Subcritical mass flux

Subcritical mass flux. The following procedure is used to estimate the subcritical mass flux. 

Subcritical mass flux. This is estimated using Equation 4.90. 

Fig. 2. Mass flux density for a large heat-capacity-fluid (C6F14) along a slightly subcritical isentrope ((s-Sc)/R=>0.05) starting at different stagnation pressures.

For bomb making, the trick is to convert a subcritical mass into a critical mass as rapidly as possible. In a power station, the neutron flux — that is, the number... 

Equation 4.55 and Equation 4.56 are used to estimate the mass flux for critical and subcritical flows, respectively ... 

Experiments at Los Alamos determined the critical masses of U235 and Pu239. Adding U235 cubes to a subcritical assembly within blocks of beryllium tamper measurably increased neutron flux. 66. The Los Alamos Tech Area. 

There has been considerable need for neutron irradiation units with high neutron fluxrfor use in research, industry, and education. Sources of various types have been used lor this purpose for maiiy years, but have lacked the intensity and volume, with level flux, for larger sample irradiation. While the research reactor can produce the desirable neutron flux, construction and operation is rather costly. A neutron multiplier has been described. .using a subcritical lattice of enriched uranium rods,with a central cylindrical flux trap. A Cf. source is used to provide the initial neutrons to drive the unit. This lattice unit was loaded at the Critical Mass Laboratory to study aspects of criticality including keff and effects of temperature, voids, and added material. 

Good multigroup cross-section data are obviously necessary if one is to perform accurate andyses of critical or subtly subcritical systems. Generation of this multigroup data from the point data requires careful weighting of all mocesMS over the resonance range. The purpose of this paper is to show how the flux spectrum as calculated by the Nordheim method and by a mote exact method can ultimately affect the calculated mult lication and/or critical mass of sli d>tty moderated bulk-oxide systems. 

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