Physical unit of radiation

A physical unit of radiation, such as a curie, indicates the activity of a source of radiation in terms of the number of nuclear decays that occur per minute. A biological unit of radiation, such as a rem, indicates the damage caused by radiation in living tissue. 

IAMAP, Terminology and Units of Radiation Quantities and Measurements, Radiation Commission of the International Association of Meteorology and Atmospheric Physics, Boulder, CO, 1978. 

Explain the difference between physical and biological units of radiation and give an example of each type. 

International Commission on Radiation Units and Measurements (ICRU) http //www.icru. org/ (accessed August 26, 2010). Established in 1925, this organization has developed recommendations on (1) quantities and units of radiation and radioactivity (2) procedures suitable for the measurement and application of these quantities in diagnostic radiology, radiation therapy, radiation biology, and industrial operations and (3) physical data needed in the application of these procedures, the use of which tends to assure uniformity in reporting (from Web page). 

There are several different terms used to measure radioactivity measures of the physical processes including units of the quantity of radioactivity present, units of radiation exposure, and units of radioactive dose. Now we will define these units and see how they are used. Table 13.1 lists the various terms used to measure radioactivity, as well as the kind of measurement for which each term is used. 

The yield of cross-linking depends on the microstructure of polybutadiene and purity of the polymer as well as on whether it is irradiated in air or in vacuum. The cross-link yield, G(X), has been calculated to be lowest for trans and highest for vinyl isomer [339]. The introduction of styrene into the butadiene chain leads to a greater reduction in the yield of cross-linking, than the physical blends of polybutadiene and polystyrene [340]. This is due to the intra- and probably also intermolecular energy transfer from the butadiene to the styrene constituent and to the radiation stability of the latter unit. 

Rep—Roentgen equivalent, physical A former unit of ionizing radiation equivalent to the dosage of 93 ergs absorbed per gram of tissue (93 erg/gm=0.93 rad). 

Max Planck (1858-1947 Nobel Prize for physics 1918) at first did not have the atom in his sights. He was more interested in thermodynamics, and especially in the laws of radiation. In 1900 he surprised the Physical Society of Berlin — and later the whole world — with an experimentally based realization that changed the world view. In contrast to time and space, energy is guantized. Thus it does not form a continuum, but is essentially "grainy". The smallest unit is the Planck constant, a fundamental natural constant. 

This fairly complete correlation shows that effects of fuel properties and perhaps vent radiation with the appearence of II7, as the physics are not evident, while these are missing in the correlation of Law [19] (Equation (11.45)). Yet Law s correlation includes the effect of a compartment shape. Also in Equation (12.64), the dimensionless groups are indicated compared to the dimensional presentation of Babrauskas, in units of kJ, kg, m, K, s, etc. 

During World War II, a different exposure situation was created in the United States by the Manhattan Project. Several hundreds of thousands of workers were recruited to a new industry in remote and secret locations. Since some of the hazards of working with radiation were recognized in advance, workers at many sites were monitored for radiation exposure. A new discipline. Health Physics, was created to provide radiological protection. The systematic collection of dosimetry records created an opportunity to investigate relationships between repeated exposure to small doses of radiation and disease. 

Equation (2.2.24) means homogeneous generation of particles A and B with the rate p (per unit time and volume), whereas (2.2.25) comes from the statistical independence of sources of a different-kind particles. Physical analog of this model is accumulation of the complementary Frenkel radiation defects in solids. Note that depending on the irradiation type and chemical nature of solids (metal or insulator), dissimilar Frenkel defects could be either spatially correlated in the so-called geminate pairs (see Chapter 3) or distributed at random. We will focus our attention on the latter case. 

As studies of the effects of exposure to all types of radiation went on, it became clear that these effects were correlated with the amount of absorbed energy, which is generally less than the exposure. In 1962 the rad was formally defined as a special unit of energy called the radiation absorbed dose with a value of 100 ergs per gram of absorbing material. The rad is a convenient physical standard that correlates well... 

Table 3. Estimated phase error 8 from imaging a 2.5 cm object at various distances using 1 THz radiation. The baseline b is an estimate of the physical size of the imaging array. Note that for distances of 5-10m, the size of the imaging array is 6-12 cm suggesting that a hand-held unit...

---