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

Long-term: Test the control system for regulating power flow in a D-T environment in ITER, with divertor
control and fluctuation detection and response. Extend to demonstration of the complete integrated
power flow regulation system, including control of fluctuations within the tolerable levels, in an environment
dominated by alpha particle heating, and at the power flow levels expected in or near those in
a commercial reactor.
Develop the means for and demonstrate active prediction, avoidance, detection, and response
to off-normal and fault events (e.g., plasma disruptions, subsystem failures): Can
the occurrence of off-normal events be reduced to levels required for power plant operation, and can reliable
response algorithms be developed for acceptable device protection?
off-normal events will occur in any complex system. means must be in place to detect them early
and respond by minimizing and mitigating their effects, followed by recovery of control or safe
shutdown, and cleanup as needed. in addition to plasma events, resulting in a rapid loss of plasma
current or “disruption,” off-normal events can result from loss of control, failures of sensors
or actuators, or other system hardware failures. in a power producing reactor, a full unmitigated
off-normal event will cause a major dump of energy on the surrounding structures with unacceptable
damage. handling of these events must be an integral part of the complete control system; it
requires sophisticated control level automated decision software for determining the best course
of action, as well as additional facilities for mitigation, recovery, and cleanup. Thrust 2 will develop
disruption prevention and mitigation techniques for iteR, which will provide a strong foundation
for this work. however, considerable challenges will remain for actively controlled, higher
pressure reactor-level plasmas, and new solutions may be needed.
Specific Challenges:
in a demo, prediction, avoidance, and mitigation methods for plasma-induced disruptions must
all be extended to greater reliability, while at the same time seeking to operate beyond passively
stable limits. This Thrust will apply techniques from Thrust 2 to determine the level of performance
that can be achieved through active control. For plasma-induced disruptions, the major
avoidance and control tools available are the same heating and current drive actuators and feedback
stabilization tools used to maintain steady state and control other transients. much more
work is needed, however, on controlling other off-normal events such as control system, sensor,
actuator, or other hardware failures. new options may also exist for eliminating the plasma-induced
disruptions, but there is little understanding of how these work. For example, non-axisymmetric
shaping, studied in Thrust 17, and flowing liquid metal walls (Thrust 11) may eliminate or
increase tolerance to disruptions, and, if results are promising, could be incorporated to enable
increased performance.
Research Plan:
Short-term: Implement those early detection, control recovery, and mitigation techniques for off-normal
events from Thrust 2 in existing experiments that can be reliably scaled to burning plasma conditions.
Initiate investigation of innovative disruption avoidance techniques.
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