Engineering topics
Ray, S.
Publications and source records attributed to Ray, S..
SiC cladding corrosion and mitigation
Silicon carbide (SiC) is a leading candidate for accident tolerant fuel. Testing of SiC in autoclaves at 360 C. degrees in simulated coolant resulted in little corrosion. However, testing of SiC tubes in the Massachusetts Institute of Technology (MIT) reactor manufactured in the same way had unacceptable corrosion levels. This in-reactor SiC corrosion issue is now being addressed by Westinghouse in tests being carried out at our Churchill, PA facility and in tests in the MIT reactor. The suspected driver for the excessive corrosion is the generation of oxidative water radiolysis products in the core. The MIT reactor was identified as running at H{sub 2} levels of ∼20 to 22 cc/kg coolant (cubic centimeters standard temperature and pressure per kilogram coolant) which were below those normally specified in operating pressurized water reactors (PWRs) of 25 to 50 cc/kg. Hydrogen is used to react with the radiolysis products to reduce them to water. The current MIT reactor tests will be run at H{sub 2} concentration levels of ∼50 cc/kg. The applicability of this approach has been supported by recent papers in the literature. Parallel testing at Churchill is being carried out to verify the efficacy of this approach using autoclaves operating at 345 C.degrees with H{sub 2}O{sub 2} injection to simulate the water radiolysis products. Various concentrations of H{sub 2} are being tested to determine the effect on SiC corrosion rate. Further studies are underway to investigate the effects of different SiC fabrication and structural parameters and to optimize for improved corrosion performance. This paper compares the results of the corrosion tests in the MIT reactor and the autoclave tests with H{sub 2}O{sub 2} injection and the effect of H{sub 2} injection on the SiC corrosion rate. The results of the autoclave tests with H{sub 2}O{sub 2} addition indicate that corrosion rates for SiC can be achieved that are much higher than those achieved in a reactor. It appears that the use of H{sub 2}O{sub 2} addition in flow through loops to simulate the corrosion rate of SiC samples in reactor is feasible. The use of H{sub 2} addition to reduce the corrosion rate in-reactor of SiC appears to be feasible.
Corrosion resistant coatings for zirconium-alloy cladding with improved accident tolerance
The Westinghouse-led accident tolerant fuel (ATF) program is evaluating Accident Tolerant Fuel (ATF) coatings of MAX phase (Ti{sub 2}AlC) and multi-layer Ti{sub x}Al{sub 1-x}N/TiN to enhance the oxidation resistance of zirconium alloy fuel cladding in both normal operation and beyond design-based conditions of light water reactors. A variety of coating technologies have been applied to deposit these coating materials onto Zircaloy-4 or Zirlo sheets and tubes, including cold spray and cathodic arc-physical vapor deposition (CA-PVD). Neutronic analysis using the elemental compositions of the coating materials showed that the coating thicknesses should be less than 30 μm for most coating materials to avoid non-negligible economic penalty. The coated samples were autoclave tested in water at 360 Celsius degrees and 150 bar or in steam at 427 Celsius and 103 bar for corrosion resistance evaluation. The initial Ti{sub 2}AlC coating made by using large particle size MAX phase powder and cold spray deposition did not provide the desired corrosion resistance due to un-optimized microstructure and porosity. Subsequent optimization including reduction in particle size and tuning of cold spray deposition parameters resulted in denser coatings less than 30 microns in thickness. Optimization of process conditions resulted in reduced oxidation kinetics and showed that the coating acts as an effective barrier to prevent the zirconium substrate from oxidizing in accident condition temperatures. High purity Ti{sub 2}AlC powder is needed to further improve oxidation resistance of the Ti{sub 2}AlC coating. The oxidation resistance of pure monolithic MAX phase compound was also found to be remarkable, and the weight gain was only 1.85 mg/cm{sup 2} for 96 hours exposure in 1200 C. degrees steam, which is consistent with the literature. The corrosion resistance of the TiAlN/TiN multilayer coating was excellent. The weight gain was negligible and no oxidation was observed on the surface of zirconium-alloy at the coating-substrate interface. (authors)
Westinghouse Accident Tolerant Fuel Program
The Westinghouse accident tolerant fuel (ATF) program is aimed at providing a significant increase in fuel robustness able to increase its tolerance to beyond design basis accidents at an economically attractive price to nuclear power providers. The Westinghouse ATF program, which began in 2004, advanced significantly during the current first phase (1A and 1B) begun in 2012 of this Department of Energy (DOE) program. Phase 1B will culminate in the manufacture of fuel rods that will undergo a 6 year exposure at steady state conditions in the Advanced Test Reactor and the Halden test reactor (Phase 2) and in transient tests in TREAT and Halden. The goal is to load lead test rods in a commercial reactor in 2022. In this paper, the current status of the ATF development and future irradiation plan is discussed in detail. Westinghouse has picked the most viable concepts that will provide maximum accident tolerance as well as economics, and those that will make the most sense for utility adoption. All three options appear to be feasible from a technical and economic point of view. (authors)
Procurement Path for Energy-Efficient Buildings
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Level lifetimes in P 32 obtained using the Doppler-shift attenuation method with thick molecular targets
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Cognitive memory
Perceptive cognition system structurally analyzed with semantic techniques for parsing and compiling