Current Super Critical Water Loop test results

1. Current Super Critical Water Loop test results • M. Anderson, K. Sridharan, M. Corradini, et.al. • University of Wisconsin – Madison • Department of Engineering Physics Presented at April SCW exchange meeting April 29th and 30th, UW-Madison Wisconsin Institute of Nuclear Systems Nuclear Engr & Engr Physics, University of Wisconsin - Madison

2. Overview of UW-SCW loop • In 625 Const. • Max Water temp = 550 C • Max Pressure = 25MPa • Flow velocity = 1 m/s • Flow rate = 0.4 kg/s • Max wall temp 625 C • Chemistry control to 200ml/min • Input power 100 KW • O2 measurement • Conductivity measurement • Wall temps • Replaceable test section • Current test section I.D 4.25 cm • Length 2x3 meters • Corrosion, Heat transfer, thermal hydraulic stability and control

3. Max flow 200 ml/min Loop volume = 14300 ml Chemistry control Cooling Bath Needle Valve HPLC Pump HPLC Pump Dissolved Oxygen sensor HPLC Reservoir Conductivity Sensor Dissolved gas control Water Sample Particle filter Hot Leg Cold Leg

4. Pressure and temperature control • Pressurizer with Ar gas piston to control pressure (maintains pressure within 100 psi with a passive pressure regulator) • Labview control of temperatures by control of lead temperature in heaters (maintain temperatures within 1 C) • Labview control of HPLC pumps to maintain constant level in a HPLC resovior (differential pressure transducer feed back to maintain level height within 0.5 inches) National Instruments SCX 1100 controlled by Labview 8 Side Internal Heaters 10 Lower Internal Heaters 4 Automated Valves Thermocouples 1 - 64 5 Pressure Transducers 15 External Heaters

5. Loop operating capabilites

6. Initial operating conditions

7. Dissolved Oxygen Concentration and Conductivity

8. Corrosion sample holder • Below is the first samples that were tested in a shake down test within the UW-SCW loop. Three samples were tested In 718, SS 316, Zirc • The picture to the right shows the samples in the current week long test that is currently under operation 8 samples separated by a AlO2 spacer

9. Turbo Molecular Pump Plasma Ions Biased Stage Ceramic Insulator - High Voltage + Pulser Schematic illustration of plasma ion implantation and deposition process Typical output from on-line process diagnostic showing voltage and current during pulse (taken during oxygen ion implantation of NERI project samples). Schematic illustration of the plasma ion implantation process

10. Modes of operation • Ion implantation of gaseous species (~50kV, N,O, Ar, C etc.) • Film deposition (DLC, Si-DLC, F-DLC) • Energetic ion mixing of film/substrate for surface alloying • Film-substrate adhesion (atomic stitching or by • ion implantation prior to deposition) • Materials removal (alteration of surface alloy chemistry • by differential sputtering, plasma cleaning) • Cross-linking thin viscous polymer films for • mechanical integrity, by energetic ion bombardment • Deposition of metallic and compound thin films

11. Substrates & plasma treatments being investigated in this NERI project • Substrates and vendors: • Inconel 718 (Aerodyne Ulbrich Alloys, Indianapolis. IN) • Zircaloy-2 (Allgheny Technologies, Albany, OR) • 316 stainless steel (Goodfellow, Berwyn, PA) • Plasma Surface Treatments: • Room temperature and elevated temperature ion implantation • Energetic ion bombardment for modification of microstructure and composition • Non-equilibrium surface alloying for a more tenacious and protective oxide

12. Surface Amorphization Base Material Amorphous Layer Materials concept underlying the plasma treatment of samples for the NERI project Surface Alloying Ion Implantation Base Material Base Material Base Material Thin Film Implanted Layer Thin Film Species Used for Implantation Base Material • O, N,C • Inert gases (Ar, Xe, Kr) • Y, Ta • Zircaloy-2 • Stainless Steel 316 • Inconel 718

13. Auger spectroscopy result showing composition vs depth below surface for a nitrogen ion implanted Zircaloy sample

14. Effects of Xe Bombardment • Scanning electron micrographs of chemically etched Inconel 718 samples before Xe+ ion bombardment (left column) and after Xe+ ion bombardment (right column).

15. Auger composition profile of a yttrium (oxide) film deposited on Inconel 718 substrate. Also shown photograph of the yttrium sputter cathode configuration and the substrate samples (with and without film) Untreated Oxidized Y coating Successful Y coating Yttrium sputter cathode

16. Auger analysis of Si-containing DLC produced using hexamethyl-disiloxane precursor (Si: ~ 20 at.%) Composition is tailored at the film-substrate interface to enhance adhesion

17. EDS analysis of coarse particles indicated that they contained Fe and V and likely originated from the loop material and adjacent Inconel 718 sample. ZrLa VKb Zircaloy-4 sample Zr Peak • SEM examination of Zircaloy-4 sample after 3-day SCW exposure • coarse and fine distribution of oxide particles, and sporadic fissures. • The finer particles were identified to be Zr-and Sn-oxide formed from the Zircaloy-4 sample • The fissures represent initial stages of corrosion failure (indicated by arrows in the photomicrograph). The finer particles were identified to be Zr-and Sn-oxide formed from the Zircaloy-4 sample Zr Peak • High magnification images of the fissures that were observed sporadically on the Zircaloy-4 sample. The Fe and Ni signals are from the oxide particles of these elements entrapped in the fissures. We are presently investigating the origins of Al, Mg, and Si. The fissures represent the initial stages of corrosion failure in this alloy.

18. Inconel 718 Sample • Surface of the Inconel 718 sample after testing in supercritical water for 3 days. Oxide particles were identified to be niobium oxide, indicating that preferential corrosion of niobium-rich precipitates in the alloy, might have occurred. Other oxide particulate debris was also observed which stemmed from the washout of the loop. Nb Peak

19. S.S. 316 Sample • Surface of 316 austenitic stainless steel after exposure to supercritical water for 3 days. Relatively less oxide debris was observed compared to Inconel 718 and Zircaloy-4 samples. The oxides as expected were identified to be those of Fe and Cr. However distinct pits (shown here at lower and higher magnifications, indicated by arrows) were observed which appear to be nucleation events for the corrosion of this alloy. Fe Peak Cr Peak

20. H2O H2O H2O Boundary layer Zr Liquid Bulk O2 Shrinking base metal Growing O2 oxide layer Zr +O2 ZrO2 Zr + 2 H2O ZrO2 + 2 H2 Integrating at constant temperatures and with constant properties For oxidation by steam • Diffusion of steam through the boundary layer fluid adjacent to the metal • Diffusion of steam into the growing oxide layer • Dissociation of water into elemental hydrogen and oxygen (O2) • Oxidation reaction between Zr and O2 • Diffusion of H2 back through the growing oxide layer CAb Concentration of steam in liquid bulk De Diffusion coefficient of steam in oxide Kg Mass transfer coefficient in liquid phase ZrO2 Molar density of the oxide layer

21. Quantification of oxidation/corrosion process • Oxide film thickness measurements (Auger Electron Spectroscopy, and cross-sectional SEM)  • Pit size distribution and density  • Oxide particulate size and distribution