Gray, unit defined

The SI unit for absorbed doses (i.e., the amount of all radiations absorbed in any material) is the gray (Gy), defined as the absorption of 1 joule of energy per kilogram of material (J/kg). In the U.S. another unit for dose is used. It is called rad, which stands for radiation absorbed Jose. One rad is equal to the absorption of 0.01 joule of energy per kilogram of material. Thus, 1 Gy = 100 rads. 

Very high doses of radiation can kill large numbers of cells. If the whole body is exposed, death may occur within a matter of weeks an instantaneous absorbed dose of 5 gray or more would probably be lethal (the unit gray is defined below). If a small area of the body is briefly exposed to a very high dose, death may not occur, but there may be other early effects an... 

SI Units—The International System of Units as defined by the General Conference of Weights and Measures in 1960. These units are generally based on the meter/kilogram/second units, with special quantities for radiation including the becquerel, gray, and sievert. 

D.3.1.2 Absorbed Dose and Absorbed Dose Rate. The absorbed dose is defined as the energy imparted by the incident radiation to a unit mass of the tissue or organ. The unit of absorbed dose is the rad 1 rad = 100 erg/gram = 0.01 J/kg in any medium. An exposure of 1 R results in a dose to soft tissue of approximately 0.01 J/kg. The SI unit is the gray which is equivalent to 100 rad or 1 J/kg. Internal and external exposures from radiation sources are not usually instantaneous but are distributed over extended periods of time. The resulting rate of change of the absorbed dose to a small volume of mass is referred to as the absorbed dose rate in units of rad/unit time. 

The SI unit of dose equivalent is the sievert, Sv, which is defined in the same way as rem but with the absorbed dose in gray thus, 1 Sv = 100 rem. 

Solution Let zone 1 represent one tube and zone 2 represent the effective plane 2, that is, the unit cell for the tube bank. Thus Aj = tcD and A2 = C are the corresponding zone areas, respectively (per unit vertical dimension). This notation is consistent with Example 3. Also put i = 0.8 with 2 = 1.0 and define R = C/D = 12/5 = 2.4. The gray plane effective emissivity is then calculated as the total view factor for the effective plane to tubes, that is, J2-1s % For R = 2.4, Fig. 5-15, curve 5, yields the refractory augmented view factor F2ji = 0.81. Then is... 

UV fluence. However, this is incorrect and misleading because the SI unit of the absorbed dose of radiation is gray/J kg (Gy) (MiUs et al., 1993). The unit Gy is related to a specific mass and it was defined for reasons of safeguarding human health in radiology. It is used in radiation protection. 

Figure 15.5 Downstream distributions of dissolved species between Vargem Grande and 6bidos the Brazilian Amazon. Distributions for each species are given for both rising-water and falling-water periods, with the particular concentration scale applicable to both periods. Aik = alkalinity, pC02 = dissolved CO2 gas, O2 = dissolved oxygen, PO4 = phosphate ion, DOC = dissolved organic carbon and NO3 = nitrate ion. Solid dashed and thick gray lines are as defined in Fig. 15.4. All units are pM except alkalimty, which is peq 1. ...

Absorbed dose. It is the amount of energy passed on by radiation to a given mass of any material. The most common unit of absorbed dose is the rad, which is defined as a dose of 100 ergs of energy per gram of the material in question (SI unit is the gray, 1 Gy = 1 J/kg). The absorbed dose may also be expressed as a rate with units of rad/h or mrad/h. 

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