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Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an atomic number that is reduced by two. An alpha particle is identical to the nucleus of a helium-4 atom, which consists of two protons and two neutrons. It has a charge of +2 e and a mass of 4 u. For example, uranium-238 decays to form thorium-234.
Background radiation is a measure of the level of ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources.
Radioactive waste is a type of hazardous waste that contains radioactive material. Radioactive waste is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, rare-earth mining, and nuclear weapons reprocessing. The storage and disposal of radioactive waste is regulated by government agencies in order to protect human health and the environment.
Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes. The amount and spread of fallout is a product of the size of the weapon and the altitude at which it is detonated. Fallout may get entrained with the products of a pyrocumulus cloud and fall as black rain. This radioactive dust, usually consisting of fission products mixed with bystanding atoms that are neutron-activated by exposure, is a form of radioactive contamination.
Radioactive decay is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha decay, beta decay, and gamma decay, all of which involve emitting one or more particles. The weak force is the mechanism that is responsible for beta decay, while the other two are governed by the electromagnetic and strong forces.
In nuclear science, the decay chain refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations. It is also known as a "radioactive cascade". Most radioisotopes do not decay directly to a stable state, but rather undergo a series of decays until eventually a stable isotope is reached.
Ionizing radiation, including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. The particles generally travel at a speed that is 99% of that of light, and the electromagnetic waves are on the high-energy portion of the electromagnetic spectrum.
A radioisotope thermoelectric generator is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect. This type of generator has no moving parts.
Radioactive contamination, also called radiological contamination, is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids, or gases, where their presence is unintended or undesirable.
A betavoltaic device is a type of nuclear battery which generates electric current from beta particles (electrons) emitted from a radioactive source, using semiconductor junctions. A common source used is the hydrogen isotope tritium. Unlike most nuclear power sources which use nuclear radiation to generate heat which then is used to generate electricity, betavoltaic devices use a non-thermal conversion process, converting the electron-hole pairs produced by the ionization trail of beta particles traversing a semiconductor.
There are two natural isotopes of iridium (77Ir), and 34 radioisotopes, the most stable radioisotope being 192Ir with a half-life of 73.83 days, and many nuclear isomers, the most stable of which is 192m2Ir with a half-life of 241 years. All other isomers have half-lives under a year, most under a day. All isotopes of iridium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.
Lead shielding refers to the use of lead as a form of radiation protection to shield people or objects from radiation so as to reduce the effective dose. Lead can effectively attenuate certain kinds of radiation because of its high density and high atomic number; principally, it is effective at stopping gamma rays and x-rays.
Radium and radon are important contributors to environmental radioactivity. Radon occurs naturally in the environment as a result of decay of radioactive elements in the soil and it can accumulate in houses built on areas where such decay occurs. Radon is among the major causes of cancer; it is estimated to contribute to about 2% of all cancer related deaths in Europe.
Strontium-90 is a radioactive isotope of strontium produced by nuclear fission, with a half-life of 28.8 years. It undergoes β− decay into yttrium-90, with a decay energy of 0.546 MeV. Strontium-90 has applications in medicine and industry and is an isotope of concern in fallout from nuclear weapons, Nuclear weapons testing, and nuclear accidents.
Radiobiology is a field of clinical and basic medical sciences that involves the study of the action of ionizing radiation on living things, especially health effects of radiation. Ionizing radiation is generally harmful and potentially lethal to living things but can have health benefits in radiation therapy for the treatment of cancer and thyrotoxicosis. Its most common impact is the induction of cancer with a latent period of years or decades after exposure. High doses can cause visually dramatic radiation burns, and/or rapid fatality through acute radiation syndrome. Controlled doses are used for medical imaging and radiotherapy.
Radon-222 is the most stable isotope of radon, with a half-life of approximately 3.8 days. It is transient in the decay chain of primordial uranium-238 and is the immediate decay product of radium-226. Radon-222 was first observed in 1899, and was identified as an isotope of a new element several years later. In 1957, the name radon, formerly the name of only radon-222, became the name of the element. Owing to its gaseous nature and high radioactivity, radon-222 is one of the leading causes of lung cancer.
The committed dose in radiological protection is a measure of the stochastic health risk due to an intake of radioactive material into the human body. Stochastic in this context is defined as the probability of cancer induction and genetic damage, due to low levels of radiation. The SI unit of measure is the sievert.
Herbert Mermagen noted x-ray pioneer and medical physicist was born on 19 April 1907 and died at the age of 73 in Rochester, New York on January 1981.
Geoffrey Gunther Eichholz, an educational leader in health physics at the Georgia Institute of Technology. Eichholz played a key role in the successful establishment of the Department of Nuclear Engineering and Health Physics. The Department has been a constant source of well-educated and well trained graduates in the field of nuclear engineering, health physics and medical physics. Professor Eichholz was involved at all levels of the educational ladder including leadership roles and participation in doctoral and masters committees.
George Samuel Hurst was a health physicist and professor of physics at the University of Kentucky.
References
- ↑ Cloutier, Roger. (January 1990).G. William Morgan Trust Fund. HPS News. XVIII(1): 20.
- ↑ Wrixon, A. D., B. Martyn R. Green, P. R. Lomas, Jon CH Miles, K. D. Cliff, E. A. Francis, C. M. H. Driscoll, A. C. James, and M. C. O'Riordan. Natural radiation exposure in UK dwellings. National Radiological Protection Board, Chilton (UK), 1988.
- ↑ O'Riordan, M. C. (1988). Notes on radon risks in homes.
- ↑ O'Riordan, M. C. (1990). Human exposure to radon in homes: recommendations for the practical application of the Board's statement. Documents of the NRPB, 1(1): 17-32.
- ↑ A Half Century of Health Physics: 50th Anniversary of the Health Physics Society. (2006). Editors: Michael T. Ryan, John W. Poston, Sr. Lippincott Williams & Wilkins. ISBN 0781769345, 9780781769341. p. 240.
- ↑ Morgan, G. W. (1948). Some practical considerations in radiation shielding. United States Atomic Energy Commission, Isotopes Division.
- ↑ Morgan, G. W. (1948). Gamma and Beta Radiation Shielding. Circular B-3 (January 1948), obtainable from Isotopes Division, US Atomic Energy Commission, PO Box E, Oak Ridge, Tennessee.
- ↑ Morgan, G. W. (1949). Surveying and monitoring of radiation from radioisotopes. Nucleonics, 4(3), 24-37.
- ↑ Morgan, G. W. (February 1950). Decontamination and disposal of radioactive wastes. In Health physics seminar for insurance company representatives, TID-388.
- ↑ Woodruff, N. H., & Morgan, G. W. (1950). Considerations for the Return of Radioactive Isotopes to Commission Facilities for Disposal. US Atomic Energy Commission, Isotopes Division, Oak Ridge, Tennessee.
- ↑ Morgan, George William and Buchanan, C.R. (19 January 1953). Air contamination and respiratory protection in radioisotope work. Oak Ridge, Tennessee: United States Atomic Energy Commission, Technical Information Service. AECU-2821.
- ↑ Frazier, Phillip Matthew, C. R. Buchanan, and George W. Morgan. (1954). Radiation Safety in Industrial Radiography with Radioisotopes. No. AECU-2967. Isotopes Division, Radiological Safety Branch, AEC.
- ↑ Morgan, G. W. (1955). The Control of Radioisotopes. Modern Sanitation, 7(11), 18-20.
- ↑ MORGAN, G.W. (1955). Facilities and equipment for isotopes program. Hospitals, 29(3), 103.
- ↑ Morgan, K. Z., POLLARD, E., COWAN, F., KUPER, J., BALBER, D., WOODRUFF, N., FAILLA, G., EISENBUD, M., BLATZ, H. & MORGAN, G. (1955). Health Physics Insurance Seminar. Technical Information Service.