The flux through a given region is proportional to the total lengths of the neutron flight paths that intersect that region. The analytical Monte Carlo procedure manufactured neutron flight paths and totaled the lengths of all paths intercepted by the regions illustrated in Figure 1. The procedure was designed to utilize the various symmetries in the lattice. / Consider a portion of the lattice whose planar cross-section is shown in Figure 5. If R is the region in which the flux is to be estimated and F the fuel rod in which the neutron originated, then flight path P results in an intercepted length whose reflection in the plane is L. On the other hand flight path P' intercepts R' with length L'. R' is not the region to be studied, but a translation of the flight path P' to F' would result in the neutron intercepting R. The origin in P was arbitrary. For each neutron originating in P another could, with equal probability, have originated in P' with parallel paths. Hence consulting L' in R' towards the total flux is equivalent to starting a neutron at P'. Thus consideration of all regions symmetric to R with respect to …

The countercurrent gas-liquid system BF3(g)—anisole·BF3(l) for the concentration of boron isotopes has been studied. The single-storage separation factor varies from 1.039 at 0°C to 1.029 at 30°C. Rate of exchange is rapid, and, with efficient contacting equipment, complete exchange may be obtained in less than 15 sec. A total separation of 1.525 has been realized in laboratory equipment. The critical-product reflux reaction is quite efficient. Only about 55 moles of BF3 remain in each million moles of effluent solvent under laboratory conditions. The vapor pressure of BF3 over the complex rises sharply as the temperature is increased. At 0°C the pressure is 150 mm Hg, and at 40°C the pressure has risen to 1800 mm Hg. From vapor-pressure measurements, an approximate upper limit of ΔH= -12kcal per mole of complex was calculated for the reaction [equation not transcribed]. Qualitative tests indicate good resistance of anisole to decomposition by BF3 under plant conditions. The uncatalyzed exchange of boron between BF3 and BCl3 was found to be too slow to be exploited in a countercurrent system. The single-stage, equilibrium separation factor for the Nitrox system is a function of acid concentration. At 26°C the factor ranges from 1.064 with 1 M acid …