Heat Transfer in Vertical Concentric Cylinders in a High Level Nuclear Waste Repositoryby Samir F. Moujaes, Univ of Nevada, Las Vegas, United States,
Yao M. Lei, Univ of Nevada, Las Vegas, United States,
Abstract: Modeling free convection heat transfer in an cylindrical annular enclosure is still an active area of research and an important problem to be addressed in the high level nuclear waste repository. The waste containers are vertically emplaced in the borehole 300 meters below ground, and in a horizontal grid of 30 × 8 meters apart. The borehole will be capped after the container emplacement. Therefore the container is surrounded by an enclosed vertical concentric air-gap inside of the borehole. The expected initial heat generated is between 3 - 4.74 kw per container depending on the type of waste. The goal of this study is to use a computer simulation model to find the borehole wall, air-gap and the container outer wall temperature distributions. The borehole wall temperature history has been found and was estimated to reach a maximum temperature of about 218 °C after 18 years from the emplacement. In the air-gap the problem is more complicated where convection and radiation effects are present. This paper will present some preliminary results of the convection only problem in the air-gap at a very early stage of the transient heating process. The simulation shows two interesting circulation patterns that have been formed indicating that the possibility of multicellular flow is real.
Subject Headings: Boring | Radioactive wastes | Heat transfer | Computer models | Walls | Temperature effects | Cylinders | Waste management
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