference: Rubin, P. There are four measures of radiation that radiographers will commonly encounter when addressing the biological effects of working with X-rays or Gamma rays.
Introduction to radiation safety and monitoring.
These measures are: Exposure, Dose, Dose Equivalent, and Dose Rate A short summary of these measures and their units will be followed by more in depth information below. For the types of radiation used in industrial radiography, one roentgen equals one rad and since the quality factor for x- and gamma rays is one, radiographers can consider the Roentgen, rad, and rem to be equal in value.
Exposure Exposure is a measure of the strength of a radiation field at some point.
It is a measure of the ionization of the molecules in a mass of air. It is usually defined as the amount of charge i. The most commonly used unit of exposure is the Roentgen R.
Specifically, a Roentgen is the amount of photon energy required to produce 1. A radiation field of one Roentgen will deposit 2. The main advantage of this unit is that it is easy to directly measure with a survey meter. The main limitation is that it is only valid for deposition in air.
A rad is defined as a dose of ergs of energy per gram of the given material. The SI unit for absorbed dose is the gray Gy , which is defined as a dose of one joule per kilogram. The size of the absorbed dose is dependent upon the the intensity or activity of the radiation source, the distance from the source to the irradiated material, and the time over which the material is irradiated.
Dose Equivalent When considering radiation interacting with living tissue, it is important to also consider the type of radiation. Although the biological effects of radiation are dependent upon the absorbed dose, some types of radiation produce greater effects than others for the same amount of energy imparted. For example, for equal absorbed doses, alpha particles may be 20 times as damaging as beta particles. The quality factor Q is a factor used in radiation protection to weigh the absorbed dose with regard to its presumed biological effectiveness.
Radiation with higher Q factors will cause greater damage to tissue. The rem is a term used to describe a special unit of dose equivalent. Rem is an abbreviation for roentgen equivalent in man. The SI unit is the sievert SV ; one rem is equivalent to 0. Doses of radiation received by workers are recorded in rems, however, sieverts are being required as the industry transitions to the SI unit system.
Dose Rate The dose rate is a measure of how fast a radiation dose is being received. Knowing the dose rate, allows the dose to be calculated for a period of time. Fore example, if the dose rate is found to be 0. The occurrence of particular health effects from exposure to ionizing radiation is a complicated function of numerous factors including:. The effects of ionizing radiation upon humans are often broadly classified as being either stochastic or nonstochastic. These two terms are discussed more in the next few pages.
Stochastic effects are those that occur by chance and consist primarily of cancer and genetic effects. Stochastic effects often show up years after exposure. As the dose to an individual increases, the probability that cancer or a genetic effect will occur also increases. However, at no time, even for high doses, is it certain that cancer or genetic damage will result. Similarly, for stochastic effects, there is no threshold dose below which it is relatively certain that an adverse effect cannot occur.
In addition, because stochastic effects can occur in individuals that have not been exposed to radiation above background levels, it can never be determined for certain that an occurrence of cancer or genetic damage was due to a specific exposure. While it cannot be determined conclusively, it often possible to estimate the probability that radiation exposure will cause a stochastic effect. The probability for genetic defects is even less likely to increase for workers exposed to radiation. Studies conducted on Japanese atomic bomb survivors who were exposed to large doses of radiation found no more genetic defects than what would normally occur.
Radiation-induced hereditary effects have not been observed in human populations, yet they have been demonstrated in animals. If the germ cells that are present in the ovaries and testes and are responsible for reproduction were modified by radiation, hereditary effects could occur in the progeny of the individual. Exposure of the embryo or fetus to ionizing radiation could increase the risk of leukemia in infants and, during certain periods in early pregnancy, may lead to mental retardation and congenital malformations if the amount of radiation is sufficiently high.
Unlike stochastic effects, nonstochastic effects are characterized by a threshold dose below which they do not occur.
In other words, nonstochastic effects have a clear relationship between the exposure and the effect. In addition, the magnitude of the effect is directly proportional to the size of the dose. Nonstochastic effects typically result when very large dosages of radiation are received in a short amount of time. These effects will often be evident within hours or days.