X.R. Wang, M. S. Tillack, S. Malang, F. Najmabadi and the ARIES Team Overall Power Core Configuration and System Integration for ARIES-ACT1 Fusion Power Plant X.R. Wang, M. S. Tillack, S. Malang, F. Najmabadi and the ARIES Team 20th TOFE Nashville, TN August 26-31, 2012

Major Parameters of the ARIES-ACT1 Power Plant   Value Major radius R 6.25 m Aspect ratio A 4 Elongation k 2.1 Toroidal field on axis Bo 6 T Plasma Current Ip 10.93 MA Fusion power Pf 1813 MW Thermal power Pth 2016 MW Recirculating power Precirc 154 MW Net electric power Pe 1006 MW Average wall load at FW Pn 2.3 MW/m2 Maximum wall load at FW 3.6 MW/m2 Power conversion efficiency ᵑth 57.9 % ARIES-ACT1 Power Core

A Comparison of the ARIES-AT and ARIES-ACT1 Power Core Major radius 5.5 m 6.25 m IB Blanket LiPb cooled SiC/SiC structure 1st OB Blanket 2nd OB Blanket HT Shield LiPb cooled SiC/SiC structure and B-FS filler He-cooled ODS steel structure Upper/Lower Divertors He-cooled W-based divertor and ODS steel cartridge Vacuum vessel Water-cooled FS structure and WC He-cooled Bainitic FS (3Cr-3WV) LT shield Water-cooled Bainitic FS and WC

Replacement Units for the Quick Sector Maintenance All the in-vessel components have a limited lifetime and require replacement. Our design approach is to integrate all the in-vessel components into replacement units to minimize the number of the coolant access pipe connections and time–consuming handling inside the plasma chamber. The integrated replacement unit must maintain a constant distance in radial direction, and no welds are used for the connections between the different components of the replacement units and between the units and the VV. The replacement units are supported at the bottom only through the VV by external vertical pillars, and can expand freely in all directions without interaction with the VV. The unit can be inserted and withdrawn by straight movement in radial direction during installation and maintenance. Replacement unit (1/16)

Overall Layout of the ARIES-ACT1 Power Core All the coolant access pipes to the sector are connected to the structural ring close to its bottom plate. Cutting/Reconnection of all the access pipes is located in the port, and all the pipes and shield blocks would be removed for sector maintenance. Control coils are supported by the structural ring and be removed to the upper corner of the VV for the sector removal. Shield blocks are arranged in the VV port to protect the coils, and they would be cooled by helium. The saddle coil can be attached to the upper shield block and removed together during maintenance. Maintenance ports are arranged between the TF coils, and there is only one vacuum door located at the end of the port for each sector. Cross section of the ACT1 power core (1/16 sector)

T-shaped Attachment and Rail System Utilized for Sector Alignment During the installation, a rail system with 2 or 3 vertical pistons would be inserted and the sector will be supported by the rail system for the vertical and horizontal alignment. There are wide gaps in the wedge allowing the precise alignment of the sector in all directions. After the alignment, the grooves of the attachment have to be filled with a suitable liquid metal (possibly a Cu-alloy) and fixed in the position by freezing the liquid metal the attachment grooves. Then, the rail system will be withdrawn. T-shaped attachment for sector support Cross-section of T-shaped attachment and rail system

Main features of the Sector Maintenance A transfer flask with the rail system and fresh sector can be docked to the port to avoid any spread of radioactivity during maintenance. After all access pipes disconnected, and the shield blocks, saddle coil, control coils and access pipes removed, the rail system would be inserted into the space between the structural ring and the VV. Using the rail system, the sector is supported by pressurizing the pistons and separated from the VV by melting the metal inside the T-shaped attachment grooves. Then, the sector can be pulled in straight way out the plasma chamber into the transfer flask. After that, the new sector can be installed in reverse order without moving the flask away from the port.

Design and Optimization of the First Wall and Blanket Modules Major objective of the blanket design is to achieve high performance while keeping attractive features, feasible fabrication, credible maintenance schemes and reasonable design margin on the operating temperature and stress limits. Design iterations were made to determine and optimize all the parameters of all the blanket segments, including: curvature of the FW/BW, thickness of the FW/SW/BW, width and depth of FW cooling channels, number of the ribs per duct, number of modules per sector. ARIES-AT-type SiC/SiC blanket modules Outer duct FW Center duct with ribs Cross-section of one OB-I module

Scope Structural Analyses for Optimizing the Geometry and Reducing SiC Volume Fraction Stress limits for using in FEM analysis: Conventional stress limits (3 Sm) can not be directly applied to ceramics. In our design, we try to maintain the primary stress to <~100 MPa and limit the total combined stress to ~190 MPa. ARIES-AT blanket ARIES-ACT1 blanket Phydrostatic=~0.8 MPa (Inboard blanket) (Inboard blanket of the ARIES-ACT1) Assumed the MHD pressure drop through the FW and blanket ∆P MHD=~0.2 MPa

Example of Definition, Dimensions of the OB Blanket Modules Inner modules of the OB-I and OB-II Inner modules 45 cm Total number of the module for each blanket sector=16, 14 inner modules with pressure balance on side walls and 2 outer modules without pressure balance on the outer side wall. (same number for OB-II) The FW/SW/BW thickness of the outer/inner ducts =5 mm (7 mm for OB-II) The fluid thickness of the annular gap=10 mm (same for OB-II) Rib thickness at 4 corners=6 mm (same for OB-II) Rib thickness on both sides=2 mm (same for OB-II) Diameter of the curvature for the FW and back wall=30 cm (45 cm for OB-II) 30 cm Outer module of the OB-I and OB-II Outer module Increase the thickness of the outer SW from 5 mm to 15 mm (22 mm for OB-II) Increase the thickness of the rib at the outer SW from 2 to 5 mm (6 mm for OB-II) Increase the numbers of the rib at the outer SW from 2 to 5 (9 for OB-II) Inner and Outer Modules of OB Blanket

Thermal Stress Results indicate the Design Limits Are Satisfied Max. thermal stress =~91 MPa Pressure stress<~50 MPa Total stresses=~141 MPa Thermal stress distribution of the inboard blanket module B.C. and loads: Free expansion, and allowing for free bending Pressure load at the bottom: 1.95 MPa at annular ducts and 1.65 MPa at the center duct Pressure load at the top: 0.95 MPa at the annular ducts and 0.85 MPa at the center duct Max. combined primary and thermal stresses are ~141 MPa at the bottom (higher primary stress, lower thermal stresses) and ~142 MPa at the top (higher thermal stresses, lower primary stress)

Integration of the He-cooled W-based Divertor in the ACT1 Power Core Fingers arranged over the entire plate Imping-jet cooling, Tin/Texit=700/800 ᵒC Allowable heat flux up to~14 MW/m2 Avoiding joints between W and ODS steel at the high heat flux region ~550,000 units for a power plant T-Tube divertor: ~1.5 cm dia. X 10 cm long Impinging-jet cooling, Tin/Texit=700/800 ᵒC Allowable heat flux up to~11 MW/m2 ~110,000 units for a power plant Plate divertor: 20 cm x 100 cm Impinging-jet cooling, Tin/Texit=700/800 ᵒC Allowable heat flux up to~9 MW/m2 ~750 units for a power plant Divertor region of the ARIES-ACT1 The selection of the divertor depends on the peak heat flux and heat flux profile of the ACT1. Plate-type divertor concept is selected for the ARIES-ACT1 based on the peak-time average heat flux of 10.6 MW/m2. Two zone divertor (any combination of the plate and finger and T-tube) Fingers for q>~8 MW/m2, plate for q<~8 MW/m2 Decreased number of finger units Tubular or T-Tube He-cooled SiC/SiC divertor Impinging-jet cooling, Tin/Texit=600/700 ᵒC Allowable heat flux up to~5 MW/m2

SUMMARY The power core configuration, system integration and maintenance scheme of the ARIES-ACT1 have been re-examined, and major new design features are discussed and highlighted. The Pb-17Li SiC/SiC blankets including the IB, OB-I and OB-II segments have been re-designed and optimized with the objective of achieving high performance (~58% power conversion efficiency) while maintaining attractive safety features, feasible fabrication process, credible maintenance scheme and reasonable design margin on the temperature and stresses. Design issues, uncertainties and R&D needs are discussed in separate presentation..