This is the first of a series of monthly reports covering details of the work of the Engineering Group of the Pile Technology Section of the Technical Department. The monthly Slug Inspection Report is being discontinued as a separate document and is being incorporated in this group report. Included is work on corrosion and blistering; graphite expansion; and irradiation studies.

The excess reactivity available in an operating pile is absorbed in poison columns and horizontal rods. The temperature distribution of the pile is determined by the relative strengths and locations of the poison columns and the configuration of control rods used. A method for adjusting poison columns and rods to improve upon the pile`s temperature distribution is given in Document {number_sign}7-2654, ``Procedure for Improving Temperature Distribution via Rods and Columns,`` Wheeler and Menegus to Jordan, September 9, 1945. A relationship between poison moment (inhour lattice units) and temperature moments (per coat) was theoretically derived in the above document and has since been measured on several occasions on the basis of operating experience. A survey of recent operating data for the F Pile has been made by H. A. Gauper, Jr. with the intent of improving the method for obtaining the temperature and poison moments and relating changes in the two. This study was concerned with only the horizontal and vertical dipole moments. The results of Mr. Gauper`s investigation are summarized in this memorandum.

This monthly report details Physics Department 100 Area technical activities for the month of April 1947.

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Included herein is a historical record of the AAF sponsored NEPA Project during the period of October 1945, to the present time, and covers in narrative form the nature of planning leading to the implementation of the project, the establishment of the operating group and its relationship to the Manhattan District (later to become the Atomic Energy Commission) and the approach to applicable technological problems bearing on both nuclear science and aeronautical propulsion engineering aspects.

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