The D Pile was down five times for scheduled shutdowns. The fifth shutdown was of short duration for the purpose of discharging temporary ``P`` columns. Details of the shutdowns are given. Three new bismuth columns were established, Special Requests were charged into seven tubes and three Special Requests were discharged. Three tubes were charged with four-inch slugs. The power level of the F Pile has been corrected for the discrepancy noted last month. Material for irradiation under the Special Request program was charged into six tubes and the B experimental hole during the month. The effect of poison columns and rods on the temperature distribution of the pile was checked for the overall content of the pile. The F Pile gained two in hours in cold, clean reactivity during the month if allowance is made for xenon poison values corresponding to 190 MW for the beginning of the month and 200 MW at the end of the month. The graphite stringer removed from the ``D`` test hole of the D Pile on 3-12-46 was studied physical radiation effects.

Report discussing trial runs of a method of recovery of uranium from salvage residue. The method involves hydrofluorination of the residue to remove large quantities of interfering silicates, followed by a fluorination treatment to remove uranium.

Abstract: Tuballoy can be effectively separated from tantalum filaments by chlorination of the filaments and subsequent distillation and condensation of tantalum chloride. Apparatus for chlorination of filaments and distillation separation in one unit is under consideration. Chemical methods of separation of tuballoy from distillation residues are being tested.

The magnitude and distribution of the fission rate per unit area produced by three energy groups of moderated neutrons reflected from a water tamper into one side of an infinite slab of active material is calculated approximately in section II. This rate is directly proportional to the current density of fast neutrons from the active material incident on the water tamper. The critical slab thickness is obtained in section III by solving an inhomogeneous transport integral equation for the fast-neutron current density into the tamper. Extensive use is made of the formulae derived in The Mathematical Development of the End-Point Method by Frankel and Goldberg. In section IV slight alterations in the theory outlined in sections II and III were made so that one could approximately compute the critical radius of a water-tamper sphere of active material. The derived formulae were applied to calculate the critical dimensions of water-tamped slabs and spheres of solid UF{sub 6} leaving various (25) isotope enrichment fractions.

Summary: "An apparatus is described which applies alternate pulses from two ion beams to a galvanometer network. The isotopic ratio is read directly from a potentiometer. The comparison is independent of ion beam intensity. This method is not practical for application to the standard Nier assay instrument because of the low ion currents normally used. It is suggested that this comparison method may have utility in a spectrometer utilizing a high intensity ion source such as capillary ore or condensed spark."

This technical report is divided into two sections addressing two different chemical effects of nuclear transformations. The first section discusses the beta decay of lanthanum to cerium. The second section discusses the beta decay of selenium to bromine.

"Three modifications of the auxiliary-stage supercharger for the V-1710-93 engine were designed and tested as part of an investigation to improve the power output and the altitude performance of the engine. A 12-vane diffuser was substituted for the standard 11-vane diffuser, and a vaneless discharge passage and a modified scroll were designed to increase the flow capacity of the supercharger and thereby to increase the performance at the high volume flows required by the engine. With the 12-vane diffuser installed and the carburetor replaced by an adapter, the equivalent volume flow at the peak efficiency point was increased 25 percent at the lowest speed investigated and 9.5 percent at the highest speed" (p. 1).

The NACA 6A-series airfoil sections were designed to eliminate the trailing-edge cusp which is characteristic of the NACA 6-series sections. Theoretical data are presented for NACA 6A-series basic thickness forms having the position of minimum pressure at 30-, 40-, and 50-percent chord and with thickness ratios varying from 6 percent to 15 percent. Also presented are data for a mean line designed to maintain straight sides on the cambered sections. The experimental results of a two dimensional wind tunnel investigation of the aerodynamic characteristics of five NACA 64A-series airfoil sections and two NACA 63A-series airfoil sections are presented. An analysis of these results, which were obtained at Reynolds numbers of 3 x 10(exp 6), 6 x 10(exp 6), and 9 x 10(exp 6), indicates that the section minimum drag and maximum lift characteristics of comparable NACA 6-series and 6A-series airfoil sections are essentially the same. The quarter-chord pitching-moment coefficients and angles of zero lift of NACA 6A-series airfoil sections are slightly more negative than those of corresponding NACA 6-series airfoil sections. The position of the aerodynamic center and the lift-curve slope of smooth NACA 6-series sections. The addition of standard leading-edge roughness causes the lift-curve slope of the newer sections …

From Summary: "Tests have been made in Langley tank no. I of a dynamic model of the Consolidated Vultee PB2Y-3 airplane. These tests were made using an alternate hull form, the purpose of which was to reduce the bow spray and eliminate the landing instability which are objectionable features of the production design. The major differences from the PB2Y-3 hull included a deeper step to improve the landing stability , and a lengthened forebody and increased beam to reduce the sway in the propellers and on the flaps. The tests showed that the spray characteristics of the revised hull form were much better than that to the production design. In addition the take-off and landing stability of the model with the alternate hull were satisfactory."