August 13, 2015

Bizarre nuclear fusion reactor in 5 years headline from Treehugger but claimed better reactor based on superconductors not expected to be ready for ten years

Treehugger has a headline "
Nuclear fusion reactor in just five years?"

The MIT design depends on getting 23 tesla superconducting magnets (currently at lab scale) scaled up for projects of this scale and beyond. The MIT researchers believe the engineering and development work on the new 23 tesla superconducting magnets could be achieved over a ten year timeframe.

It is strange that they would talk about a nuclear fusion reactor in five years if the key component advance is only hoped to be ready in ten years. There is also the details about actually getting the funding and doing the work to build would still be a very complex reactor. The main benefit is that it should be an easier project than the ITER tokamak and the planned path after ITER to get to a working commercial tokamak fusion reactor in the 2060s.


The affordable, robust, compact (ARC) reactor is the product of a conceptual design study aimed at reducing the size, cost, and complexity of a combined fusion nuclear science facility (FNSF) and demonstration fusion Pilot power plant. ARC is a ∼200–250 MWe tokamak reactor with a major radius of 3.3 m, a minor radius of 1.1 m, and an on-axis magnetic field of 9.2 T. ARC has rare earth barium copper oxide (REBCO) superconducting toroidal field coils, which have joints to enable disassembly. This allows the vacuum vessel to be replaced quickly, mitigating first wall survivability concerns, and permits a single device to test many vacuum vessel designs and divertor materials. The design point has a plasma fusion gain of Qp ≈ 13.6, yet is fully non-inductive, with a modest bootstrap fraction of only ∼63%. Thus ARC offers a high power gain with relatively large external control of the current profile. This highly attractive combination is enabled by the ∼23 Tesla peak field on coil achievable with newly available REBCO superconductor technology. External current drive is provided by two innovative inboard RF launchers using 25 MW of lower hybrid and 13.6 MW of ion cyclotron fast wave power. The resulting efficient current drive provides a robust, steady state core plasma far from disruptive limits. ARC uses an all-liquid blanket, consisting of low pressure, slowly flowing fluorine lithium beryllium (FLiBe) molten salt. The liquid blanket is low-risk technology and provides effective neutron moderation and shielding, excellent heat removal, and a tritium breeding ratio over 1.1. The large temperature range over which FLiBe is liquid permits an output blanket temperature of 900 K, single phase fluid cooling, and a high efficiency helium Brayton cycle, which allows for net electricity generation when operating ARC as a Pilot power plant.

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