Research Needs for Magnetic Fusion Energy Sciences - US Burning ...

introduction
harnessing fusion power for useful purposes will require significant advances in the understanding
of fusion fuel cycle and power extraction. iteR and later demo (an energy demonstration reactor)
will be significant extensions beyond present experience (as described in the detailed harnessing
Fusion Power theme chapter), requiring the successful operation of systems that currently
have never been fabricated, demonstrated, or tested in a relevant in-service environment. The
primary focus of this Thrust is to address this situation by developing the science base and technological
readiness for safe and reliable: 1) power handling and extraction 2) operation of the fusion
fuel cycle, and 3) tritium breeding and extraction. The flows of power and tritium associated
with this Thrust are shown on Figure 1:
Figure 1. Schematic of power and tritium flow covered in Thrust 13.
Plasma Chamber (“In-vessel”) Considerations — tritium breeding and power extraction are key
features of the plasma chamber surrounding the burning plasma, including the breeding blanket
with integrated first wall, shield, and divertor. but the various components of the plasma chamber
are subjected to an extreme fusion nuclear environment with many challenging conditions: (a) an
intense flux of 14 mev neutrons that access many high-energy threshold nuclear reactions to produce
highly nonuniform nuclear heating, tritium, helium and other gases, atomic displacements,
and many transmutation products; (b) intense fluxes of charged particles and radiation absorbed
on surfaces exposed to the plasma; (c) strong magnetic fields with temporal and spatial variations;
(d) electromagnetic and thermal coupling to the plasma including transient events like plasma disruptions
and edge localized modes (elms); (e) high vacuum conditions; (f) high temperature operation;
and (g) strong chemical activity. Understanding the behavior of components in this fusion
nuclear environment represents a challenge requiring important advances in many scientific
fields, engineering disciplines and technology development. This area is usually referred to as Fusion
nuclear science and technology (Fnst). Thus, the in-vessel components are constrained primarily
by a) survival in an extreme environment and b) the need for infrequent maintenance.
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