Comparison Of 252Cf Time Correlated Induced Fisssion With AmLi Induced Fission On Fresh MTR Research Reactor Fuel

Abstract

The effective application of international safeguards to research reactors requires verification of spent fuel as well as fresh fuel. To accomplish this goal various nondestructive and destructive assay techniques have been developed in the US and around the world. The Advanced Experimental Fuel Counter (AEFC) is a nondestructive assay (NDA) system developed at Los Alamos National Laboratory (LANL) combining both neutron and gamma measurement capabilities. Since spent fuel assemblies are stored in water, the system was designed to be watertight to facilitate underwater measurements by inspectors. The AEFC is comprised of six He detectors as well as a shielded and collimated ion chamber. The He detectors are used for active and passive neutron coincidence counting while the ion chamber is used for gross gamma counting. In the past, most of the active interrogation systems along with the AEFC were calibrated by AmLi neutron source. In this study, experiments were performed to calibrate the AEFC instrument and compare use of the Cf spontaneous fission source and the AmLi (α,n) neutron emission source. MCNP simulations were carried out to benchmark experiments. This thesis analyzes time correlated induced fission (TCIF) from fresh MTR fuel assemblies due to Cf and AmLi active interrogation sources. Benchmarking showed MCNP singles and doubles count rates agree with experimental singles and doubles within 5% and 4% respectively in the case of full assembly. After normalizing Cf to the AmLi source strength, AmLi resulted 1.228 times more IF singles rate, while Cf resulted 1.176 times more IF doubles rate. This indicates the boost in the doubles rate with Cf source is due to the TCIF effect.