Several improvements have been made in the gamma scintillation counter (GSC). The Model V gamma scintillation counter uses a canned thallium activated sodium iodide crystal as a detector. Although the electronic components remain unchanged, a modification of the sample support has been made to improve reproducibility of geometry. To assure comparable results between various counters, they must be operated at the same energy threshold and counting yield. Methods have been developed to assure operation at a preferred energy threshold of 0.1 Mev and an arbitrarily fixed counting yield of 3.36% for Cs-Ba-137. Partial pulse height discrimination against U 237 is also accomplished.

In connection with the study of aqueous-tributyIphosphate (TBP) systems, the study of the interactions of various diluents with the TBP has been extended. The diluents used were mineral oil, Amsco 125-90W, dodecane, n-hexane, cyclohexane, benzene, n-octyl bromide, carbon tetrachloride, chloroform and pentachloroethane. The solubility of TBP in water from solutions of these diluents and the solubility of water in the organic phase was determined. For the paraffin hydrocarbons as diluents the solubility of TBP in water was found to increase with increasing molal volume of the diluent. No evidence for the formation of TBP-water complex of simple mole ration was found.

A continuous gamma-monitoring instrument capable of measuring the activity of the product of the Uranium Recovery plant has been developed and applied under process conditions. It has a detection limit of 15% and a normal range of up 1000% of the activity of natural uranium. Activity measurements made with this instrument have shown good correlation with laboratory determinations and are contributing to improved control of the solvent extraction process.

The approaches to the solution of the problem of removing or nullifying the effect of the hydrolysis of uranyl ion on acid titrations were: 1) use of a complexing agent and titration technique suitable for micro samples; 2) addition of a reagent that reacts with uranium to release 1 or 2 equivalents of acid per mole of uranium present (this permits correcting the titration value for the acid contributed by the uranium, or conversely permits an alkimetric titration of uranium); 3) separation of the uranium and acid with subsequent titration of the acid; and 4) direct titration of the sample with base. All these approaches yielded at least one method suitable for titrating acid in micro samples of uranium nitrate solutions.

Foils of plutonium 239 and uranium 235 have been mounted back to back in a dual ionization fission chamber in the diffracted beam of the Hanford neutron crystal spectrometer. A quantity proportional to the ration of fission cross sections of Pu239 to U235 has been measured as a function of neutron energy from 0.020 to 1.0 electron volts. The results of this investigation are presented graphically in the text.

Gamma scintillation monitor Model 3 is designed to continuously monitor and record the gamma activity of a process solution.