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Deep geologic repository progress—2025 Update
Editor's note: This article has was originally published in November 2023. It has been updated with new information as of June 2025.
Outside my office, there is a display case filled with rock samples from all over the world. It contains a disk of translucent, orange salt from the Waste Isolation Pilot Plant near Carlsbad, N.M.; a core of white-and-bronze gneiss from the site of the future deep geologic repository in Eurajoki, Finland; several angular chunks of fine-grained, gray claystone from the underground research laboratory at Bure, France; and a piece of coarse-grained granite from the underground research tunnel in Daejeon, South Korea.
T. Kunugi, M. Z. Hasan
Fusion Science and Technology | Volume 19 | Number 3 | May 1991 | Pages 1024-1029
Blanket Technology | doi.org/10.13182/FST91-A29477
Articles are hosted by Taylor and Francis Online.
Convective heat transfer in the thermally developing region in a circular channel of the first wall and limiter/divertor plates of a fusion reactor has been analyzed numerically. The surface heat flux on a coolant channel in these plasma facing components varies circumferentially. The flow is assumed non-MHD fully-developed laminar and turbulent in a circular tube. The nonuniformity of surface heat flux greatly affect the Nusselt number and thermal entry length. For the cosine distribution of surface heat flux, the steady-state Nusselt number can be reduced at the point of maximum heat flux by as much as 38%, 62% and 37% for fully-developed laminar Poiseuille, laminar slug and turbulent flows, respectively. Thermal entry length can be increased by up to 2.4 times for laminar flow and 3.5 times for turbulent flow due to the nonuniformity of surface heat flux. If this reduction of Nusselt number due to the nonuniformity of surface heat flux is disregarded, the film temperature drop in the coolant channels of plasma facing components of a fusion reactor will be underestimated by 37% to 62%. This will result in an underestimation of the maximum structure temperature. The increase in entry length is not likely to affect the thermal-hydraulic design of a conventional divertor plate.