K.A. Werley

The ARIES-III D-/sup 3/He tokamak reactor: design-point determination and parametric studies

The multi-institutional Advanced Reactor Innovation and Evaluation Study (ARIES) has examined the physics, technology, safety, and economic issues associated with the conceptual design of a tokamak magnetic-fusion reactor. The ARIES-I variant envisions a deuterium-tritium (D-T) fueled device based on advanced superconducting coil, blanket, and power-conversion technologies and a modest extrapolation of existing tokamak physics. Key aspects of the ARIES-I physics model are summarized, and the engineering and costing models are discussed. Results of parametric studies leading to the identification of a design point to be subjected to detailed analysis and integration as well as to characterize the ARIES-I operating space are presented.<<ETX>>

Lessons learned from the Tokamak Advanced Reactor Innovation and Evaluation Study (ARIES)

Lessons from the four-year ARIES (Advanced Reactor Innovation and Evaluation Study) investigation of a number of commercial magnetic-fusion-energy (MFE) power-plant embodiments of the tokamak are summarized. These lessons apply to physics, engineering and technology, and environmental, safety, and health (ES&H) characteristics of projected tokamak power plants. Summarized herein are the composite conclusions and lessons developed in the course of four conceptual tokamak power-plant designs. A general conclusion from this extensive investigation of the commercial potential of tokamak power plants is the need for combined, symbiotic advances in both physics, engineering, and materials before economic competitiveness with developing advanced energy sources can be realized. Advances in materials are also needed for the exploitation of environmental advantages otherwise inherent in fusion power.

The ARIES-III D-3He tokamak-reactor study

A description of the ARIES-III research effort is presented, and the general features of the ARIES-III reactor are described. The plasma engineering and fusion-power-core design are summarized, including the major results, the key technical issues, and the central conclusions. Analyses have shown that the plasma power-balance window for D-/sup 3/He tokamak reactors is small and requires a first wall (or coating) that is highly reflective to synchrotron radiation and small values of tau /sub ash// epsilon /sub e/ (the ratio of ash-particle to energy confinement times in the core plasma). Both first and second stability regimes of operation have been considered. The second stability regime is chosen for the ARIES-III design point because the reactor can operate at a higher value of tau /sub ash// tau /sub E// tau /sub E/ approximately=2 (twice that of a first stability version), and because it has a reduced plasma current (30 MA), magnetic field at the coil (14 T), mass, and cost (also compared to a first-stability D-/sup 3/He reactor). The major and minor radii are, respectively 7.5 and 2.5 m.<<ETX>>

Energy confinement and future reversed field pinches

Energy confinement within the reversed field pinch (RFP) is governed by three plasma regions: a poorly confined plasma core characterized by parallel (radial) transport and flux surfaces destroyed by m=1 tearing mode activity associated with dynamo relaxation; a medium confined edge limited by ideal pressure gradient driven modes; and a good confinement region located near the reversal layer. The good confinement region determines the global confinement characteristics of the RFP, and, if limited by resistive interchange modes, would be consistent with the Connor-Taylor scaling that has provided a good fit to international RFP results. After establishing a two parameter fit of confinement scaling to the RFP database, the scaling relation is used to project the physical characteristics of, and costs associated with, next step and ignition experiments for ohmically heated RFPs. The RFP projects to smaller and less expensive machines than the tokamak with comparable performance

Overview of the TITAN-I fusion-power core

The TITAN reactor is a compact (major radius of 3.9 m and plasma minor radius of 0.6 m), high neutron wall loading (~18 MW/m 2 ) fusion energy system based on the reversed-field pinch (RFP) confinement concept. The reactor thermal power is 2918 MWt resulting in net electric output of 960 MWe and a mass power density of 700 kWe/tonne. The TITAN-I fusion power core (FPC) is a lithium, self-cooled design with vanadium alloy (V-3Ti-1Si) structural material. The surface heat flux incident on the first wall is ~4.5 MW/m 2 . The magnetic field topology of the RFP is favorable for liquid metal cooling. In the TITAN-I design, the first wall and blanket consist of single pass, poloidal flow loops aligned with the dominant poloidal magnetic field. A unique feature of the TITAN-I design is the use of the integrated-blanket-coil (IBC) concept. With the IBC concept the poloidal flow lithium circuit is also the electrical conductor of the toroidal-field and divertor coils. Three dimensional neutronics analysis yields a tritium breeding ratio of 1.18 and a molten salt extraction technique is employed for the tritium extraction system. Almost every FPC component would qualify for Class C waste disposal. The compactness of the design allows the use of single-piece maintenance of the FPC. This maintenance procedure is expected to increase the plant availability. The entire FPC operates inside a vacuum tank, which is surrounded by an atmosphere of inert argon gas to impede the flow of air in the system in case of an accident. The top-side coolant supply and return virtually eliminate the possibility of a complete LOCA occurring in the FPC. The peak temperature during a LOFA is 991 °C.

The reversed-field-pinch (RFP) fusion neutron source: A conceptual design

The conceptual design of an ohmically heated, reversed-field pinch (RFP) operating at ∼5-MW/m2 steady-state DT fusion neutron wall loading and ∼124-MW total fusion power is presented. These results are useful in projecting the development of a cost effective, low-input-power (∼206 MW) source of DT neutrons for large-volume (∼10 m3), high-fluence (3.4 MW yr/m2) fusion nuclear materials and technology testing.

Start-up simulations of the PULSAR pulsed tokamak reactor

Start-up conditions are examined for a pulsed tokamak reactor that uses only inductively driven plasma current (and bootstrap current). A zero-dimensional (profile-averaged) model containing plasma power and particle balance equations is used to study several aspects of plasma start-up, including: (1) optimization of the start-up pathway; (2) tradeoffs of auxiliary start-up heating power versus start-up time; (3) volt-second consumption; (4) thermal stability of the operating point; (5) estimates of the divertor heat flux and temperature during the start-up transient; (6) the sensitivity of the available operating space to allowed values of the H confinement factor; and (7) partial-power operations.

Tokamak and RFP ignition requirements

A plasma model is applied to calculate numerically transport-confinement (n tau /sub E/) requirements and steady-state operation points for both the reversed field pinch (RFP) and tokamak. The CIT tokamak and RFP ignition conditions are examined. Physics differences between RFP and tokamaks and their consequences for a DT ignition machine are discussed. The ignition RFP, compared to a tokamak, has many physics advantages. These advantages, coupled with important engineering advantages translate into significant cost reductions for both ignition and power reactor. The primary drawback of the RFP is the uncertainty that the present confinement scaling will extrapolate to reactor regimes. The 4-MA ZTH was expected to extend the n tau /sub E/ transport scaling data three orders of magnitude above ZT-40 M results, and if the present scaling held, to achieve a DT-equivalent scientific energy breakeven, Q=1. A base-case RFP ignition point is identified with a plasma current of 8.1 MA and no auxiliary heating.<<ETX>>

Conceptual design of a reversed-field pinch fusion neutron source☆

The conceptual design of an ohmically-heated, reversed-field pinch (RFP) operating at 5 MW/m2 steady-state DT fusion neutron wall loading and ∼ 100 MW total fusion power is presented. These results are useful in projecting the development of a cost effective, low input power (∼ 200 MW) source of DT neutrons for large-volume (∼ 10 m3), high-fluence (3.4 MW y/m2 per year at 80% availability) fusion nuclear technology testing.

Fusion reactor options and alternatives for the RFP

The poloidal-field-dominated confinement properties of the Reversed-Field Pinch (RFP) are exploited to examine physics and technical issues related to compact, high-power-density fusion reactors. Past studies of the Compact RFP Reactor (CRFPR) were based on a liquid-metal-cooled fusion power core (FPC) that confined high-density plasma at high beta with fields generated by resistive coils. These early framework studies combine with a better conceptual understanding of RFP confinement, impurity control, and current drive to justify further study. A comprehensive systems and trade study has been conducted as part of an ongoing in-depth reactor assessment. Optimal reactor designs, directions, and design sensitivities emerging from this study are described.