NMIS PLUS GAMMA RAY SPECTROMETRY FOR VERIFICATION OF WATER AND B4C CONTENT OF THE ISOLATING MATERIAL FOR STORAGE AT HEUMF

The Nuclear Materials Identification System (NMIS) with gamma ray spectrometry can be used to verify the water and B4C content of BoroBond??, which is the material in the rackable can storage boxes (RCSB) of the Highly Enriched Uranium Materials Facility (HEUMF) at the Y-12 National Security Complex. The water in the BoroBond?? slows down neutrons so that they can be captured by the boron. The fast neutron transmission measured by NMIS depends on the water content, and the capture events in boron depend on both the water content and the B4C content. Having determined the water content from fast neutron transmission measurements, the B4C content can be estimated from the measurement of the 478 keV boron-capture gamma rays. A variety of measurements were performed with BoroBond?? blocks of varying thickness, B4C content, and water content, as well as with a mockup of a RCSB of fixed water and B4C content. These measurements were aimed at establishing a method to verify the water and B4C content of the RCSBs at the production site, or subsequently at the Y-12 National Security Complex before or during the operating lifetime of the RCSB at the HEUMF.