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General Kenneth Nichols and the Manhattan Project
Nichols
The Oak Ridger has published the latest in a series of articles about General Kenneth D. Nichols, the Manhattan Project, and the 1954 Atomic Energy Act. The series has been produced by Nichols’ grandniece Barbara Rogers Scollin and Oak Ridge (Tenn.) city historian David Ray Smith. Gen. Nichols (1907–2000) was the district engineer for the Manhattan Engineer District during the Manhattan Project.
As Smith and Scollin explain, Nichols “had supervision of the research and development connected with, and the design, construction, and operation of, all plants required to produce plutonium-239 and uranium-235, including the construction of the towns of Oak Ridge, Tennessee, and Richland, Washington. The responsibility of his position was massive as he oversaw a workforce of both military and civilian personnel of approximately 125,000; his Oak Ridge office became the center of the wartime atomic energy’s activities.”
Ahmed Hassanein
Fusion Science and Technology | Volume 30 | Number 3 | December 1996 | Pages 713-719
Divertor Design and Experiments | doi.org/10.13182/FST96-A11963020
Articles are hosted by Taylor and Francis Online.
Damage to plasma-facing components and structural materials of fusion reactors during abnormal plasma instabilities such as hard disruptions, edge-localized modes (ELMs), and vertical displacement events (VDEs) is considered a serious life-limiting concern for these components and materials. Plasma-facing components (PFCs) such as the divertor, limiter, and first wall will be subjected to intense energy deposition during these plasma instabilities. High erosion losses of material surfaces, large temperature increases in structural materials, and high heat flux levels and possible burnout of coolant tubes are critical issues that severely limit component lifetime and therefore diminish reactor safety and economics.
A comprehensive model that integrates various stages of plasma interaction with plasma-facing materials (PFMs) is extended to analyze and evaluate the damage that results from various plasma instabilities. Models for thermal evolution and phase change of a multilayer structural material, for the developed vapor cloud magnetohydrodynamics above the surface of the material, and for calculating the resulting radiation and its transport through this vapor cloud due to plasma/vapor interaction are dynamically coupled in a self-consistent way to evaluate various aspects of detailed time-dependent responses of PFMs. The extent of the damage to PFMs, structural materials, and coolant channels depends mainly on the total deposited plasma energy, deposition time, and the coating or surface material. During short disruption events (τd ≤ 1 ms), the initially intense evaporated material can significantly shield the PFM and reduce its further erosion. When plasma instabilities occur at longer durations, however, such as in VDEs (τd=100-300 ms), no significant self-shielding is expected; therefore, serious erosion and melting can occur. In addition, hydrodynamic instabilities and other mechanisms will further erode melt layers of metallic PFMs. Plasma instabilities of longer duration may also allow more time for conduction of deposited plasma energy from the surface to the structural material and finally to the coolant channels, where it can cause burnout. These events are analyzed parametrically for the expected range of plasma parameters for various surface materials such as beryllium, carbon, and tungsten, and for structural materials such as copper.
