From introductory paragraph: "This is the first quarterly report of the Biology Division of the Argonne National Laboratory. During the three-month period covered by this report, a large share of the time of many investigators has been spent in collating work done under the Biology Section of the Metallurgical laboratory for publication in the Plutonium Project Record. The large amount of work done under wartime pressure has made this, as in other divisions and projects, an important part of the transition to the post-war period."

Abstract. A particle ionization chamber of sensitivity sufficient to detect a source of one neutron per second has been used to measure the neutron yield from a thick target of sulfur upon bombardment with polonium alpha particles. The high-geometry boron trifluoride chamber used had an efficiency of 1.9 percent for fission neutrons. The neutron yield from a thick target of sulfur was measured by this instrument and found to be .0035 +- .0013 neutrons per million incident polonium alpha particles.

A uniform intensity flat top spill-out cannot be obtained by manual control for two reasons: 1. The horizontal density of the internal beam of the Cosmotron is far from uniform. As a result, a manually controlled linear motion of the internal beam into a target will result in a non-uniform spill-out intensity. 2. Stability requirements of the Cosmotron magnet voltage are not easily met without feedback because of inherent component stability. The proposed servo system will sense the external beam intensity, and correct the magnet voltage to keep this intensity constant. This servo must operate through the transfer function of the main ignitron system and the flat top filter. Both of those transfer functions impose special problems.

The possible hazards from the refining and processing of thorium are of wide interest in atomic energy work. A review of the data available was made at Hanford in the last year to support consultations on the hazards of radioisotopes with other plants which may handle thorium. Since a major discrepancy between the published values of air MPC's and the metabolic data was noted, a review of the calculations on thorium was made in order to obtain the best estimates available. This document tabulates the pertinent data and applies them to the calculation of the MPC of thorium.

Equipoise-2, a two-dimensional, two-group neutron-diffusion code in R-Z geometry, has been programmed for the IBM-7090 computer. This code was designed to permit the running of large numbers of cases without requiring excessive machine time. Typical running times are of the order of one to three minutes per case for a 1000-point problems. The maximum number of mesh points that can be used is 1444.