Using the Time-Correlated Induced Fission Method to Simultaneously Measure the ²³⁵U Content and the Burnable Poison Content in LWR Fuel Assemblies

The uranium neutron coincidence collar uses thermal neutron interrogation to verify the ²³⁵U mass in low-enriched uranium (LEU) fuel assemblies in fuel fabrication facilities. Burnable poisons are commonly added to nuclear fuel to increase the lifetime of the fuel. The high thermal neutron absorption by these poisons reduces the active neutron signal produced by the fuel. Burnable poison correction factors or fast-mode runs with Cd liners can help compensate for this effect, but the correction factors rely on operator declarations of burnable poison content, and fast-mode runs are time-consuming. This paper describes a new analysis method to measure the ²³⁵U mass and burnable poison content in LEU nuclear fuel simultaneously in a timely manner, without requiring additional hardware.