Optimization of steady-state beam-driven tokamak reactors

Abstract

VXSftUBD IDK 981 0.8. OBRMtBMCMT OF MHCT,. wro** annum u«-AC02-76-ca&-3073. .. ; >CTni(lllTinN Of THIS OOCHMEHT IS IMIPCT MOTICg This report was prepared as an .ABSTRACT Recent developments in neutral beam technology prompt us to reconsider the prospects for steady-state tokamak reactors. A mathematical reactor model is developed which includes the physics of beam-driven currents and reactor power balance, as well as reactor and beam system costs. This model is used to find the plasma temperatures which minimize the reactor cost per unit of net electrical output. The optimum plasma temperatures are nearly independent of P and are roughly twice as high as the optimum temperatures for ignited reactors. If beams of neutral deuterium atoms with near-optimum energies of 1-2 MeV are used to drive the current in an INTOR-sized reactor, then the optimum temperatures are typically T e = 12-15 keV and T t = 17-21 keV for a wide range of model parameters. Net electrical output rises rapidly with increasing deuterium beam energy for E^ < 400 keV, but rises only slowly above E^ ~ 1 MeV. tfe estimate that beam-driven steady-state reactors could be economically competitive with pulsed-lgnition reactors if cyclic-loading problems limit the toroidal magnetic field strength of pulsed reactorsto < 85% of that allowed in steady-state reactors.nvnuiilv two' 'e'-Bti mow a' th<! United SMt«i GovorfnGnt 0i aflf agency thsicol

Continuous tokamak operation with an internal transformer

“…The plasma parameters Include ion and electron temperatures deterrained by power balances which Include various possible anomalous electron and ion losses as well as ion energy losses due to toroidal field ripple, as described in Section 2.1. Current-drive efficiency is determined by generalizing our previous analytic approximation from the case of strict steady state [6] to the present case of an internal transformer cycle, as described in Section 2.2. Our model for computing the relative cost of electrical generating capacity includes fixed costs proportional to the engineered reactor volume cost of installed neutral beam power, and cost of convert.…”

“…'ng thermal to electrical power, as in our previous work [6]. The simple generalization of our previous model required to treat a transformer cycle is described in Section 2. the complexity of our multidimensional parameter search, but the fusion power production and current-drive efficiency are normalized to profiles from the 1-u BALK;" transport code and the ion orbit code 10, as In our previous paper [6].…”

“…The energy balance equations are [6]. Unless otherwise noted, 811 formulas in this paper are in Gaussian units.…”

“…Previous studies have shown that such methods are feasible if an efficient external source can be found which drives at least 0.1 ampere of plasma current for every watt of power absorbed :'n a high density plasma [6]. Unfortunately, there are still questions whether such efficient current drive can be achieved .…”

“…Wa also calculate fusion power output, current-drive efficiency, resistive decay of induced currents, and the ratio of time spent in the coast and drive phases, tfe determine the efficiency of current drive and the plasma power multiplication factor Q averaged over a cycle of transformer operation. But since a previous study showed that neither of these two quantities is an adequate measure of reactor performance [6], we will concentrate on optimizing the relative cost of electrical generating capacity. We will compare the relative $/watt computed for various methods of current drive as a function of maximum allowed plasma pressure and cycling of heat loads .…”