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A meeting was held on May 17 to review possible alternate designs of horizontal rods for 105-C. The system used on ``C`` must operate satisfactorily at an anticipated graphite temperature of 380 C (760 F) with the possibility expressed by the Technical Division that this temperature limitations may be raised if satisfactory new pile atmospheres can be developed. The design will be based on a maximum graphite growth of 3 inches at a distance of 3 feet from the edge of the graphite block. This value ignores the anticipated favorable results from graphite coring, and is greater than the growth expected in ``C`` based on experience with present reactors. A satisfactory rod end seal configuration is required for these conditions. It was decided that a round control rod with external seal would be recommended to meet these conditions.

This volume presents the quarterly results of that portion of the research and development which is directed towards establishing new techniques and instruments and towards improving present methods for determining levels of radioactivity accurately and safely. The locally developed amplifier of high gain and of wide dynamic range has been shown to provide plateaus suitable for the simultaneous counting of alpha and beta particles. Commercially available amplifiers have failed to exhibit suitable plateaus when used under the same conditions. This locally developed amplifier in conjunction with the Nuclear Instruments PC1 chamber has made it possible to estimate beta energies down to 0.02 million electron volt, which is to be compared to a former lower limit of 0.1 million electron volt. A fast neutron survey meter must be simple, lightweight, portable and efficient and must provide discrimination against gamma rays. The first step, which is the design of a suitable detecting device has been successfully completed as good efficiency and good discrimination against gamma rays have been achieved. The necessary electronic circuits must now be engineered to provide the requisite simplicity lightweight and portability.

This is a progress report of the production reactors on the Hanford Reservation for the month of April 1951. This report takes each division (e.g., manufacturing, medical, accounting, occupational safety, security, reactor operations, etc.) of the site and summarizes its accomplishments and employee relations for that month.