Exclusion distance

Fig. 5. Probabilities pn of observing n water-oxygen atoms in spherical cavity volumes v. Results from Monte Carlo simulations of SPC water are shown as symbols. The parabolas are predictions using the flat default model in Eq. (11). The center-to-center exclusion distance d (in nanometers) is noted next to the curves. The solute exclusion volume is defined by the distance d of closest approach of water-oxygen atoms to the center of the sphere. (Hummer et al., 1998a)... 

For poly(methylene), an exclusion distance (hard sphere diameter) of 2.00 A was used to prevent overlap of methylene residues. The calculation reproduced the accepted theoretical and experimental characteristic ratios (mean square unperturbed end-to-end distance relative to that for a freely jointed gaussian chain with the same number of segments) of 5.9. This wps for zero angular bias and a trans/gauche energy separation of 2.09 kJ mol". ... 

A preferable system is poly(p-fluorostyrene) doped into poly(styrene). Since rotations about the 1,4 phenyl axis do not alter the position of the fluorine, the F spin may be regarded as being at the end of a long "bond" to the backbone carbon. In standard RIS theory, this polymer would be treated with dyad statistical weights to automatically take into account conformations of the vinyl monomer unit which are excluded on steric grounds. We have found it more convenient to retain the monad statistical weight structure employed for the poly(methylene) calculations. The calculations reproduce the experimental unperturbed dimensions quite well when a reasonable set of hard sphere exclusion distances is employed. 

The hard sphere exclusion distances for this system were chosen as follows nonbonded backbone carbons, 4.60 R (twice the C-H bond distance plus van der Waals radius for H) non-neighboring fluorines, 2.70 R (twice van der Waals radius for F) neighboring fluorines, 6.39 R (distance across phenyl ring using dimensions of Table I and van der Waals radius for Hof... 

Figure 6 shows the importance of having separate exclusion distances for neighboring and non-neighboring fluorines. The neighbor fluorine exclusion is the main determinant of overall chain dimensions, serving to keep phenyl groups separated in the same manner as dyad statistics would have done. 

Modified Gouy- Chapman theory provides a model of Vex through the parameter dex, the exclusion distance. For a 1 1 electrolyte solution [23]... 

The public access exclusion distance (PAED) provides protection analogous to the inhabited-building distance for explosives. The hazard PAED zone calculated from the MCE shall represent that arc from the agent source containing no more than 10.0, 4.3, and 150,0 mg-min/m of GB, VX, or HD, respectively. Positive means shall be taken to assure that no persons, not directly associated with chemical weapons operations, enter areas so defined. 

FIG. 1 Variation of the local concentration, C, of the monovalent counterion of radius 0.3 nm with the radial distance, r, from the axis of the cylindrical polyion of radius a = 0.8 nm. The average counterion concentration is marked by Cav, d is the exclusion distance from the polyion axis to the center of the counterion, and/is the fraction of free counterions. The value of the charge density parameter A = 2.83 is typical for aqueous solutions of poly(styrenesulfonates) at 25°C, and the value of the radius of the cell R = 65.2 nm corresponds to the polyelectrolyte concentration CP = 5 X 10 4 monomol dm3. 

The right side of Eq. 1.16 is the relative probability that a univalent anion will not be found at a point x near a negatively charged planar surface, integrated over all x values from 8 outward. Thus the mean exclusion distance is equal to the probability that an ion is excluded from the region between x and x h dx, summed over all such regions. The integral in Eq. 1.16 can be calculated with the help of a transformation based on Eqs. 1.11 and 1.13 ... 

Indeed, since the 1950s, the US Reactor Safeguards Committee , set up by the Atomic Energy Commission with the task of defining the guidelines for nuclear safety, had indicated that, for a non-contained reactor, an exclusion distance (without resident population) should be provided. This distance, R, had to be equal, at least to that given by Eq. 1.1. 

For a 3000 MW reactor (the usual size today), this exclusion distance is equal to approximately 30 km, which is equal to the distance evacuated after the Chernobyl accident (Bourgeois et al, 1996). Evidently, the reference doses for the short-term evacuation were roughly the same for the two cases. An exclusion distance of this magnitude poses excessive problems to siting, even in a country endowed with abundant land such as the USA, therefore, the decision of adopting a containment is practically a compulsory one. 

In Equation 7.26, is the solid area per unit of mass where the ion is excluded and is the exclusion distance, the (effective) distance from the surface where the solution is depleted of X. It is a function of concentration and can be evaluated... 

The Safeguards Conunittee letter acknowledged the complexity of site evaluation. While admitting that a large number of variables had to be considered from site to site, the committee believed it brought a consistent philosophy to site assessment. The letter focused on Commissioner Graham s concern about exclusion distances and population density... 

The draft criteria, presented to the environmental subcommittee in late August 1960 and to the full Safeguards Committee a month later, established three distances for a reactor of any given power level. Beck labeled them "benchmarks"—spedfically, an exclusion distance, an evacuation distance, and a population-center distance. The exclusion area, under the complete control of the reactor owner, had an outer-limit distance at which, following the onset of a maximum credible accident, the total radiation dose received by an individual in two hours... 

The 1962 siting criteria reflected and were consistent with prior site decisions on commercial power reactors. This was shown through the application of the criteria s calculations to several reactor projects that had been proposed or were authorized for construction. The Commonwealth Edison Dresden reactor, for example, with a power level of 630 megawatts thermal, had a calculated exclusion distance of 0.5 miles, which corresponded exactly with the actual exclusion distance at the... 

Outside the exclusion area, it was stipulated that the calculated radiation exposure should be less than 300 rem (which is roughly the threshold for a lethal dose), or evacuation should be possible. For a 50 Mwt plant, the rule of thumb gives an exclusion distance of 1.73 miles (2.77 km). For a 3000 Mwt plant like many currently used to produce electricity, the rule of thumb would give an exclusion distance of 17.3 miles (27.8 km). 

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