Nuclear engineering and design/fusion : an international journal devoted to the thermal, mechanical, materials, structural, and design problems of fusion energy最新文献

Fusion reactors will exhaust large volumes of hydrogen species and helium, and cryopumps can satisfy the pumping needs. Two programs described here were undertaken to develop the high performance, continuous operation required. The capability of charcoal as a cryogenic sorbent was optimized and improved by use of specific charcoal types and grades, and by use of thermally conductive bonds for attaching the charcoal to the cryogenically cooled substrate. A 30% demonstrated pumping speed improvement is significant for a system in which the pump dimensions are measured in tens of square meters.

An automatically controlled continuous duty cryopump system was developed, fabricated and demonstrated. The system pumps deuterium, and can be readily modified to pump helium by addition of a sorbent such as charcoal. This two-unit system has one unit being regenerated while the other unit is pumping. It is prototypical of a fusion reactor pump in which five units would be pumping for each unit that is being regenerated. Low tritium holdup is projected for an operational installation.

Of the many components and systems comprising a fusion reactor like the Tokamak Fusion Test Reactor (TFTR), few, if any, are subjected to more extreme and severe conditions than the protective armor for the interior vacuum vessel wall. The primary TFTR limiter, referred to as the Phase II bumper limiter, provides protection of the inner vacuum vessel wall from neutral beam shine through, normal plamsa loads, and major disruptive instabilities. The highly transient nature of forces and temperatures induced by these conditions produces significant dynamic responses in various parts of the bumper limiter structural system. This paper addresses the incorporation of a finite element dynamic analysis in the study of bumper limiter behavior when subjected to several electromagnetic load scenarios. These loads, due to a variety of realistic plasma conditions, were used in the interactive design and optimization of limiter components and support locations and flexibilities which enable the structure to perform within established criteria.

Optimal Control Theory is used to analyze the laser-heating of plasmas confined in strong solenoidal magnetic fields. Heating strategies that minimize a linear combination of heating time and total energy spent by the laser system are found. A numerical example is used to illustrate the theory. Results of this example show that by an appropriate modulation of the laser intensity, significant savings in the laser energy are possible with only slight increases in the heating time. However, results may depend strongly on the initial state of the plasma and on the final ion temperature.

A medium-sized DT burning tokamak has been designed with low-activation Al-alloys. We can obtain a large plasma current up to 4.5 MA with an elongation of 2.3, by taking advantage of the good shell effect of Al-alloy vessel and by applying the appropriate feedback control system. Such a large current is effective for the improvement of confinement and high β-value.

To obtain these plasma parameters, PF coils are placed inside TFC. Single pancake windings and their connection by welding remove complexity originated from this configuration. By the use of keys in the extended wedge region and large shear panels the displacement of TFC caused by large overturning moment is suppressed to be less than 1 mm.

For reduction of induced activity, almost all the components have been designed with Al-alloys except TFC and inboard PFC conductors. The newly developed Al-alloy has been applied to the vacuum vessel, where the new structure of one-turn break is adopted using Al₂O₃ ceramic spraying. Gamma-rays from activated copper conductor in TFC and inboard PFC are shielded by a lead plate located between the vacuum vessel and PFC. This concept would be extended to devices which aim at Q ⪢ 1 and much longer burning time, if all the coils are made of Al-alloy of which contents of impurity and alloying element are well-controlled.

Organic coolants offer a unique set of characteristics for fusion applications. Their main advantages include high temperature (670 K) but low pressure (2 MPa) operation, limited reactivity with lithium and lithium—lead, reduced corrosion and activation, good heat transfer capabilities, no MHD effects, and an operating temperature range that extends to room temperature. The major disadvantages are decomposition and flammability.

The organic fluid characteristics are described in sufficient detail to allow fusion system designers to evaluate organic coolants for specific applications. Analyses are presented for organic-cooled blankets, first walls, high heat flux components and thermal power cycles. Designs are identified that take advantage of organic coolant features, yet have fluid decomposition related costs that are a small fraction of the overall cost of electricity. Particularly interesting applications include organic-cooled high heat flux components (up to about 8 MW/m²) for use with liquid metal cooled blankets.