NDA Technology for Safeguarding Uranium Hexaflouride

The measurement of uranium hexafluoride is an important safeguards activity which is conducted on a regular basis during inspections of facilities handling UF the past six to eight years, most of the measurements of UFg for safeguards purposes have been made upon solid UF^ contained in large storage cylinders. This technique combines the weighing of cylinders with a determination of the U-235 enrichment accomplished by gamma ray spectroscopic measurement of the material. To enhance the reliability of cylinder measurements, new weighing instrumentation is now being used, consisting of a small, portable load-cell apparatus which can be used in conjunction with existing cylinder handling equipment. With it, an independent confirmation can be made of weight of UFg in cylinders. Recently, the "UFg Gas Phase Enrichment Monitor" has become available. This instrument can be used to measure the uranium-235 enrichment of a sample of gaseous UF&; the enrichment is determined directly by simultaneous measurement of the U-235 and total uranium concentrations. Calibration using standards of known enrichment is easy and reliable and the accuracy and precision is better than those of measurements on solid UFf,. It has a direct application at enrichment facilities but it could also be used to measure samples of UFg gas collected from storage cylinders. 6. For