CHARACTERISTICS OF A TOKAMAK FUSION NEUTRON SOURCE FOR SPENT NUCLEAR FUEL TRANSMUTATION
W. STACEY, J. MANDREKAS, A. MAUER, C. KIRBY, J. NOBLE, D. STOPP, E. HOFFMAN, G. KESSLER and D. ULEVICH
FUSION RESEARCH CENTER GEORGIA INSTITUTE OF TECHNOLOGY ATLANTA, GA 30332 USA
OUTLINE SYSTEMS STUDY OF ELECTRICAL POWER CHARACTERISTICS CONCEPTUAL DESIGN STUDY OF TOKAMAK NEUTRON SOURCE (CONCEPTUAL DESIGN STUDY OF SUBCRITICAL FAST REACTOR)
PRESENTED AT INTERNATIONAL WORKSHOP ON BLANKET AND FUSION CONCEPTS FOR THE TRANSMUTATION OF ACTINIDES, SAN DIEGO, CA, 3/21-23/01 SYSTEMS STUDIES*
The effective transmutation (fission) rate is
SSkΣ TR=Σv N = f f −Σ ν − 11kka ()
The input electrical power required to produce S fusion neutrons per second is
ESPPfus ES fus η fus PQfus =+=+fus fusaux fus fus 1 aux b in, eηηηfus fus fus p η fus bbQQp aux pESfus fus aux
The electrical energy amplification (Qe) factor is
k ()+ ε fus 1 E ηblkt ++ν fis e 11Qp ()1− k E η fus fus fus e fus= ηη fus fus Qeeb P fus η fus 1+ Q aux b p η fus SEfus fus aux
where Qp = plasma Q Efus = 17.6 MeV/fusion Efis = 195 MeV/fission ε = enhancement of fission energy by other exoergic reactions fus Paux = power required to operate auxiliary systems fus ηb = heating energy into plasma/electrical energy into heating system fus ηaux = efficiency of converting electrical power to power to auxiliary systems fus ηe = efficiency of converting fusion plus auxiliary heating energy to electricity blkt ηe = efficiency of converting fission energy to electricity
Similar expressions can be written for an ATW facility.
* Nuclear Fusion, 41, 135 (2001).
PHYSICS SYSTEMS STUDIES WERE PERFORMED TO IDENTIFY RANGE OF TOKAMAK PARAMETERS FOR A NEUTRON SOURCE TO DRIVE A SPENT FUEL TRANSMUTATION REACTOR
Parameter Nominal Database Advanced Database H-confinement 1.0 1.5
βN 2 -- 3 2 – 3 Qp 2 -- 5 2 – 5 B (T) 5.5 5.5
τign (s) 55 κ,δ 1.7, 0.5 2.0, 0.8 q95 44 n/nGW 0.4 – 1.0 0.2 – 0.6 R (m) 3 - 5 2 – 3 I (MA) 6 - 10 6 – 10 Pfus (MW) 10s – 100s 10s – 100s
Table 1. Characteristic Parameters of Tokamak Fusion Neutron Sources That Could Produce Transmutation Rates of Hundreds-to-Thousands of Kg/FPY in Transmutation Reactors with k = 0.9.
ENGINEERING SYSTEMS STUDIES HAVE NOT BEEN PERFORMED, BUT ON THE BASIS OF PREVIOUS WORK IT IS ESTIMATED THAT THE MINIMUM SIZE OF A SUPERCONDUCTING TOKAMAK FOR THE TRANSMUTATION MISSION IS R0 = 4.5--5.5m.
IN ORDER TO REALIZE THE MINIMUM SIZE ALLOWED BY THE PHYSICS CONSTRAINTS (R0 ≈ 3.0m), IT APPEARS TO BE NECESSARY TO USE NORMAL MAGNETS. GEORGIA TECH DESIGN STUDY TOKAMAK-DRIVEN SUBCRITICAL TRANSMUTATION REACTOR
• IN JANUARY, 2001 A FACULTY-STUDENT CONCEPTUAL DESIGN STUDY OF A TOKAMAK-DRIVEN SUBCRITICAL TRANSMUTATION REACTOR WAS INITIATED AT THE GEORGIA TECH FUSION RESEARCH CENTER.
• OBJECTIVE—IDENTIFY THE PHYSICAL PARAMETERS AND PERFORMANCE CHARACTERISTICS OF A SUBCRITICAL FAST TRANSMUTATION REACTOR DRIVEN BY A TOKAMAK FUSION NEUTRON SOURCE.
• DESIGN BASIS
- EXISTING TOKAMAK PHYSICS DATABASE, BUT WITH ADVANCES IN CURRENT DRIVE FOR LONG PULSES
- EXISTING FUSION TECHNOLOGY
- ADAPTATION OF NUCLEAR TECHNOLOGY (METAL FUEL, PB-BI COOLING, PYROMETALLURGICAL PROCESSING) THAT IS BEING DEVELOPED FOR ATW PROJECT. ADAPTATIONS FOR - TRITIUM BREEDING - TOKAMAK GEOMETRY
• DESIGN ANALYSIS EMPHASIS
- TOKAMAK PHYSICS
- LONG-BURN COPPER MAGNET SYSTEM
- SUBCRITICAL REACTOR PHYSICS*
- TRANSMUTATION FUEL CYCLE ANALYSIS*
* PAPER BY E. A. HOFFMAN, et al. AT THIS WORKSHOP. Tokamak Design
Ohmic Toroidal Heating Field Plasma Reflector, Coils Coils Chamber Shield & Vacuum Vessel
First Reactor Wall 1 Meter Region Methodology for determining tokamak reactor parameters • Starting from the performance and power balance equation, ()nTτ nTτ = E ∞ E + 5 1 Qp
21 -3 where (nTτE)∞ is the nTτE value required for ignition (~ 5×10 m keV.s), Qp is the plasma Q, and using the ITER IPB98(y,2) scaling for τE:
τκ= 0.93 0.15 0.41 1.97−− 0.58 0.69 0.19 0.78 E 0.0562HI B n19 R A P M and using the following physics and radial build constraints:
• q95 ≥ 3, where 223 1121.2++−κδδ()− ε = 5BR0 1.17 0.65 q95 AI2 2 −ε 2 2 MA ()1 I • ββ≤ MA β N aB ( limit) I ≤ MA • nG20 n (Greenwald density limit) π a2 ∆ =−−BTF rs • BA0 1 (radial build limit) Aa
• For a given set of κ, δ, H, Gn, βn, q95, BTF and A we can solve for the plasma current, I, and then all the other basic tokamak parameters (R, a, B0, Pfus, etc.) are fully determined.
• Since the various inequality constraints have been treated as equality constraints in this formulation, the performance characteristics of the resulting design should be regarded as an upper limit. Sufficient operational flexibility should exist by operating below the various limits (β limit, Greenwald density limit, etc.) Reactor Sizing A = 3.47 10 14 7 Q = 5 p ∆ = 0.4 m RS β = 2 % 6 n (T) n / n = 0.75 B 0 e GW 0 B 8 12 5
4 R 0 3 I 6 10 p Plasma Current (MA)
Major and minor radii (m) 2 a Magnetic Field on Axis, 1 4 8 8 10121416 B (T) TF Midplane Radial Build ∆ ∆ OH gap ∆ ∆ ∆ ∆ ∆ TF in 2a reac ou TF
Rfc Rmag Ro
Rfc = flux core radius = 1.20 m ∆ ∆ OH = OH solenoid =0.25 ∆ ∆ TF = TF coil =0.35 ∆ in = inner refl/shld = 0.40 a = minor radius = 0.90 ∆ reac = reactor = 0.40 ∆ ou = outer refl/shld = 0.30 ∆ gap = outer gap = tbd Ro = major radius = 3.10 Rmag = magnet radius = 1.80
Note: refl/shld includes first wall, reflector, shield, and vacuum vessel R = 3.1 m, a = 0.89 m, I = 9.39 MA, B = 8.16 T 20 0 p 0 2.5x10 H = 1.1, n / n = 0.75 600 e GW
2.0x1020 500
400 1.5x1020
300 1.0x1020
200
19 Neutron Rate (#/s)
Fusion Power (MW) 5.0x10 100
0.0 0
0.010 0.015 0.020 0.025 0.030 Normalized Beta, β n
R = 3.1 m, a = 0.89 m, I = 9.39 MA, B = 8.16 T 3.5 0 p 0 H = 1.1, n / n = 0.75 e GW 0.8 3.0 0.7 ) 2
2.5 )
0.6 2
2.0 0.5
0.4 1.5 0.3 1.0 0.2
0.5 First /m Load (MW Wall 0.1 Neutron Wall / Load (MW m
0.0 0.0
0.010 0.015 0.020 0.025 0.030 Normalized Beta, β n Reactor Performance R = 3.1 m, a = 0.89 m, I = 9.39 MA, B = 8.16 T 600 0 p 0 Q p 8 500 H = 1.1 P H = 0.9 fus
400 6 aux P /
300
Q 4 fus
p P = 200 p Q
Fusion Power (MW) Fusion Power 2 100
0 0 1.0 1.5 2.0 2.5 3.0 3.5 Normalized Beta, β n Reference Design, H(y,2) = 1.1, α = 0.1 n 5 Q
9 4 3 n GW 7 )
-3 400 β 5 n
m 200 2.5
20 3 0.75 n GW 3.0 > (10
e 11 500 n < 1.5 P 1.3 300 fus 2 7 100 11 2.0 P/P 953 thr 1.0 1 2 4 6 8 10 12 14 16 18
OH SOLENOID
1 Provide 2 start-up V-s ∆=φπ2 =11 ∆ φ = µ8Ro − rB o Rnl 1.75 I fcOH 22 inda plasma
ASME stress limits
= µ BNILOH o 1σ 2 r u NI 11fc 3 σµ=+<= ten om ∆ Slarger Lr23 2σ y 3 Heat removal
ρL PI == 2 T LhTTL() − p T ohmAc cond cool
TOROIDAL FIELD COILS
BNIRφ = µo 2π
ASME stress limits
µ 2 1+ (RR) σ =<1 oNI bore o ten π lnAScm 241−(RR) bore o
Heat removal PRELIMINARY MAGNET PARAMETERS
OH Solenoid TF Coils Conductor BeCu OFHC Cu Coolant LN2 LN2 Field @ Conductor (T) 10 14 Volt-sec capability 46 Cross section area (m2) 0.8 0.22/coil coolant fraction (%) 15 20 structure fraction (%) tbd 25 Maximum tensile stress 273 226 (MPa) ASME allowable Sm 280 268 (MPa) Ohmic heating (MW) tbd 407 Coolant mass flow tbd 185 (kg/s) SUMMARY
TOKAMAK NEUTRON SOURCE ELECTRICAL POWER REQUIREMENTS MORE FAVORABLE THAN FOR AN ACCELERATOR NEUTRON SOURCE
PHYSICS DESIGN BASIS —PRESENT TOKAMAK DATABASE ---EXTENDED DATABASE FOR LONG PULSE NON-INDUCTIVE CURRENT DRIVE.
TOKAMAK PARAMETERS R0 ≈ 3 m B0 ≈ 8 T βN < 2 QP ≈ 2 – 5 Pfus ≈ 200 MW 20 S ≈ 10 n/s 2 Γn ≈ 1.0 MW/m 2 qfw ≈ 0.25 MW/m
COPPER MAGNETS BTFC ≈ 14 T B0H ≈ 10 T