ESS-Bilbao Initiative Workshop. R&D Towards mitigation of cavitation damage in the SNS mercury target vessel

ESS Bilbao Initiative Workshop
Multi-MW Spallation Neutron Sources:
Current Challenges and Future Prospects
March 16-18, 2009
Bilbao, Spain

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2 Managed by UT-Battelle
for the U.S. Department of Energy

Target-to-core vessel
inflatable seal
Mercury vessel

Target-to-Hg
piping seal

Water shroud


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200 WNR pulses on test target

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WNR: Weapons Neutron Research facility at the Los Alamos Neutron Science Center

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Mercury filled test target being Simulation of test target response to
prepared for in-beam test beam show mercury pressure evolution

[Pa]

Mercury in state of cavitation

What is the tensile strength of mercury?
1.5 bar

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ABS: 3 pairs of
acoustic transducers
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SNS Target Test Facility

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– Specimens (DTS)
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50.8 mm

25.4 mm
Bubbler #1 Storage
Tank
Mercury Pump
1.5 mm


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A B C

Bubbler #1 Bubbler #2 Bubbler #2
Helium Argon Helium
Series average Series average Series average
VF = 3.56E-04 VF = 1.34E-03 VF = 1.37E-03


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99 =
2.0E-03

1.8E-03
B1 01D-S01_04D-S02S07S08 140 sccm, Total VF = 1.29E-03
B2 140 sccm, Total VF = 4.74E-03
04D-S09S11
1.6E-03
B1 04Dec06State03 300 sccm, Total VF = 2.61E-03
B2
Number density [n/mm ]

300 sccm, Total VF = 3.46E-03
04Dec06State10
3

1.4E-03

1.2E-03
Smallest bubble:
0.12 mm equivalent radius.
1.0E-03

8.0E-04
Corresponds to 2005
damage test condition.
6.0E-04

4.0E-04

2.0E-04

0.0E+00
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2

Radius [mm]


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For coaxial flow For cross flow

6.0
A Edge

Bubble Diameter [mm]
Transmission
5.0
Acoustic
4.0

UL = 0
3.0

2.0

1.0

UL = 0 ; QHe = 10 sccm 0.0
4.5
B 4.0

UL = 0.63 m/s
3.5
3.0
2.5
2.0
1.5
1.0
0.5
UL = 0.63 m/s; QHe = 10 sccm
0.0
3.0
C

2.5 UL = 0.96 m/s
2.0

1.5

1.0

0.5
UL = 0.63 m/s; QHe = 100 sccm
0.0
0.1 1 10 100 1000
Gas flow rate [SCCM]

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bubble coalescence
Db =1.196 mm Db =1.049 mm

Fluent
CFX
Db =1.064 mm (measured)


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SNS Target configuration
TTF Target only has main flow


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Replaceable insert
Ri = 41 mm

Outer acrylic window

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Mercury flow quasi-
stagnation point.

Viewport

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Nominal Hg Flow,
Gas Flow = 1000
sccm

7A31903
Gas injection

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Mercury flow left to right

Gas Injected at this Nozzle

Vertical grooves (0.5 mm pitch, V 30 deg)

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Flow guides
increase flow
Hg Flow
velocity to more
prototypic SNS
conditions

Test surface with
33 mm
surface texturing

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3 test surfaces
per target


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HIGH intensity
1 σ_X = 13.5 mm
1 σ_Y = 4.5 mm
2σ

Rectangular target interior
4.8 MW SNS eq,

1.625 x 5.625”
MEDIUM intensity
1 σ_X = 21 mm
1 σ_Y = 7 mm
2σ
2.0 MW SNS eq.

LOW intensity
1 σ_X = 30 mm
1 σ_Y = 10 mm
2σ
1.0 MW SNS eq.

Total energy deposited in targets is maintained between conditions.
Intensity varied by changing beam spot size.

1

protons / Maximum
σ_X σ _Y
Target – Test No. of Pulses pulse length Comment
pulse Intensity
µ
x 1012 [µs] [mm] [mm] [p/mm2 x 1010]
(approx.) (half width) (half height)

LDV & PCD testing. Varied
RECT – LDV
95 0.1 – 27 0.3 14.8 – 33.6 4.6 – 10.4 5.6 intensities by changing profile and
various beam
protons

RECT – High Request smallest possible beam
100 26.5 0.3 15.4 5.2 5.25
Intensity spot with 3:1 aspect ratio

RECT – Medium This condition roughly splits low
100 26.6 0.3 20.2 6.1 3.43
Intensity and high

RECT – Low This is about the largest beam that
100 26.3 0.3 32.5 9.5 1.36
fits inside target at 2 σ
Intensity

RECT – textured Cone type textured test surface;
100 26.5 0.3 21.2 6.7 2.95
surface Gas puffing suspected not correct

RECT – Long Long pulse beam conditions still
100 45 ? 833 20.4 6.1 6.0 ?
pulse under study

Primary damage dependence on intensity scope


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Velocity (m/s)

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-2
1.2 1.4 1.6 1.8 2
Time (ms)

1. Band pass velocity data (15 – 300 kHz)
Omit 10 µs after pulse
2.
0.1
High
CPD = V 2 dt
intensity
CDP (mm2/s)

Medium
intensity
0.05

Low intensity
Interesting artifact is consistent
2 ms after incidence
0
2 3 4
Time (ms)

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ESS-Bilbao Initiative Workshop. R&D Towards mitigation of cavitation damage in the SNS mercury target vessel

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ESS-Bilbao Initiative Workshop. R&D Towards mitigation of cavitation damage in the SNS mercury target vessel