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
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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
Chemistry control
Max flow 200 ml/min Loop volume 14300 ml
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
15 External Heaters
Thermocouples 1 - 64
5 Pressure Transducers
5
Loop operating capabilites
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Initial operating conditions
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Dissolved Oxygen Concentration and Conductivity
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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
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
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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
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
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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
Zircaloy-4 sample

• 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).

Zr Peak
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.

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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
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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
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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
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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