Session: CS-15-02 Mechanical Properties of Nuclear Graphite and Their Implementation in Codes and Standards (Joint with MF-29) – 2

Paper Number: 106469

106469 - Probabilistic Assessment Tool for Graphite Component Reliability 

Assessment of graphite component reliability is important in providing the technical basis to support the safe operation of advanced non-light water reactors. Computational modeling of aging and degradation in graphite components would enable quantitative assessments of stress generation, failure, and associated uncertainties. A graphite modeling tool has been developed in a finite element framework, MOOSE, which was created at Idaho National Laboratory. This tool was developed for the assessment of graphite components intended for nuclear applications. The tool is capable of computing stresses in graphite which result from temperature and irradiation gradients in graphite components. The effect of irradiation creep is included in the graphite behavior model. The graphite tool is also capable of modeling the effects of oxidation.  This includes computing temperature dependent density profiles which can be generated by the reaction between graphite and oxygen. Stresses in the oxidized graphite can be computed using material properties which are implemented as a function of mass loss. The tool has been parameterized for graphite grade IG-110, but other grades of graphite can be assessed by providing the necessary material properties. The tool was also developed to work with the graphite assessments in Subsection HHA in Section III Division 5 of the ASME BPVC. These assessments use a Weibull-based probabilistic approach to assessing a graphite component. Python codes have been created which implement the full and simplified assessments in the 2021 version of the ASME BPVC and utilize the outputs from the MOOSE-based analysis. Initial verification and validation work using this tool has produced promising results.

Presenting Author: Joseph Bass Nuclear Regulatory Commission

Presenting Author Biography: Dr. Joseph Bass has a strong background in modeling and simulation of mechanical systems and materials behavior. In addition, he has sound experience with American Society of Mechanical Engineers (ASME) Code and Standards (C&S) for high temperature materials and component performance. Upon receiving his doctoral degree, Dr. Bass started his professional career at the Idaho National Laboratory (INL). He developed several finite element models to assess materials degradation and component performance, intended for nuclear applications. More recently, he has focused his attention in developing probabilistic models to assess nuclear graphite aging and degradation, under harsh environments. After leaving INL, he joined the the Nuclear Regulatory Commission as a reactor engineer.

Authors:

Joseph Bass Nuclear Regulatory Commission
Raj Iyengar Nuclear Regulatory Commission
Christopher Ulmer Nuclear Regulatory Commission