NUCLEAR FORENSICS TECHNIQUE DEVELOPMENT FOR SAMPLES OF SPENT RESEARCH REACTOR FUEL

Weak safeguards and potentially attractive materials provide significant reasons for development of research reactor technical nuclear forensics techniques. Due to the complex operation of research reactors, some traditional means of spent fuel characterization provide inaccurate results. Nuclear forensics techniques for spent research reactor fuel were developed using a combination of spent fuel radiochemical analysis and results from reactor physics simulations. Samples were acquired from research reactor spent fuel at Savannah River National Laboratory using a glovebox inside a hotcell. Models were also prepared using design blueprints, assembly shipper/receiver declarations, and other sources. The simulated output isotopics were then compared to the spent fuel appendix information and radiochemical analysis to verify and validate the reactor physics code used as a forward model in an inverse analysis. The spent fuel sample burnup, initial enrichment, and cooling time were initially reconstructed using analytic calculations. Then using numerical methods the results were perturbed until convergence was achieved. The sample’s power history may also be determined by comparison of different monitor isotopes. In the event of a research reactor spent fuel diversion and seizure, application of this work could potentially reconstruct identifying information about a sample and be used in an attribution methodology.