FEA-aided investigation of the effective thermal conductivity in a medium with embedded spheres

Toptan

Hales

et al. 2021

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This document demonstrates completion of the goals described in the technical narrative of the FOA project titled: "Modeling and Simulation Development Pathways to Accelerating KP-FHR Licensing" regarding fission product transport in the Kairos-proposed fuel pebble by Idaho National Laboratory and Kairos Power. Showcased in this report are code developments and simulations in BISON that extend the state of the art in computation and understanding of fission product transport in a TRISO fuel particle and pebble.These enhancements lay the foundation for making predictions of fission product transport that can be used as input in the fuel licensing process. This was achieved by installing existing fuel material models originally used in PARFUME, developing a new failure probability method that is efficient and multidimensional, employing material homogenization, and expanding verification and validation simulations to demonstrate the efficacy of the work. All this work is leveraged to spotlight the main deliverable-a three-dimensional model and corresponding demonstration simulation of a pebble, which will serve as the starting point for models used to predict fission product release.

Section: Homogenizationmentioning

confidence: 99%

Section: Analytical Modelsmentioning

confidence: 99%

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Fission Product Transport in TRISO Particles and Pebbles

Toptan

Hales

et al. 2021

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“…. Over the last few years, the Bison fuel performance code [1] has undergone significant development to expand its tri-structural isotropic (TRISO) particle fuel performance modeling capabilities [2,3,4,5,6,7,8]. Such development included the implementation of material models from PARFUME [9] and the capability to perform statistical failure analysis on large sets of samples, utilizing a Monte Carlo (MC) scheme to execute fast-running, one-dimensional (1-D), spherically symmetric models.…”

mentioning

confidence: 99%

Efficient Failure Probability Calculations and Modeling Interface Debonding in TRISO Particles with BISON

Singh

Hales

et al. 2021

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This document constitutes completion of the NEAMS milestone, which is titled: Demonstrate efficiency improvements in TRISO failure probability calculations and the effect of debonding on fission product transport in TRISO fuel particles in Bison. In this report we present the development of : (1) the anisotropic elasticity model of pyrolytic carbon and extended material models using the local coordinate system for aspherical particle geometry, (2) a capability of modeling interface debonding in TRISO particles , (3) an efficient high-fidelity approach to calculate the failure probability of TRISO particles. Benchmark problems and AGR-2 tests are used to verify the models and demonstrate these new capabilities.

“…Until now, engineering-scale modeling efforts in Bison [1] have focused on the thermo-mechanical properties of the TRISO particle and its constituent layers [2,3,4,5,6]. Extensive study has also been devoted to the code in order to compute the homogenized response of the graphite matrix (containing TRISO particles) thermal conductivity [7]. In this study, we aim to survey graphite material models widely used in HTGRs and then implement them into Bison, as well as perform benchmark examples using these models in order to conduct an early assessment of the needed material and/or physical models for future studies.…”

mentioning

confidence: 99%

Matrix Graphite Material Models In Pebbles and Compacts For Bison

Toptan

Novascone

et al. 2021

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The cores and reflectors in high-temperature gas-cooled reactors (HTGRs) are made of graphite materials, with the graphite acting as a moderator, a fuel host matrix, or the foundation for various structural components. This study aims to survey the models in the literature for graphite materials being used as host matrices in pebble/fuel compacts and to implement those surveyed models into Bison to conduct an early assessment of graphite's thermomechanical response under various reactor conditions. In this study, thermal (e.g., thermal conductivity, and specific heat capacity) and mechanical (e.g., elastic properties, thermal expansion, irradiation-induced dimensional changes, and irradiation-induced creep) material models for various graphite grades (e.g., H-451, IG-110, G-348, 2020, A3-3, and A3-27) are incorporated into Bison. Two benchmark problems are then exercised utilizing these new graphiterelated capabilities: (1) modeling an Advanced Gas Reactor (AGR)-2 fuel compact, and (2) modeling the debonding of a particle-matrix interface. ACKNOWLEDGMENTThe authors would like to thank Dr. Adam X. Zabriskie of Idaho National Laboratory (INL) for his help in reviewing and providing technical support on the automatic differentiation (AD) conversion of the relevant material properties, and Dr. Joseph Bass of INL for his help in providing relevant references on the properties of various graphite grades.