CERAMIC BREEDER BLANKET FOR ARIES-CS A. R. Raffray (University of - PowerPoint PPT Presentation

CERAMIC BREEDER BLANKET FOR ARIES-CS A. R. Raffray (University of California, San Diego) S. Malang (Fusion Nuclear Technology Consulting) L. El-Guebaly (University of Wisconsin, Madison) X. Wang (University of California, San Diego) and the ARIES Team Presented at the 16th ANS TOFE Madison, WI September 14-16, 2004 1 September 14-16, 2004/ARR

Outline • Summary of ARIES-CS engineering plan of action • Ceramic breeder modular design layout • Power cycle selection: Brayton cycle • Optimization studies • Conclusions 2 September 14-16, 2004/ARR

Engineering Activities During Phase I of ARIES-CS Study • Perform Scoping Assessment of Different Maintenance Schemes and Blanket Concepts for Down Selection to a Couple of Combinations for Detailed Studies During Phase II - Three Possible Maintenance Schemes: 1. Field-period based replacement including disassembly of modular coil system (e.g. SPPS, ASRA-6C) 2. Replacement of blanket modules through small number of designated maintenance ports (using articulated boom) 3. Replacement of blanket modules through maintenance ports arranged between each pair of adjacent modular coils (e.g. HSR) - Different Blanket Configurations 1. Self-cooled flibe blanket with advanced ferritic steel 2. Self-cooled Pb-17Li blanket with SiC f /SiC composite as structural material 3. Dual-Coolant blanket concept with He-cooled steel structure and self-cooled liquid metal (Li or Pb-17Li) 4. Helium cooled ceramic breeder blanket with ferritic steel structure 3 September 14-16, 2004/ARR

Considerations on Choice of Module Design and Power Cycle for a Ceramic Breeder Concept • The blanket module design pressure impacts the amount of structure required, and, thus, the module weight & size, the design complexity and the TBR. • For a He-cooled CB blanket, the high-pressure He will be routed through tubes in the module designed to accommodate the coolant pressure. The module itself under normal operation will only need to accommodate the low purge gas pressure (~ 1-10 bar). • The key question is whether there are accident scenarios that would require the module to accommodate higher loads. If coupled to a Rankine Cycle, the answer is yes (EU study): - Failure of blanket cooling tube + subsequent failure of steam generator tube can lead to Be/steam interaction and safety-impacting consequences. - Not clear whether it is a design basis (<10 -6 ) or beyond design basis accident (passive means ok). • To avoid this and provide possibility of simpler module and better breeding, we investigated the possibility of coupling the blanket to a Brayton Cycle. 4 September 14-16, 2004/ARR

Low-Pressure Requirement on Module Leads to “Simpler” Design • Modular box design with coolant flowing through the FW and then Be pebble beds through the blanket FW cooling channel Breeder - 4 m (poloidally) x 1 m (toroidally) Stiffening plate pebble beds module - Be and CB packed bed regions aligned parallel to FW - Li 4 SiO 4 or Li 2 TiO 3 as possible CB • In general modular design well suited for CS application - accommodation of irregular first wall geometry - module size can differ for different port location to accommodate port size 5 September 14-16, 2004/ARR

Arrangement of the Breeder and Beryllium Pebble Beds • Inside the breeding zone, each breeder bed is enclosed by two cooling plates. • This assembly is filled outside the blanket box with ceramic pebbles, and closed. • All the cooling plates are welded to larger manifold plates before inserting the breeding zone into the blanket box. - Use of ODS FS in high temperature location would allow for higher • Beryllium pebbles are filled into temperature and cycle efficiency. any empty space inside the box, - Joining is a key issue because of and compacted by vibrating the difficulty of producing high strength module. welds with ODS FS. 6 September 14-16, 2004/ARR

Access Tube + Shielding Plug (~3% fractional coverage) for Cutting Tube Prior to Removing Blanket Module Shielding plug Blanket Permanent Shield • Cut the assembly weld in the front disk at the FW first. • Pull out the shielding plug with inner tube. • Cut the outer tube weld located behind the permanent shield. • Open/Remove the attachment bolts. • Pull out the blanket module. 7 September 14-16, 2004/ARR

Steps to be Performed for an Exchange of Ceramic Breeder Blankets* Pull out first the Closing Plugs from access port • Open and remove the first and second doors. • Cut the coolant access tubes from back. • Pull out the closing plug and insert the articulated boom into the plasma region. The boom has to be equipped with two classes of tools: • Tools for opening attachment bolts, inserted from the plasma region through radial gaps between the modules. • Tools for cutting/re-welding the front disk at the FW as well as the coolant access tubes at the back of blanket module. Remove other blanket modules • Cut the weld in the front disk at the module FW and remove module shielding plug. • Cut the weld of the coolant access tubes at the back of blanket. • Remove the attachment bolts. * See X.R. WANG, S. MALANG, A.R. RAFFRAY and the ARIES Team, “Maintenance Approaches for ARIES-CS Power Core,” 16 th TOFE 8 September 14-16, 2004/ARR

Ceramic Breeder Blanket Module Configuration • Number and • He flows through the FW cooling tubes in thicknesses of Be and alternating direction and then through 3- CB regions optimized passes in the blanket for tritium breeding (TBR ≥ 1.1) and high cycle efficiency for given wall load based on: - T max,Be < 750°C - T max,CB < 950°C - T max,FS < 550°C (<700°C for ODS) - k Be =8 W/m-K - k CB =1.2 W/m-K - δ CB region > 0.8 cm • 6 Be regions + 10 CB regions for a total module radial thickness of 0.65 m* * See L. EL-GUEBALY, et al., and the ARIES Team, “Benefits of Radial Build Minimization and Requirements imposed on ARIES Compact Stellarator Design,” 16 th TOFE 9 September 14-16, 2004/ARR

Two Example Brayton Cycle Configurations Considered Brayton I: - Blanket outlet He is mixed with divertor outlet He (assumed at - A more conventional ~750°C and carrying ~15%of total configuration with 3- thermal power) and then flown stage compression + 2 through HX to transfer power to the inter-coolers and a single cycle He with ∆ T HX = 30°C stage expansion To/from In-Reactor - Minimum He temperature in cycle Components or Intermediate (heat sink) = 35°C Heat Exchanger η Turbine = 0.93; η Compressor = 0.89; - T out T in ε Recuperator = 0.95 10 - Total compression ratio < 2.87 9 Intercoolers 1 Recuperator ε rec 3 Compressor 8 Turbine 5 6 7 P out IP LP HP η C,ad Compressors 1B η T,ad Generator P in 4 2 Pre-Cooler 10 September 14-16, 2004/ARR

Brayton II* He Blanket Coolant Brayton Cycle with 4- T in T in T in T in T out T out T out T out Stage Compression + Inter-Coolers, and 4- Re-Heaters Stage Expansion and Re-Heaters Heater 1A 1D 1B 1C G 2A 2B 2C e n 5A e 4-Stage r Compression a 5B t 4B o 5C r 4C s 5D 4D 6 2D 4A 4-Stage 3 Turbine Recuperator Expansion Inter-Coolers Pre-Cooler *P.F.PETERSON, "Multiple-Reheat Brayton Cycles for Nuclear Power Conversion With Molten Coolants," 11 Nuclear Technology , 144, 279 (2003). September 14-16, 2004/ARR

Comparison of T-S Diagrams of Brayton I and Brayton II T 1 Brayton I: 1B • 3-stage compression + 2 inter- 10 2´ coolers and a single stage 2 expansion 9´ 3 7´ 5´ 9 6 8 4 S T Brayton II: 1A 1B 1C 1D • 4-stage compression + 3 2D´ 6 inter-coolers and 4-stage 2A 2B 2C 2D expansion + 3 re-heaters 5D´ • More severe constraint on 5A´ 5C´ 5B´ 3 5D temperature rise of blanket 4D 4C 4B 4A coolant S 12 September 14-16, 2004/ARR

Example Optimization Study of CB Blanket and Brayton Cycle • Cycle Efficiency ( η ) as a 0.6 function of neutron wall load T max,Be <750°C;T max,CB <950°C ( Γ ) under given constraints ∆ blkt,radial =0.65m; ∆ T HX =30°C 0.55 T out,div =750°C • For a fixed blanket thickness Brayton with q'' plasma =0.5 MW/m 2 ( ∆ blkt,radial ) of 0.65 m (required 4-comp.+ 4-exp. for breeding), a maximum Γ T max,ODS-FS <700°C 0.5 of 5 MW/m 2 can be Cycle Efficiency P pump /P thermal >>0.05 accommodated with: T max,FS <550°C; η ~ 35% 0.45 T max,FS <700°C; η ~ 42% T max,ODS-FS <700°C 0.4 • The max. η corresponds to Γ Brayton with 3- P pump /P thermal <0.05 ~3 MW/m 2 : comp.+ 1-exp. T max,FS <550°C; η ~ 36.5% 0.35 T max,FS <550°C T max,FS <700°C; η ~ 44% P pump /P thermal <0.05 0.3 • The max. η ~ 47% for Γ ~3 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 MW/m 2 for Brayton II. Neutron Wall Load (MW/m 2 ) • However, as will be shown, P pump /P thermal is unacceptably high in this Brayton II case. 13 September 14-16, 2004/ARR