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Determination of the 14-Mev Li7 (n,n'a)T Cross Section from Sphere Multiplication and Transmission Measurements: By utilizing lithium spherical shell transmission and multiplication measurements, the Li7(n,n'y)Li7 and the He6-production cross sections, it is possible to deduce that the 14-Mev Li (n,n'a)T cross section is 325 ± 75 mb. A spectrum for neutrons degraded in energy between 0 and 12 Mev is also given.
Neutron Emission by Polonium Oxide Layers: The following report calculates how many neutrons are produced by the O-16([alpha]-n) reaction in a thin and uniform polonium oxide layer.
Consolidation and shaping of boron ; summary of previous work: From abstract: "The deposit on the rods is in the form of a brittle uneven tube which is cracked off and subsequently pulverized to a 200-mesh powder. This report is chiefly concerned with methods of consolidating this powder and shaping it into forms required, though it also discusses to some extent other methods of shaping boron or born-rich materials."
Heat Treatment and Machinability of Beryllium Rod: Purpose: "The purpose of this investigation was to determine whether or not the machinability of extruded beryllium rod could be improved by appropriate heat treatment. It was thought that this could be accomplished in the extruded Be rod by recrystallization without further growth of these grains. This should impart a certain degree of ductility to the metal. The investigations was divided into two parts: Part I - Heat Treatment of Beryllium Rod; Part II - Machinability of Beryllium Rod."
Survey of Los Alamos and Pueblo Canyon for Radioactive Contamination and Radio Assay Tests Run on Sewer-Water Samples and Water and Soil Samples Taken From Los Alamos and Pueblo Canyons: "Report of the Survey of Los Alamos and Pueblo Canyon for radioactive contamination and radioassay tests run on sewer water samples and water and soil samples taken from Los Alamos and Pueblo Canyons." The objective of this report was to determine the extent and sources of radioactive contamination in the areas studied.
Problems of Air-Borne Contamination in Handling of Pu F₄ Powders: Abstract: Studies were made of the air-borne contamination present during the operation of reducing plutonium tetrafluoride powder to the metal. Equipment design changes were made and operation technique changes were made until the amount of contamination present during operations was well below tolerance levels.
A Method for Rolling Uranium Foil: "This report gives briefly a rather simple method for fabricating foils from uranium buttons. Two log sheets one of a U-238 run and one of a U-255 run are given."
Fraunhofer Diffraction Pattern Produced by a Slit of Varying Width and its Application to High Speed Cameras: Abstract: "A theoretical and experimental investigation is made of the diffraction pattern produced by a slit, whose aperture varies uniformly from a constant value A to zero. The results of this investigation are applied to a proposed high speed camera. It is shown that diffraction effects are very serious and cannot be neglected. It seems, unless the suggested design of this high speed camera is changed, the camera will be of little use for accurate measurements, and photographs will show too much blue to give details."
Methyl Methacrylate Casting Resin: Abstract: "This report describes work done to improve the casting characteristics of methyl methacrylete resin under CMR-6-18 authorization. The experimental program was initiated with the objectives of decreasing casting time, bubble formation and shrinkage. It has been found that by use of a common solvent for monomer and polymer concentration in monomer can be attained greater than any previously reported in preparation of a methacrylate casting resign. Incorporation of this greater amount of polymer has produced the desired effects. A bibliography of relevant literature is included to which reference is made in the text."
Installation of a Chemical Research Laboratory: Installation of a chemical research laboratory.
The Neutron Energy Distribution in the Center of the Los Alamos Plutonium Reactor: The following report examines the fission counter, fission plates and activation results of the neutron energy distribution in the center of the Los Alamos plutonium reactor.
Determination of Particle Size Distribution and Surface Area by Photometry: The following report describes procedures taken to utilize the photelometer to procure the most rapid and reliable determinations, but the goal of the tests presented was to create satisfactory dispersions of particles to analyze.
Effect of Temperature and Reactivity Changes in Operation of the Los Alamos Plutonium Reactor: The operation of the Fast Reactor is considered in terms of normal equilibrium conditions and normal shut-down. The proposed loading, control rod adjustment and subsequent "floating" operation are discussed. Safety devices and interlocks are described. Temperature and reactivity changes are examined with respect to various system failures, phase changes, and "flashing" of the reactor. Slow changes due to faulty slug cooling are also considered. The calculations were initially based upon 10 kw operation. Performance tests of the mercury system now indicate that 20-kw operation may be feasible.
The Mathematical Development of the End-Point Method: Detailed study of the mathematically developed end-point method and its application to the Milne kernel.
Isolation of High Activities of Xe¹³⁵ at the Omega Water Boiler: This report records two samples of Xe-135 that have been isolated with activities sufficient for the measurement of the cross section of Xe by the velocity spectrometer technique.
Safety Tests on Hand Stacking of U-235 Cubes: From abstract: "Critical assembly tests have been made on the Pajarito Universal Machine to determine the safety limits of handstacking cubes of 95% U-235 in spherical geometries preparatory to making critical assemblies of U-235 in an "infinite" tuballoy tamper. The U-235 cubes were stacked as pseudospheres in a cavity at the top of a tuballoy block 12" high and 8" on a side, and the assembly tamped by locating it inside a doughnut shaped water tank whose tamping effect is equivalent to the tamping caused by personnel necessary for hand stacking."
An Analysis of Project Data on the Corrosion of Uranium in Various Media: This is a summarizing and reviewing report in which almost all the experimental data representing Project work done prior to 1949 on the corrosion of pure uranium are brought together and analyzed. New data obtained in this laboratory on corrosion rates in laboratory atmosphere and on the identification of corrosion products by electron diffraction are included. The data for corrosion in each of several different media have been plotted according to logarithm-of-the-rate versus reciprocal-temperature coordinates; and from these plots values for the energies and entropies of activation of the corrosion reactions have been obtained. By theoretical treatment of the role of oxygen as a negative catalyst, it is shown that this element may be expected to "poison" the corrosion rection and then act as a corrosion inhibitor. A practical significance of these data analyses is that they explain why machined uranium parts stored in inert atmospheres (helium or argon) containing only very small amounts of water vapor will corrode relatively rapidly with the formation of loose powdery oxide, whereas similar parts may be kept in dry air almost indefinitely with formation on their surface of only a discoloring, but adhered, oxide coating.
A Modified Decade Scaler: Final Report on Project Authorization Number CMR-3-5: Final report describing the development and usage of an automatic decade scaler which operates for a fixed number of counts, developed for use with a Geiger tube.
Fabrication of Uranium Wire: From abstract: "The present report describes experimental work performed to establish a procedure for the production of uranium metal wire. In all cases, the size of the initial rod was 1/2 inch diameter. Three materials were used: hot extruded tuballoy rod, high purity cast tuballoy rod, and cast U-235 rod."
Spontaneous Fission of 48: Report discussing an experiment to reinvestigate the spontaneous fission of 48 (Pu-238) in an effort to determine a more accurate value for the spontaneous fission constant that was found in a previous experiment.
Preliminary Report on Thermal and Electrical Conductivities of Some Plutonium-Aluminum Alloys: Abstract: "The thermal and electrical conductivities of a series of Pu-Al alloys have been determined in the range 0.12 atomic percent Pu. The conductivities are approximately proportional to the volume of free aluminum."
Oralloy Hydride Critical Assemblies: Part I of this report covers critical-mass determinations for pseudospheres of oralloy hydride composition (approximating UH3) in 8"-thick Tu and Ni tampers and in the Tu tamper with Ni liner. The critical mass of a hydride cube in the thick Tu also is given. Data on weight and dimensional changes of hydride pieces during the period of use are included. In Part II are presented the results of Rossi time-scale measurements on the hydride assemblies. Values of alpha at delayed critical and its variation with mass in the neighborhood of delayed critical are given. Measurements on the activation of various detectors within the hydride assemblies are described in Part III. Results as a function of radial position are given for Au, for Au shielded by Au and by Cd, for S and for fission catchers with U235 and U238. Reactivity changes resulting from the introduction of foreign materials into the hydride assemblies are discussed in Part IV. Apparent regularities with respect to Z and qualitative interpretations of variations with radius are pointed out. From data for various radial positions, changes in critical mass corresponding to small changes in composition and density are computed.
Oralloy Shape Factor Measurements: Measurements have been at the Pajarito remote control laboratory to determine the effect of change of shape on system reactivity for oralloy cylinders. Systems tested include cylindrical configurations with various height-to-diameter ratios ranging from slabs to rods. Each system reactivity is referred to that of a sphere in the same tamper. Reactivity tests were made on bare (untamped) Oy configurations, as well as on systems In tuballoy tampers 1.12,1.87,and 8.0 thick. The amount of reactivity change associated with a particular cylinder height-to-diameter ratio is feud to be a function of tamper thickness, and is greatest for very thin tampers.
The Reaction of Tritium and Stopcock Grease: This investigation was begun as a result of a mass spectrometric measurement of two samples of tritium which had been stored for several months in Pyrex glass bulbs using stopcocks. The first of these was originally supposed to be of extremely high isotopic and chemical purity. What was observed at this time was 1.45 H had accumulated, and that tritiated methane, CT4, was also present to the extent of 0.18%. A consistent attempt had been made in this sample to protect the gas from contact with the grease by covering the stopcock with mercury. the second sample was a composite of T2 samples of various degrees of enrichment with an isotopic analysis of 92% T. No protection had been attempted during its storage, and 0.86% CT4 to be present.
A Design for a Rotary Reactivity Control for a Test Reactor: Tests made on the Oy-Tu reacting assembly at Pajarito indicate that the lateral displacement of two halves of the active material within the assembly can be used as a control mechanism on this type of reacting assembly. This report describes a reacting assembly using a rotary control mechanism based on this principle and indicates the sensitivity of control possible with such a device.
Development of Forging Techniques for Uranium: Uranium has been successfully forged using a Lobdell-Nazel forging hammer and a forging temperature range of 500 to 650 degrees centigrade. Using standard forging techniques, the metal readily flowed at the temperature chosen. A noticeable increase in tensile strength, yield strength and percent elongation was obtained in forged metal as compared with cast metal. To obtain complete recrystallization and uniform grain size, a minimum of approximately 75 percent reduction in cross section by forging followed by an anneal within the range of 500 to 600 degrees C is required.
Development for Techniques for Rolling Uranium Metal: Uranium can be rolled from cast metal or forged ingot to sheet satisfactory for cupping, deep drawing, and similar fabrication procedures by a combination of hot breakdown in the neighborhood of 600 deg C and warm finishing at 225 to 325 deg C. Sheet may also be obtained by hot rolling alone and by warm rolling alone. However, it is difficult to secure a uniform, controlled grain size by hot rolling only and warm rolling is time consuming because of the limited reduction per pass obtainable. The combination of hot and warm rolling afforded best and most practical method to secure good quality sheet in the quantity required. The percent reduction by hot working does not appear to be critical, but at least 60% warm reduction is desirable to obtain complete and controlled grain size by recrystallization with high ductility and strength properties. Except for research investigation, rolling of uranium below 225 deg C is not recommended. In the temperature range considered (below 225 deg C), reduction is difficult and must be limited to one to two percent if edge cracking is to be avoided. Hot rolling of unplated uranium from the as-cast or as-forged surface is recommended, using a bath of 35% Li2CO3 plus 65% K2CO3 for a heating medium. No further preparation other than washing the salt from the hot rolled surface is required before warm rolling, and a bath of Meltemp No. 7 oil is recommended for warm rolling. Work roll speeds and temperatures are not critical, and moderate to light reductions per pass are recommended for easiest rolling and best results. Alternate cross-rolling is recommended during hot breakdown, but continuous rolling in one direction during warm finished is satisfactory. Starting with an as-cast tensile strength averaging 60,000 psi, as-rolled sheet up to 230,000 psi was produced, …
Neutron Energy Distributions Inside the Fast Reactor: This technical report presents results of nuclear plate work carried out to determine the neutron energy distribution inside the Los Alamos fast reactor. Most of the distributions which were investigated are valid over the energy region from 0.4 to 6 Mev. The results show that at the center of the reactor pot about 65% of the neutrons are located below 1 Mev in a rather narrow energy region which has a maximum in the neighborhood of 0.5 to 0.6 Mev. Above 2 Mev the energy distribution is similar to that of a plutonium fission neutron spectrum, i.e. the spectrum decreases exponentially, diminishing by a factor of 10 in intensity over an energy range of about 4 Mev. The leading geometry of the reactor pot does not seem to appreciably affect the spectrum at the center of the pot. However, spectra determined outside the pot can be significantly altered by the particular viewing geometry employed to examine the neutrons coming from the center of the reactor.
Impact Extrusion of Uranium: Uranium has been successfully impact extruded into typical cylindrical shapes of conventional design. Extrusion was carried out in the "gamma" region by heating cast uranium slugs to a temperature of approximately 1050 degrees C. Protection against oxidation was afforded by surrounding the slugs during heating with an inert atmosphere of argon gas. Impact extruded shapes possessed physical properties which are better than the properties of as-cast metal. Also, extruded shapes show a uniform internal structure with flow lines characteristic of commercial impact extruded pieces formed from other metals. Impact extrusion, as a fabricating processes for uranium, maybe applied successfully to produce complicated shapes or forms not practical by casting or where savings in metal and machining time is desired. The process would not appear to be commercial unless a large quantity of pieces was required.
Short Period Gamma-Rays from U235 Fission Products: A search for gamma-ray activities with period 1-100 msec from thermal neutron fission of U235 gave negative results. 0.43 +- 0.03 sec was the shortest observed. The period of B12 was found to be 27 +- 3 msec. The cyclotron beam was pulsed to supply 1-10 msec neutron bursts. coincidence scintillation deters were employed.
A Spectrophotometric Determination of Multimicrogram Amounts of Plutonium: A spectrophotometric method for the determination of plutonium wing sodium alizarin sulfonate has been developed. The red plutonium-alizarin sulfonate color is developed in solutions having a pH of about three in the presence of a formic acid-sodium formate buffer, and the resulting absorption is measured at 530 millimicrons. Most interfering cations, particularly iron(III), are removed from the plutonium solutions by means of electrolysis using a mercy cathode. Aluminum(III), in quantities up to 3 percent of the plutonium content, may be tolerated in this procedure. Chloride and nitrate ions produce no interference over the concentration range studied, while tartrate, citrate, oxalate, and fluoride ions cause low results. The analysis of a large series of pure plutonium solutions, ranging from about 25 to 150 micrograms of plutonium in 10 milliliters, have a standard deviation of 0.92 percent for the determined plutonium content.
Energy Distribution of Fast Neutron Beam: Experimental techniques are described for the spectral measurement of a collimated fast neutron beam. A hydrogen filled cloud chamber, proton recording nuclear plates, and threshold fission foils were used as neutron detectors in the measurements. As an application of the above technique, the energy distribution and absolute flux of the fast neutron beam emerging from port 5W of the Los Alamos fast rector has been measured from 0.1 Mev to 18 Mev. The result show a spectral curve possessing a maximum between 9.25 and 0.30 Mev and having an exponential decrease at energies above 1.5 Mev. The mass energy of the distribution is at 0.55 Mev and the slope of the exponential section is 3.1 - 0.1 Mev per decade of intensity decrease.
The Nickel-Plutonium System: A tentative nickel-plutonium constitutional diagram was based on data obtained by thermal analysis, metallography, and x-ray-diffraction techniques. The systema is a complex one with the following important features. Nickel is soluble in epsilon plutonium, extending the epsilon field to 4.3 at.% nickel at 465 deg C. Nickel and plutonium form six intermetallic compounds, PuNi, EnNi/sub 2/, PuNi/sub 3/, PuNi/sub 4/, PuNi/sub 5/, and PuNi/sub 9/. The compound PuNi/ sub 5/ forms congruently from the melt at approximately l300 deg C, whereas the other compounds form peritectoidally. The extended epsilon field terminates in a eutectoid reaction at 415 deg C and l.5 at.% nickel. Epsilon plutonium and the compound PuNi form a eutectic system at 465 deg C with a eutectic composition of l2.5 at,% nickel. Nickel and the compound PuNi/sub 9/ form a eutectic system at l2l0 deg C with a eutectic composition of 92 at.% nickel. Plutonium forms a limited solid solution with nickel.
A Study of an Accidental Radiation Burst: An accidental burst of radiation occurred at the laboratory on 1 February 1951 during remote control operation of a critical experiment. There was no personnel hazard. Normal operations were resumed within 24 hr, and the active material involved in the burst returned to service within three weeks. An unforeseen brief excursion into the prompt critical region was engendered in the act of scramming the assembly at the end of a series of measurements. This report describes the effects of the burst and analyzes the probable causes in some detail.
Radiologic Hazards Predicted for a Given Height Burst of an Atomic Bomb: Abstract: An appraisal is made of the radiologic hazard created by a 1000-ft. high air burst of a nominal sized nuclear bomb. Three sets of graphs are included which show the relations between dose rate (milliroentgens per hour), time post-shot, and distance from Ground Zero for a soil having given constituents. Estimates are given for fall-out activity (gamma) for distances up to about 200 miles from Ground Zero immediately after fall-out. It is pointed out that the radiologic hazard due to fall-out in the example cited is insignificant; further, that the radiologic hazard from similar nuclear bombs bursting at different heights above the ground will vary to a considerable extent.
Forming of Uranium in the Gamma Phase Temperature Range: It has been found relatively easy to form uranium in the gamma phase temperature range by hot pressing, forging, or extrusion. The metal is quite plastic and flows readily to form a shape. Several temperatures from 800 degree C to 1000 degree C were investigated. No forming difficulties were experienced with the metal at the several temperatures concerned. The major difficulty in gamma phase hot pressing or extruding was associated with the tools. Metals or ceramics were not successful as tools for one or more reasons concerned with: lack of hot strength, reactions with the uranium, failure in thermal shock, and tendency to spall. Graphite was found to be the best material available, but it is not entirely satisfactory because of low strength. Uranium formed in the gamma phase possesses some refinement of grain structure as compared with as-cast metal; however, the grain size is quite large. No physical properties of the gamma phase formed metal were determined.
The DD and TD Cross Sections: The total cross sections of the reactions DDp, DDn, TD at 10 kev to 10 Mev are estimated from a review of the experimental data up to January 1951. Maxwell averages for DDp and TD computed from these estimates are given, together with some fitted analytic expressions provided for machine use. A collection of the identifiable earlier estimates is also included for reference and for comparison with the new figures. For relative order of magnitude purposes, cross sections and the derived Maxwell averages are given down to 50 ev using the theoretical Gamow slopes for the extrapolation. Gamow plots for the derived cross sections above l0 kev arc also given. Much of the primary experimental data exists in the form of thick target yields and we find the most uncertain factor in converting these thick targets yields into cross sections is the magnitude of the D/sub 2/O stopping cross section. The particular D/sub 2/O stopping cross section relation used in this derivation together with some of the earlier stopping cross sections are given. Thick target yields are included for both DD and TD on D/sub 2/ targets, at 0.01 to 1 Mev, experimental values being supplemented by calculated values.
The Decontamination of Uranium from Fission Products by the Use of the Uranyl Oxalate Precipitation Reaction: Abstract: "Decontamination factors of the order of 10-4 were obtained for Beta and Gamma emitters present as fission products when uranium was precipitated from 50 mC activity level solutions as uranyl oxalate under normal uranium yield conditions for three cycles (~60%). Factors of the order of 10-3 were obtained by the use of this reaction with similar solutions under relatively high uranium yield conditions for three cycles (~90%). The uranium peroxide precipitation reaction proved to be of no value on such solutions, yielding decontamination factors of only 17.1 Beta emitters and 1.2 for Gamma emitters for three cycles."
The Polarographic Determination of Uranium in the Presence of Plutonium: Strubl's polarographic method for the determination of uranium in the presence of iron can be used for the determination of uranium in plutonium solutions. A hydroxylamine hydrochloride solution (2M) is used as the supporting electrolyte. This reduces the plutonium to the plus three oxidation state without reducing the uranium. The uranium may then be determined polarographically by measuring the height of the uranyl reduction wave (UVI to UV) at -0.35 volts (vs. S.C.E.) applied potential. Solutions with a U/Pu weight ratio as low as 3.5 x 10(-3) were analyzed with an error of less than 2%. This error increased to 6% for solutions of 1 x 10(-3) U/Pu ration and is considerably larger for smaller U/Pu ratios.
Exploratory Studies of Hydrazine Formation by Radioactive Ionization: The production yields of hydrazine by various ionization methods are compared. The maximum value of M/N (number of molecules reacting per ion pairs) for electric discharge was 0.25 and for beta particles on liquid ammonia, M/N = 0.31. A 1-Mev reactor could produce 1.6 kg of hydrazine per hour if M/N = 0.04 as determined by alpha particles on liquid ammonia. About 300 ev of energy were needed to form a hydrazine molecule. (C.J.G.)
The Inhour Equation for the Tuballoy Tamped Oralloy sphere: Exponential rise times, T, of neutron flux in an Oy-Tu assembly have been measured for a set of points essentially equally spaced reactivity-wise in the interval between delayed and prompt critical corresponding to [infinity] > T > 5 seconds. The relationship between positive period and reactivity thus obtained is used to decide (preferentially) between two currently used but divergent collections of delayed neutron data, specifically with respect to the relative abundances of delayed neutrons in the different decay periods. Results of other reactivity measurements supplementing the positive period data are also given.
Gas Discharges : Lecture Series: Most books on the subject of gas discharges describe the multiple banded structure which appears in the flow between two electrodes. This structure is actually due to the difficulty in getting electrons out of the cathode to support the discharge. These electrons are obtained by having a large enough potential drop near the cathode so that the positive ions may strike it hard enough to product secondary electrons. If one substitutes a hot cathode to produce a copious quantity of electrons, the banded structure will be radially changed. Hence the banding is not a pure property of the discharge, but is a complication brought on by the presence of electrodes.
The Pressures and Temperatures Developed During the Reduction of Uranium Tetrafluoride by the Bomb Method: The pressure and temperature cycles developed during the bomb reduction of uranium tetrafluoride by calcium have been determined. Data for the 250, 500, and 1000 gram scale reductions are given, and the apparatus used is described.
Determination of Bismuth in Plutonium-Bismuth Solutions: Bismuth analytical methods were investigated for the purpose of selecting procedures which are satisfactory for the analysis of solutions containing plutonium and bismuth. The gravimetric procedure which is recommended for samples containing these two elements includes removal of the plutonium by peroxide precipitation, separation of the bismuth by precipitation with sodium carbonate, and final ignition of the bismuth as a phosphate. Necessary equipment and experimental technique are described. In the analysis of eight known samples by the recommended method, the average recovery of bismuth was 99.76 percent, with a standard deviation of 0.22 percent. The known samples contained about 35 mg of bismuth and 25 mg of plutonium. For similar samples in routine work, the confidence limits at the 95 percent level for the average of triplicated determinations are +- 0.30 percent of the bismuth in the the sample. Other methods investigated and having possible application for some Pu-Bi analysis problems include electrodeposition of bismuth on a mercury cathode and gravimetric analysis with BiCr(CNS)6 as the weighed product.
Determination of Cadmium in Plutonium-Cadmium Solutions: Determination of cadmium in plutonium-cadmium solutions was successfully accomplished by separating the plutonium as an insoluble peroxide, evaporating the solution containing the cadmium, and weighing the latter as a sulfate. with 5 t0 20 mg of cadmium and similar amounts of plutonium, the 95% confidence limits for the average of triplicate determinations was to be +- 0.3 percent of the cadmium in the sample. When samples contained as little as 5 mg of cadmium, it was necessary to correct the weight of cadmium sulfate with a carefully determined reagent blank which originated mainly from the action of hydrogen peroxide on glass containers.
Remote Control Equipment for Plutonium Metal Production: Design and construction of remote control equipment for plutonium metal production are described. Criteria for the design of the equipment included the following: rubber gloves were to be completely eliminated; all mechanisms were to be built as integral units to facilitate replacement through use of the plastic- bag technique; no accessory equipment such as switches, valves, piping, or cylinders were to be inside the contaminated enclosure unless required to handle the plutonium; and all units were to be tested in mockups before final design. The chemical process, general layout, and operating function are outlined. Descriptions are given of all mechanical units, electrical systems, hydroxide slurry systems, ventilation systems, and chemical tanks and manifolds. (W.L.H.)
Three-Velocity Neutron Diffusion Calculations for an Untamped Oralloy Sphere: The results of a series of neutron diffusion calculations relating to an untamped Orally sphere are presented in detail in this report. The three-velocity neutron transport theory was taken as the basis for the analytical work preceding the computations. This particular theory, also known as the transport approximation, is defined in LA-1271 and known to be quite accurate for assemblies primarily involving materials of large atomic weight. For a sphere of uniform density and atomic composition the transport theory has another advantage. It can readily be formulated in terms of simultaneous integral equations (in our case three), relatively simple in form, involving the collision densities [formula] and a set of parameter values describing the materials. Nb(r) is , as indicated, a function of the radial distance [formula] and the velocity index g, g - 1, 2, 3. The parameters, fifteen in number for the three-velocity theory, are comprised of the velocities, the inverse mean free paths, and the transfer coefficients.
Oralloy Cylindrical Shape Factor and Critical Mass Measurement in Graphite, Paraffin, and Water Tampers: Critical mass of an Oy (93.9%) sphere in graphite is given as a function of graphite tamper thickness. It was shown that approximately 20(in) of graphite is effectively infinite and that the approximately 17(in) used herein is approximately 98% infinite. Critical mass measurements of Oy (93.9%) spheres and cylinders of different diameters are given for approximately 17(in) graphite tamper, for effectively infinite paraffin tamper, and for effectively infinite water tamper. From these measurements cylindrical shape factors were computed. Both shape factors and critical masses are shown in Figs. 22 and 23 as function of the critical height to diameter rate of the cylinders.
The Relative Physiological and Toxicological Prosperities of Americium and Plutonium: The relative physiological and toxicological properties of americium and plutonium have been studied following their intravenous administration to rats. The urinary and fecal excretion of americium was similar to that of plutonium administered as Pu(N03)4. The deposition of americium the tissues and organs of the rat was also similar to that observed for plutonium. The liver and the skeleton were the major sites of deposition. Zirconium citrate administered 15 minutes after injection of americium increased the urinary excretion of americium and decreased the amount found in the liver and the skeleton at 4 and 16 days. LD305° studies showed americium was slightly less toxic when given in the acute toxic range than was plutonium. The difference was, however, too slight to be important in establishing a larger tolerance dose for americium. Survival studies, hematological observations, bone marrow observations, comparison of tumor incidence and incidences of skeletal abnormalities indicated that americium and plutonium have essentially the same chronic toxicity when given on an equal basis. These studies support the conclusion that the tolerance values for americium should be essentially the same as those for plutonium.
The Reaction of Uranium With Purified Water: Report discussing the reaction of uranium with pure water. The reaction was followed by using a method of measuring hydrogen evolution.

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