Types of Ionizing Radiation

2 BRIEF CLASSIC DESCRIPTION OF IONIZING RADIATION 1.2.1 Types of Ionizing Radiation 

Main Radiation Types and Their Sources Irradiation Type/Description 

Ionizing Radiation Alpha (a, helium nuclei), 4-9 MeV P /c beam (P particles or accelerated electrons), velocity less than the velocity of light, energy 10 keV-10 MeV (positrons P+ belong to the same range) 

Gamma (y)-rays (velocity 3x10 m/s in free space), wavelength 0.1 nm, energy 10 keV X-rays, wavelength 10-0.001 nm, energy 100 eV-1 MeV Neutrons (n) 

Thermal neutrons 0.4 eV Intermediate neutrons 0.4 eV-200 keV Fast neutrons 200 keV 

Neutrons, emitted from nuclear detonations, particle accelerators and nuclear weapon assembly facilities and not found in fallout, can penetrate deeply, causing 

Depending on the dose, dose rate and route of exposure, radiation can cause Acute Radiation Syndrome (ARS), cutaneous injury and scarring, chorioretinal damage (due to exposure to infrared energy), and increased long term risk for cancer, cataract formation (especially due to neutron irradiation), infertility and fetal abnormalities, such as growth retardation, fetal malformations, increased teratogen-esis and fetal death (2). 

Radiation injury causes two types of effects on biologic symptoms, stochastic and deterministic. Stochastic effects are aU or nothing effects. At increasing doses, the probability of a stochastic effect increases, but once the stochastic effect occurs, further inaeases in exposure will not worsen the severity of the effect. A conunon stochastic effect is radiation-associated malignancy. In comparison, the severity of deterministic effects is proportional to the dose. Examples of deterministic effects include suppression of hematopoiesis, cataract formation and fertility impairment (4). 

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Relative Biological Effectiveness (RBE)—The RBE is a factor used to compare the biological effectiveness of absorbed radiation doses (i.e., rad) due to different types of ionizing radiation. More specifically, it is the experimentally determined ratio of an absorbed dose of a radiation in question to the absorbed dose of a reference radiation (typically 60Co gamma rays or 200 keV x rays) required to produce an identical biological effect in a particular experimental organism or tissue (see Quality Factor). 

Smirnova and coworkers studied the influence of various types of ionizing radiations on the physiomechanical characteristics of a statistical polymer of butadiene and acrylonitrile137. Although the polymer is a statistical polymer, the nature of its thermo-mechanical curve indicates a block nature of the polymeric basis of the rubber there is a... 

Radiation weighting factors for various types of ionizing radiations... 

Table 32.2 Radiation Weighting Factors for Various Types of Ionizing Radiations...

Relative biological effectiveness (RBE) The biological effectiveness of any type of ionizing radiation in producing a specific damage (i.e., leukemia, anemia, carcinogenicity). See Radiation dose. 

The other types of ionizing radiation mentioned above are also used in processing of polymeric systems, but not as frequently as electron beams and mainly for specialized applications. 

Electron beam processors generate two types of ionizing radiation their primary product is high-energy electrons, and their secondary product is x-rays resulting from their interaction with matter. The ionizing radiation is damaging because of its capability of penetration into the human body. 

Relative Biological Effectiveness (RBE) Factor used to compare the biological effectiveness of different types of ionizing radiation inverse ratio of the amount of absorbed radiation required to produce a given effect to a standard radiation required to produce the same effect. 

HPhe Fricke dosimeter (ferrous sulfate solutions) has been used to measure A the radiation intensity of various types of ionizing radiation sources since its development by Fricke and Morse in 1927 (2). It is widely accepted because it yields accurate and reproducible results with a minimum of care. This system meets many of the requirements specified for an ideal dosimeter (5, 9) however, it has a limited dose range, and for our applications it has been necessary to develop a dosimeter covering larger doses. Of the systems reviewed (6, 7), two (ferrous sulfate-cupric sulfate and ceric sulfate) showed the most promise for use with the radiation sources at the U. S. Army Natick Laboratories (8). Of these, the ferrous-cupric system has received the most use, and this paper describes our experience in using this system and suggests procedures by which it may be used by others with equal success. 

Thus, the effect the different types of ionizing radiation produce in a medium is the effect produced by charged particles. It is to the different physical and physicochemical processes induced in a molecular medium by charged particles our present review is devoted. 

Radiation hazard identification. The hazard identification process is trivial in the case of radiation, because all types of ionizing radiation are assumed to be hazardous and, thus, all radionuclides are assumed to be hazardous substances (see Section 3.2.2). While some responses may not occur at low doses (e.g., damage to the lens of the eye), other responses are assumed to occur with some probability at any dose (e.g., cancer induction). 

We must therefore rely on detectors of one sort or another to determine the amount of ionizing radiation present. It is outside of the scope of this book to discuss the wide variety of radiation detectors. Suffice it to say, there are many types of devices for detecting and quantifying the various types of ionizing radiation. The interested student should consult a modern nuclear chemistry textbook for more details regarding radiation detection and instrumentation. 

Because the amount of energy deposited in a given material will depend on the type of ionizing radiation, we must separately quantify the radiation exposure... 

The detection of radiation is based on the interactions of the various types of ionizing radiations with matter. The differences between the interactions and the penetrating abilities of the various radiations are very relevant to radiation detection and measurement—e.g. they partly explain the variety of detector types and designs. 

For radiation protection purposes, several theoretical dosimetric quantities have been created that attempt to normalize the responses of different tissues and organs of the body from irradiation by different types of ionizing radiation so that uniform radiation protection guidelines can be promulgated that are insensitive to the particulars of any given irradiation scenario. The traditionally used quantity has been the dose equivalent (DE), which is defined as the absorbed dose (D) multiplied by the quality factor Q. The unit of dose equivalent has been the rem, which is dimensionally the same as the rad the SI unit is the Sievert (Sv). Recently, the DE has been replaced by a similar concept called the equivalent dose. The equivalent dose depends on the relative biological effectiveness rather than on Q. 

Types of ionizing radiation and their methods of generation... 

Figure 1 Penetration ofthe different types of ionizing radiation.

General. A nuclear burst results in four types of ionizing radiation neutron, gamma, beta, and alpha. Neutrons and gamma rays characterize the initial burst while the residual radiation is primarily of alpha, beta, and gamma rays. Blast and thermal injuries in many cases will far outnumber radiation injuries. However, radiation effects are considerably more complex and varied than are blast or thermal effects. 

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