Role of Defects in Swelling and Creep of Irradiated SiC
- Univ. of Wisconsin, Madison, WI (United States)
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Silicon carbide is a promising cladding material because of its high strength and relatively good corrosion resistance. However, SiC is brittle and therefore SiC-based components need to be carefully designed to avoid cracking and failure by fracture. In design of SiC-based composites for nuclear reactor applications it is essential to take into account how mechanical properties are affected by radiation and temperature, or in other words, what strains and stresses develop in this material due to environmental conditions. While thermal strains in SiC can be predicted using classical theories, radiation-induced strains are much less understood. In particular, it is critical to correctly account for radiation swelling and radiation creep, which contribute significantly to dimensional instability of SiC under radiation. Swelling typically increases logarithmically with radiation dose and saturates at relatively low doses (damage levels of a few dpa). Consequently, swelling-induced stresses are likely to develop within a few months of operation of a reactor. Radiation-induced volume swelling in SiC can be as high as 2%, which is significantly higher than the cracking strain of 0.1% in SiC. Swelling-induced strains will lead to enormous stresses and fracture, unless these stresses can be relaxed via some other mechanism. An effective way to achieve stress relaxation is via radiation creep. Although it has been hypothesized that both radiation swelling and radiation creep are driven by formation of defect clusters, existing models for swelling and creep in SiC are limited by the lack of understanding of specific defects that form due to radiation in the range of temperatures relevant to fuel cladding in light water reactors (LWRs) (<1000°C). For example, defects that can be detected with traditional transmission electron microscopy (TEM) techniques account only for 10-45% of the swelling measured in irradiated SiC. Here, we have undertaken an integrated experimental and modeling effort to discover the previously invisible defects in irradiated SiC and to determine the contributions of these defects to radiation swelling. Knowledge of the most stable defect structures and the rate controlling processes during defect evolution is essential for development of predictive models for swelling and creep as a function of temperature and radiation dose. This research has been enabled by state-of-the-art imaging techniques, such as the aberration corrected scanning transmission electron microscopy (STEM) (FEI TITAN) closely coupled with multi-scale models of stable defect clusters and their evolution.
- Research Organization:
- Univ. of Wisconsin, Madison, WI (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy (NE). Nuclear Energy University Programs (NEUP)
- DOE Contract Number:
- AC07-05ID14517
- OSTI ID:
- 1237072
- Report Number(s):
- DOE/NEUP-12-3357; 12-3357; TRN: US1600291
- Country of Publication:
- United States
- Language:
- English
Similar Records
Microstructures of beta silicon carbide after irradiation creep deformation at elevated temperatures
Comprehensive Fuel Performance Model Development and Simulation for TRISO Fuel
Related Subjects
22 GENERAL STUDIES OF NUCLEAR REACTORS
PHYSICAL RADIATION EFFECTS
SILICON CARBIDES
CREEP
SWELLING
RADIATION DOSES
TEMPERATURE RANGE 0400-1000 K
TEMPERATURE RANGE 1000-4000 K
FRACTURES
WATER MODERATED REACTORS
CRYSTAL DEFECTS
REACTOR MATERIALS
WATER COOLED REACTORS
STRAINS
STRESSES
ATOMIC DISPLACEMENTS
STRESS RELAXATION
TEMPERATURE DEPENDENCE
INSTABILITY
COMPUTERIZED SIMULATION