Metal detector study for Hanford

This study was undertaken at the request of the Hanford Works to investigate the possibility of detecting 3/8 inch diameter boron-steel control-balls which become lodged within cracks between the graphite blocks of an atomic pile. The cracks concerned occur radially from 4 3/16 inch diameter holes which pass vertically through the pile. The problem is complicated by the following facts: The graphite blocks are conducting and will therefore give rise to spurious signals primarily due to the cracks between blocks. Numerous aluminum tubes containing water and bars of uranium pass horizontally through the pile at distances closer to the hole than the ball at its extreme position. The vertical holes themselves are warped in an arbitrary manner. Calculations were made to determine theoretically whether or not the ball could be detected. Best operating frequency and coil design were also determined. Tests were made utilizing a specially designed search coil and a test section of graphite pile. Measurements of particle voltage vs. position relative to the coil were made and compared with that resulting from the graphite