The recent production by Thompson, Ghiorso, and Seaborg of a radioactive isotope of berkelium (atomic number 97) makes it possible to investigate the chemical properties of this transuranium element by means of the tracer technique. This isotope has been prepared through the bombardment of Am{sup 241} with about 35 Mev helium ions in the 60-inch cyclotron of the Crocker Laboratory and is believed to have the mass number 243, or possibly 244. This Bk{sup 243} has a half-life of 4.6 hours and decays by electron capture with about 0.1% branching decay by alpha-particle emission. In the present tracer chemical experiments, the radiations accompanying the electron capture process were used as a means of detection and were counted in two ways. Where the sample deposits on the platinum plates were essentially weightless, as was the case following the evaporation and ignition of the elutriant solutions in the column adsorption experiments, a high efficiency was obtained by using a windowloess proportional counter to count the Auger electrons. The thicker samples from the precipitation experiments in which carrier materials were used were counted close to the thin window (3 mg/cm{sup 2} mica) of a bell type Geiger counter filled with 10 cm. xenon …

The purpose of this memorandum is to present and analyze, in terms of the current status of knowledge of radiation damage to graphite, the data available at the present time on the expansion status of the graphite in the piles, and suggest, in terms of this analysis, several possibly feasible curative and preventive measures. The portion of the data to be covered in this memorandum consists of that obtained during the last four years from pile motion measurements and from tube bowing measurements, and particularly that from graphite mining operations during the last six months. The objective to be attained is twofold: (1) the information developed here should permit a better understanding of the need for and development of future corrective measures to be applied to the present piles, and (2) this summary will serve as a basis for further experimental work necessary to place the conclusions on a more firm foundation. This memorandum is being issued at this time, although present ideas and conclusions are in a somewhat uncertain state, in the hope that the currently most feasible preventive measure might be applied to the DR Pile before startup.

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This paper presents the requirements of a nuclear amplifier of short resolving time, designed to accept pulses of widely varying amplitudes. Data are given which show that a proportional ionization chamber loaded with a 1,000-ohm resistor develops pulses of 0.5 microsecond duration and several volts amplitude. Results indicate that seven basic requirements are imposed on the amplifier when counting soft beta and gamma radiation in the presence of alpha particles, without absorbers. It should, (1) have a fast recovery time, (2) have a relatively good low frequency response, (3) accept pulses of widely varying heights without developing spurious pulsed, (4) have a limiting output stage, (5) preserve the inherently short rise time of the chamber, (6) minimize pulse integration, and (7) have sufficient gain to detect the weak pulses well below the chamber voltage at which continuous discharge takes place. The results obtained with an amplifier which meets these requirements is described. A formula is derived which indicates that redesign of the proportional ionization chamber might eliminate the need for an amplifier. This may be possible if the radioactive particles are collimated parallel to the collecting electrode.

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Uranium is recovered as an aqueous solution of uranyl nitrate and nitric acid in both the tributyl phosphate metal recovery process and the Redox separation process. The streams are designated as RCU and IIIEU in the respective processes. For metal recovery these streams are combined. The purpose of the nitric removal operation is to minimize equipment corrosion and to restrict contamination of the final uranium oxide with corrosion products which might be formed in the elevated temperature reactor employed for the decomposition of uranyl nitrate to the oxide. Because of the large quantities of uranium being processed it is desirable to conduct the concentration of the combined RCU and IIIEU streams in a continuous type process to reduce the operating and fixed charges. Determination of the physical and chemical properties of the dilute aqueous uranyl nitrate -- nitric acid system, as it progresses toward an essentially nitric acid free concentrated state, is necessary to define the optimum operating conditions.

A series of experiments on exposure of man and rats to tritium gas (HT) or tritiated water (HTO) are reported. In one human experiment 3 millicuries of HTO was administered in 200 milliliters of water by ingestion. Absorption into the blood stream was linear with time and complete in about 45 minutes. Body water turnover was measured over a period of six days by weighing all food and fluid intake and all excretory output. For four days water turnover was kept near normal (2.7 liters per day). During the last two days water turnover was increased to 12.8 liters per day. Tritium excretion rates was determined on eight other human subjects in which water turnover in which measured less precisely. The biological half-life of HTO in nine human subjects varied from 9 to 14 days on ad libitum and was reduced to 2 1/2 days in one subject on high water intake. The tritium activity in sweat, expired water vapor, septum and urine was found to be essentially the same as that in water from the blood. Rats were continually exposed to various concentrations of tritium in inspired air (0.000001 to 0.03 microcuries per ml) for periods up to 145 …