The Detection of Enrichment of Uranium System: A Portable System for Nondestructive Assay of TRIGA Spent Nuclear Fuel

The Detection of Enrichment of Uranium System (DEUS) is a portable nondestructive assay system capable of measuring the U-235 mass remaining in TRIGA Isotope General Atomics) spent nuclear fuel (SNF). The DEUS is described and results from DEUS assay of irradiated TRIGA ® (Training, Research, and® fuel elements performed at the University of Texas Nuclear Engineering Teaching Laboratory (UT) and the Texas A&M University Nuclear Science Center (TAMU) are presented. These measurements were performed February 24-28, 2003, at TAMU and November 10-14, 2003, at UT. Irradiated fuel elements assayed at TAMU consisted of three 20 percent-enriched-U-235- by-weight uranium in an UZrH matrix, which are commonly called standard-plain (STD-PLN), and five 70 percent-enriched- U-235-by-weight uranium in an UZrHEr matrix, which are commonly called FLIP (Fuel Lifetime Improvement Program). The fourteen irradiated fuel elements assayed at UT were all STDPLN. The U-235 mass solutions derived from these measurements are generally within ±5 percent of the declared U-235 mass values. Two FLIP elements measured at TAMU produce a reduced neutron interrogation response that may be associated with fuel-matrix damage. Monte Carlo Neutron Particle (MCNP) calculations show that when fissile materials are diverted from the STD-PLN fuel meat and replaced with nonfissile materials, the DEUS is able to detect this with definitive statistical significance.