ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
Division Spotlight
Robotics & Remote Systems
The Mission of the Robotics and Remote Systems Division is to promote the development and application of immersive simulation, robotics, and remote systems for hazardous environments for the purpose of reducing hazardous exposure to individuals, reducing environmental hazards and reducing the cost of performing work.
Meeting Spotlight
International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C 2025)
April 27–30, 2025
Denver, CO|The Westin Denver Downtown
Standards Program
The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
Latest Magazine Issues
Apr 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
May 2025
Nuclear Technology
Fusion Science and Technology
Latest News
TerraPower begins U.K. regulatory approval process
Seattle-based TerraPower signaled its interest this week in building its Natrium small modular reactor in the United Kingdom, the company announced.
TerraPower sent a letter to the U.K.’s Department for Energy Security and Net Zero, formally establishing its intention to enter the U.K. generic design assessment (GDA) process. This is TerraPower’s first step in deployment of its Natrium technology—a 345-MW sodium fast reactor coupled with a molten salt energy storage unit—on the international stage.
Kenneth M. Wasywich, William H. Hocking, David W. Shoesmith, Peter Taylor
Nuclear Technology | Volume 104 | Number 3 | December 1993 | Pages 309-329
Technical Paper | Special Issue on Waste Management / Radioactive Waste Management | doi.org/10.13182/NT93-A34893
Articles are hosted by Taylor and Francis Online.
In the Canadian research and development program on fuel storage, used CANDU (Canada deuterium uranium) UO2fuel bundles are being exposed in experimental vessels to both dry and moisture-saturated air environments at 150°C. At intervals of several years, individual fuel elements, which were deliberately defected before storage, are recovered for destructive examination to determine the extent of UO2 oxidation that has occurred. The most recent examinations took place after 99.5 and 69 months of storage under dry and moist conditions, respectively. The progress of oxidation in the two different storage environments is compared, and the results of fuel examination by optical microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD) are described. In dry air, oxidation proceeds mainly on exposed UO2 surfaces near the cladding defect and penetrates the fuel along grain boundaries adjoining cracks and the fuel-sheath gap, which provide primary pathways for access of oxygen to the fuel. An oxidized rind, resembling α-U3O7, is visible around UO2 grain cores near the oxide front. In moist air, oxidation is more generally distributed throughout the length of the fuel element. It proceeds along grain boundaries and is most extensive in regions of the fuel expected to have the highest porosity or grain-boundary inventory of fission products. This oxidized layer is too thin to observe by optical microscopy or identify by XRD, but XPS results indicate a higher degree of oxidation at the exposed grain boundaries (U6+/U4+ often »1.0) than in fuel specimens oxidized in dry air (U6+/U4+ usually <1.0). Interpretation of the results is complicated by the different O2/UO2 ratios in the two types of storage vessel and the fact that oxygen was completely consumed during at least some of the storage intervals. Nonetheless, it is clear that the presence of moisture promotes a more generally distributed oxidation of UO2 grain boundaries. The probable involvement of radiolytic processes in the moist oxidation reaction and possible reasons for the sensitization of certain regions of the fuel to moist oxidation are discussed. In addition to oxidation of UO2, the XPS spectra provide evidence for the radiation-induced incorporation of oxygen and nitrogen into adventitious carbon (adsorbed hydrocarbons) on the UO2 surfaces.
