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Atlanta, GA|Atlanta Marriott Marquis
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Fusion Science and Technology
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The U.S. Million Person Study of Low-Dose-Rate Health Effects
There is a critical knowledge gap regarding the health consequences of exposure to radiation received gradually over time. While there is a plethora of studies on the risks of adverse outcomes from both acute and high-dose exposures, including the landmark study of atomic bomb survivors, these are not characteristic of the chronic exposure to low-dose radiation encountered in occupational and public settings. In addition, smaller cohorts have limited numbers leading to reduced statistical power.
Jeffrey A. Crowell, James P. Blanchard
Fusion Science and Technology | Volume 39 | Number 2 | March 2001 | Pages 434-438
Advanced Designs | doi.org/10.13182/FST01-A11963274
Articles are hosted by Taylor and Francis Online.
A model of the induced currents and resultant electromagnetic forces and stresses during a disruption event in the ARIES-RS tokamak design is presented. Like many other power reactor concepts, the ARIES-RS has a modular design consisting of toroidally segmented internal structures to limit disruption induced currents and facilitate maintenance. During a disruption, currents driven in these structures cross the large toroidal magnetic field producing substantial electromagnetic forces.
To consider these effects, a transient three-dimensional electromagnetic finite element model of the ARIES-RS device was created, implemented by the commercial code ANSYS. The same code was used for dynamic structural analysis.
The model includes all major components (the first wall, blankets, divertor plates, stabilizing shells, vacuum vessel, shields) electromagnetically coupled together. The magnets are assumed to remain energized during the disruption. The plasma current decay is prescribed, not coupled with the current in the structure. Halo currents and and vertical displacement events, which may produce larger forces than found in this study, are not considered.
The results illuminate important design tradeoffs. For a centered fast plasma current quench, the outboard first wall/blanket modules were found to experience the most severe loading. Current in the sidewalls generate forces that produce large torques on these structures. Supports are needed to react these loads; however, thermal stress considerations drive designs toward a first wall with a compliant support system. Thus, supports needed to reinforce against disruption loads can lower the maximum permissible heat flux on the first wall. Further, electromagnetic pressure on the first wall requires a factor of two reduction in the coolant channel width in some regions, resulting in higher pumping power.
Extension of the results to other modular tokamak designs is discussed.
Color versions of the figures are available on the world wide web at http://silver.neep.wisc.edu/disrupt or by contacting the authors.