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Slowing-down power

Moderator Slowing-down power, cm" Moderating ratio... [Pg.432]

The slowing down power (SDP) of a moderator depends in addition on the neutron scattering cross section and number of scattering atoms per unit volume (Nq) ... [Pg.524]

Atomic- Number Z Name Chemical Atomic Weight A Denaity (P) gjyfcc, 20 C 760 an Hg Nuclei per cc (X 10-34) N (l-b) Arg. Lag Energy Ipsa ( n Neut ermal ron Cr cr) in (0.025 ev) MS Sections )sms Ibermal (0.025 ey) Macroscopic Cross Sections, oN Ibermal (0.025 er) Mean Free Path cm Slowing Down Power No-gf Moderating Ratio (crs/cr ) Xf... [Pg.556]

Naturally, this formula does not hold for the bottom part of the energy region where the number of resonance levels per unit logarithmic energy range is small. One may remember that Q is essentially inversely proportional to the slowing down power of the moderator. [Pg.172]

To compute the thermal utilization from the thermal neutron densities in the three regions, we must first compute the total slowing down powers, Pq and P2 of the water and the graphite. Taking the effective hydrogen scattering cross section to be 15 X 10 (which underestimates the scattering power of the water), we have... [Pg.277]

Again, (4) and (5) contain two terms. The first corresponds to fast neutrons and in this c(E) = 1/( E) where is the slowing down power of the material (.158 for carbon). The second term refers to thermal neutrons. In this / c E) dE is the ratio of total scattering cross section and total absorption cross section per unit cell, multiplied by the thermal disadvantage factor (about 1.4 in the usual arrangement). (This means, of course, that the f c(E)dE of this term is the number of collisions a neutron suffers while it is thermal.)... [Pg.510]

In this, Eq is the energy of thermal neutrons, r = ]nE/Eo where E is the neutron energy, D, which may be a function of r, is one-third of the transport mean free path, (r, x,y,z) is the smn of the velocities of those neutrons for which ItiE/Eq is in imit interval at r and which are in unit volume at ar, y, z, 5 = (7 is the slowing down power, a being the scattering cross section per... [Pg.530]

In this Do is one-third of the transport mean free path for thermal neutrons. So the value of the slowing down power S for r = 0, i.e., for thermal neutrons. [Pg.531]

Actually, this is not altogether justified since the slowing down power does change at low energies because of the effects of chemical binding and lattice structure. These effects are not properly within the scope of the pile equations which we use, just as the whole notion of thermal neutrons is inaccmrate. Since, however, there is no better theory available at present, this difiiculty will be disregarded. [Pg.532]

This relation is plotted in Figure 1. We see that for hydrogen the value of M2 first increases as the effective mass increases, and then decreases. The behavior is very similar to that of the slowing-down power... [Pg.31]

Figure 1. Slowing down power and M2 are plotted as a function of the ratio of neutron mass to effective mass of the moderating atom. Figure 1. Slowing down power and M2 are plotted as a function of the ratio of neutron mass to effective mass of the moderating atom.
Figure 2. The theoretical slowing-down power of graphite at 300°K is plotted as a function of incident neutron energy and compared with the same quantity for a free... Figure 2. The theoretical slowing-down power of graphite at 300°K is plotted as a function of incident neutron energy and compared with the same quantity for a free...
The binding of the moderating atoms reduces the slowing-down power of the moderator near thermal energies and, therefore, leads to a harder thermal spectrum than would obtain if the moderating atoms were free at the same temperature. [Pg.35]

In Figure 4 we show the calculated slowing-down power for a hydrogen atom in water compared to the same parameters for an ideal monatomic gas of hydrogen atoms. It is seen that there is a considerable similarity between the two cases, leading one to believe that the spectra calculated for free hydrogen should be quite similar to the actual spectra in mixtures of absorber and water. This is borne out by the results in Figure 5, where the free hydro-... [Pg.36]

This quantity is usually denoted by which we avoid here to eliminate confusion with the slowing-down power. [Pg.59]

The table illustrates the advantage of light elements as moderators. The moderating qualities of a substance depend, however, on other factors too. The slowing down power (SDP) of a moderator includes the scattering cross section for neutrons a ) and the number density (N ) of scattering atoms (in number of atoms per cubic centimeter [cm ], for instance) ... [Pg.2627]

Moderating properties of different compounds scattering cross section for epithermal neutrons (er in barn) absorption cross section for thermal neutrons (average logarithmic energy decrement slowing down power (SDP) (cm ) and moderating ratio (MR)... [Pg.2628]

Table 3.2. Slowing-Down Power and Moderating Ratio... Table 3.2. Slowing-Down Power and Moderating Ratio...
As a moderator, graphite is characterized by a reasonably good slowing-down power 0.06 cm" and a low absorption cross section (3.4 mb),... [Pg.228]


See other pages where Slowing-down power is mentioned: [Pg.432]    [Pg.432]    [Pg.453]    [Pg.453]    [Pg.432]    [Pg.432]    [Pg.168]    [Pg.275]    [Pg.283]    [Pg.511]    [Pg.71]    [Pg.79]    [Pg.27]    [Pg.30]    [Pg.30]    [Pg.60]    [Pg.67]    [Pg.72]    [Pg.81]    [Pg.81]    [Pg.81]    [Pg.142]    [Pg.222]   
See also in sourсe #XX -- [ Pg.432 ]

See also in sourсe #XX -- [ Pg.432 ]

See also in sourсe #XX -- [ Pg.432 ]

See also in sourсe #XX -- [ Pg.524 ]

See also in sourсe #XX -- [ Pg.146 , Pg.262 , Pg.2476 , Pg.2482 , Pg.2627 ]




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