Year
1990
Abstract
Several kilograms of plutonium or highly enriched uranium could be shielded inside a standard 200-liter waste drum so as to assay at 100g or less with current measurement procedures. Because such drums are in common use for transferring transuranic and low-level waste from material access areas to locations of substantially lower security, they could be vehicles for diverting significant quantities of plutonium or highly enriched uranium. The paper suggests practical solutions to this critical safeguards problem. Detection of either excessive neutron shielding, or neutron or gamma ray emissions exceeding an alarm threshold, would be cause to open a waste container and examine its contents. For waste containers that contain uranium and/or plutonium, a valuable tool for penetrating and investigating a \"suspect\" region in a drum is active bremsstrahlung interrogation employed in a computerized tomographic mode. Use of this technique at separate bremsstrahlung endpoint energies offers the possibility of detecting the inclusion of excessive neutron shielding and/or excessive special nuclear material in a 200-liter drum. For plutonium-containing 200-liter waste drums which are known to not contain highly enriched uranium, it might be practical to base anomaly detection on \"poor man's radiography\" plus passive neutron counting that yields the ratio (or a modified ratio) T^/T^of true doubles and triples coincidence counts .