31 session corrosion of spent nuclear fuel canisters bryan sand2017 5541 pe

31 session corrosion of spent nuclear fuel canisters bryan sand2017 5541 pe

• 1.
  Spent Fuel andWaste Science and Technology Session: Corrosion of Spent Nuclear Fuel Canisters SFWST Working Group Meeting May 24, 2017 Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND17-5541 PE
• 2.
  Spent Fuel and WasteScience and Technology Session Schedule  Charles Bryan (SNL): Status Update, SCC Experimental Work at SNL  Scott Gordon (CSM): Field Test at Maine Yankee ISFSI  Dave Olson (CSM): Stress Analysis – Modeling vs. Mockup Data  Robert Sindelar (SRNL): SCC Testing at SRNL  Glenn Grant (PNNL): Friction Stir Welding  Discussion: Opportunities for Collaboration (as time allows!) May 24, 2017 SFWST Working Group Meeting, Las Vegas 2
• 3.
  Spent Fuel andWaste Science and Technology Status Update, SCC Experimental Work at SNL Eric Schindelholz and Charles Bryan Sandia National Laboratories Zhenzhen Yu and Xin Wu Colorado School of Mines Jenifer Locke and Timothy Weirich Ohio State University SFWST Working Group Meeting May 24, 2017
• 4.
  Spent Fuel and WasteScience and Technology May 24, 2017 SFWST Working Group Meeting, Las Vegas 4 Overview  Time line for SCC of spent nuclear fuel canisters  Major events, collaborators and roles – Incubation period – Pitting initiation and growth – Pit-to-crack transition – Crack growth  FY17 Experiments – Stability of sea-salt brines – Evaluating pitting initiation and growth – Evaluating controls on pit-to-crack transition – Evaluating crack growth rates  Planned work for FY18
• 5.
  Spent Fuel and WasteScience and Technology May 24, 2017 SFWST Working Group Meeting, Las Vegas 5 Canister SCC: Important Processes Begin Storage Pit Initiation Crack Initiation Penetration Incubation Pit Growth Crack Growth Storage Time SNL — Surface Environment, Brine Stability SNL/OSU — Pitting initiation and growth, Pit-to crack transition (experimental) CSM/SNL — Pitting initiation and growth (effect of stress) CSM — Pit-to-Crack Transition (Modeling) CSM/NCSU (SNL) — SCC growth rates OSU (SNL) — SCC growth rates
• 6.
  Spent Fuel and WasteScience and Technology Salt and Brine Stability Experiments  Previous work: Demonstrated ammonium chloride or nitrate salts cannot persist at elevated temperatures in the solid state, nor can a brine containing NH4 + and Cl- or NO3 -.  Current efforts evaluate the stability of brines formed by sea-salt deliquescence.  Sea-salt brines assumed to be those predicted by thermodynamic modeling of brine evaporation (deliquescence is the reverse process): initial deliquesced brines are Mg-Cl-rich, evolving to Na-Cl-rich brines with increasing RH. May 24, 2017 SFWST Working Group Meeting, Las Vegas 6 0.0001 0.001 0.01 0.1 1 10 100 0.250.350.450.550.650.750.850.95 Concentration,molal aw Cl Mg Br B C Na S K Ca Deliquescence
• 7.
  Spent Fuel and WasteScience and Technology Brine Stability  However— equilibrium modeling fails to consider – Effects of atmospheric exchange reactions occurring prior to corrosion — CO2 and acid gas (H2SO4, HNO3) absorption, HCl degassing – Once corrosion initiates, effects of cathodic reactions on surface brine compositions (hydroxide generation, carbonation)  FY 17 Experimental efforts – Effects of CO2 absorption/carbonate precipitation on MgCl2 brine stability – Effects of cathodic reactions on surface brine films (composition and distribution) May 24, 2017 SFWST Working Group Meeting, Las Vegas 7
• 8.
  Spent Fuel and WasteScience and Technology MgCl2 Brine Stability  Brines may degas, or absorb HCl, depending on background acid gas concentrations.  Current experiment (FY17) focuses on the effects of CO2 exchange on Mg-chloride brines May 24, 2017 SFWST Working Group Meeting, Las Vegas 8 0 20 40 60 80 100 120 140 160 1.E-121.E-111.E-101.E-091.E-081.E-071.E-061.E-051.E-04 Temp,ºC HCl partial pressure, bars 0 20 40 60 80 100 120 140 160 1.E-121.E-111.E-101.E-091.E-081.E-071.E-061.E-051.E-04 Temp,ºC HCl partial pressure, bars Urban Cont. Marine MgCl2 deliquescence Corrosion possible  MgCl2 brine stability is a function of temperature and atmospheric HCl concentration; brine may absorb CO2 and convert to Mg-carbonate  Other acid gas reactions (e.g., H2SO4) may be more important under field conditions.  However, carbonation may be VERY important for laboratory experiments (e.g. CRIEPI).  MgCl2 brine stability experiments in progress (one- month sampling showed little reaction (low gas flow rates?) Mg2+ + 2Cl– + CO2(g) + H2O  MgCO3(s) + 2HCl(g)
• 9.
  Spent Fuel and WasteScience and Technology MgCl2 Brine Stability May 24, 2017 SFWST Working Group Meeting, Las Vegas 9 CO2 absorption/carbonation may be VERY important for some laboratory experiments. For instance, CRIEPI. At 80ºC, 35% RH, air exchange of only a few cubic meters would be necessary to convert the small amount of MgCl2 present in the sea-salts to carbonate, drying out the brine. Shirai et al. (2011)
• 10.
  Spent Fuel and WasteScience and Technology Pitting Damage Quantification Experiments: Inform Probabilistic Models and Pit-Crack Transition Knowledge Gaps: • Pitting kinetics, damage distributions (max pit size?) under ISFSI-relevant environmental conditions (T, RH, salt load) • Pit-crack transition controlling factors Goals: 1) Quantify relationship between environment and pitting damage distributions and rates 2) Identify hierarchical weakest links for pit corrosion feature to SCC crack transition May 24, 2017 SFWST Working Group Meeting, Las Vegas 10 Approach: • Parametric coupon-level pitting experiments in ISFSI-relevant environments • Constant load marker band SCC tests in same environments to determine corrosion features that act as crack initiation sites Frequency Pit Depth t2 t3 t1 Principle Curvature Madison, 2014 Environment 1 Micromorphological characterization of pit-crack initiation sites ??Horner, 2011 Horner, 2011 Donahue, 2016 Pit number, size, shape distributions K  Kth
• 11.
  Spent Fuel and WasteScience and Technology Pitting Kinetics and Damage Distributions: Coupon-Level Studies May 24, 2017 SFWST Working Group Meeting, Las Vegas 11 High-throughput Approach for Building Parametric Datasets Inkjet printing for high- throughput salt loading Optical profilometry and pit analysis (OSU) Pitting kinetics and shape distributions (SNL/OSU) Frequency Pit Depth ISFSI-Relevant Conditions X-ray Microtomography (SNL) Approach: • 304H coupon and tensile test bars loaded with artificial sea salt and exposed to fixed environmental conditions for up to 2 years • Material details: • 304H, unsensitized and sensitized • Mirror, 120 grit “mill” finish • 10 and 300 ug/cm2 seasalt Serial Sectioning (SNL) Pit Micromorphology Characterization Horner, 2011
• 12.
  Spent Fuel and WasteScience and Technology Pit to Crack Transition Study May 24, 2017 SFWST Working Group Meeting, Las Vegas 12 • Variables: – Pit features (ex. narrow vs. wide) – Corrosion morphology (Single vs. Satellite Pits) – Material type • Method: SCC testing – Gauge length of longitudinal tensile bars will be loaded with salt and corroded in a humidity controlled chamber. – Constant load with intermittent high R ripple fatigue loads during SCC tests to determine corrosion features that act as crack initiation sites. Short Transverse = .250” Longitudinal Vary salt loading & environment to change pit morphology on the coupon. Goal: Quantify the hierarchical weakest link for corrosion feature to SCC crack transition J. R. Donahue and J. T. Burns, Effect of chloride concentration on the corrosion-fatigue crack behavior of an age-hardenable martensitic stainless steel, International Journal of Fatigue 91 (2016), 79-99.
• 13.
  Spent Fuel and WasteScience and Technology Plans – (2) SCC Testing May 24, 2017 SFWST Working Group Meeting, Las Vegas 13 • How does corrosion morphology affect crack initiation? • Use same environmental conditions as coupon corrosion tests for SCC testing. – Pitting characteristics fully characterized for corrosion coupons/sacrificial tensile bars. This data will help explain cracking results. • Load salt and corrode side of coupons (red) • Remove from humidity chamber and print salt on face of coupon (green) – Extra salt on face will contribute electrolyte to the crack tip during propagation Sampling plan for corrosion coupons Environment Salt Load 1 wk 2 wk 1 mo. 6 mo. 12 mo. 18 mo. 24 mo. 35°C, 40%RH 300 µg/cm2 X X X X X X X 35°C, 75%RH 10 µg/cm2 X X X X X X X 35°C, 75%RH 300 µg/cm2 X X X X X X X *Matrix same as coupon tests, but with low-humidity / low-salt-load samples removed
• 14.
  Spent Fuel and WasteScience and Technology Impact of Corrosion on Surface Environment, Damage Distributions, and Rates: Inform Deterministic Models May 24, 2017 SFWST Working Group Meeting, Las Vegas 14 Knowledge Gaps: • Relevance and accessible limits of existing deterministic damage models relative to canister conditions Goals: 1) Characterize electrolyte coverage and chemistry distribution during exposure in ISFSI-relevant environment 2) Quantify impact on electrochemical processes driving pitting and SCC maximum pit size crack growth rate (?) NaCl on steel MacDonald, 1991Chen et al. 2008 SNL: Eric Schindelholz, Charles Bryan, Chris Alexander OSU/EFRC: Jen Locke, Tim Weirich CSM: Zhenzhen Yu, Xin Wu Schindelholz, 2014
• 15.
  Spent Fuel and WasteScience and Technology Impact of Corrosion on Surface Environment, Damage Distributions, and Rates: Coupon-Level Studies May 24, 2017 SFWST Working Group Meeting, Las Vegas 15 Approach: • Post-exposure surface analyses of coupons from pitting experiments: • TOF-SIMS, MicroRaman/FTIR, Auger Spectroscopy • Cathodic kinetics of 304 in analog surface chemistries (sea-salt brines, carbonate brines) • Establish variance in max pit size model predictions due to evolving electrolyte, extend knowledge to CSM SCC electrochemical model Inkjet printing for high- throughput salt loading ISFSI-Relevant Conditions Extent of electrolyte coverage and chemistry distribution Cathodic and anodic kinetics in analog surface chemistries TOF-SIMS Chen and Kelly, 2010 NaOH NaCl 1 mm SEM-EDS 4000 3500 3000 2500 2000 1500 1000 500 0.0 0.2 0.4 0.6 0.8 1.0 Atmospheric Exposure Dawsonite Reference log(1/R) Wavenumber (cm-1 ) Figure 1. FTIR spectra for various point analyses taken across the exposed Al 1100 coupon with 0.6 M NaCl droplet. Spectra are compared to a dawsonite reference spectra shown in blue. Raman
• 16.
  Spent Fuel and WasteScience and Technology Linkage of Material Variance to Electrochemical Corrosion/Cracking Processes for Prediction of Damage Initiation Sites May 24, 2017 SFWST Working Group Meeting, Las Vegas 16 Knowledge Gap: How material characteristics (microstructure, stress/strain) and environment (T, RH, salt load) impact electrochemical processes governing SCC Goal: Prediction of pitting/repassivation characteristics of 304 under varied static stress loads Approach: • Microelectrochemical mapping of CSM 4-point bend specimens as a function of stress load • Develop model to capture pitting characteristics as function of stress/strain with correlation to CSM 4-point bend exposures CSM Microelectrochemical mapping (SNL) 500 µm Andretta, 2016 stresspotential Epit Erp Newmann, 2016 Pit distribution on atmospherically exposed samples (CSM) Stress effect on localized corrosion susceptibility SNL: Eric Schindelholz, Charles Bryan, Chris Alexander CSM: Zhenzhen Yu, Xin Wu
• 17.
  Spent Fuel and WasteScience and Technology FY17 Technical Progress  Stability of Deliquescent Sea-salt Brines – Thermodynamic calculations suggest Mg-Cl brines are not stable at elevated temperatures – Significant implications for timing of deliquescence, conditions of corrosion – Long-term experiments underway (after one month, little or no effect)  Pitting Damage Quantification and Pit-Crack Transition – 2 year coupon test initiated – OSU tensile specimens and will be added to test, Q3 – Post analysis of first coupon pulls (1 wk, 2wk, 1 month) planned for Q3, 4  Surface Chemistry/Electrochemistry Characteristics – Demonstrated ability to map cathodic chemistry using TOF-SIMS – Chemistry mapping of first coupon pulls (above), Q4 – Cathodic kinetics in concentrated seawater and catholyte brines, Q3,4 – Variance in max pit size predictions using Chen-Kelly model with above inputs, Q4  Electrochemical Pitting-Stress Linkage – Coordination with CSM for experimental design and sample acquisition, Q1 – Adapt microcapillary platform and demonstrate mapping of 4-point bend specimen, Q4 May 24, 2017 SFWST Working Group Meeting, Las Vegas 17
• 18.
  Spent Fuel and WasteScience and Technology Distribution of Canister Mockup Samples  SNL Full-Diameter Cylindrical Canister Mockup – Stress measurements completed and final report issued in late 2016 – Weld and base metal samples cut from the canister for dissemination to interested parties  Additional Corrosion Test Materials purchased by SNL (4 x 8 x 5/8 plates) – 304L – 304H (almost all distributed)  Samples shared with the following entities – Colorado School of Mines (IRP) – materials characterization/corrosion testing – EPRI – NDE development and testing – Massachusetts Institute of Technology – stress measurements (neutron beam) – NAC International – NDE testing – North Carolina State University(CSM IRP) – corrosion testing – Ohio State University (EFRC) – corrosion testing – ORNL – mechanical properties testing – SRNL – materials characterization/corrosion testing – SwRI – corrosion testing  One-half of the canister left—will be sectioned into samples in FY18 May 24, 2017 SFWST Working Group Meeting, Las Vegas 18
• 19.
  Spent Fuel and WasteScience and Technology FY18 Planned Experiments  Once pit characterization techniques are demonstrated, increase pitting corrosion test matrix (additional T, RH, salt loads)  Impact of salt morphology/configuration (salt particle size and distribution)  Electrochemical mapping of canister mockup weld/HAZ – Potential Galvanic effects – Degree of sensitization  Coupon Size Effect – Chen and Kelly (2010) model predicts cathodes larger than our current coupon size  Corrosion testing of large mockup specimen – Link between lab tests on homogeneous specimens and corrosion in real weld zones – Possible weld/HAZ/base metal galvanic effects (potentially affect pit sizes, locations, morphology) – Locations of SCC initiation in weld zones – SCC crack orientations/morphologies May 24, 2017 SFWST Working Group Meeting, Las Vegas 19
• 20.
  Spent Fuel and WasteScience and Technology May 24, 2017 SFWST Working Group Meeting, Las Vegas 20 Summary: Current Efforts Begin Storage Pit Initiation Crack Initiation Penetration Incubation Pit Growth Crack Growth Storage Time SNL — Surface Environment, Brine Stability SNL/OSU — Pitting initiation and growth, Pit-to crack transition (experimental) CSM/SNL — Pitting initiation and growth (effect of stress) CSM — Pit-to-Crack Transition (Modeling) CSM/NCSU (SNL) — SCC growth rates OSU (SNL) — SCC growth rates Timing of corrosion and extent of damage Environmental controls on pit size and crack initiation, pit size/shape controls on crack initiation SCC crack growth rates: effect of environment IMPACT: Improved prediction of timing of corrosion initiation, SCC initiation and growth, and potential canister penetrations times. Will provide critical information for development of ASME standard for canister inspections, and system Aging Management Plans.