Current Super Critical Water Loop test results

M. Anderson, K. Sridharan, M. Corradini, et.al.

University of Wisconsin – Madison

Department of Engineering Physics

Wisconsin Institute of Nuclear SystemsNuclear Engr & Engr Physics, University of Wisconsin - Madison

Presented at April SCW exchange meeting April 29th and 30th, UW-Madison

TC1

3TC

TC2

5TC

4TC

48

47TC

TC

6TC

TC7

TC8TC

9

TC10TC

11TC15

TC34

TC33TC

32

TC31TC

30

16TC

17TC

18TC

19TC

20TC

21TC

25TC

28TC

29TC

TC38

TC43

TC42

TC41

TC40

TC39

TC26

TC27

TC12

TC13

14TC

L M S

22TC

TC23

24TC

35TC 36

TC 37TC

L

M

S

L M S

44TC

45TC

46TC

L

M

S

1EH

EH2

EH3

5EH

4EH

EH6

EH7

EH8

EH10

EH11

EH12

14EH

EH13

15EH

EH9

Cooler #1

Cooler #2

Heater #1

Heater #2

Hot coolant return

Coolant supply

Hot coolant return

Coolant supply

Remote operatedthrottle valves

Inline flow transducer(orfice type for temp issues??)

Primary coolant pump

To building drain

From building supply

TC52

51TC

50TC

49TC

Inline flow transducer

Remote operatedthrottle valve

54TC TC

53

55TC

Primary coolantsurge tank

Primary coolantpressure transducer

Remote operatedstop valve

Pressurized gas in

Remote operatedstop valve

Pressurized water in

EH16

TC56

Primary inlet

U-tube heat exchanger

Primary outlet

EH17

TC57

Manual Bleed Valve

Manual bleed valve

Water level transducer

Tap #2

Tap #1

Supercritical surge/makeup resevoir

High pressure (4Kpsi)water in

Manual stop valve

Manual stop valve

Surge pressure transducer

High pressure (4Kpsi)gas in

Coil in temp bath as throttle

Test water out for analysis

Tap #3

Experimental water inHPLC pumps

Remote operatedstop valve

Stop valvePort #4

Test section drain

Test sectionpressure transducer

Test sectionmechanical pressure gauge

Remote operatedstop valve

62.000

62.000

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

Cooling Bath

Needle Valve

Dissolved Oxygen sensor

ConductivitySensor

Particle filter

Dissolved gas control

HPLC Reservoir

Water Sample

HPLCPump

HPLCPump

Chemistry control

Hot Leg Cold Leg

Max flow 200 ml/minLoop volume = 14300 ml

15 ExternalHeaters

Thermocouples1 - 64

8 SideInternalHeaters

10 LowerInternalHeaters

4 AutomatedValves

5 PressureTransducers

National Instruments SCX 1100 controlled by Labview

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)

Loop operating capabilites

0 20000 40000 60000 80000 100000390

392

394

396

398

400

402

404

406

408

410

412

414

TH 1 [C] = 407.60 +/- 0.8 TH 38 [C] = 405.45 +/- 0.8 TH 29 [C] = 404.86 +/- 0.9 TH 25 [C] = 404.92 +/- 0.9 TH 16 [C] = 401.79 +/- 1.4

Temperature of SCW in C

for different locations around the loop

Arbitrary time (s)

Initial operating conditions

0 20000 40000 60000 80000 1000000

2

4

6

8

10

12

14

16

18

20 SENSE O2 [PPB] SENSE K [uS]

Disolved O

2 concentration and conductivity

Arbitrary steady state Time (s)

Dissolved Oxygen Concentration and Conductivity

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

- High Voltage+ Pulser

Ceramic Insulator

Biased Stage

Turbo Molecular Pump

Plasma Ions

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

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

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

Bas

e M

ater

ial

IonImplantation

Implanted Layer Thin FilmB

ase

Mat

eria

l

Surface Alloying

Amorphous Layer

Bas

e M

ater

ial

SurfaceAmorphization

Species Used for Implantation

• O, N,C• Inert gases (Ar, Xe, Kr)• Y, Ta

Base Material

• Zircaloy-2• Stainless Steel 316• Inconel 718

Materials concept underlying the plasma treatment of samples for the NERI project

Thin Film

Bas

e M

ater

ial

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

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).

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

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

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).

The finer particles were identified to be Zr-and Sn-oxide formed from the Zircaloy-4 sample

Zr Peak

ZrLEDS analysis of coarse particles indicated that they contained Fe and V and likely originated from the loop material and adjacent

Inconel 718 sample.VK

• 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.

Zr Peak

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

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. 

Cr Peak

Fe Peak

Zr + O2 ZrO2

Zr + 2 H2O ZrO2 + 2 H2

Zr

Growingoxide layer

Bou

ndar

y la

yer

H2O

Liqu

id B

ulk

H2O

O2

O2

Shrinking base metal

H2O

( )( ) ( )( )tLdt

d

DtLk

COZ

eg

bA

r 212ρ=

+

Integrating at constant temperatures and with constant propertiesFor oxidation by steam

CAb Concentration of steam in liquid bulkDe Diffusion coefficient of steam in oxideKg Mass transfer coefficient in liquid phaseZrO2 Molar density of the oxide layer

•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

( ) ( )2

22

OZ

Ab

ge r

tC

k

tL

D

tL

ρ=+

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