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 <T > (keV) e COPPER MAGNET DESIGN CONSTRAINTS 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.