Cutaway of ARIES-RS Power Core
The Boeing Company
P.O. Box 516, St. Louis, MO 63166-0516, USA
One of the key objectives of the ARIES-RS study was to investigate and develop a high performance fusion power core that would lead to an operationally and economically attractive, central-station, electrical generation, power plant for the potential owners and operators. Not only must the power core be designed to ensure the ability to assemble and maintain the power core systems, it must be designed to enable the entire power core and plant to maintain high plant availability and ease of operation. The power core and plant designs have been refined to significantly improve the overall plant availability without compromising the overall objective to minimize the cost of electricity.
Availability is the ratio of the time the plant is available for power production compared to the total calendar time. The two factors that determine the plant availability are the time between failures (scheduled replacement and unscheduled failure) and mean time to repair or replace the failure. The former is not well characterized as the designs are not finalized and certainly tested. Hence this portion of the study dealt with the ability to design a power core configuration that could be efficiently maintained. .
Tokamak power cores are recognized to be difficult to construct and maintain. Experimental tokamaks have relied on in-place, internal refurbishment, but prior power plant conceptual designs have proposed modular replacement of the power core elements as a possible means for efficient maintenance and improved availability. The ARIES-RS design modified the traditional D-shape and the cross-section of the TF coils to improve accessibility and removal of power core components horizontally between the TF coil legs while retaining the proper magnetic field shaping of the reverse shear plasma. The outer PF coil set also has been designed so that no coils are in the port area, which enables horizontal access without coil movement. The removal and replacement of the module is accomplished completely from outside the core, through the port region only, to minimize the in-vessel remote operations and, hence, reduce the maintenance time. .
The power core elements are grouped according to their in-vessel lifetime. This will allow removal and replacement of the inner components while the outer power core components are refurbished and returned to the power core to attain full utilization of their lifetime. The divertor plates are designed so that they have a lifetime identical with the remainder of the first wall, thus allowing a common change-out period. The next layer of blanket/reflector/structural hardback is designed to have a change-out period as a multiple of the inner wall/blanket lifetime. Shielding elements are designed as life-of plant components. An innovative hardback structure integrates all the inboard, outboard and divertor elements into a single removable sector. The shields on the outboard region also function as the vacuum door and are an integral part of the removable sector. .
The removable sector module is mainly supported on the bottom. For installation, the module is inserted on rails containing a molten alloy within alignment slots. After the module is aligned, the alloy solidifies in the slots and secures the module into place, thus allowing transfer of the loads into the permanent structure. A close-fitting vacuum vessel encases the low temperature shield, yet allows room for a vacuum duct to connect upper and lower vacuum pumping chambers. Large maintenance ports are provided for access to remove and replace the core sector modules. .
Special transporters have been designed to contain the remote handling equipment for the sectors and to transport the used and new sectors to the maintenance ports. A range of transporter sizes have been evaluated for this purpose. The building surrounding the power core has been conceptualized to assess the ability to efficiently maintain the power core. The midplane level is dedicated to the periodic maintenance system, with a circular corridor surrounding the power core. In addition to the periodic maintenance of the core, the core and the building were designed to allow for unplanned maintenance of the entire core. The dome of the cryostat is removable to allow vertical removal of the upper PF coils, TF coils and the remainder of the power core if necessary. A redundant set of PF coils are provided below the core so that the core elements will not have to be disassembled to replace one of the lower PF coils. .
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* Work supported by the US Department of Energy under contract DE-AC03-95ER-54299 and UCSD Purchase Order 10087872.
** Institutions participating in the ARIES Team, in addition to The Boeing Company, include Argonne National Laboratory, General Atomics, Los Alamos National Laboratory, Massachusetts Institute of Technology, Princeton Plasma Physics Laboratory, Raytheon Engineers and Constructors, Rensselaer Polytechnic Institute, University of California-San Diego,and the University of Wisconsin-Madison.