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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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DOE OSTI2026

FY26 Progress on Demonstration of a Multiphysics Steady State Capability for Modeling Core Radial Expansion in SFRs

Under the U.S. Department of Energy Office of Nuclear Energy Advanced Modeling and Simulation (NEAMS) Program, an integrated multiphysics approach is being developed to model the core bowing phenomena important to liquid metal-cooled fast reactors. Core bowing is an important passive safety mechanism in liquid metal-cooled fast reactors and involves multiphysics effects including radiation transport, fluid flow, heat transfer, and mechanical response to temperature and flux gradients. This report summarizes recent progress on developing a multiphysics, MOOSE-based workflow to predict core bowing and associated reactivity feedback. Significant new capabilities in the reactor physics code Griffin - sodium backfill and pin power reconstruction for deformed geometries - were applied in this effort. This year’s work included verification, code comparisons, sensitivity studies, and coupled demonstrations that advance the state of MOOSE-based core bowing workflow. Griffin’s sodium backfill capability was verified by demonstrating that its automated treatment of geometry expansion and material-density updates reproduces manual calculations exactly, confirming solid mass conservation and proper coolant backfilling in expanded geometries. Reconstructed pin powers were compared for Griffin’s ductheterogeneous and ring-heterogeneous treatments in single-, seven-, and nineteen-assembly cases, with best agreement observed in lower-leakage configurations and the duct-heterogeneous approach offering substantially lower computational cost. Thermal-hydraulic sensitivity sensitivities showed that MOOSE SCM, SAM, and CFD are expected to produce similar deformation predictions despite variances in their temperature predictions, and that explicit treatment of inter-assembly flow becomes increasingly important as gap flow rate increases. Finally, coupled demonstrations on small multi-assembly configurations using Griffin, MOOSE Solid Mechanics, MOOSE SCM, and Heat Conduction produced physically consistent reactivity feedback from thermal expansion and bowing. The coupled demonstrations simulated grid plate expansion as well as resultant core bowing at full power conditions. Simplifications were made in current workflow, namely the assumption of instantaneous full power conditions following hot zero power, and pre-expanding the Griffin geometry axially due to lack of an axial fuel pin expansion model and temperature feedback to Griffin.

Wozniak, Nicholas↗
DOE OSTI2022

On the Mechanism of the Steady-State Gamma Radiolysis-Induced Scissions of the Phenyl-Vinyl Polyester-Based Resins

The major societal problem of polymeric waste necessitates new approaches to break down especially challenging discarded waste streams. Gamma radiation was utilized in conjunction with varying solvent environments in an attempt to discern the efficacy of radiolysis as a tool for the deliberate degradation of model network polyesters. Our EPR results demonstrated that gamma radiolysis of neat resin and in the presence of four widely used solvents induces glycosidic scissions on the backbone of the polyester chains. EPR results clearly show the formation of alkoxy radicals and C-centered radicals as primary intermediate radiolytic products. Despite the protective role of the phenyl groups on the backbone of the radiation-induced polyester chains, the radiolytic-glycosidic scissions predominate. Among the following three solvents used in this study (water, isopropyl alcohol, and dichloromethane), the highest radiolytic yield of glycosidic scission was achieved using water. The •OH radicals produced in the radiolysis of phenyl unsaturated polyester aqueous suspensions very rapidly abstract H atoms from the methylene group, which is followed by a very rapid glycosidic scission. The lowest glycosidic yield was found in the dichloromethane solutions of these polyester resins due to scavenging by the fast electron capture reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗