The development of nuclear reactors and other sources of nuclear particles has provided the analyst with a new method which has been successfully applied to the determination of microgram and even submicrogram quantities of many elements. In this method, known as "radioactivation analysis," the element to be determined is "activated" through some type of nuclear reaction which produces a radioactive isotope of the element. Since the radioisotope produced decays with its own characteristic radiation and half-life, it is possible, through radiochemical measurements following radioactivation, to devise a method of analysis which is very specific for particular elements. Whenever necessary, the radioisotope is separated by chemical means and its radioactivity is then measured by some type of radiation counter.

Report containing ongoing projects and experiments undertaken by the Oak Ridge National Laboratory's Molten-Salt Reactor Program.

Samples containing 5 to 10 mg of uranium were extracted with hexone (methyl isobutyl ketone) and titrated coulometrically in sulphate media. Relative standard deviations of 0.45% for samples containing 5 mg and 0.56% for 10 mg were determined by precision studies.

The initial and long-term nuclear characteristics of two internally cooled heterogeneous, graphite-moderated, two-region, molten-salt reactors have been studied. These reactors have doubling times of 22.5 years and 27.5 years. Methods of decreasing the doubling times by removing the Pa233 from the core and be increasing the specific power of the reactor are described.

The fire involved approximately 30 liters of isopropyl alcohol as a result of the ignition of about 16-18 liters of isopropyl alcohol and a slurry of thoria and ammonium nitrate in a 20-liter glass carboy. This material was undergoing a volume reduction by boiling in a floor-type metal hood with Plexiglas sides and 3 sliding door on the front of ordinary glass. The alcohol vapor was vents directly into the hood (Fig1.)

A series of critical experiments with blocks of 2% U235-enriched UF4-C25H52 has been initiated at the ORNL Critical Experiments Facility. Thus far assemblies with H:U235 atomic ratios of 195 and 294 have been built in parallelepipedal and simulated cylindrical geometries, both reflected and unreflected. From the results the minimum critical masses for reflected spheres have been determined to be 16.3 and 8.5 kg of U235 for fuel mixtures with H:U235 atomic ratios of 195 and 294, respectively. The minimum critical masses for unreflected spheres of these two fuel mixtures are 24.3 and 12.7 kg of U235, respectively.

A general program has been written to plot curves on the Oracle curve plotter. The supplement includes changes to slow down some of the loops and minimize the possibility of read-around errors and changes to handle special cases.

A qualitative theory for cake formation in ThO2 slurries is presented. The sphere formation which occurs in "Standard" slurry can be explained on the same basis. The irregular and unpredictable yield strength is easily fitted into the theory. On the basis of this theory, the writer has been led to the conclusion that only colloidally stable slurries, or slurries with crystallites or comminution-resistant particles which are large enough to overcome colloidal effects (probably larger than 0.1u) can be used with assurance in the ThO2 reactor system. This conclusion holds for 300 gm/kg slurries as well as for more concentrated mixtures.

In analyzing stresses, deflections, and forces in piping and certain structural systems, it is useful to have a set of equations giving the deflections at any point of a curved beam in terms of the various loads acting on the beam. This technical report presents the deflection equations for a curved circular-arc beam of variable length. The cases treated include in-plane and out-of-plane bending due to forces and moments applied to the end of the beam in three principal directions, and uniformly distributed loads applied along the beam in these three directions. Deflections were calculated by the strain energy method using Castigliano's theorem.

Report issued by the Oak Ridge National Laboratory discussing quarterly progress of the Homogeneous Reactor Project. Progress of operations, design, development, and analysis is presented. This report includes tables, illustrations, and photographs.

In order to test the effect of chromate ion on the corrosion of Zircaloy-2, a 0.04 m uranyl sulfate solution (enriched) containing added acid, copper sulfate and 557 ppm of Cr (VI) was autoclaved with rocking at 280 degrees C for about eight days in the HB-5 facility of the LITR. The average corrosion rate established by the rate of consumption of oxygen was 9.9 mpy at a power density of 4.9 w/ml. It is indicated by comparison with a previous corrosion study under LITR radiation that the presence of Cr (VI) had no significant effect on the radiation corrosion of Zircaloy-2 by enriched uranyl sulfate solutions. However, the data are not conclusive and may be interpreted as showing a low corrosion rate for a limited period (i.e. a short term inhibition) followed by correspondingly rapid corrosion.

A prototype sampler for obtaining samples of high radioactive UO2SO4 solution for use in the HRT is presented. It was successfully operated in conjunction with a low pressure water system and a high pressure, high temperature UO2SO4 system.

A direct titrimetric method for the determination of trivalent uranium in uranium trifluoride and mixtures of fused fluoride salts was developed. The method is based on the stoichiometric oxidation of trivalent uranium to the tetravalent oxidation state with an acidic solution of methylene blue. The sample containing trivalent uranium is dissolved at room temperature in an excess of standard methylene blue solution in a carbon dioxide atmosphere; the excess oxidant is variation of the method is 1.5 per cent for 5 mg quantities of trivalent uranium. The method was applied to various mixtures of fluoride salts containing both trivalent and tetravalent uranium.

Diffusion in an arc plasma across a magnetic field is investigated. The geometry is similar to that reported in ORNL-1890 but with the addition of magnetic mirrors on the ends of the arc chamber. It is shown that mirrors do not eliminate the "short circuit" effect. Comparison of the e-folding length, rₒ, of the radial ion density with and without mirrors, affords a direct measurement of ℓ/λ where ℓ is the arc length and λ the mean-free-path. In addition rₒ is independent of gas pressure with mirrors and varies as √p without mirrors. The condition for the elimination of the "short circuit" effect is discussed, as well as the case in which the "short circuit" is still present but the ions diffuse (rather than stream) to the end walls. In this case rₒ is directly proportional to the gas pressure. These effects are compared to some experimental results of Neidigh

This quarterly progress report discusses ongoing work at the Metallurgy Division at the Oak Ridge National Laboratory. Topics discussed include thorium research, the preferred orientation of uranium, studies in the ceramics laboratory, the homogenous reactor program, studies in the x-ray laboratory, studies in the metallographic laboratory, the experimental plate-cladding program, and fuel and control element fabrication.

From abstract: "An investigation of the radiation stabilities of aqueous solutions of sodium ethylenediamine tetraacetate and sodium acetate was made using a 3000-curie Co⁶⁰ source...A study of the behavior of the standard-size Beckman type glass pH electrodes in a solution containing 0.36 curie of Ce¹⁴⁴-Pr¹⁴⁴ activity per milliliter showed the useful electrode life to be of the order of two to eight days."

This report presents "Results of a critical literature review on pressure drop due to isothermal turbulent flow in noncircular geometries" (introduction).

Technical report summarizing one phase of work done to develop methods of bonding uranium to a metal which is a good conductor of heat. Silver was chosen for contact with uranium because it is easy to plate on uranium and there is no danger of brittle Ag-U compounds being formed at elevated temperatures. [From Abstract]