09 fnst meeting preliminary neutronics analysis for ib shielding design on fnsf (standard aspect...
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09 FNST meeting
Preliminary Neutronics Analysis for IB Shielding Design on FNSF (Standard Aspect Ratio)
Haibo Liu Robert Reed
Fusion Science and Technology Center, UCLAAugust 19th, 2009
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Objective
To maximize the TBR of the FNSF design with an effective IB
shielding of a given thickness.
Approach:
Within a 50-cm IB shielding, the damage rates are kept below the
allowable limits by investigation of various IB configuration/material
choices, type of magnet insulators, etc.
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How to Achieve Shielding Effectiveness
IB total thickness: 50cm
Case1: FW(2cm) + PbLi(7cm) + Reflector(5cm) + Shield(36cm)
Case2: FW(2cm) + Be(5cm) + Reflector(5cm) + Shield(38cm)
Case3: FW(2cm) + PbLi(2cm) + struc(0.5cm) + Be(5cm) + struc.(0.5cm) + PbLi(5cm) + Reflector(5cm) + Shield(30cm)
Case4: FW(2cm) + PbLi(2cm) + struc.(0.5cm) + Be(3cm) + struc.(0.5cm) + PbLi(5cm) + Reflector(5cm) + Shield(32cm)
Case5: case3 IB + Full Coverage OB
Shield: 5%Water + 5%SS + 25%B4C + 65%W
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Model and Code
Model: based on GA FDF design and the VNS design of Ho&Abdou(1996) 3D Calculation: MCNP XS Library: FENDL/MC-2.1
Normal magnet is used.
FNSF parameters assumedElongation: 2Aspect Ratio A: 3.5Major Radius R: 2.5mNeutron Wall Load: 2MW/m2
Peak Inboard Fluence: 6 MWa/m2
A DCLL blanket (83.4cm) is used on the outboard in all calculations. 20o Model
(CAD Model Generated by MCAM)
Reflective Boundary
Reflective Boundary
Vacuum Boundary
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Magnet Case
Magnet Case
TFC
IB
OHC
OB
PFC
PFC
VV
Components Description
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IB Design Cases
IB total thickness: 50cmCase1: FW(2cm) + PbLi(7cm) + Reflector(5cm) + Shield(36cm) Case2: FW(2cm) + Be(5cm) + Reflector(5cm) + Shield(38cm)Case3: FW(2cm) + PbLi(2cm) + struc(0.5cm) + Be(5cm) + struc.(0.5cm) + PbLi(5cm) + Reflector(5cm) + Shield(30cm)Case4: FW(2cm) + PbLi(2cm) + struc.(0.5cm) + Be(3cm) + struc.(0.5cm) + PbLi(5cm) + Reflector(5cm) + Shield(32cm)Case5: case3 IB + Full Coverage OB
1-D Diagram of IB Design Cases
Shield: 5%Water+5%SS+ 25%B4C+65%WPbLi: 90%enriched 6LiFW: 40%FS+60%HeReflector: 100%FS
Plasma Side
case1
case2
case3/5
case4
IB 50 ( D im ens ion in cm )
F W
L iP b R eflectorS hie ldB e
S tructure
2
2
2
2
7 5 36
5 5 38
2 5 5 5 30
2 3 5 5 32
Insulator
O H C
V V
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Case3 Case5 – Full OB Coverage
Difference Between Case3 and Case5
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Radial Dimension and Materials CompositionComponent Radial thickness (cm) Composition
TFCCoil 106 60%Copper+25%Water+15%insulator
Insulator 0.2 40%Epoxy+60%Al2O3
Case 7 100%SS316L(N)-IG
OHCCoil 7.8 60%Copper+25%Water+15%insulator
Insulator * 0.2 40%Epoxy+60%Al2O3
VV Void 2 -
Inboard (Case3**)
Shielding 30 5%Water+5%SS+25%B4C+65%W
Reflector 5 100%FS
PbLi 5 100%PbLi (90%enriched)
Struc. 0.5 100%FS
Be 5 100%Be
Struc. 0.5 100%FS
PbLi 2 100%PbLi (90%enriched)
FW 2 40%FS+60%He
SOL 5 void
Plasma 132 Neutron Source
SOL 5 void
Outboard DCLL TBB 83.4 From Dr. Youssef (DEMO)
** one of five cases * organic insulator
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Design Limit for Damage Rates
Limit dose for epoxy insulator ~109 Rads (10 MGy)
Limit fast neutron fluence for epoxy insulator ~ 5×1021n/m2
Limit dose for ceramic insulator Generally ~1012 Rads
but > 1012 Rads for MgAl2O4(spinel)
Limit fast neutron fluence for MgAl2O4 ~2×1026 n/m2
Limit VV He production rate 1 He appm
Copper Magnet Electrical Resistivity Change
∆ρtrans = KNiCNi + KZnCZn, where KNi = 11.2 nΩm, KZn = 3.0 nΩm, and CNi & CZn are
atomic percentages. ∆ρrad,def ≈ A(1-e-B·DPA), where A is the saturation resistivity change. A=1.2 nΩm for
pure copper and 1.6 nΩm for DS and Cu-Cr-Zr copper alloys at 100oC. B=100. The
electrical resistivity of pure copper is 17.1 nΩm at 20oC.
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0.0
0.2
0.4
0.6
0.8
1.0
1.2
Tri
tium
Bre
ed
ing
Ra
tio
case1 case2 case3 case4 case5
IB OB Total
Tritium Breeding Ratio Peak VV He appm
Case3, with a sandwich IB configuration, has larger IB TBR and the total is 1.04. The TBR can be further increased to 1.24 by extending the OB to the divertor region. But does it feasible from the engineering point of view of FNSF?
The peak VV SS helium production rate for all the cases are below the reweldability limit of 1appm. The maximum is 0.33 He appm from Case5.
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
VV
Pe
ak
He
ap
pm
case1 case2 case3 case4 case5
VV
6MWa/m2
TBR and Peak VV He appm
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0
1
2
3
4
5
6
7
Insu
lato
r D
ose
(1
010
rad
s)
case1 case2 case3 case4 case5
neutron gamma total
6MWa/m2
0
1
2
3
4
5
6
7
Insu
lato
r D
ose
(1
010ra
ds)
case1 case2 case3 case4 case5
neutron gamma total
6MWa/m2
Peak Insulator Dose with Epoxy Insulator Peak Insulator Dose with Spinel Insulator
Peak Insulator Dose
The epoxy insulator doses for all the cases are much higher than 109 rads. The ceramic insulator is suggested to be used in the FNSF design for its much higher dose limit. The dose in spinel insulator case5 is 4.7×1010rads.
If the epoxy insulator is preferred, the IB shielding thickness has to be increased.
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0
1
2
3
4
5
6
7
8
9
OH
C P
ea
k F
ast
Ne
utr
on
Flu
en
ce (
10
19 n
/cm
2 )
case1 case2 case3 case4 case5
epoxy spinel
6MWa/m2
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
0.050
Pe
ak
OH
C D
PA
case1 case2 case3 case4 case5
epoxy spinel
6MWa/m2
OHC Peak Fast Neutron Fluence OHC Peak DPA
The maximum OHC peak fast neutron fluence is from spinel insulator Case5, which is 8.6×1019n/cm2, higher than the result of epoxy insulator case5. The maximum OHC peak copper DPA is also from spinel insulator Case5, which is 0.05DPA.
Peak Fast Neutron Fluence and DPA
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OHC Resistivity Change with Epoxy Insulator OHC Resistivity Change with Spinel Insulator
The resistivity change for two kinds of insulators are about 1.2 nΩm, about 7% increase to the total copper electrical resistivity. The DPA-induced electrical resistivity increase in magnet pushes its resistivity almost to the saturation value of 1.2 nΩm for pure copper.The transmutation induced resistivity change is very small because of the low neutron fluence.
Peak Magnet Electrical Resistivity Change
0.01
0.1
1
OH
C r
esi
stiv
ity c
ha
ng
e (nΩ
m)
case1 case2 case3 case4 case5
trans. defect
6MWa/m2
0.01
0.1
1
OH
C r
esi
stiv
ity c
ha
ng
e (nΩm
)
case1 case2 case3 case4 case5
trans. defect
6MWa/m2
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IB Nuclear Heating Rate
Case1 IB Nuclear Heating Rate Case3 IB Nuclear Heating Rate
The peak nuclear heating rate in Case3 is about 14 w/cc in the FW-FS, about 23 w/cc in the 1st PbLi layer, which occurs before the beryllium multiplier layer, and this could be because of the effect of the neutron multiplication and reflection from the beryllium. In Case1, the PbLi layer heating rate is also increased along the IB depth because of the reflective neutron induced gamma from the FS reflector.
0 2 4 6 8 10 12 14 16 18 200
2
4
6
8
10
12
14
Nu
cle
ar
He
atin
g R
ate
(w
/cc)
Depth in IB (cm)
Case12MW/m2 NWLFW-FS
PbLi
Reflector-FS
Shield-SS
0 2 4 6 8 10 12 14 16 18 200
2
4
6
8
10
12
14
16
18
20
22
24
Nu
cle
ar
He
atin
g R
ate
(w
/cc)
Depth in IB (cm)
Case32MW/m2 NWL
FW-FS
PbLiBe
PbLi
Reflector-FS
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Summary
Five FNSF IB cases with 50cm IB thickness have been calculated. Taking into account the high damage rate, ceramic insulator is suggested to be used in FNSF. The MgAl2O4 could be a good choice based upon its good mechanical and electrical properties.
For getting tritium self-sufficiency, the Case5, PbLi & Be & PbLi sandwich IB design with full OB coverage, is confirmed better choice. The TBR from Case5 is 1.24, which is larger than the other cases.
The DPA-induced increase in magnet electrical resistivity is the dominant part
of the total increased resistivity under the low neutron fluence.
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Thank you for your attention!