Geometrically Controlled Partially Filled Interrogation Volume: A Nontraditional Approach to 235U Enrichment Measurement by Portable Germanium Spectrometer

Enrichment measurements to determine nuclear material control and accountability (NMC&A) are easily performed via the gamma spectrometry enrichment meter method for large cylinders containing a wide range of enrichments. In this work, the same method has been applied to measuring small sample cylinders. The prohibitively large negative bias imposed by the incomplete filling of the detector’s view has been overcome by calibrating with the same type of cylinder as that containing the sample. Normally, the system is calibrated with sources such as the NBS-SRM-969 U the end by a small diameter Germanium detector, these standards are essentially infinitely thick and wide with respect to the 185.7 keV gamma peak due to the self-shielding of the U words, the entire view of the detector is filled. This requires that the geometry of the sample be such that it covers the entire region of interrogation of the detector or a calculation to offset the void area is performed. The latter proves to be very cumbersome. In this work, calibration was performed using UF with certified samples measured were also contained in 1S cylinders. Even though a significant portion of the detector’s view was void of UF geometry of the material was held constant for the standards and samples resulting in highly successful measurements. A positioning device was utilized to couple the cylinder to the detector face, resulting in geometrical reproducibility. The result was an extremely low bias and standard deviation of the enrichment measurements while maintaining the speed of the enrichment meter method. 235U content in UF6 for3O8 standards. Viewed from3O8. In other6 standards235U enrichments contained in type 1S cylinders. The6, the