Bayesian Calibration of Irradiated Graphite Property Models under High Temperatures
Journal Article
·
· npj Materials Degradation
- Idaho National Laboratory
Graphite is a crucial material for advanced nuclear reactors such as very-high-temperature reactors, thermal molten-salt reactors, fluoride-salt-cooled high-temperature reactors, and various microreactors. Ensuring the long-term performance of graphite components under high temperature and irradiation with significant spatial gradients is essential for reactor safety and reliability. This paper addresses the modeling and prediction of key graphite properties, which are imperative for finite-element simulations used in reactor component design. We present a comprehensive Bayesian calibration approach to quantify uncertainties in graphite property models, with a significant focus on incorporating model discrepancies through a Gaussian process term. This term accounts for biases between the model predictions and experimental data, providing a probabilistic treatment that captures uncertainties stemming from model parameters, experimental noise, and inadequate model forms. The calibration employs a hierarchical structure for variance modeling, which is essential for capturing group-level and across-group noise in the data. By considering four critical graphite properties (irradiation-induced dimension change, creep, Young's modulus change ratio, coefficient of thermal expansion change ratio) across five graphite grades (IG-110, NBG-18, PCEA, NBG-17, 2114) using two predictive models, we demonstrate a substantial improvement in predictive performance achieved through the inclusion of the Gaussian process model discrepancy term. When model discrepancy is accounted for, the predictive error reductions are, on average, $$47\%$$, $$62\%$$, $$17\%$$, and $$12\%$$ for irradiation-induced dimension change, creep, Young's modulus change ratio, and coefficient of thermal expansion change ratio, respectively. The impact of accurate property predictions on component performance is further illustrated through a multiphysics model of a very-high-temperature reactor prismatic core reflector brick, analyzing the stresses resulting from high neutron fluences and temperatures. Our results underscore the importance of accounting for model discrepancies and provide a robust framework for the reliable design of graphite components in advanced reactors.
- Research Organization:
- Idaho National Laboratory (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy (NE)
- Grant/Contract Number:
- AC07-05ID14517
- OSTI ID:
- 3014403
- Report Number(s):
- INL/JOU-25-85711
- Journal Information:
- npj Materials Degradation, Journal Name: npj Materials Degradation Journal Issue: 0 Vol. 0
- Country of Publication:
- United States
- Language:
- English
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