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."

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.

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.

Measurement of the color intensity of the uranium thiocyanate complex is discussed as a method for the quantitative determination of uranium. Two procedures for amounts from 1 microgram to 1 milligram are described, and standard curves are shown. The effects of numerous foreign ions are shown, and methods of removal for some of these are discussed.

A method using photographic emulsions for the study of neutron distributions is described. The construction of a simple machine for producing experimental critical assemblies in which the method has been used is reported. Sources of error are discussed. Curves of the perturbations when small spheres of various materials are placed in the center of the assembly are shown.

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 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.

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 conductivity of ionized gases is treated by a method similar to that used by Alfven in his book "Cosmical Electrodynamics". The results differ from those of Alfven. In particular, it is shown that Alfven's conclusion, that whenever the Hall current disappears the conductivity becomes independent of the magnetic field, is not true in general. Moreover, it is not true under just the conditions of interest for the "Pinch Effect". The main conclusions of the present paper are (1) of currents down a tube, the ion component is the small fraction of m/M of the electron current, regardless of the magnitude of the magnetic field; (2) the conduction along the tube depends on the transverse motion of neutral mass, i.e. on the radial velocity of u(r) of the gas in the tube.

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.

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 …

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.

A new method to procure RaLa sources was proposed by Group CMR-10, Los Alamos Scientific Laboratory. This method depended upon irradiation of small-diameter U235 wire in the Materials Testing Reactor, Arco, Idaho. A procedure for cladding and sealing U235 wire in stainless steel tubing, by drawing, plugging the tube ends, and welding, was developed, tested, and proved to be satisfactory.