ENGINEERING DESIGN AND TRANSIENT FLUID DYNAMIC SIMULATIONS OF
THE SECOND GENERATION OF LOW DIMENSION COLD MODERATOR FOR
THE EUROPEAN SPALLATION SOURCE ESS
2019-10-15 I ICANS XXIII, CHATTANOOGA I Y. BEßLER, G. NATOUR
OUTLINE
1. ESS Moderator & Reflector System status
2. First generation of ESS Moderators (BF2)
3. BF1 vs. BF2
4. Design criteria and solution
5. Heat deposition
6. Material properties
7. Start conditions of CFX
8. Uncertainties
9. Simulation results
10. Validation of simulation results
11. Outlook Red: Jülich deliverables
ESS MODERATOR & REFLECTOR SYSTEMPROJECT OVERVIEW
Moderator & Reflector Unit
Shaft & mountingSocket & MRP
Frames (shielding) Final twister assembly
Crown
Axial bearing
Shaft
Frame
Bucket
Rotation Unit
Twisterweight: 13 tHeight: 6,5 m
MRS TIK3.1
Cold Moderators
Thermal Moderator
Irradiation module
Pre Moderator
FIRST GENERATION OF ESS MODERATORS (BF2)DESIGN SOLUTION & STATUS OF MANUFACTURING
MRS TIK3.1FIRST GENERATION OF ESS MODERATORS (BF2)DESIGN SOLUTION & STATUS MANUFACTURING
Final assembly
NDT’s
Ready for delivery!
BF1
BF2
BF1 MODERATOR VS. BF2 MODERATOR, [1]WHY NEW DESIGN BEFORE THE OLD ONE IS IN USE?
• Minimal structure material content (neutronic)
• Material, location and time-dependent neutronic heat
• Pressure pm≈10 bar (pd=17 bar)
• Temperature Tm≈18,5 K (dT≤3 K)
• >99,5% para hydrogen
• Consideration of irradiation
• Compressibility of LH2
• Avoid (local) boiling
• RCC-MRx calculation
• Manufacturability
• Weldability
• …….7
BF1 MODERATOR STUDYDESIGN CRITERIA
8
BF1
Second generation of ESS
cold Moderators…..
BF1 MODERATOR DESIGN SOLUTION, [2]
Manufacturing concept
36 m
m
Cold Neutrons
Fast Neutrons
≈1l para LH2 volume
Dimensions: 250 x 200 x 36
Structural material Al6061-T6
𝑟 = y2 + 𝑧2
BF1 MODERATORHEAT DEPOSITION =F(MATERIAL,X,Y,Z), [2]
𝑟 = y2 + 𝑧2
0
2
4
6
8
10
12
14
16
18
20
22
24
26
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0
Gi(t)
=q
P∙q
i/qm
ax
[-]
t [ms]
Weighting factor for the time-dependent heat
qLH2
qm
qAl
BF1 MODERATORHEAT DEPOSITION =F(MATERIAL,X,Y,Z,T), [2]
0
50
100
150
200
250
300
0,0 1,0 2,0 3,0 4,0 5,0
qV
m(t
) [W
/cm
3]
t [ms]
Average volumetric heat in the pulse
qH2P
qAlP
qH2m
qAlm
11
BF1 MODERATORSTART CONDITIONS OF CFX, [2]
12
0,1
1
10
100
1000
10 15 20 25 30 35 40
log
p [b
ar]
T [K]
Phase diagram of para H2
GasLiquid
Solid
critical. point
0
20
40
60
80
100
120
140
160
0 50 100 150 200 250 300
λ[W
/mK
]
T [K]
Thermal conductivity of aluminum 6061-T6
λ
λirrad
BF1 MODERATORMATERIAL PROPERTIES, [2]
13
BF1 MODERATORUNCERTAINTIES OF HEAT DEPOSITION, [2]
1. Mass flow control valves! (∑ei≈ ±1%)
2. Outlet pressure control of PCB and pressure sensor! (∑ei≈ ±3,5%)
3. Inlet Temperature control of HX and temperature sensor (∑ei≈±2,5%)
4. Manufacturing Tolerance using for CFX the max wall thickness!
5. Material properties comparison with other libraries (∑ei≈ ±1%)
6. CFX??? experiment (PIV)
14
BF1 MODERATORADDITIONAL UNCERTAINTIES, [2]
15
25
27
29
31
33
35
37
39
41
43
0 20 40 60 80 100 120 140 160 180 200
T [K
]
Iteration-No. [-]
Temperature
T-AL-MAX T-AL-MAX-AVE T-H2-MAX T-H2-MAX-AVE
BF1 MODERATORSS RESULTS (TEMPERATURE), [2]
Heat averaged over time!(results used as start condition for pulsed simulation)
16
9,7
9,8
9,9
10,0
10,1
10,2
10,3
10,4
10,5
10,6
0 20 40 60 80 100 120 140 160 180 200
p [b
ar]
Iteration-No. [-]
Pressure
p-MIN p-AVE p-MAX p-IN
BF1 MODERATORSS PRE RESULTS (PRESSURE), [2]
Heat averaged over time!(results used as start condition for pulsed simulation)
17
0
5
10
15
20
25
30
0 1 2 3 4 5
Gi(t)
[-]
t [ms]
Time steps
0
1
2
3
4
5
6
7
8
0 200 400 600 800 1000 1200 1400
dt [m
s]
No. [-]
Time stepping
BF1 MODERATORTIME DISCRETIZATION (TIME STEPPING), [2]
18
1600 Time steps, 20-50 iterations each 128 CPU’s, Simulation time ≈70 h
0
10.000
20.000
30.000
40.000
50.000
60.000
70.000
80.000
90.000
0 200 400 600 800 1.000 1.200 1.400 1.600
q [W
/s]
t [ms]
Heat pulse at 1, 3 and 5 MW P-beam power
Heat-Al Heat-H2
BF1 MODERATORHEAT INTEGRAL VALUES, [2]
>109 Load changes per lifetime
19
-0,4
-0,2
0,0
0,2
0,4
0,6
0,8
1,0
0,0
0,5
1,0
1,5
2,0
2,5
0 200 400 600 800 1.000 1.200 1.400
dp [b
ar]
dT
[K
]
t [ms]
dT and dp at 1, 3 and 5 MW P-beam power
BF1 MODERATORDT, DP, [2]
20
17
19
21
23
25
27
29
31
33
35
0 200 400 600 800 1.000 1.200 1.400
T [K
]
t [ms]
Temperature at 1, 3 and 5 MW P-beam power
T-IF-MAX T-IF-AVE T-H2-AVE T-H2-OUT T-H2-IN T-AL-AVE T-Al-MAX
BF1 MODERATORTEMPERATURE DISTRIBUTION, [2]
Without any uncertainties!TB=31,24 K; TMAX=30,75
BF1 MODERATORPRELIMINARY RESULTS OF PARTICLE IMAGE VELOCIMETRY MEASUREMENT (PIV), [2]
-0,1
0,0
0,1
0,2
0,3
0,4
0,5
20 21 22 23 24 25 26 27
vy
[m/s
]
x [mm]
MP3-PIV
MP3-CFX
0,0
0,1
0,2
0,3
0,4
0,5
-26 -24 -22 -20 -18 -16 -14 -12 -10 -8
vy
[m/s
]
x [mm]
MP4-PIV
MP4-CFX
Comparison of the velocity profiles (left) and mean velocities (right) in the measuring Points [PIV (blue) and CFX (green)]
-25
-20
-15
-10
-5
0
5
10
15
20
1 2 3 4 5 6 7 8
vm,u
m[m
/s]
MPi [-]
Measured and simulated mean velocities as a function of MPi at Re=8,4∙105 (=ESS Moderator)
BF1 MODERATORPRELIMINARY RESULTS OF PARTICLE IMAGE VELOCIMETRY MEASUREMENT (PIV), [2]
23
15
17
19
21
23
25
27
29
31
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5
TIF
-MA
X[K
]
Pm [MW]
Interface temperature as a function of the proton beam power
TB(pmin) T-IF-MAX(Pm)
P-Beam+
MCNPX
Boiling temperature TB=f(p)
Estimated CFX error
(preliminary)
BF1 MODERATORMAX “THEORETICAL” BEAM POWER (PRELIMINARY RESULTS), [2]
• Design and CFX simulation of BF1 Moderator are completed!
• Comparison with PIV measurement is still in progress
• Max Proton beam power will be around ≈4MW (based on current requirements)
• For 5 MW local boiling can occur (possible cavitation needs to be analyzed)
• Prototyping will be completed in January
• PhD thesis will also be published in January
OUTLOOK
SOURCES
[1] Zanini, L., et al. The neutron moderators for the European Spallation Source. Oxford : 22nd meeting of the
International Collaboration on Advanced Neutron Sources (ICANS XXII), 2017
[2] Bessler, Yannick. Strömungsmechanische Simulation und experimentelle Validierung des kryogenen
Wasserstoff Moderators für die Europäische Spallationsneutronenquelle ESS.
Unpublished PhD, RWTH Aachen.
[3] europeanspallationsource.se
Y. Beßler Seite 25
[3]