Ignition analysis for burn control and diagnostic developments in ITER

Abstract

The temporal evolutions of the operating point during the ignition access and ignited operation phases are analysed on the basis of zero dimensional (O-D) equations in order to clarify the requirements for safe control of ignited operation and for the development of diagnostic systems in ITER. A stable and safe method of reaching the ignited operating point is identified as the `higher temperature access' method, being compatible with the H mode power threshold constraints. It is found that the ignition boundary can be experimentally determined by a `thermonuclear oscillation' of the operating point without knowing the power balance equation. On the other hand, the ignition boundary determined by the power balance equation has a larger error bar depending on the accuracy of the diagnostic system. The plasma waveform response to sudden changes in the various plasma parameters during ignited operation is also calculated, and fusion power regulation is demonstrated by feedback control of the fuelling and auxiliary heating power

Chapter 6: Steady state operation

“…In addition, in a steady state reactor plasma, burn control will certainly become an important component of fusion research. Theoretical analyses have already attempted to simulate the ignition access and the operation of an ignited plasma [273] to determine the ignition boundary of a steady state fusion reactor. The simulation demonstrates the fusion power regulation by feedback control of the fuelling and auxiliary heating power.…”

Analyses of Diagnostic Failure Effect and Fail-Safe Ignited Operation in a Tokamak Fusion Reactor

“…19,20 This control algorithm to keep such quantities has been confirmed to work well for the case of a sudden change in the plasma parameters, such as a sudden change in the confinement factor, alpha ash confinement time, sudden injection of impurities and ab-sorbed fuels, sudden increase in the alpha-particle loss, etc. 16 We should note that as for the sudden change in the plasma position, although this feedback control has not been tested yet, the same feedback control algorithm for an ignition burn is expected to manage this situation. This is because the change in the plasma position affects the confinement time through the change in the major radius in the confinement scaling or affects the alpha ash due to compression or expansion of the plasma volume.…”

“…in the ex-vessel components 1 and invessel LOCA initiated by the loss of plasma control, 2,3 the magnet failure, 4 and the other failure scenarios [5][6][7][8][9] have been analyzed for the International Thermonuclear Experimental Reactor~ITER!, the safety aspect caused by the diagnostic failure effect on the ignited operation has not been considered so far despite the active development of various diagnostic system and ignition analyses in a tokamak reactor. [10][11][12][13][14][15][16][17] Therefore, the TAC-12 report has recently recommended that the fail-safe operation in ITER related to the diagnostic system should be considered and analyzed. 18 This type of analysis on failure modes and effects analyses of each diagnostic system is also necessary for developing a fusion reactor.…”

“…2 , which includes the relativistic effects, torus effects, and the nonreflecting surfaces such as holes. 15,16 The coefficient A s is given by A s ϭ 2.5 ϫ 10 Ϫ56 T e~0 ! 4 g i 1.5 $ f D ϩ f T ϩ 10g i ϩ f a % 1.5 b~0!…”

A proposed set of diagnostics for core ignition burn control in a tokamak reactor

“…In order to solve the above issues, we have been considering ignition burn characteristics so as to associate the results with designs of diagnostic systems since 1995 and have presented some results [12]. In our earlier published work [13] we tried to analyse various burn conditions and consider how to identify the ignition condition experimentally. There, we demonstrated that the proportional control algorithm based on fusion power can control ignition burn, but only in limited situations.…”