Ground concentration

Figure 26-52 shows the effect of height on the downwind concentrations due to a release. As the release height increases, the ground concentration downwind decreases since the resulting plume has more distance to mix with fresh air prior to contacting the ground. 

For releases at ground level, the maximum concentration occurs at the release point. For releases above ground level, the maximum ground concentration occurs downwind along the centerline. The location of the maximum is found using... 

The ingestion dose contributes very little to the dose from a severe reactor accident and is usually not computed. However, the food pathway is a major determinant of bow the exposed area must be treated in the months and years following the accident. If the ground concentration is high, the land may be interdicted from agricultural u.se or grazing. 

Gases from stacks witli diameters less tlian 5 feet and heights less tlian 200 feet will liit tlie ground part of the time, and ground concentrations may be excessive. In such cases, the plume becomes unpredictable. 

The maximum ground concentration of stack gases subjected to atmospheric diffusion occurs about 5-10 effective stack heights dow tiw ind from the point of emission. 

Ground concentrations can be reduced by the use of higher stacks. The gromid concenuntion varies inversely as tlie square of the effective stack height. 

Table 32.15 Radionuclide Concentrations in Selected Samples from the Pacific Proving Grounds (Concentrations are in becquerels/kg fresh weight [FW] or dry weight [DW].)...

Figure 5-5 Increased release height decreases the ground concentration.

Figure 6.17 Typical plot comparing relative ground concentration in the cooling tower stack direction. Ground-level concentrations are normally averaged over the year.

Cl = ground concentration of the toxic cloud (re., mean concentration of low est 6-ft. stratum),... 

Tall stacks emit gas into the upper layer of the atmosphere and lower the ground concentration of the pollutants. 

Warning Concentrated H2O2 may not be poured onto the ground. Concentrated H2O2 will cause fire when poured out, and allowed to sit for extended periods of time. If one has concentrated H2O2 on hand, and does not want to proceed with the dicycloacetone peroxide synthesis, then one may dump the concentrated H2O2 into a liter of water. 

These topics are discussed in detail in monographs and reviews (NAS 1975, IPCS 1991, Barceloux 1999, Mastromatteo 1986, Sunderman 1984, 2001a). Nickel constitutes less than 0.008% of the Earth s crust. The world s nickel production is obtained primarily from sulfide ores (e.g., pentlandite and nickeliferous pyrrhotite) and, to lesser extent, from oxides ores (e.g., laterite). Nickel sulfide ores, usually mined underground, are crushed and ground, concentrated by physical methods, converted to nickel subsulfide matte, and roasted to nickel oxide. The nickel oxide may be refined electrolytically to yield nickel cathodes or refined by the Mond process, which involves reduction with hydrogen, reaction with carbon monoxide to yield nickel carbonyl, and thermal decomposition to deposit pure nickel. Nickel oxide ores, usually mined in open pits, are smelted to produce ferronickel for use in stainless steel. 

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