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Fusion Science and Technology
August 2025
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DOE fast tracks test reactor projects: What to know
The Department of Energy today named 10 companies that want to get a test reactor critical within the next year using the DOE’s offer to authorize test reactors outside of national laboratories. As first outlined in one of the four executive orders on nuclear energy released by President Trump on May 23 and in the request for applications for the Reactor Pilot Program released June 18, the companies must use their own money and sites—and DOE authorization—to get reactors operating. What they won’t need is a Nuclear Regulatory Commission license.
Yu. Turkin, H. Maassberg, C. D. Beidler, J. Geiger, N. B. Marushchenko
Fusion Science and Technology | Volume 50 | Number 3 | October 2006 | Pages 387-394
Technical Paper | Stellarators | doi.org/10.13182/FST06-5
Articles are hosted by Taylor and Francis Online.
The magnetic configuration of the Wendelstein 7-X (W7-X) stellarator is optimized following a set of criteria including a rotational transform profile with low shear and minimized bootstrap current that must be controlled for proper functioning of the island divertor. This paper studies the compensation of residual bootstrap current by using electron cyclotron current drive (ECCD). The modeling shows that the loop voltage induced by ECCD leads to a redistribution of the current density with a diffusion time of ~2 s. The relaxation time of the total current is much longer, however - for W7-X plasma parameters the total toroidal current reaches steady state after several L/R times requiring hundreds of seconds. In order to keep the toroidal current and its profile in the acceptable range, a feed-forward or predictive control method using ECCD as actuator is proposed. The main steps are as follows: (a) calculate the bootstrap current distribution using plasma parameters measured in the online transport analysis and (b) determine and apply ECCD as needed. For the current control to work properly and to avoid long relaxation times, the reaction time of the control loop must be less than the current skin time.