Measurements were taken to provide experimental evidence for determining the feasibility of a proposed method for converting Pu240 to 241 by exposing shielded plutonium to selectively transmitted pile neutrons.

The remodeling, fabrication, and instrumentation of a high vacuum system are described. The faults encountered with the old system and their solution are outlined. Tests were made on diffusion pump oils and on the reduction of pump oil back diffusion. The measurement of high vacuum pressures by a cold cathode ionization gage at various points on a vacuum system are discussed.

This report refutes earlier calculations made in the flux level of exponential piles. The results of the earlier calculations made on subcritical assemblies using critical assembly equations are in error. The calculations used in this report were more successful.

In view of the increasing number of methods for determining plutonium in terms of weight rather than radioactivity, a need has arisen for a plutonium compound that can be used as a gravimetric standard. An easily prepared compound that dissolves readily in nitric acid is desirable. The present study was made to determine the feasibility of using plutonium triflouride as a plutonium standard. The preparation, composition, stability, and ignition of the compound are discuss, as are certain properties of the plutonium dioxide resulting from ignition of the trifluoride.