J. Eigenbrodt “Spent Fuel Measurements: Passive Neutron Albedo Reactivity (PNAR) and Photon Signatures”, Ph.D. Dissertation, Nuclear Engineering, Texas A&M University, College Station, TX (2016).
The International Atomic Energy Agency (IAEA) has the objective of timely detection of diversion of nuclear material from the peaceful uses of nuclear energy to weapons production. An important IAEA task towards meeting this objective is the ability to accurately and reliably measure spent nuclear fuel (SNF) to verify reactor operating parameters and verify that none of the fuel has been removed from reactors or SNF storage facilities. This work looks at two methods to improve the state-of-the-art of nuclear material safeguards measurements: passive neutron albedo reactivity (PNAR) and passive spectral photon measurements. The methodology developed based on PNAR was used for measurements of SNF in Japan as well as fresh fuel pins at Los Alamos National Laboratory (LANL). The measured PNAR signal was shown to trend well with neutron multiplication and nuclear fissile content of the SNF. The PNAR measurements showed a 73% change in signal for a fuel burnup range of 7.1 to 19.2 GWd/MTHM of spent mixed-oxide (MOX) Fugen fuel and a 40% change in signal over a range of initial 235U enrichment from 0.2% to 3.2% in UO2 fuel. Photon measurements were performed on a wide range of SNF pins to determine which photon signatures are visible in different sets of fuels. These signatures were then investigated and tested using a sensitivity analysis to determine which spent fuel parameters each signal is most sensitive to.