The critical mass of 94-239 and the corresponding critical dimensions of homogeneous mixtures of 94-239 with various moderating media been calculated as a function of the concentration of 94. A simple transformation makes the figures applicated to92-235. the results are in essential agreement with the preliminary estimated made independently by Oppenheimer and Serber. The problem of the stability of a chain reaction in solution and questions of protection are discussed.

The following report investigates cross sections for the absorption of slow neutrons of heavy isotopes. The purpose of these measurements was to determine the cross section of an isotope of element 94 for the process of fission by the absorption of a slow neutron, relative to the cross section of U235 for the same process, that is, to measure R.

Synopsis: Metal Hydrides Incorporated was a pioneer in the production of uranium metal on a commercial scale and supplied it to all the laboratories interested in the original research, before other methods for its production were developed. Metal Hydrides Inc. supplied the major part of the metal for the construction of the first experimental pile which, on December 2, 1942, demonstrated the feasibility of the self-sustaining chain reaction and the release of atomic energy.

The following report discusses the toxicity of fluorine as described in literature on fluorine intoxication and case studies of Roholm's experimental observations.

The following report studies the reactions of vapor phase hydrolysis of the trichlorides of lanthanum, praseodymium, samarium, and americium with gas mixtures of HCl and H2O passing over the solid materials mounted on a cantilever-type quartz fiber microbalance. This report calculates the values of the heats and entropies of the reactions, as well as the heat formation of LaCl3, 1254.9 kcal mol-(-1) that was obtained by determining the heat of the solution of La metal in 1.5M HCl.

From abstract: "This report contains the theoretical analysis of a plant to concentrate deuterium from 2 atoms% to 90 atoms% by the NH3-H2 exchange reaction."

The average energies of neutrons emitted from a graphite column at 22 degrees C were compared by measurement of the cross section of boron for neutrons which are stopped by cadmium. At a distance from the neutron source great enough to insure that the neutrons were in thermal equilibrium the average energies of the emerging neutrons were found to be proportional to the temperature within the limits of the experimental error. A measurement made with boron absorbers which had been thus standardized in the graphite column indicated neutrons emerging from the chain reacting pile to have an average temperature approximate 60 +- 50 degrees above that of thermal neutrons emerging from the graphite column at 22 degrees C. Such a measurement made inside the chain reacting pile indicated the average temperature of neutrons therein to be about 65 degrees +- 15 degrees above the average temperature of neutrons in the graphite column.

The temperature coefficient is calculated for various lattice arrangements, taking into account the variation of [formula], suggested by Fermi. Four contributions are included: leakage, levelling of the dip in thermal neutron density in the lump, resonance absorption, and hardening of the neutrons as they penetrate a metal lump. The departure of neutron temperature from lattice temperature decreases the total coefficient. Values are given for 3 typical piles; in general, the larger the uranium elements, the less stable the pile. A rod lattice tends to be more stable. A pile with metal lumps over 50 lbs. will be unstable.

The multiplication factor and minimum pile size for a multiplying pile using UO2 powder of density 1 have been computed. It appears that a k of 1.0177 is possible for a volume ration of V/V001=3.33.

The most important source of radioactivity at the exit manifold of the pile will be due to O19, formed by neutron absorption of O18. A recent measurement of Fermi and Weil permits to estimate that it will be safe to stay about 80 minutes daily close to the exit manifolds without any shield. Estimates are given for the radioactivities from other sources -- both in the neighborhood and farther away from the pile.

Abstract: "This paper gives an arithmetic method of computing the number of sections required in a catalytic tower to produce a given enrichment. It also tells how to calculate the enrichment of a tower with a given number of sections. The problem of the most economical design of catalytic towers is solved. Methods are given for determining the temperature, the efficiencies of catalyst beds and strippers, the relative production rate, and the water vapor-hydrogen gas ratio which give the optimum combination of operating pressure, cross sectional area, number of sections, and volume of catalyst in the tower. Simple directions as to how to make the calculations are included."

Report discussing the reduction of nitric acid that results from its use at the cathode for the electrolysis of uranyl nitrate. From introduction: "It is the purpose of this report to give the results of studies on the reduction of nitric acid of different concentrations, at different types of electrodes, and for various current densities in order to ascertain the effects of such changes."

The following report was written to replace previous directions submitted in the February 6, 1943 report on the preparation of the solution X(OC₂H₅)₅.

The resonance absorption of uranium for neutrons has been investigated between 20 degree C and 1000 degree C. Experiments were caried out on both UO2, density 4.63, and metal. The resonance activity was measured with respect to that of an iodine monitor at several different temperatures and the ratio of activity at temperature T to that at 20 degree C was determined. The increase in activity is 0.9 per cent per 100 degree C for the oxide and 1.1 percent per 100 degree C for the metal. The period of U239 was found to be 23.54 +- 0.05 min.

Abstract: Since the viscosity-temperature relationships of fluorocarbons are somewhat unusual, when compared to hydrocarbons, for example, it was decided to measure the viscosities, at several temperatures, of various fluorolube oils. The calculation of the viscosity of a blend of oils is at best an uncertain operation, varying considerably with the method used. A comparison of various methods was indicated, in order that reasonably accurate values might be assumed for theoretical composites. The densities were measured at corresponding temperatures for use in converting viscosities, and for their value, per se.

Lecture notes from a training program. "It is the function of the section on radiation chemistry to determine the effects of all radiations and high energy particles produced under the various operating conditions on all the materials which will be exposed to them."

The importance of fast neutron fission (i.e., fission caused by neutrons before being slowed down) was recognized by Szilard, and calculations similar to the present one have already been carried out by him, Feld, Ashkin, Wheeler, Wigner and others. The purpose of the present paper is to give a general formula for the contribution of fast fission to the multiplication constant, which will include all the cases already considered and will be applicable to more complicated geometries than those considered by the previous writers.

Technical report that information has bee obtained on the effect of beta and gamma radiation on the electrical resistance of insulating materials The results are summarized. The recovery to original resistance values has been measured. In general, the initial rate is rapid for the first few hours; the rate then decreases sharply. Certain samples show evidence of complete recovery. Effects on mechanical properties of several plastics has also been studied. Data on gas evolution from several organic materials including those suggested by the physiological shield have been extended to include both beta and deuteron bombardments. Samples of "Press-wood" are being evaluated. The effect of current on the H2O2 production in water containing I- has been studied at several I- concentrations. Water contain-dissolved CO2 shows the presence of oxidant (presumably H2O2). H2O2 has been produced by recoil protons from the scattering of fast neutrons in de-oxygenated water. Radioactive solutions do not greatly affect the applicability the glass electrode providing the electrode is thoroughly washed with distilled water before immersion in the standard buffer solution.

The following represents a summary of calculations on the multiplication constant of homogeneous mixtures of uranium and different moderators. These calculations were made possible by Fermi's determination of the age of neutrons and by the extrapolation to higher scattering cross-sections of the resonance absorption of uranium as measured by C. Creutz. According to Fermi, the former quantity is 120 sq. cm. The latter is given in the two attached graphs. The first (Fig.1) of these goes as high as a scattering cross-section of 70 x 10-24 cm.2 per uranium atom, and its highest point is taken from a measurement of Cruetz's in which a mixture of U3O8 and graphite was used.

The following report provides data taken from investigations on radiation and the different biologic effects on it.

"In this report are presented three figures which show how the relative activities (expressed as percentages of total activity) of the individual fission elements (produced by neutron bombardment of uranyl nitrate) vary with cooling time."

The following sources of contamination in cooling water of the P-9 plant are considered: (1) Fission recoils, (2) Corrosion of metal, (3) Recoil from aluminum, (4) Induced activity in the water. It is found that for a P-9 plant of 3.5 x 10(4) KW contamination of the river at "X" should not exceed the .1 r criterion unless coating failure occurs. Tables of the amount of coating failure permissible are given as a function of holdup time.

Abstract. The precipitation of Pa233 with MnO2 from a solution of thorium nitrate has been studied in some detail and seems quite satisfactory up to 36 gm Th(HO3)4 4H2O per 100 cc solution. The concentration of Pa233 with respect to the manganese dioxide carrier and the thorium precipitated with the carrier appears to be accomplished quite well by either a series of MnO2 cycles or thorium iodate cycles. Volatility methods for both the separation of Pa233 from the original thorium and for its separation from MnO2 are now under investigation. It has been decided that thorium carbonate will the the thorium compound used in the pile at Site X.

From abstract: "This paper gives a method for determining Uranium using sodium cresotate as a colorimetric reagent. A precision is obtained of better than 2%. In carrying out analyses for Uranium in corrosion products by existing methods such as ignition to the oxide, silver reductor, or titration with ceric sulfate, it became apparent that a rapid, fairly accurate method for determining uranyl ion would be of great value. Such a method is described in this paper. The most logical color to use is that given by the ferrocyanide complex, but upon studying this, it proved to be unsatisfactory. Sodium salycilate also gives a color which has been used with some success, but its color appears to fade and is not very sensitive. A similar compound, sodium cresotate, was found to give an orange-red color and is the reagent used in the method to be described."