The Design Basis for Pinhole Gamma-Ray Cameras*

This report presents the results of a study of the design and use of pinhole gamma-ray cameras in examining irradiated fuel rods nondestructively. A theory is presented for the performance in terms of sensitivity, resolution, field of view, contrast, and magnification. The performance is described in terms of parameters that are analogous to those used in describing ordinary visible-light cameras. Several cameras were built of depleted uranium to achieve a desired level of resolution and sensitivity. All the cameras have been used successfully to examine irradiated fuel pins nondestructively, and are capable of demonstrating damage, swelling, and cracking in fuel rods. Resolution is of the order of 10 to 20 mils depending on the average photon energy of the source being viewed; they have a 3½-in.-diam field of view at a distance of 2 ft from the camera's center.