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Title: Physical and mechanical metallurgy of zirconium alloys for nuclear applications: a multi-scale computational study

In the post-Fukushima world, the stability of materials under extreme conditions is an important issue for the safety of nuclear reactors. Because the nuclear industry is going to continue using advanced zirconium cladding materials in the foreseeable future, it become critical to gain fundamental understanding of the several interconnected problems. First, what are the thermodynamic and kinetic factors affecting the oxidation and hydrogen pick-up by these materials at normal, off-normal conditions, and in long-term storage? Secondly, what protective coatings (if any) could be used in order to gain extremely valuable time at off-normal conditions, e.g., when temperature exceeds the critical value of 2200°F? Thirdly, the kinetics of oxidation of such protective coating or braiding needs to be quantified. Lastly, even if some degree of success is achieved along this path, it is absolutely critical to have automated inspection algorithms allowing identifying defects of cladding as soon as possible. This work strives to explore these interconnected factors from the most advanced computational perspective, utilizing such modern techniques as first-principles atomistic simulations, computational thermodynamics of materials, diffusion modeling, and the morphological algorithms of image processing for defect identification. Consequently, it consists of the four parts dealing with these four problem areas precededmore » by the introduction and formulation of the studied problems. In the 1st part an effort was made to employ computational thermodynamics and ab initio calculations to shed light upon the different stages of oxidation of ziraloys (2 and 4), the role of microstructure optimization in increasing their thermal stability, and the process of hydrogen pick-up, both in normal working conditions and in long-term storage. The 2nd part deals with the need to understand the influence and respective roles of the two different plasticity mechanisms in Zr nuclear alloys: twinning (at low T) and crystallographic slip (higher T’s). For that goal, a description of the advanced plasticity model is outlined featuring the non-associated flow rule in hcp materials including Zr. The 3rd part describes the kinetic theory of oxidation of the several materials considered to be perspective coating materials for Zr alloys: SiC and ZrSiO4. In the 4th part novel and advanced projectional algorithms for defect identification in zircaloy coatings are described. In so doing, the author capitalized on some 12 years of his applied industrial research in this area. Our conclusions and recommendations are presented in the 5th part of this work, along with the list of used literature and the scripts for atomistic, thermodynamic, kinetic, and morphological computations.« less
Authors:
 [1]
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States)
Publication Date:
OSTI Identifier:
1170305
Report Number(s):
INL/EXT--14-32426
TRN: US1500017
DOE Contract Number:
AC07-05ID14517
Resource Type:
Technical Report
Research Org:
Idaho National Laboratory (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; REACTOR ACCIDENTS; FUKUSHIMA DAIICHI NUCLEAR POWER STATION; ZIRCALOY 2; ZIRCALOY 4; PROTECTIVE COATINGS; OXIDATION; SOLUBILITY; HYDROGEN; HYDRIDES; SENSITIVITY; THERMAL DEGRADATION; SILICON CARBIDES; SILICON OXIDES; ZIRCONIUM OXIDES; ALGORITHMS; CLADDING; HYDROGEN; HCP LATTICES; ZIRCONIUM; PLASTICITY; SLIP; TWINNING; MORPHOLOGY; FUEL RODS; DEFECTS; COMPUTERIZED SIMULATION; IMAGE PROCESSING; NUCLEAR INDUSTRY; PHYSICAL METALLURGY; STABILITY; SPENT FUEL STORAGE; THERMODYNAMICS; CALCULATION METHODS; CRYSTALLOGRAPHY; DIFFUSION; INSPECTION; CHEMICAL REACTION KINETICS; MICROSTRUCTURE; OPTIMIZATION; REACTORS; RECOMMENDATIONS; REACTOR SAFETY ZIRCONIUM ALLOYS