Nuclear fuel irradiation testbed for nuclear security applications

Abstract

The nuclear security community has long been interested in the identification and quantification of nuclear material signatures to understand a material’s provenance, use, and ultimate application. New forensics signatures and methods intended for non-traditional or advanced nuclear fuel applications require fuel irradiation experiments to demonstrate viability and validity. Integral fuel irradiations have historically required significant costs and long timelines to design, irradiate, and characterize. This paper describes how a recently developed nuclear fuel irradiation testbed can be used to provide a low cost, rapid turnaround, modular test environment for irradiation and evaluation of nuclear fuel specimens for nuclear security applications. The irradiation testbed houses six small ‘MiniFuel’ samples within hermetically sealed capsules inside targets that can be removed in between each ∼25-day operating cycle of the High Flux Isotope Reactor (HFIR). As many as nine targets can be irradiated using a single irradiation position (reflector region) in HFIR, allowing for varying irradiation temperatures and burnups. A suite of hot cell capabilities have been established to perform post-irradiation examination for measuring performance (e.g., fuel swelling, fission gas release) and facilitating experiment disassembly for subsequent property measurements, microstructural analysis, or chemical assay. This new testbed allows fuel irradiations to be conducted on an accelerated timeframe to enable rapid proof of concept testing and to provide reference material for nuclear fuel security applications. Recent applications using this testbed include the testing of isotopic taggants in UO2 fuel (intentional forensics), testing of U-10Mo fuel for down-conversion of highly enriched uranium–fueled reactors, and the production of irradiated UO2 fuel material for signature analysis of its isotopic composition (plutonium, fission gases, etc.).

Using in situ UO2 bicrystal sintering to understand grain boundary dislocation nucleation kinetics and creep

“…79,80 The nuclear nonproliferation community has also proposed "tagging" UO 2 fuels with small quantities of chemical additives containing tailored isotopic ratios as a means of identifying material pedigree. 81 The elements chosen for isotopic taggants mirror those chosen for conventional fuel dopants, and their impact on sintering, microstructure, and viscoelastic behavior would be analogous. This work persists, despite the uncertainty in the literature regarding the dominant mechanisms of thermal creep in UO 2 .…”

Comparing Sensor Fusion and Multimodal Chemometric Models for Monitoring U(VI) in Complex Environments Representative of Irradiated Nuclear Fuel

“…The HFIR reactor was chosen because fuel samples are currently being irradiated as part of an active research effort into intentional forensics concepts for nuclear fuels. 25 Details pertaining to Monte Carlo N-Particle and SCALE software simulations of FP ingrowth during reactor burnup are provided in the Supporting Information. 28 ■ RESULTS AND DISCUSSION Optical Spectra.…”

“…The simulation of the FP ingrowth in nuclear fuel was modeled for a natural, 5, and 20% enriched UO 2 fuel sample irradiated in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (Figure S2). The HFIR reactor was chosen because fuel samples are currently being irradiated as part of an active research effort into intentional forensics concepts for nuclear fuels . Details pertaining to Monte Carlo N-Particle and SCALE software simulations of FP ingrowth during reactor burnup are provided in the Supporting Information…”

“…This study demonstrates how optical techniques, including LIFS, Stokes Raman scattering, and UV–vis–NIR spectrophotometry techniques; experimental design; and chemometrics can be harnessed together for the accurate quantification of multiple chemical species. The developed methodology is widely applicable in many fields. ,,,, This work highlights the following: (1) sensor fusion and MM data were compared to quantify uranium­(VI) and multiple lanthanides [samarium­(III), europium­(III), praseodymium­(III), and neodymium­(III)] in the milligram-per-liter range with varying HNO 3 and CP levels; (2) the D-optimal sample selection method was extended to a seven analyte system; and (3) nuclear reactor modeling was applied to identify ratios of lanthanide FPs for use as burnup indicators. This work addresses the challenges of modeling numerous species and presents a novel approach for advanced monitoring applications.…”

Analysis of trace elements in uranium by inductively coupled plasma-optical emission spectroscopy, design of experiments, and partial least squares regression

“…25 This new approach enables the analysis of trace elements and U simultaneously, which is expected to greatly improve the timeliness and efficiency of ICP-OES measurements in niche applications like U production, trace element determination in nuclear fuel, and intentional forensics. 25,26 It also provides a viable option to measure elements which are difficult to chemically separate from U (e.g., Zr, Nb, and Th). This state-of-the-art approach can be extended to many applications within and beyond the nuclear eld.…”