NSUF 23-4695: Measuring the microstructural changes and elastic properties of oxidized neutron-irradiated graphite

Oxidation in nuclear graphite components can limit the lifetime of a graphite core. During the regular operation of a reactor, graphite can be in contact with oxidant species in the form of contamination in the coolant gas (chronic oxidation) or due to the accidental ingress of oxygen into the core (acute surface oxidation). In the current project, the authors propose a series of oxidation experiments using neutron-irradiated samples followed by characterization to determine microstructural and elastic property changes associated with oxidation-induced porosity. Samples of ETU-10 in the as-received state and in neutron-irradiated conditions will be oxidized at temperatures close to 500°C and 700°C. Oxidation at these two temperatures will generate uniform and acute surface oxidation. Uniform oxidation closely mimics the effects of chronic oxidation while acute surface oxidation reproduces behavior associated with rapid air ingress into the reactor core. The purpose of these oxidation experiments is to evaluate if chronic or acute surface oxidation proceed more rapidly in neutron-irradiated samples. Neutron irradiation generates defects in the crystal lattice that can serve as active sites for oxidation. Also neutron damage generates nanopores that increase the surface area where oxidation can occur. Uniform and surface oxidation are associated with different changes in graphite porosity and elastic properties. Uniform oxidation removes material throughout the bulk of the graphite, increases the size of pores that already exist in the structure, and reduce the mechanical properties throughout the volume. Acute surface oxidation primarily produces increased porosity at the sample surface and damage is localized to this region. However, it is not known if neutron irradiation would affect this behavior. To assess the long-term operation of gas-cooled reactors in the U.S., it is crucial to understand if neutron irradiation can significantly enhance the rate of oxidation and degradation in graphite components.

Additional Info

Field Value
Abstract Oxidation in nuclear graphite components can limit the lifetime of a graphite core. During the regular operation of a reactor, graphite can be in contact with oxidant species in the form of contamination in the coolant gas (chronic oxidation) or due to the accidental ingress of oxygen into the core (acute surface oxidation). In the current project, the authors propose a series of oxidation experiments using neutron-irradiated samples followed by characterization to determine microstructural and elastic property changes associated with oxidation-induced porosity. Samples of ETU-10 in the as-received state and in neutron-irradiated conditions will be oxidized at temperatures close to 500°C and 700°C. Oxidation at these two temperatures will generate uniform and acute surface oxidation. Uniform oxidation closely mimics the effects of chronic oxidation while acute surface oxidation reproduces behavior associated with rapid air ingress into the reactor core. The purpose of these oxidation experiments is to evaluate if chronic or acute surface oxidation proceed more rapidly in neutron-irradiated samples. Neutron irradiation generates defects in the crystal lattice that can serve as active sites for oxidation. Also neutron damage generates nanopores that increase the surface area where oxidation can occur. Uniform and surface oxidation are associated with different changes in graphite porosity and elastic properties. Uniform oxidation removes material throughout the bulk of the graphite, increases the size of pores that already exist in the structure, and reduce the mechanical properties throughout the volume. Acute surface oxidation primarily produces increased porosity at the sample surface and damage is localized to this region. However, it is not known if neutron irradiation would affect this behavior. To assess the long-term operation of gas-cooled reactors in the U.S., it is crucial to understand if neutron irradiation can significantly enhance the rate of oxidation and degradation in graphite components.
Award Announced Date 2023-06-01T09:03:08.21
Awarded Institution None
Facility None
Facility Tech Lead Kory Linton
Irradiation Facility None
PI James Spicer
PI Email nsuf@inl.gov
Project Type RTE
RTE Number None