Johnna B Marlow

Technical Basis for the Use of a Correlated Neutron Source in the Uranium Neutron Coincidence Collar

Active neutron coincidence systems are commonly used by international inspectorates to verify a material balance across the various stages of the nuclear fuel cycle. The Uranium Neutron Coincidence Collar (UNCL) is one such instrument; it is used to measure the linear density of 235U (g 235U/cm of active length in assembly) in fresh light water reactor fuel in nuclear fuel fabrication facilities. The UNCL and other active neutron interrogation detectors have historically relied on americium lithium (241AmLi) sources to induce fission within the sample in question. Californium-252 is under consideration as a possible alternative to the traditional 241AmLi source. This work relied upon a combination of experiments and Monte Carlo simulations to demonstrate the technical basis for the replacement of 241AmLi sources with 252Cf sources by evaluating the statistical uncertainty in the measurements incurred by each source and assessing the penetrability of neutrons from each source for the UNCL.

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

Abstract 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.

Integrated test program for comparison of 10 B lined proportional counting systems with 3 He based counters for safeguards applications

To address the urgent need to find a viable 3He replacement technology, Los Alamos National Laboratory has developed an integrated test program for performance evaluation of 3He replacement technologies with focus on safeguards specific parameters. In addition, a dedicated experimental setup was built to support the experimental activities. Current activity focuses on evaluation of 10B lined proportional counters. This paper presents an overview of the test program as well as the first results from the GE/Reuter-Stokes 10B lined system.