SNS Studies towards a rotating solid target. Thomas McManamy (SNS)

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for the U.S. Department of Energy

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2 Proton Beam Profiles Studied Target Configuration
2-D Gaussian: Tungsten & Ta clad height 7 cm
Vertical Sigma - 1.5 cm Diameter 1.2 m
Horizontal Sigma - 4.5 cm Tungsten & Ta clad radial depth 25 cm
Flat: D2O Channel heights 1.5 mm
Vertical: 6 cm Steel shroud thickness 1 cm
Horizontal: 18 cm
Proton Energy: 1.3 GeV
Repetition rate: 20 Hz
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5. quot;# $%&
Vertical cut
H2 0
Beryllium
Horizontal cut
On mid-plane
H2
ss
protons
W
Horizontal cut
Through moderator
*
1.5 mm D20
cooling channels
* Lower moderator not modeled
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6. '
An optimized Para-hydrogen moderator configuration and center cooling
channel step location in the target was calculated with MCNPX for
maximum moderator brightness
• H2 radius 11cm
• Target height: 7 cm
• H2 height 12 cm
• Step Location of central cooling
• Moderator axis with regard to channel: 7.5 cm
target nose: 11 cm
Rotating target configuration gave nearly the same cold
moderator brightness as the STS mercury target ( + 7% for
flat profile, + 3% Gaussian profile).
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7. ( # )*+ , ! quot;
-
Central D2O
Central Tantalum
Bulk tungsten Channel
Cladding
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8. . /0 12 3 / 2 4
1 MW
.5 mm clad
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9. ! # #% 5 /0 12
Shaft
Gas conduction – 5 mm gap to 50 C
surface plus radiation ( ε = 0.8 all
external surfaces)
k=1.5 w/m-k
1.5 mm gas gap with radiation
5 mm ( 10% steel
( ε = 0.2 all internal surfaces)
ribs)
and water vapor or air
12 mm
Stainless Steel Shell
Nu=3
Tungsten & clad .035 m
Steel hub
18 kW uniform heat generation
.1 m
.6 m .3 m
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10. /6 72
# 8# 69
0.55
0.50
0.45
Temp (°C)
0.40
500
450
0.35 400
350
0.30 300
250
y
200
0.25
150
100
0.20
0.15
0.10
0.05
0.00
0 0.1 0.2 0.3 0.4 0.5 0.6
x
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12. /6 12 #%
• The proposed SNS target includes several layers of defense:
• Seismic qualification for core vessel components and target
• Primary cooling system with UPS low flow capability
• Independent backup (UPS) cooling within structural shell
• 3 mm diameter holes on 30 spacing
• 1 m/s water flow ( ~ 10 gpm total)
• Passive radiation and gas conduction to reflector assemblies
• 5 mm gaps to reflector/shielding assemblies
• 0.8 emissivity coating on target and reflectors
Backup Cooling Channels
Target
Segments
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13. / 2 quot;(: ;
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Comparison for Gaussian Beam
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External Cooling
3 3 ' D! !
Neutronic Performance loss with center cooling < 3%
Center Cooling
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14. < !
Peak = 152 0C
30 0C water inlet temperature
25 l/s flow
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15. #
Thermal Hydraulic Conditions for Flat Profile, 60rpm, 0.1s after pulse
100 1.40E+06
90
1.20E+06
80
1.00E+06
70
Temperature (C)
Heat Flux (W/m^2)
60
8.00E+05 Water Temperature
50 Surface Temperature
Heat Flux
6.00E+05
40
30 4.00E+05
20
2.00E+05
10
0 0.00E+00
0 10 20 30 40 50 60
Distance Along Flow Channel (cm)
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16. 8
5 bar pressure
Gravity & inertia
Flat beam profile
~ 210 MPa peak Von Mises
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All stress levels are well below 500 MPa unirradiated
tungsten yield or 180 MPa Tantalum yield and have margin
for fatigue and irradiation effects
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+# ! -
5000 Beam Hours = 1 year
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for the U.S. Department of Energy

19. :
Backup Cooling Coupling
Water Coupling
• This arrangement provides
for hands-on maintenance
access after a few days of
decay time. Proton Beam
Window Module
• The drive unit can be
replaced without removing
the target module
• Potential water or grease Core Vessel
leaks from rotating seals
outside of vessel
• The drive, seal and bearings Rotating
are located away from the Target
high radiation area.
Activated target cooling Reflector
water is expected to
generate approximately 1
G/hr in the drive enclosure Proton Beam
during beam-on operations.
Moderators
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20. Concentric Shaft
Channels
Gun Drilled Hub
Circumferential
Manifolds
Tantalum Clad
Tungsten Blocks
Shroud Cooling
Channels
• ' &% %& G! & ' %& &<
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21. > >
Lower Bearing
Ports on Shaft
Drive/Target
Mechanical
Joint
Seals
Intermediate
seal ring
Upper Bearing
Graphite packing seal with
intermediate gas injection
Lower Section
Upper Section
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Proton Beam
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Moderator Cart
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23. > <8 5 #
#
Support frame
Mechanical water seal
Water boundary tube
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24. Rails for
Removable
Moderator
target Monolith Maintenance Cells
Shielding
Service Cell
cask
The use of curved beam guides is expected to eliminate the need
for large vertical shutters within the monolith
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25 Managed by UT-Battelle
for the U.S. Department of Energy

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27. ! quot;
Rotating target configuration gives about the same neutron performance
as STS stationary mercury target ( + 7% for flat profile, + 3% Gaussian
profile).
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for the U.S. Department of Energy

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π σ
• R= sqrt(π/2)*D/σhorizontal
– For D ~ 1 m and σhorizontal ~ 50 mm this gives
factors of ~ 25 increase in life and reduction in
Managedaverage heating
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